After 86 ECM change....
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
After 86 ECM change....
I switched out ECM's on my E86 today. The ECM in the vette had a unknown chip that I was told was programmed for timing. The vette was running rich and the "mystery" chip was one of my concerns. I have a 88 ECM that I changed out today. Well after the change, it started right up, but idled high. I checked timing and it was way advanced. I disconnected the EST and reset timing to 6* BTDC and shut off engine and connected the EST back up. When I rechecked timing it had gone back to where it was before (like 20* advanced +). My coolant temps before never got over 180* and the fan came on at about 170*. Now the fan doesn't cut on until 226*. So now I assume that the mystery chip was programmed for more than timing. With the 88 ECM, it still runs rich which I know will take a little time for the ECM to learn the fuel curve. Now back to the timing. Before when I set it this way it stayed on 6*. Why is it advancing when I connect the EST back up?
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
The old chip stayed at 6 even after the est was re-connected?
There should be between 20-26 degrees of advance at idle rpm and load conditions with the est connected (based on my 88 ABTR bin).
Something strange going on with the other chip. Must've been a real dog off idle with only 6 degrees.
Good luck working you problem. Sounds like you're making progress.
There should be between 20-26 degrees of advance at idle rpm and load conditions with the est connected (based on my 88 ABTR bin).
Something strange going on with the other chip. Must've been a real dog off idle with only 6 degrees.
Good luck working you problem. Sounds like you're making progress.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by tequilaboy
The old chip stayed at 6 even after the est was re-connected?
There should be between 20-26 degrees of advance at idle rpm and load conditions with the est connected (based on my 88 ABTR bin).
Something strange going on with the other chip. Must've been a real dog off idle with only 6 degrees.
Good luck working you problem. Sounds like you're making progress.
There should be between 20-26 degrees of advance at idle rpm and load conditions with the est connected (based on my 88 ABTR bin).
Something strange going on with the other chip. Must've been a real dog off idle with only 6 degrees.
Good luck working you problem. Sounds like you're making progress.
Yes, that is correct. With the old chip I could disconnect the EST and set timing at 6* BTDC and reconnect EST and it would still be at 6*. Now with the 88 ECM, I set it at 6* and reconnect EST and it's at like 20* +. I finally got it to idle pretty good with the old chip even at 6*. Now with the 88 Chip it idles around 1000 rpm. I will need to reset minimal idle and TPS to get it lower. So, even at idle the 20-26* of advance is o.k.?
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
Yes 20-26 degrees of advance is normal for 800 rpm and less for all loads between 0 and 144, once load goes over 160 advance will begin to drop in this rpm range.
At 1000 rpm, you could see between 20 and 36 degrees depending again upon load.
Here's what the table contains (sorry for hard to read format) load increases as you go across starting with 32 and increasing in increments of 16. Idle load should be low, unless car is stalling.
400 rpm ->20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 16.2 14.1 9.5 9.5
600 rpm ->20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 16.2 12.0 8.1 8.1
800 rpm ->20.0 26.0 26.0 20.0 20.0 20.0 20.0 20.0 17.9 14.1 9.1 9.1
1000 rpm ->20.0 32.0 32.0 35.9 35.9 34.1 34.1 28.1 26.0 20.0 12.0 12.0
At 1000 rpm, you could see between 20 and 36 degrees depending again upon load.
Here's what the table contains (sorry for hard to read format) load increases as you go across starting with 32 and increasing in increments of 16. Idle load should be low, unless car is stalling.
400 rpm ->20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 16.2 14.1 9.5 9.5
600 rpm ->20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 16.2 12.0 8.1 8.1
800 rpm ->20.0 26.0 26.0 20.0 20.0 20.0 20.0 20.0 17.9 14.1 9.1 9.1
1000 rpm ->20.0 32.0 32.0 35.9 35.9 34.1 34.1 28.1 26.0 20.0 12.0 12.0
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Thanks for the reply, Patrick. After the swap the engine seems to be at a higher RPM. I didn't notice the timing drop any after idling for a few seconds. Later today I will readjust the minimal idle and TPS and see it that helps. I drove it to work this morning and it seemed like I had to hold the brakes a little harder or it would want to go without pressing the throttle. Just seems a little odd because with the other ECM and chip I would set it at 6* and it would stay at 6*. It idled better than the 88 ECM but the TPS and minimal idle needs to be rechecked. Thanks
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
I just got home and set timing again. It is as *6 BTDC with EST disconnected and the balancer mark is at 12 o'clock with EST reconnected. I readjusted minimal idle and TPS. My RPM guage doesn't work so I went by ear and got the minimal idle down real low, but just before the engine wants to die. Set TPS at .54v and went for a spin. I have a popping in the TB that I can feel in the accelerator at about 1200-1500 RPM. That is the only RPM range I feel/hear it at. When I slowed to a stop I could barely hear the engine run, almost like it died, but still running. Now my idle is about right but still rich smelling. Did a Field Service Mode and the SES blinks one time/sec when driving and the SES stays for a on for a few seconds during accelerating and decelerating. I guess the ECM didn't solve my rich exhaust problem.
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
I'm thinking the MAF calibration in both chips no longer fits your actual MAF behavior as installed in the car for whatever reason, and over estimated airflow is the result.
I could send you a chip (Eprom only) with modified MAF calibration, but without scan data it'd be a shot in the dark based on what works in my car.
I could send you a chip (Eprom only) with modified MAF calibration, but without scan data it'd be a shot in the dark based on what works in my car.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by tequilaboy
I'm thinking the MAF calibration in both chips no longer fits your actual MAF behavior as installed in the car for whatever reason, and over estimated airflow is the result.
I could send you a chip (Eprom only) with modified MAF calibration, but without scan data it'd be a shot in the dark based on what works in my car.
I could send you a chip (Eprom only) with modified MAF calibration, but without scan data it'd be a shot in the dark based on what works in my car.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
With the MAF unplugged, that should put you in Limp Home Mode.
As I understand it, fuel is then rather crudely contolled proportionally to the tps. I wouldn't expect it to run very well in Limp Home Mode.
The two options that I can see now would be to reduce fuel pressure, or a custom chip programmed to lean things out. I can help with a chip, but due to the distances invovled, the feedback loop would be rather slow.
One thing to note: I don't have any spare memcals, but I do have several spare eproms. For this to work you would need a moates style adaptor that would allow you to plug in new eproms and still retain your stock memcal.
The other option would be to use a socketed memcal, but you would most likely have to make one. I have seen some aftermarket chips that were socketed, so you may want to take a look at the custom chip you have, just in case it was socketed. I think Ed Wright is in Oklahoma, perhaps that's where your chip came from.
As I understand it, fuel is then rather crudely contolled proportionally to the tps. I wouldn't expect it to run very well in Limp Home Mode.
The two options that I can see now would be to reduce fuel pressure, or a custom chip programmed to lean things out. I can help with a chip, but due to the distances invovled, the feedback loop would be rather slow.
One thing to note: I don't have any spare memcals, but I do have several spare eproms. For this to work you would need a moates style adaptor that would allow you to plug in new eproms and still retain your stock memcal.
The other option would be to use a socketed memcal, but you would most likely have to make one. I have seen some aftermarket chips that were socketed, so you may want to take a look at the custom chip you have, just in case it was socketed. I think Ed Wright is in Oklahoma, perhaps that's where your chip came from.
Last edited by tequilaboy; May 29, 2006 at 11:03 AM.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
These where the last options I came to also. I could adjust fuel pressure lower and hope that it might decrease fuel consumption. I am on the high side of normal fuel pressure with larger than stock injectors. I intend on getting a scan in the next few weeks and maybe a little more info on whats going on. I contacted Alvin on a tuned chip. I know that the 24lb injectors can be adjusted with the chip. I guess the scan first, AFPR, and tune. We'll see. Thanks
