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Tuning a truck for a friend of mine, having problems with closed loop idle. The truck will go into closed loop while driving, then when you come to a stop it goes in and out from opened to closed, then stays open. I noticed in the log that for some resaon AE is going active at idle for no reason. Here is a short log at idle.
Couple things that stand out is low vacuum/higher MAP at idle, 104 BLM so is that the bottom of your bin? and not much timing?
So big cam?
Raise idle, lower VE and increase timing at idle. This will get things hot for O2 sensor and increase MAP so AE does not come in at idle.
There's so many settings for AE in $0D, one flag for Sync fuel at idle, look at others to increase MAP AE qualifiers. Looks like the higher MAP at idle could be causing the Sync AE Flag which is making it even richer.
Just took a quick look at the log and did notice a few things. First, is this a stock engine or does it have an aggressive cam ? If it is anywhere near stock the MAP readings at idle are way too high. The MAP pressure shouldn't be above 40kpa at idle in gear. I suspect that the AE is going active because the MAP readings are bouncing around enough to trigger AE. Was the A/C on and possibly cycling during the log ? The idle was also a little high as well which could explain the MAP readings. Another thing I noticed was the coolant temp. I know that 188 degrees isn't very low, but depending on what the starter bin was, closed loop idle temps are kind of high in some of the stock bins I have noticed. I had a similar issue after swapping a 427 PCM into my firebird and finally noticed some of the closed loop qualifiers in the BJYL bin. The car could go into closed loop pretty easy while driving, but would have issues with going into open loop at idle. I'm sure others will chime in too, but those were a couple of things I noticed.
Min temp for closed loop is 2*C. The truck has a small cam in it, its a rebuilt 350 TBI, with TBI heads. Could there be a vaccum leak? So if I give it more timing at idle it will bring the MAP down? I thought around 20 degrees at idle was good. Idle is set to 700 RPM in the warmer temps. My plan was to emulate and tune the idle VE table while in closed loop. My wide band is in my truck right now so I could not tune it in open loop.
At one point iin the log the truck was in gear, no AC on.
His IAC counts were up around 63 at idle no load, so I cracked the throttle blades open some to get them down, then reset the PCM.
Its one of those deals where he is always busy and in a hurry so I do not have much time to tune on it. Plus he is standing over my back asking 1000 questions making it hard to concentrate...I told him he is going to have to leave it with me for a day.
Here is the bin he is running now
The 104 BLM means nothing in open loop right? It needs to be in closed loop for that to update?
Like we both saw, the low vacuum/higher MAP so thought it was a bigger cam. But if small cam then yes it could be a vacuum leak. But IAC count of 63 does not indicate vacuum leak? Yes more timing with large cams will increase vacuum/lower MAP.
Beginning of that log was dead? Took awhile to get going then was short.
Your right about open loop, but if OL BLM should be 128? So I'm confused...
What is that bin based off?
Hey Mark, dont forget about my supposedly small cam, and the problems it caused here. Seems to be an epidemic. 104 is way pig rich though, I have seen 108 on mine in drive.
Yeah I dont know why the log did that. He is going to check for vaccum leaks. I think the BLM'S were at 104 after a drive. When we came to a stop it went back into open loop which is when I restarted a new log to capture what it was doing. I know the thing is really rich. I am thinking that he may have pretty crappy cam as well. He is trying to dig up the cam card, but said it was recomended to him by this guy who said this guy....so I dont know yet. I do know its flat tappet, I mentioned the "RV CAM" he said that sounded right. Anyway, I am going to try and get cam specs, he is going to look for leaks. The motor is only about a year old.Quote:
Originally Posted by EagleMark
I used the stock bin from my 94 Blazer, this truck used to have a 6 cyl. in it and its a 93 so we swapped in a 7427 when he went V8. Here is the stock bin I used for a starting point.
Also here is another log while driving, if anyone wants to look, like I said, I know its rich.
What kind of problems were you having? What cam do you have?Quote:
Originally Posted by jameslleary
Comp 12-388-4
Surging idle, constantly low BLM's....always 118 or below.
I am still having some issues every now and then, vac in drive, per the data dash, is 15"
But comp swears up and down its not the cam.
I'd like to see both the cam cards if you can?
A vacuum gauge, mechanical! Is also a useful tool to look for shake in reading. Won't find it in a log... is vacuum steady at idle? No shake in reading? Accelerate and differences should be smooth, no shake.
There was or still is a 290 HP 350 Chevy engine that just sucked for idle and by specs should not been that bad. There's always a degree issue when installing a cam, or at least check and see how far it's off? Push the cam specs to .224 duration @ .050 and this degree is more crucial with idle!
Or who adjusted the rockers?
15" of vacuum is easily tunable if it's a steady vacuum. But 15" of vacuum could be 17 or 13 depending on elevation.
I am working on getting the cam card, I did not build this motor, it was built by a machine shop. As far as adjusting the rockers, I always 1/2 to 3/4 turn past zero lash.Quote:
Originally Posted by EagleMark
I have a mechanical vaccum gauge, so I will stick it on the truck next time he brings it by. I am also going to lower the idle speed and raise the timing at idle to see if it helps. If everything else comes out OK.
I turned closed loop idle off with my built 350 running $0D. For some reason while sitting idling it would cut the BLM all the way down to 90 and stall. You could see my wideband going way lean as it was cutting the BLM but it continued to lean it out anyway. Open loop idle has been fine and the wideband shows the a/f is good.
I'd be interested in seeing your cam card too! I was watching this happen here to in last log but not convinced it is the cam yet, I think there are other issues.
What your describing is to much cam for EFI CL Idle, either duration or overlap and your getting reversion/EGR at idle. there's a point where you can't raise idle, advance timing and lean fuel enough to get good exhaust to O2 sensor. The Narrow Band O2 sensor is lieing, or more acuratly being lied to. When that happens Open Loop Idle is the answer! As you found.
An RV cam will not cause this. But a vacuum leak will, just a little vacuum leak to one cylinder on O2 sensor side and POOF! Data is wrong!Quote:
Originally Posted by 96lt4c4
I looked at the bin and log. Couple things I didn't like was Max Timing increased past 41.8, not good to go past a built in fail safe of firing wrong cylinder. Then Main Spark Bias of this bin is 9.8. Your's is 0? But your timing table is about the same around idle, way more other areas. I never change this in bin because there's to many other things that could be affected. The $0D XDF says this bias is built into mask, that said timing table should be actual. Now without bias where is it? I don't know, it's just something I was taught to leave alone, do leave alone and work on bin as is. You definatly can change bias if you know how it affects every other spark setting. But that's to much work for me... KISS works well here and you don't find an extra 9.8 degrees somewhere! :yikes:
"So where do you say your timing is?" Check with a timing light and compare to data.
Idle does not look steady? Timing and cells are constantly changing, timing is varying a few degrees, so flatening timing at idle could help.
But that is not what I found that could be affecting this. You've changed a lot! All I saw was good tuning. Except some of the 02 settings I don't understand, like Mean/Rich, Proportional and Lean limits. Some are same both ends? I started looking closer at these differences from stock bin when I saw cross counts stop while still Closed Loop. Also saw INT of 128 and BLM of 99 and stay there with no cross counts, still Closed Loop... I'd copy in stock 02 settings for now and see what happens. Also pull power and clear BLM learn, it's probably a disaster at this point.
HTH! :rockon:
I'm curios and would be intrested in hearing results of timing at timing marks as is. Then with Main Spark Bias back in place as well.
Cam in my truck is actually very mild. It's a stock F-body LT1 cam (204/207@.050). If the cam was the problem, then the wideband would also be reading incorrectly. My wideband read it fine, and I could see watch the AFR spike lean before it stalled. FWIW, closed loop idle was unchecked in my factory bin. I turned it on to help band aid any issues with my VE tuning, but disabled it since it caused problems.
if this was not a recent affair, I'd swear you were talking about me.Quote:
Originally Posted by 96lt4c4
Sent you a PM......
LOL...no man not you...I tune better and quicker when I can concentrate on what I am doing, not talking, or being rushed, just the way it is. PM replied.Quote:
Originally Posted by 93chevytbi
Just doing some testing on my personal truck, 7427 $0d. 383 tbi. Noticed my idle map was high too around 40 kpa, never dropped in the 30's. I had idle set to 700, timing was around 20 degrees. My truck does go closed loop at idle though. I to was getting AE going active randomly. Never noticed it before. So, I started raising timing at idle and the Map started coming down, but my BLM's went rich. Once the timing got over say 26 degrees I was getting a flutter in my tach that I could see on the gauge and on the gauge in the log. This would cause the truck to almost die. Can you only advance so much at idle? Or do I have mechanical problems, spark scatter, bad module? It seemed like 25 degrees was as high as I could go, but BLM's went down so I put it back where it was for now.
With 40kpa I would not even try to push it. Yes you can add to much at idle and you found it.
Your truck is idling at 40kpa which is good. The other one is at 55kpa which is worse, this is the one to push some timing at idle to get more vacuum or idle better because of cam. Were still guessing right? No specs? Bigger cams can take 30+ degrees at idle, then need to drop for acceleration. The cam overlap causes an EGR effect and that mixture needs MORE timing!
You really need to check timing at timing marks and compare to timing table to see if it is accurate! That bin had a bias change and 10+ degrees added in places... and the bias was 9.84 so you may have added 20 degrees!
"So where did you say your timing was set?"
I based the .bin on Johnnys truck off of mine, I still have the 9.84 bias in mine. I think when I initially tuned his truck over a year ago I started taking the bias down as an easy way to see how the truck responded to more timing and I may have forgot to put it back. I am putting it back in his tune, and adding it back to the spark tables so they do not go down. When he brings it back over I will check with a timing light with the bias back in. I still do not know his cam specs. He is having problems with leaky valve seals, smokes on start up, so he is putting on a new set of TBI heads machined for the better seals. I told him to check everything to see if there were any signs of a vaccum leaks. So, when I get it back the whole top half of the motor will have been taken off and put back on.Quote:
Originally Posted by EagleMark
Should it be possible to get 30 degrees at idle? Becasue my truck would not do it, 26 is about all I could do. Just trying to find out if I still have something going on in the distributor.
Both of these trucks have the distributors timing set to dead zero by the way, with timing wire unplugged and checked with a timing light. When I get his I will make sure his is set to 0 at the distributor.
I'd like to hear what timing is with/without bias, will be a shocker to people!
The oil burning can really mess up an 02 sensor reading.
Most people couldn't find a vacuum leak if you told them exactly how to. Carb and choke cleaner does not work, brake clean does not work, even nowadays something has changed in starting fluid and it does not work where old starting fluid was fantastic! But spraying flammable fluid around an engine is not a safe procedure anyway... I'm back to propane soldering tourch and a long rubber hose. It's about half as good as old starting fluid. So harder to hear engine change when propane finds vacuum leak, even harder if it's a big vacuum leak because engine is running so bad you can't hear/feel a change. There was a home made way to make a smoke machine I read somewhere. At first I had a laugh at how they made it, then anyone who tried and improved the build all had great results.
No your not going to get 30 degrees advance at idle without a large cam/low vacuum, that is the indicator. The only reason it works on large cams is the overlap and exhaust gases getting into fuel air mixture at idle. EGR effect. As soon as engine increases RPM and flow is returned the high advance used to make it idle needs to go away! Your truck should be fine at 20-21, you already proved 25-26 is max and getting worse, this proves the 4-6 degree retard when finding detonation.
OK I will experiment and see what the timing is with the bias out compared to the log before I put it back in.Quote:
Originally Posted by EagleMark
Finally got this one done...Bad battery cables, bad ground to PCM, bad 12 volt wire to 02 sensor, TBI leaking gas, broken regulator spring...Completely rebuilt TBI, splice in 12 volts to 02, fixed battery cables and PCM ground. Retuned the truck for a really rich idle, raised timing at idle and raised idle speed to 700 RPM. The truck smoothed out and the MAP went down to 42 KPA. Truck runs great now....what a pain..
Didn't mess with checking the timing with the bias out, I just put it back in and retuned the truck. I was a little frustrated...
Very very rarely do I get a vehicle to tune that does not have mechanical issues, that effect tune...Quote:
Originally Posted by 96lt4c4
:thumbsup:
and they always blame everything on the tune. Heard that somewhere recently.Quote:
Originally Posted by EagleMark
To be honest, I have done it myself. After dealing with TBICHIPS, it WAS often true. I had a random high idle for the past year and just brushed it off thinking it was in the tune. I finally bought a multi meter and checked the TPS, which was at .34. adjusted back to .54 and all is good.
So true! I believe it's one of the reasons many shops simply won't touch this stuff. And I love the words "Oh, this engine was rebuilt by the best in the business!", which somehow makes the tuning even more suspect.Quote:
and they always blame everything on the tune. Heard that somewhere recently
the shop that built my motor did in fact blame everything on the tune. however, that blame was well-placed. Easy to blame a mail-order tune, not so on a in-person tune.
Mail order=poop
ya think?Quote:
Originally Posted by 96lt4c4
Oh, and brinako's comment is true too. The guy I wanted to build my motor said he would do so in stock form only. He would not do anything beyond that b/c if it ran wrong, he could be blamed. His exact words were "I won't touch it". surprised the hell out of me really.
slight derail here.... but you can get cylinders of starting fluid that your propane soldering torch head will screw on to. These are the cylinders made for ether start systems for diesel equipment. It works better than any starting fluid in a can than I have been able to find.Quote:
Originally Posted by EagleMark