Log Review

Hi, I'm just starting out with 7747 platform. I have a 88 K1500 that originally came with the 305. I bought the truck with the motor blown with the intention of swapping to the 350 completely stock. It's a CA truck with 2nd Air. I bought a 130k mile used motor with 180 compression on all cylinders and replaced all the gaskets, timing chain and oil pump. I'm using 350 injectors, knock sensor, and ESC module. The entire distributor is brand new. The 2nd Air is working and back in the truck.


My goal was to find completely stock everything, so I wouldn't have to tune the chip right away. I have 2 ECM's the original and one I got from pick and pull, but I have 3 bcc's; ADTD the original 305 with air and auto; ASDZ this came with the second ECM, but doesn't have 2nd Air; AMUS I pulled this one from a truck with a 350, 2nd Air, and Auto.


When I first attempted to start the truck it wasn taking too long for fuel to get to the TB and it took too long to start. It was also dying under load. On some newer vehicles, this is a sign of a bad fuel pump, so I changed out to the EP381 Vortec pump (Found out later, the fuel system is supposed to depressurize after key off, turned out to be the fuel pump relay). Currently, the regulator is adjustable, and I've set it to 13 PSI as that seems to be the consensus ideal pressure. However, the truck is running rich. My thinking is the fuel pressure is too high for the stock setup, and 13 PSI is for those who have the tunning capability, (I will, but not right now).


I've attached a couple of logs that I've run. This morning I swapped out to the ASDZ and other ECM to ensure the readings were consistent and not an ECM issue. So log 11-13a is ASDZ, and the 11-12c is the last log I ran on the AMUS and the chip I'll need to run in order to pass smog. Both logs show my BLM low. I'm comparing my log to a reference log posted under the 7747 thread.


SO my question is, how do the logs look. Does it look like fuel pressure is my issue, if so how can you tell? If fuel pressure is an issue, is there way to use my logs to calculate the best fuel pressure for my setup?


Also, I noticed that I have counts that spike low and sometimes high, is this normal for 7747, or is this a cable issue? I've attached a picture of my connector.

The attached screen shot shows the BLM averages from a 1227747 TBI engine. BLM's below 128 are rich. BLM's above 128 are lean. Ideally the BLM averages between 123 to 133 are considered good.

Adding fuel pressure generally makes the BLM's go more rich. Reducing fuel pressure generally makes the BLM's go more lean.

Usually the stock Spark Advance Table works well with a stock engine. If the engine is not stock the stock Spark Advance Table will likely need to be optimized.

Passing an emission test for an engine that is not stock, will likely require tuning of both the fuel table and spark advance table.

Tuning for an emission test will likely be successful with the use of an automotive Gas Analyzer; CO. HC, CO2, O2, NO, &NO2.

dave w

I'm back with the same truck. I have been gimping it around the country, now I'm in Texas. Short story is that I've got it running well by sound and no CEL on. I am currently using the ADSU prom, and the smog gear has been removed. I need to use this truck for towing within the next two weeks. While I was towing a trailer (Empty 16ft enclosed trailer), the truck was overheating real bad and throwing a code 43. I replaced the open circuit knock sensor and the CEL is no longer on, but the truck still struggles pulling the same trailer, the temp is going too high, and WoT feels too sluggish. The attached log shows idle, 0-70 unloaded, idle, and 0-45 loaded. It's stock except for a better fuel pump and 13 psi fuel pressure. I'm not expecting much, but hoping for more. Any ideas would be greatly appreciated.

Happy 420

Not to sure what overheating has to do with the ECM, sounds like you have other mechanical issues.

That was my thought too. I don't look at logs all the time, so I'm not sure what could be wrong. Since it's all stock, I shouldn't need a tune at least not until it's running properly. I was hoping that something would be obvious on the log to give me a starting point. I hate throwing parts at a problem. Thanks for the reply.

did you replace the water pump when you swapped engines? What about thermostat? I replace them every 5 years regardless of milage. I would pull the rad and get it checked out/tested. I would also replace the fan clutch, Rockauto still sells GM clutches for your era truck (I just bought one). Did you set timing to factory spec? pull the EST connector and set to 0*...

Hi Mwtvvo, could you please publish your bins here.I have the amc304 engine in my car and would like to test these bins on it.

he doesn't have any bin files he has been swapping ecu's obtained from the wrecker.... why don't you look at all the bin files on this website

When I did the swap, I didn't start out with a working motor, so I refreshed as much as I could. I put on a new water pump and thermostat. I recently swapped over to an 11 blade. The radiator is original to the truck, so it could be an issue. I replaced the whole distributer when I did the swap.

Before running the recent log, I checked the timing (est disconnected) because I thought it might be the reason for the lack of power and overheating. It was at 12 (not sure how), and I adjusted it down to 0-2. The truck runs better, but lacks power. The radiator could be a weak point, but it shouldn't cause power loss.

Any other ideas? Are logs not a good diagnostic tool? Thanks for the responses.

@tayto, in general you are right but I couldn`t find the ADTD nor the AMUS!

Is the 11 blade a plastic blade? I put one on a friend's 1992 gmc c2500 a year ago along with a new clutch. I am going to run one on my squarebody this summer. Is your clutch new or original? I would get your cooling problem sorted out first. pull the rad and get it checked out. have you done a compression or leakdown test to see if the engine is healthy? don't have enough evidence at this time but failed headgasket can cause overheating and lack of power.

The 11 blade I installed is plastic: although, I think they also are made with steel.

The original radiator failed on me. The wire to the temp sensor (near the exhaust manifold) fell off, so I the temp gauge in the dash wasn't working. Luckily I stopped for gas and smelled radiator fluid, otherwise I the truck would have overheated going 75 mph. I now have a new radiator.

That was not the source of my lack of power though. I'm going to do a compression test and fuel pressure test today maybe that will give me more insight. (I'm new to Data Logging) I believe the fuel pressure is too high. My BLMs are very low across the range. The truck has a fuel pump in from a 95 TBI, but I think it's too much pressure still. I adjusted the regulator until it bottomed out and still had low BLMs. Also, my injector Duty Cycle is over 100, even over 1000. Do I need a custom chip to read this setting correctly ("the hack") or is this also showing my fuel pressure is too high? What is a good range for this?

don't you have the wrong calibration currently? setting your fuel pressure to bring the BLMs in is a bandaid fix at best and fools errand IMO. Vortec or TPI pump is an excellent upgrade even on a bone stock setup. 13 psi, again is fine on stock stuff and where i target on stock or lightly modified.

is your engine a 350 or 305? is a stock TBI motor or originally a carb'd engine? previously you stated you had 350 injectors. are these GM used or aftermarket?

Thanks for your response. I'm really not sure what the problem is. I'm guessing at best. My blms are really low and the only thing I have to go off is my fuel pressure. I've put 305 injectors in and they made my blms too high and cannot adjust down to 128. The 350 injectors won't adjust up to 128.

It's an original tbi 350 I bought from a junk yard said to have 180 compression on all cylinders. The injectors are also used from junk yard, all sets.

I just finished a the compression test and the numbers are 145-150 psi. Kinda low, but consistent, and I'm not getting any smoke.

I've been really just trying to get this thing to run in stock form. I have several logs, but I'm not sure what I'm looking at yet. The only thing that sticks out is the low blms and the injector duty cycle

I'm open to options.

get the injectors professionally cleaned and tested. i have had bad injectors cause the BLMs to be low (rich). you also need to get the correct calibration and/or burn a chip with the correct calibration. re-read this thread, we discussed this already.

Ya, I've been considering the injectors too. I pulled some injectors from the salvage yard to see if my conditions would change, but turns out I grabbed 305 injectors instead.

I found a big problem yesterday. In an earlier post, I stated my timing was off by 12 degrees. I rechecked the timing yesterday and realized that I disconnected the wrong wire on the firewall. My 90 Chevy I had years ago was in this same area, so I didn't even think twice about disconnecting it. Yesterday I saw a second disconnect and it was brown. After disconnecting that wire and setting the timing again, the truck is running much better. Self inflicted problems are the worst.

I still need to adjust my fuel pressure a bit, but the truck feels a lot better.

The prom I'm currently using is ASDU. I believe that one is close to my setup. Why do you think it's the wrong calibration? This comment throws me off, please explain.

leave your fuel pressure at 13psi and get your 350 injectors cleaned. i thought you were still rinning a 305 calibration, it seems you have one more matched now, I assume you have a 700R4 and the lockup works. glad you figured out the timing. once you get fuel squared away you can probably set minimum idle if havent already.

Okay, that makes more sense. Yeah, it's 700r4, and the lockup does work. Finally feeling a little relieved. Thanks for your help.

Repost, sorry

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Originally Posted by mecanicus

Hi Mwtvvo, could you please publish your bins here.I have the amc304 engine in my car and would like to test these bins on it.

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I happen to have an AMUS .bin file (for a '7747) but, IT IS NOT STOCK, It has a fairly aggressive timing table and, IIRC, fuel table (last modified 12/29/2018 so, I don't remember much about it). It also has the BPW and Spark Advance Hack patch. If you're interested let me know, YMMV.

That's interesting. I don't have a way to burn chips yet, but I will in the future if you want to shoot it my way.

Do you remember any of the mods done before creating that file?

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Originally Posted by Mwtvvo

That's interesting. I don't have a way to burn chips yet, but I will in the future if you want to shoot it my way.

Do you remember any of the mods done before creating that file?

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This .bin is from when I 1st started tuning my 88 5.7L (with the help from Dave w) with a 46mm bored Throttle Body, 20LB spring, Edelbrock 3704 intake, Summit Racing aluminum heads, Lunati flat tappet 208/213 cam with fUll roller 1.6 rockers giving me .466/.484 lift and 112° LSA, shorty headers with JBA "Y" to 3" high flow cat and Borla Pro XS straight through muffler. After a few logs and tunes we decided I should go to with the much faster EBL Flash-II and a WBO2. Personally, if you can afford it, I'd go with the EBL :rockon:

Like I said, IT IS NOT STOCK! USE AT YOUR OWN RISK!

Thanks for the .bin and the info. I will look into the EBL Flash. I'm just happy to have the truck running good for the first time since I've owned it lol.

Thanks for the info Tayto. I'm curious why you would recommend setting the fuel pressure by pressure and not by logging and knocks?

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leave your fuel pressure at 13psi and get your 350 injectors cleaned. i thought you were still rinning a 305 calibration, it seems you have one more matched now, I assume you have a 700R4 and the lockup works. glad you figured out the timing. once you get fuel squared away you can probably set minimum idle if havent already.

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i HIGHLY doubt your knock counts are from a rich mixture. they are either from timing, a lean condition or false knock (exhaust hitting frame, bad knock module/sensor, etc). GM's spec for fuel pressure is 9-12 psi. I have seen/felt gains on totally stock setups by putting the pressure at 13psi as that's the number these injectors were flowed at from factory. they also say thay the higher the pressure for TBI injectors the better they atomize the fuel.

The computer gives direct feedback on it's running condition even if it's slow. Is there no way to tune the fuel pressure by watching the computer's feedback?

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Originally Posted by Mwtvvo

The computer gives direct feedback on it's running condition even if it's slow. Is there no way to tune the fuel pressure by watching the computer's feedback?

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You can look at your INT and BLM while in CL to see if you're close to 128 for an indication. O2 feedback and Cross Counts can help too. A WBO2 will give you better feedback. It's better to have known fuel pressure/injector flow 1st. Then tune INT/BLMs.

That makes sense. I have a spare set of 350 injectors I need to send out to have them tested/cleaned. Then I'll know those are good. I don't have a WB02 yet, but it's on my list. On my log, my injector duty cycle is pretty high.

Could that be an indication of a bad injector?
OR Is that part of the hack?
What's a normal operating range?

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Originally Posted by Mwtvvo

The computer gives direct feedback on it's running condition even if it's slow. Is there no way to tune the fuel pressure by watching the computer's feedback?

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this is a HACK way to do things. this is what people did back in the 80s and 90s before PROM tuning had been developed. you have mixed and matched your engine and ECU and expect it to run like stock. Once you are no longer stock TUNING is required. I realize you have a "stock" 350, but we don't know what cam, pistons, etc are in it, so it is a guessing game. it sounds like it is running better than before but your calibration is NOT paired for your engine. there are also a bunch of other factors like injectors (mentioned already), general engine health (compression, worn timing chain, etc), etc etc. you can throw what ever calibration/ecu at an engine, if the engine ain't right it ain't gonna run right. period.

these injectors were meant to be ran @13 psi. can you run less pressure? yes, but they will output less fuel and usually engine performance suffers.just leave the pressure at 13 psi and move on. this is the ideal pressure for a stock application.

Im here to tell ya that you cannot trust "BLM" to be spot on accurate..

I just put in my new AEM 30-0300 and at idle i am at 14.x but BLM has me at 140's!!


Food for thought...

some of that also has to do with the use of ethanol. back when these vehicles were tunes by the factory it was "pure" gas. not uncommon to see the fuel trims off. however this is the beauty of a closed loop system, the ecu can and does correct for this.

I understand that every engine comes from the factor different and even over the years parts can be changed out of even worn. In my original post, I said that I pulled the motor apart and changed every gasket, oil pump, timing chain, even lapped the valves. I do not know anything about the cam. The compression test I did a week ago showed 140-145 which is low, but I think that was a gauge issue, but the values were very close to each other.

I guess I'm missing something here. I want to tune this soon, but right now I'm just trying to adjust things for optimal performance. The Blms are adjusting the fuel to reach stoich.

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Re: INT & BLM clarification
No. An INT or BLM value of 128 is neutral. Not adding or subtracting fuel.

If either is higher then 128, the ECM is adding fuel. IOW, the ECM found that the exhaust AFR was on the lean side and is bringing it back to stoich (or there abouts').

A value lower then 128 (INT or BLM) is removing fuel. the ECM found that the exhaust AFR was richer then stoich, and is trimming it back to the proper value.

RBob.

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So even with my blm low 107 the computer is still reaching stoich in CL, but not in OL. This is assuming my injectors and O2 sensor are working correctly. I don't understand why that would be optimal, besides better atomizing, (there must be a way to gauge this too?)

Being that every engine is different from the factory, should be a reason to use the computer to adjust the fuel to optimal performance. That's the beauty of a computer system. I guess I'm asking how do you use the computer to tell if it's optimal.

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Im here to tell ya that you cannot trust "BLM" to be spot on accurate..

I just put in my new AEM 30-0300 and at idle i am at 14.x but BLM has me at 140's!!

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How do you know 14.x is optimal.

Also, can someone answer my injector duty cycle question?

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Originally Posted by Mwtvvo

Also, can someone answer my injector duty cycle question?

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With the '7747 ECM you need to apply the patch for BPW and Spark Advance.
Attachment 18245

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With the '7747 ECM you need to apply the patch for BPW and Spark Advance.

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Okay just making sure, thanks.

Your EBL Flash sent me down a rabbit hole of info. I'm thinking about swapping to the 7427 ecm now. The thread is cluttered with information though. The ebl Flash comes with support lol.

To my understanding, 128 BLM is whatever you set "STIOCH" to in scalars...

So if you set it to 15.3:1 in the computer 128 is 15.3:1.. Could be wrong but pretty sure i am right.

I am just saying that a good wideband is the (ONLY WAY) to go.. Sure idle ya want somewhat leaner, especially if you don't have converters.. No reason to own a vehicle that burns ya eyes out idling. That is crazy. But driving around you want those tables close to 128 so the computer isn't struggling to keep it near whatever you set stioch at..... Then for power, you can work the P.E mode to give ya what ya want..

Yeah i get the whole "14:!" may not be great, one guy claims he gets best mileage and power at 13.x:1.. Saw it at thirdgen.org. All i am saying is don't trust just BLM for tuning...

I'm actually thinking of doing a single 4" converter when i upgrade and supercharge everything. I mean yeah i will lose some power, but how much ya need past 530whpo?!? I mean honestly!?!?

16197427 Data Log Information

Attachment 18246

Attachment 18247

Attachment 18248

Attachment 18249

Attachment 18250

Attachment 18251

EBL P4 AFR Averages

Attachment 18252

Attachment 18253

Thanks for posting that log Dave. I assume you're showing the Blms vs WBO2 and how they show rich while the wide band does not. That's interesting to see. Has anything been done to the engine or the .bin from the log you posted?

My engine is completely stock, so my thinking was to use the Blms to tune the fuel pressure to an ideal setting. I was hoping that a factory tune and factory engine the Blms could be used to adjust the fuel pressure. I also understand a more precise method is a wideband.

The 16197427 data logs (after tuning) were from a "kitchen sink full of go faster parts" modified 5.7 liter. Go faster parts require AFR tuning for optimal performance.:thumbsup:

I knew BLM vs actual AFR was wrong.. Don't know why.. Yours is the (SAME) as mine.. Damn thing screams 140's+ at idle but is 14.7:1 perfect...


Crazy stuff huh?