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Diagnostic Scan Reading

Look at the actual chip that's in there, and make sure the four letter code is the right one for your ECM, and make sure it's printed on with a printer, if it's hand written in pen or has some other logo on it, you're going to know its an after market or homemade job. There's a table I've seen somewhere on this site that gives you the codes and the ECM numbers it works with. I'll see if I can find it, or you may be able to cheat and go look at ECM's for sale on a certain website that rhymes with dock auto and see what PROM say goes with which ECM.

All that aside, you've disconnected the battery and let it sit for a few minutes since this all started, right? It sounds like a mechanical issue with the trans, especially since you added something to it and it stopped behaving badly. However, you are also describing an issue with the TCC lockup, which is controlled by the computer, so it could be either or both. Also, be aware that the PROM chip is very sensitive to static electricity. If you handled it without grounding yourself first, you may have fried some or all of the programming. There are a lot of guys who know a lot more about PROM issues than me, but I do know that they all look the same, but if you have damage to yours or it's not the right one, you can end up chasing that gremlin for a long time before you figure it out.

Here's a starter table that may help, this isn't the one I was talking about, but it's similar: https://xtronics.com/wiki/GM_ECU_eproms.html
 
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I was thinking about this yesterday, one thing I have not done is checked the connections at the trans. I have read on here a couple of times where guys have found issues with them.
The only time I have messed with the ECM was to check voltages at the connectors. I know the PROM program number via live data streaming. I have not put eyes on the actual chip. I have a site that has an extensive list of callouts. http://www.scotthansen.net/BCCLookup.pdf
I finally found the code and does fit my build. The only exception is a callout for an '87.
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Took the Jimmy out to do an errand and she it back to stumbling all over herself. Back in the barn. I think I am going to change out the IAC. The reading never reaches what I have been led to believe is normal. Have done an IAC reset a few times. Not to mention the IAC motor sound horrible.
 
wow leaded compatible means no cats. i thought every 1500 in 87 would have cats. The no closed loop might explain the cross count, showing zero.
 
Wes Harden said:
wow leaded compatible means no cats. i thought every 1500 in 87 would have cats. The no closed loop might explain the cross count, showing zero.
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Had no idea what "Leaded Compatible" was supposed to mean, so good to know. The "no closed loop" puzzled me also. I have closed loop as you can see in the pics. Even though I can see the crosscounts in a datastream it may explain why I cant record it. That last part sounds silly but who knows.
 
chevyjunky77 said:
Had no idea what "Leaded Compatible" was supposed to mean, so good to know. The "no closed loop" puzzled me also. I have closed loop as you can see in the pics. Even though I can see the crosscounts in a datastream it may explain why I cant record it. That last part sounds silly but who knows.
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Some of the trucks made for government use came with no cats, but not many. That may also be the reason for the rare PROM code. I'm going to see if I can find out what the closed loop issue is. If it helps, I can send you a log from my truck which is running well so you can compare...like you said, I've never seen a printout of what's normal, either.
 
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anwat said:
Some of the trucks made for government use came with no cats, but not many. That may also be the reason for the rare PROM code. I'm going to see if I can find out what the closed loop issue is. If it helps, I can send you a log from my truck which is running well so you can compare...like you said, I've never seen a printout of what's normal, either.
Click to expand...

I can confirm this was not a mil or govt issue vehicle. I would love to compare readings.
 
chevyjunky77 said:
I can confirm this was not a mil or govt issue vehicle. I would love to compare readings.
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I emailed my chip programmer, and I'll send you a couple logs when I get home, they are on my other computer. I have a similar setup...5.7, 700r4, 4x4, but I'm running 35" tires and a 205 case, so my final ratio is a bit different. Just want to make sure you plugged that brown wire back in that you disconnect when you set the timing...
 
anwat said:
I emailed my chip programmer, and I'll send you a couple logs when I get home, they are on my other computer. I have a similar setup...5.7, 700r4, 4x4, but I'm running 35" tires and a 205 case, so my final ratio is a bit different. Just want to make sure you plugged that brown wire back in that you disconnect when you set the timing...
Click to expand...

Sounds good...and yes I did.
 
check your conversation thing...I can't attach the logs because they are an .xml...so maybe I can email them to you.
 
chevyjunky77 said:
A little history... Vehicle was having issues with acceleration above 50mph. Under 50mph ran well with a slight shudder/miss. Kickdown at WOT is lacking. Slight surging at idle (200-250 rpm). Overall high idle.

Rebuilt TBI. Front vacuum ports seriously restricted. Overall condition probably the worst I have seen. Mechanically sound.

After rebuild idle issue is resolved. All other symptoms remained. Vehicle now stumbles from full stop through 40mph. "Chugging" while driving has now manifested itself.

After a couple days "chugging" and shudder increased significantly. No CEL. Hooked up scanner and found CODE 32 "EGR SW FAULT". I am assuming a bulb was removed at some point. Reset codes. Symptoms returned to previous condition until code tripped. The EGR was in fact bad. Replaced and code has not returned. Driving performance slightly better.

Could the carbon build-up in the TBI "tricked" the ECU from requiring the EGR to operate?

Just for fun I dropped out of OD. "Chugging" and shuddering very light throughout driving range. Beginning to wonder if I have multiple problems. A torque converter or lock-up issue?
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I had a shudder like that and it was torque converter.
From what you described, I think you have multiple problems.
 
imiceman44 said:
I had a shudder like that and it was torque converter.
From what you described, I think you have multiple problems.
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Agreed on the TC especially since there was a huge change when I used the additive. Still a slight shudder. Had the tires pressure checked, rotate, and balance which seemed to help also. Going to have the driveshaft checked and the rear end inspected. I removed the driveshaft once already but didnt find anything obvious.
 
So, did we get this figured out? I asked an old-timer (older than me, at least) about the chip and he looked it up in a book he had at his garage and told me the following:
AKAJ is for a 1987 G3, R1, R2, V1, or V2 application (Vans and possibly SUV’s). 1227747 ECM, L05 5.7L TBI, MD8 700R4, NA5 federal emissions, NA6 altitude requirements, -NM8 leaded fuel (means NOT for leaded fuel use).
 
It was briefly mentioned, but do a thorough check of EVERY ground wire. Make sure every ground is clean and with a good connection. I chased an issue for months until I found one ground that was suspect. When I fixed it, everything cleared up.
When you say that your O2 sensor counts are all over the place, are they swinging low to high to low rhythmically or do they seem to be totally erratic?
Importance of O2 sensor Cross Counts: A Cross Count is when the reading from the O2 sensor crosses the mid-point (I forgot the exact number but in the 400's), can get into the 10's of thousands on a long drive. Ideally the reading swings low to high to low - if you graph it it looks like a nice sine wave. The ECM is looking for a certain number of cross counts per second. If it does not see a cross count, then it interprets that as being rich or lean (depending on which side of mid-point it reads) and adjusts the INT which in turn moves your BLM to adjust the fuel curve.
As long as your INT is at or near 128, then you can assume that your BLM is stable. The 144 you saw is just the computer self adjusting to slightly enrich the fuel curve at idle. If you increase fuel pressure a bit, that BLM number will come down.
If you really do see 0 cross counts and a INT of 129, then something is not working (I suspect you are not getting into closed loop). Closed loop just means the system is interpreting the 02 sensor for feedback as described above.

What I would check
- Ground wires/connections
- I have not seen anyone ask about Fuel Pressure yet. Do you have a fuel pressure gauge? Do you know what your fuel pressure is?
- 02 sensor: Is yours good? Is it a 1 wire or 3 wire? Where is it located in your exhaust system (close to headers or further down the pipe)? Your 02 sensor needs to operate at a high temp. If single wire and down the exhaust pipe, it may not be heating up enough.
- Vacuum Leaks - are you confident that you don't have any?
- Keep an eye on Open/Closed loop. Are you sure you are in closed loop?
- Are you getting up to operating temp? The system will not go into closed loop if not hot enough (not sure what your ECM is set at)

In general, it is tough to interpret the ECM readings from a static snap-shot. It really takes looking at a running history reading to see what is going on.
 
@Keitha No issues with the o2 once replaced. Scanner shows switching of loop once sufficient temp is reached. No apparent vacuum leaks. No change in idle using various troubleshooting methods. Since so much maintenance has been done it is possible for fuel pressure to be an issue. Not able to do anything about it currently.

Quit a few miles put in watching active stream.
 
Check your ground wires. Look closely behind the motor for any missed wire.
Fuel pressure could be an issue, but fairly easy to determine. Keep an eye on your BLM numbers on the higher load/higher RPM ranges where it stumbles. This is where a Wide Band O2 is so valuable.

What pattern is your O2 reading - you say it is "all over the place" is it rhythmic or random?
 
@Keitha once I replaced the O2 the readings became normal to what everyone else sees. The BLM and integrator numbers also worked themselves out to normal. Nothing changed when stumbling/ shuddering happens. I will do more runs when I get back to the house.

From what I gather I have a normal PROM. No one has mentioned what they are running for me to comp.
 
chevyjunky77 said:
@Keitha once I replaced the O2 the readings became normal to what everyone else sees. The BLM and integrator numbers also worked themselves out to normal. Nothing changed when stumbling/ shuddering happens. I will do more runs when I get back to the house.

From what I gather I have a normal PROM. No one has mentioned what they are running for me to comp.
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It sounds like you have two issues...as was already suggested. I think the o2 sensor cleared up the computer issues, but it sounds like you may have a trans/torque converter issue, also. Shuddering is usually mechanical in nature. As far as I know the only way you can really know about the PROM is by looking at it and seeing if it has the codes printed on it from the factory, but even then, someone may have overwritten the factory programming and you'd never know. If the diagnostic readings are all within normal ranges, it sounds like that issue has been fixed. If that's the case, then let's move on under the assumption that there's another problem causing the stumbling/shuddering. I'm going to read back through and see what we've already established and maybe what might not have been checked. I'm sure other folks will be chipping in shortly.
 
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