Strange Spark Plug issue

[Purv-Dawg]

I've been trying to eliminate any potential causes of pinging so I changed back to the plugs that allegedly were original equipment but it barely runs, backfires, and has no power. Does anyone have any insight into this? I've asked multiple people over the last twenty five years, trying to get some insight and no one has any answers.

My vehicle is a 1989 GMC C1500 5.7l. The plugs that every cross reference tells me are original equipment are CR43TS. They do not work for my application. I spent two years trying to figure this out twenty years ago and found out by dumb luck that the problem is those plugs. Although everything I read tells me it's not the plugs. It runs just fine on R43TS and R44TS plugs but I was trying to eliminate potential causes of pinging.

The only difference I know of is that the "C" in the recommended plugs stands for commercial. That tells me nothing. I can visually see that the electrode is larger on the commercial plug but most people swear by them on these trucks.

Any insight is welcomed.

[ralmo94]

I don't have any insight, but both cr43ts and r43ts both cross to the same NGK, both appear to be projected type, same heat range. I usually get NGK copper myself for everything, that's just me.

[Purv-Dawg]

I know a lot of people get good results with NGK plugs on these trucks and they are finicky about which plugs are used. I just can't be totally sure of false knock without eliminating anything other than the original plugs. I'm going to unplug the knock sensor tomorrow and see what happens. I emailed ACDelco and asked them for insight but I'm doubtful they will have any.

[ralmo94]

If you just unplug it you will get a cel and probably retarted timing if not disabled in tune. Do you have hardware to rewrite?I didn't see elsewhere that you posted?

[Purv-Dawg]

Initially I was using the stock ecm. Now I'm using EBL II and it's significantly worse now than it was originally.

[PlayingWithTBI]

Initially I was using the stock ecm. Now I'm using EBL II and it's significantly worse now than it was originally.

Maybe a little more history would help. Have you done the normal tuneup like, cap, rotor, wires? How old is your ignition coil and distributor? What heads are you running? What is your fuel pressure? Have you done very many VE Learns yet? Maybe your SA tables aren't dialed in?

Low fuel pressure, or lack of flow, can cause lean pops. Loose exhaust or a rattling Cat can cause KCs too.

Edit: How about throwing a WBO2 on it and logging with your WUD?

[Purv-Dawg]

I have other issues I do need to address understanding how to customize my spark tables to reduce spark knock but the plugs themselves have nothing to do with the EBL system. This issue has persisted for twenty five years back to when the vehicle was totally stock and the tuneup is fresh.

I'm going to have to wait until I can buy a WBO2 kit and hopefully that won't be a lot longer. The vehicle is drivable normally but I live in an area with tons of minor foothills and I'm getting spark knock when climbing them and I haven't figured out how to completely eliminate false knock yet to rule them out.

What's caused my biggest confusion is which strategy to take to reduce knock. I've gotten lucky with my intuition but many settings in tunerpro are confusing, just don't give quite enough information to understand, or appear to conflict with and change other settings that on the surface appear completely unrelated.

I've done enough VE learns to get it dialed in close enough to be nearly acceptable. My primary issue is pinging when climbing hills. The first half of the life of thus truck was spent in the flat lands of Georgia so this was never an issue but now it is with a 2.73 rear gear and 32 inch tires in different terrain and I'm not a formally trained mechanic and i have health issues that cloud my thinking so I'm very slow in finding the obvious.

I changed the ignition coil and distributor about five years ago to a Davis unified 12620BK and a Pertronix D3002 coil. I'm running an EDL3702 cam with the stock heads which I'm reasonably certain are 193's.

I've been looking for rattles and I'm not finding anything yet.

[ralmo94]

a 2.73 rear gear and 32 inch tires in could equal pinging when climbing hills. original open throttle spark map wasn't designed for that much load. Probably need a couple degs out of high kpa on main map?

[PlayingWithTBI]

I have the EBL Flash-II on my 88 5.7L too. I guess what I'm getting at is, I find it curious that your plugs are causing your issue(s). I've run ACDelco plugs in different heat ranges, NGKs in 2 steps cooler range, now I'm running Accel 416S "header plugs" (long reach with Gasket Seats instead of Taper Seats). I have not seen a lot of differences with spark knock.

In the EBL you have "SA-Launch Mode" which adds spark based on MAP vs RPM. I was getting KCs at low RPMs until I noticed it was adding more spark while my SA tables are fairly aggressive for my aluminum heads. Can you data log and trap SA before and during KRs? Then maybe lower Launch Mode by 50% to see if KCs go down. If you're running too lean, you'll get more KCs too. Watch your O2 voltage too.

[PlayingWithTBI]

a 2.73 rear gear and 32 inch tires in could equal pinging when climbing hills. original open throttle spark map wasn't designed for that much load. Probably need a couple degs out of high kpa on main map?

Agreed, I was hoping that was a typo and he actually has 3.73s, :happy:

[Purv-Dawg]

I think that changing the plugs fried my ignition coil. You have any suggestions for a new one? The pertronix was fine I guess but I'd like it to last longer than five years like this one did.

[tayto]

sounds like you got a bad plug or cracked one installing it 25 years ago. millions of people run stock ac delco plugs and have no issues with them, including myself. do you check&set the gap on your plugs or install them as is? pertronix is known garbage i would run stock stuff here. i have never used davis stuff but have heard its OK.

[Purv-Dawg]

sounds like you got a bad plug or cracked one installing it 25 years ago. millions of people run stock ac delco plugs and have no issues with them, including myself. do you check&set the gap on your plugs or install them as is? pertronix is known garbage i would run stock stuff here. i have never used davis stuff but have heard its OK.



I'm starting to think I understand what's going on. I suspect that the larger electrodes on the commercial grade plugs increase resistance just enough to destroy coils that may already have enough mileage on them to finish them off. Which is exactly what appears happened this time. Maybe the coil should be replaced when installing these plugs the same way a weakened battery will destroy a new alternator. I went through four alternators in three months on a Mustang when I was a kid. I just assumed I was getting poor remanufactured parts because they were from AutoZone, which is often a legitimate thing. Since they had lifetime warranties it wasn't a big deal to swap them out.

[Purv-Dawg]

a 2.73 rear gear and 32 inch tires in could equal pinging when climbing hills. original open throttle spark map wasn't designed for that much load. Probably need a couple degs out of high kpa on main map?

I've had to reduce the spark tables down to 12 degrees in the cruising speed range to get the ping down enough while climbing after dropping down out of overdrive. The locked torque converter only worsens the problem and I have added about 15 degrees of retard when it's locked.

I'm going to replace the rear gear within the next couple of weeks but I'm trying to decide on a 3.42 or 3.73 ratio. My main goal has always been to get the best fuel mileage possible so I will likely try the 3.42's. I just don't want to be pissed off at myself for being unable to either stop the ping or decreasing my fuel mileage to the point I don't want to drive it any distance. Power is great but this engine has serious limitations without more modifications than I can afford. These are the main reasons I've stuck with the stock heads, which most people consider garbage. If I dropped a pile of cash on a set of summit racing heads it would still cap out at around 330 horses unless I change the intake, injectors, etc. It would be far less expensive to swap to an LS and it would still get better mileage.

I never intended to increase my tire size as much as I did but I found that there are tons of people who buy brand new jeeps and want wider tires. I don't understand the logic but they sell brand new sets of wheels with tires for considerably less than a set of new tires on the original wheels. I got sick of replacing the original hubcaps every few months. The jeep wheels do require adapters and about an hour of grinding out the ring that prevents them from fitting the spacers but it's not difficult. Although I wouldn't advise an inexperienced person to to it.

[Fast355]

I've had to reduce the spark tables down to 12 degrees in the cruising speed range to get the ping down enough while climbing after dropping down out of overdrive. The locked torque converter only worsens the problem and I have added about 15 degrees of retard when it's locked.

I'm going to replace the rear gear within the next couple of weeks but I'm trying to decide on a 3.42 or 3.73 ratio. My main goal has always been to get the best fuel mileage possible so I will likely try the 3.42's. I just don't want to be pissed off at myself for being unable to either stop the ping or decreasing my fuel mileage to the point I don't want to drive it any distance. Power is great but this engine has serious limitations without more modifications than I can afford. These are the main reasons I've stuck with the stock heads, which most people consider garbage. If I dropped a pile of cash on a set of summit racing heads it would still cap out at around 330 horses unless I change the intake, injectors, etc. It would be far less expensive to swap to an LS and it would still get better mileage.

I never intended to increase my tire size as much as I did but I found that there are tons of people who buy brand new jeeps and want wider tires. I don't understand the logic but they sell brand new sets of wheels with tires for considerably less than a set of new tires on the original wheels. I got sick of replacing the original hubcaps every few months. The jeep wheels do require adapters and about an hour of grinding out the ring that prevents them from fitting the spacers but it's not difficult. Although I wouldn't advise an inexperienced person to to it.

With 32" tall tires, I would go no taller than 4.10 and probably 4.30 or 4.56. 700r4 with 4.10s and 32" tall tires is 1,800 rpm at 60 and 2,100 rpm at 70. I had a buddy that had a 91 RCSB 4x4 on 33s. It had the stock 350 and 3.42 gears. The only place it ran well even in 3rd gear was downhill and the truck would not even pull overdrive.

[ralmo94]

My 94 has 3.42's, 265/70's almost seem too much in oD . Fine empty, but it really runs a lot better at about 2k rpm.

You could consider a smaller tire? Cheaper, or keep it out of OD

[1project2many]

The only difference I know of is that the "C" in the recommended plugs stands for commercial. That tells me nothing. I can visually see that the electrode is larger on the commercial plug but most people swear by them on these trucks.

Any insight is welcomed.

The only difference is that the electrode is larger. Each time a spark occurs, metal is transferred from the electrode. A smaller electrode wears out faster. GM put a ton of work into making sure TBI trucks were as reliable as possible, including "longer lasting" commercial plugs.


I think that changing the plugs fried my ignition coil.

Typically new plugs, properly gapped, require less voltage to create a spark.


The pertronix was fine I guess but I'd like it to last longer than five years like this one did.
That's not a bad timeframe. It's very, very hard to find quality parts these days. I'd expect a used GM original coil to outlast most new Chinese made parts.


I'm starting to think I understand what's going on. I suspect that the larger electrodes on the commercial grade plugs increase resistance just enough to destroy coils that may already have enough mileage on them to finish them off.
Larger electrodes do not significantly alter resistance across the plug. Plug gap significantly alters resistance. If the gap is the same it would not make sense to blame plugs without actually finding a problem in the plug.


My main goal has always been to get the best fuel mileage possible so I will likely try the 3.42's.
Sometimes, keeping the rpm low increases load to the point where you lose economy. I've played the same game you're playing now, and the truth is that you can achieve better fuel mileage running a numerically high gear such as 3.73 or 4.10 and tall, skinny tires than you can find with wide tires and numerically low gears. During cruise, a wider tire generally has higher wind resistance and requires more energy to sustain speed. During acceleration a wider tire will generally have greater mass and will require more energy to accelerate. How does the work and money for new tires compare to the cost and effort required for a gear change?

[PlayingWithTBI]

I think that changing the plugs fried my ignition coil. You have any suggestions for a new one? The pertronix was fine I guess but I'd like it to last longer than five years like this one did.

I fried a Pertronix Flame Thrower and a Spectra Premium ICM in ~2000 miles. As @Tayto said they're junk. If I can find it, I'll run ACDelco GM Original Equipment, more so than their other lower tier stuff. A lot of times, if your coil goes out, your ICM is probably toast too. Yeah, they're somewhat expensive - you get what you paid for.

https://www.amazon.com/dp/B08NMVWW8H?psc=1&ref=ppx_yo2ov_dt_b_product_details

https://www.amazon.com/ACDelco-D1984A-Original-Equipment-Ignition/dp/B0013FY548/ref=sr_1_7?crid=1EGLAGA0S5G26&keywords=ACDelco+D1948a+ICM&qid=1665931149&s=automotive&sprefix=acdelco+d1948a+i%2Cautomotive%2C1232&sr=1-7&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

[Purv-Dawg]

My 94 has 3.42's, 265/70's almost seem too much in oD . Fine empty, but it really runs a lot better at about 2k rpm.

You could consider a smaller tire? Cheaper, or keep it out of OD

I appreciate your info. I may go to a smaller tire and I don't mind dropping out of overdrive on uneven roads.

[Purv-Dawg]

The only difference is that the electrode is larger. Each time a spark occurs, metal is transferred from the electrode. A smaller electrode wears out faster. GM put a ton of work into making sure TBI trucks were as reliable as possible, including "longer lasting" commercial plugs.



Typically new plugs, properly gapped, require less voltage to create a spark.


That's not a bad timeframe. It's very, very hard to find quality parts these days. I'd expect a used GM original coil to outlast most new Chinese made parts.


Larger electrodes do not significantly alter resistance across the plug. Plug gap significantly alters resistance. If the gap is the same it would not make sense to blame plugs without actually finding a problem in the plug.


Sometimes, keeping the rpm low increases load to the point where you lose economy. I've played the same game you're playing now, and the truth is that you can achieve better fuel mileage running a numerically high gear such as 3.73 or 4.10 and tall, skinny tires than you can find with wide tires and numerically low gears. During cruise, a wider tire generally has higher wind resistance and requires more energy to sustain speed. During acceleration a wider tire will generally have greater mass and will require more energy to accelerate. How does the work and money for new tires compare to the cost and effort required for a gear change?

The r44TS plugs I was running before the change were gapped @ .045. I installed the CR43TS plugs with the stock .035 gap. I remember that these trucks had issues with a lot of electrical noise.

I have noticed that my average fuel mileage improves when taken out of overdrive on uneven roads. The tires I'm using now are actually slightly more narrow than the stock @ 225. Your point is exactly why I don't understand the reason why so many people want a wider tire on a jeep whenever it not only decreases mileage it decreases traction. Sure, it looks cooler but it's impractical.

[Purv-Dawg]

I fried a Pertronix Flame Thrower and a Spectra Premium ICM in ~2000 miles. As @Tayto said they're junk. If I can find it, I'll run ACDelco GM Original Equipment, more so than their other lower tier stuff. A lot of times, if your coil goes out, your ICM is probably toast too. Yeah, they're somewhat expensive - you get what you paid for.

https://www.amazon.com/dp/B08NMVWW8H?psc=1&ref=ppx_yo2ov_dt_b_product_details

https://www.amazon.com/ACDelco-D1984A-Original-Equipment-Ignition/dp/B0013FY548/ref=sr_1_7?crid=1EGLAGA0S5G26&keywords=ACDelco+D1948a+ICM&qid=1665931149&s=automotive&sprefix=acdelco+d1948a+i%2Cautomotive%2C1232&sr=1-7&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

I thank you for your input. I know the pertronix modules get terrible reviews on summit racing. They have about six immediate failure reviews listed on them. I suspect the pertronix coil was recommended was because it's 50% cheaper and one of only two coils that boast 45k volts on summit racing website specifically for this truck. The other is the Davis unified and the reviews put the ratings almost identical. That's really not a truly reliable way to determine quality but without professional input it's all there really is available.

[ralmo94]

I have noticed that my average fuel mileage improves when taken out of overdrive on uneven roads. The tires I'm using now are actually slightly more narrow than the stock @ 225. Your point is exactly why I don't understand the reason why so many people want a wider tire on a jeep whenever it not only decreases mileage it decreases traction. Sure, it looks cooler but it's impractical.

I agree

I run 225/75 -16 on my 454 with 3.73's, I think more room in the wheel wells look better than them being over filled. You are right a narrow tire has less rolling resistance and more lbs per square inch = more road traction. Shorter sidewall less flex = better handling.

OD = more parasitic loss, I think you are better off with tall gears or tall tires and no OD. Exception is if you want to tow, gear for towing in 3rd, and empty cruising in od,

[tayto]

My squarebody with 30" tires, 700R4 and 3.42s OD is pretty much useless. going up hills suck too. I am wanting to goto 4.11s or 4.56s next year.

I would go with AC delco for plugs, coil and module. I think the Davis stuff would be fine for coil and module, but have only heard good things as i stated before.

[ralmo94]

Yeah nearest I can tell the best thing to do is tune cruise rpm,
2200-2400 @75-80mph seems to be a good target for aerodynamic cars,
2200 @ 70-75 fairly good for trucks, JMHO

[Fast355]

Yeah nearest I can tell the best thing to do is tune cruise rpm,
2200-2400 @75-80mph seems to be a good target for aerodynamic cars,
2200 @ 70-75 fairly good for trucks, JMHO

My van is a little under geared. Needs a 4.10 gear and has a 3.73. 30.47" tall tires and a 4L85E.

[LeMarky Dissod]

I've had to reduce the spark tables down to 12 degrees in the cruising speed range to get the ping down enough while climbing after dropping down out of overdrive.
The locked torque converter (with 2.73) only worsens the problem and I have added about 15 degrees of retard when it's locked.

I'm going to replace the rear gear within the next couple of weeks but I'm trying to decide on 3.42 or 3.73.
My main goal has always been to get the best MpG possible so I will likely try 3.42.
I just don't want to be pissed off at myself for being unable to either stop the ping or decreasing my fuel mileage to the point I don't want to drive it any distance.
Power is great but this engine has serious limitations without more modifications than I can afford.
These are the main reasons I've stuck with the stock heads, which most people consider garbage.
If I dropped a pile of cash on a set of summit racing heads it would still cap out at around 330 horses unless I change the intake, injectors, etc.
It would be far less expensive to swap to an LS and it would still get better MpG.Purv-Dawg,
I daily drive an '02 Tahoe Z71 - L59, 4L60E, 3.73, 265/65R18 (31.56" tall) - all over NY, NJ, CT (and occasionally PA RI & MA).
If I could afford 4.10 for both front & rear axles, I'd do it immediately, without reservation or regret.
4.10 would make things easier on both the L59 & the 4L60E in terms of durability and longevity.
4.10 would actually let me spend even more time in lean cruise than 3.73 - basically whenever the TCC would be locked while in 3rd or 4th.
(Lean cruise, formerly known as highway mode, yeah?)

For whatever it's worth to you.

[Purv-Dawg]

How does the work and money for new tires compare to the cost and effort required for a gear change?

Believe in or not the cost will be about the same amount after a gear swap. The five 18 inch wheels and tires were just under $350 and they had less than 5k miles. The hub centric wheel adapters were $120 and summit racing has a set of gears for another $122. The quote for new tires on the original wheels was over $600 for four

[Purv-Dawg]

Interesting perspective. You've given me something to think about. I appreciate that!

[LeMarky Dissod]

Sometimes, keeping the RpM (too) low increases load to the point where you lose MpG.
... truth is that you can achieve better MpG running a numerically high gear such as 3.73 or 4.10 ....
Reminds me of my ol '94 Caprice wagon, came with 2.56.
Without a downhill or a tailwind, 4th gear was utterly USELESS. That wagon spent so much more time in 1st or 2nd or 3rd than in 4th.


... and tall skinny tires, than with wide tires and numerically low gears.
During cruise, a wider tire generally has higher wind resistance and requires more energy to sustain speed.In that same wagon, 235/75R15 always got better MpG than 255/60R15, 255/65R15, or 255/70R15.

How does the work and money for new tires compare to the cost and effort required for a gear change?In NYC, going from 2.56 to 3.42 a few years ago cost me $750, including a limited slip diff.
Without a doubt, best $800 I ever spent on that wagon. 4th gear finally became useful.
$750 in tires would never be able to do that.
Believe in or not the cost will be about the same amount after a gear swap.
The five 18 inch wheels and tires were just under $350 and they had less than 5k miles.
The hub centric wheel adapters were $120 and summit racing has a set of gears for another $122.
The quote for new tires on the original wheels was over $600 for four.For a given tire load rating, going from a taller tire to a shorter tire - I.E. 31.6" tall to 30.4" tall - is not going to change the effective axle ratio all that much.
1750RpM, 2.73, 4th gear, 31.6" tall tires = 86.08MpH
1750RpM, 2.73, 4th gear, 30.4" tall tires = 82.82MpH

Not enough gear for a Caprice wagon, nevermind heavier trucks with a worse drag coefficient, AND more drag area.

Going from 2.73 to 4.10 is FAR more dramatic.
1750RpM, 4.10 4th gear, 31.6" tall tires = 57.32MpH
1750RpM, 4.10 4th gear, 30.4" tall tires = 55.15MpH

To be redundant, I'd prefer to stay in 3rd or 4th with the TCC locked for as long as reasonably possible - even without lean cruise.

[Fast355]

I agree

I run 225/75 -16 on my 454 with 3.73's, I think more room in the wheel wells look better than them being over filled. You are right a narrow tire has less rolling resistance and more lbs per square inch = more road traction. Shorter sidewall less flex = better handling.

OD = more parasitic loss, I think you are better off with tall gears or tall tires and no OD. Exception is if you want to tow, gear for towing in 3rd, and empty cruising in od,

With a 4L80E/4L85E I gear to tow in overdrive. Easier to get rolling from a stop having 4 useable gear ratios with the deeper gears available to get you rolling. 700r4 and 4L60Es can barely hold up moving a light 305 TBI powered car around much less a truck towing a trailer.

[ralmo94]

Agreed. 80 & 85 were made to tow in oD, I call the other ones half ton tranies, and they were not, nor were they made for too low of input shaft speed, pump doesn't run enough, at least that's the way it was explained to me.

[Fast355]

Agreed. 80 & 85 were made to tow in oD, I call the other ones half ton tranies, and they were not, nor were they made for too low of input shaft speed, pump doesn't run enough, at least that's the way it was explained to me.

I have always been told not to run a 700r4 or 4L60E much under 2,000 rpm especially in overdrive unless the load is very low. Even the upgraded pump has weak output and the cooler circuit robs both the TCC apply circuit and overdrive clutch apply pressures at low rpm.

[ralmo94]

I have always been told not to run a 700r4 or 4L60E much under 2,000 rpm especially in overdrive unless the load is very low. Even the upgraded pump has weak output and the cooler circuit robs both the TCC apply circuit and overdrive clutch apply pressures at low rpm.

My understanding also, they also have a higher OD ratio than the HD trans do.

Also, a 4l60e, or a 4l80e with no lockup in 2nd, will burn up pulling a heavy load up a pass, the tc isn't meant to run that hard unlocked, temps sore unlocked, and at that area torque multiplication doesn't really do any benefit, and in my opinion actually hurts performance.

[Purv-Dawg]

I have always been told not to run a 700r4 or 4L60E much under 2,000 rpm especially in overdrive unless the load is very low. Even the upgraded pump has weak output and the cooler circuit robs both the TCC apply circuit and overdrive clutch apply pressures at low rpm.


This may explain an issue I tried to figure out for years. After remanufacturing my transmission I couldn't get the new torque converter to stop locking and unlocking around 40 mph unless I sped up or slowed down out of the range of lockup. The EBL cured it but I couldn't figure it out.

[Purv-Dawg]

Just to let you all know, the misfires I was having was my fault. two plug wires were crossed. I checked them twice but the second time my blood sugar level was low and a woman was distracting me so I had to give up.

But I have another question. How to you think of "steps" in tunerpro? I'm having difficulty imaging them because normally I would think of more steps taking longer but that's not the case. More steps is faster.

[1project2many]

It depends on the table you're editing. Maybe it helps to think of walking down the stairs... one step at a time takes longer than if you can take 2 or 3 steps each time?

[Purv-Dawg]

It depends on the table you're editing. Maybe it helps to think of walking down the stairs... one step at a time takes longer than if you can take 2 or 3 steps each time?


Okay, I can remember that. Thanks.

My next issue is that my idle is ignoring the idle SA and idling at the maximum SA. Are there any known settings that conflict with the Idle SA?

[tayto]

is the IDLE flag set when you are at idle? if your throttle blades are opened too far or TPS isn't set correctly it may not be in idle mode at all.

[Purv-Dawg]

is the IDLE flag set when you are at idle? if your throttle blades are opened too far or TPS isn't set correctly it may not be in idle mode at all.

It is indicating idle. The only other things I noticed that I don't understand are when I shut the engine off and turn the key on to enable electricity the async and launch mode flags are indicated.

[1project2many]

I'm not sure I would be concerned with the flags set during key on, engine off conditions. They may be relevant but I would focus on what's happening at idle.

Is the engine idling at a speed that is below the stall saver speed? Stall save mode recognizes that engine rpm is dropping too low and adds spark advance, IAC, and sometimes fuel as well. There is a stall saver flag in the datastream of some calibrations.

Is the engine idling at a speed that is below the the crank rpm ( or REFerence pulse duration)? The ecm will treat crank rpm differently than idle rpm.

Is RPM stable at idle? If the ecm is determining that engine rpm is accelerating too quickly it may be attempting to enable fuel injector pulses and extra spark advance. Watch the Acceleration Enrichment flag or BPW value to try to determine the answer.

[Purv-Dawg]

I'm not sure I would be concerned with the flags set during key on, engine off conditions. They may be relevant but I would focus on what's happening at idle.

Is the engine idling at a speed that is below the stall saver speed? Stall save mode recognizes that engine rpm is dropping too low and adds spark advance, IAC, and sometimes fuel as well. There is a stall saver flag in the datastream of some calibrations.

Is the engine idling at a speed that is below the the crank rpm ( or REFerence pulse duration)? The ecm will treat crank rpm differently than idle rpm.

Is RPM stable at idle? If the ecm is determining that engine rpm is accelerating too quickly it may be attempting to enable fuel injector pulses and extra spark advance. Watch the Acceleration Enrichment flag or BPW value to try to determine the answer.


This suggestion helped. Thank you!
There was a launch mode overlap causing it to surge during idle.

I installed a wideband and now for some strange reason I can't figure out why it will no longer go into closed loop. It's killing my fuel mileage and annoying me. Does anyone know any settings that may be conflicting?