dahammer

Hello all .
I recently swapped out the engine in my 87 troc from my GTA . I had Idiling issues which I managed to resolve with help here and a lot of redoing to get it right . Now the only thing left really is I have a miss at around 2000 rpm when cruising in 5th or 4th . It will miss and the tach jumps a bit 200 or 300 rpm . Shift light flickers on and off occasionally . A search here found people with similar issues but no real fixes that I have found . SO I am looking to pick everyones brains with a fresh thread as the others seemed fairly old . This is the new parts list that have been put into the motor in the last few months while it was in the GTA and now in the iroc. It ran like a top in the GTA .
So
New distributer , cap , rotor
New wires and plugs
New fuel filter
New CTS sensor
Newer MAF sensor
New Knock sensor
New injectors
I have checked and set the TPS,IAC
Fuel pressure is over 40 psi and holds. If anything I would think it is to high as I have seen it as high as 50 psi but no idea if this would affect anything at a certain rpm
I am not sure where else to go other than tomorrow I will put the car back up on the hoist and check to make sure I have the knock sensor and Fan sensor plugs on the right sensors as I am not positive on that . I have timed it to 6 degrees BTDC . Would advancing the timing a bit be beneficial to this problem ? Only reason I ask is I noticed that someone had previously put a paint mark at the 8 dergee mark .

dahammer

?

ploegi

Manual or automatic trans?

dahammer

It is a 5 speed trans .I checked the other night and seen some arcing on the new plug wires . I went through and solved that , but still getting the same burp or hesitation in the same rpm range . It is defiantly
ignition relaters

dahammer

So after some experimenting , I have found that if I leave the bypass wire unplugged the miss goes away or is at least not noticable I also set the timing to about 4* or so . The engine seems to smooth out while idling to . When i have the wire plugged back in there is a noticeable miss again at idle and at the 2000 rpm. So could this indicate that my problem lies in the ecm possibly , or the eprom ?

dahammer

Man can't keep up with all the suggestions in here lol .
So This morning I had to run to town , about a 30 min drive . It was still stuttering and missing a bit . I stop after 10 min and unhooked the est wire . Ran smooth and did all the way to town without ecm advance. I stopped , fueled up . And the car barely turns over like it is advanced to much . I left the distributor snug but enough to move. I jumped out . Backed it like a hair . I mean I barely moved it , and rehooked the est wire back up . It fired right up and ran fine . I drove around town for an hour or so and then home on the hwy. It ran smooth as can be . No miss at rpm . Starts fine . Still stalls when you first fire it up unless you give it some throttle for a sec. I think that is curable in the prom once I get my programmer . Just for a test , I have a ecm form my 88 that i had with me . I threw it in part way home and tried it to see if there was any difference . Other than what you would expect with it being from a different car , such as shift light staying on in 5th and a low idle stumble when sitting in neutral , it also ran fine .I swapped back to the original ecm after a ten min drive . And the rest of the way home the car ran fine . I am wondering if , when setting base timing , do you need to run with the ecm advance disconnected to give the computer a chance to relearn this setting for a bit ? I have never seen anything to say this is the case in anything I have read. But I am really doubting the miniscule amount I moved that distributer is the fix all to a weeks worth of testing and timing .

ploegi

Is the module failing??

aseychell

Have similar issue to you and have been struggling with it for the past month. My Thread

Only difference is that I hit the issue at approx. 3000 RPM. While in Neutral/Park the rev counter doesnt go past 3000 and the display (digital dash GTA) drops to 0 and then when I release the gas pedal it goes back up again. While driving the car stutters in the regions of 3000 RPM and then it clears and continues climbing up the revs.
Everything works fine with the EST cable unplugged. Base timing is at 8BTDC.
So far I checked all cables and connectors, checked for HT lead arching, changed Rotor, changed ignition control module (the one in the distributor).
No SES. Had a custom chip with vette bin and 6E definition. Removed the custom chip and thus restored to stock (AKXZ). Still the same.
From tunerpro I can see TPS is set correctly (0.54V at idle) and the MAF is not dead. BLM is between 112 and 145.
Tried unplugging the MAF sensor without any effect.

Currently at a big loss. Will check fuel pressure while on load today or tomorrow.
Would appreciate anyone who can help out here. The issue is that as the car is working fine with the EST bypass disconnected, I am assuming that Fuel, Plugs, Leads are not the issue. Will re-check base timing. And will also check if the balancer has slipped perhaps?

aseychell

Wanted to add a question. In a quest to ensure that all sensors are working fine, while doing datalogging with tunerpro using 1227165_160 definition I only have a very few items to acquire. Is there perhaps a more item rich adx file for the $32B ECM?

dahammer

I dont think the pickup in mine is the issue , or was. The distributer was brand new in there . I am so far still running decent with no misses at speed. My next step now is waiting on a prom burner and a adsl cable for data logging so I can try and get an enrichment setup for cold start and and figure out the rich fuel I see on and off.

Aseychell I am still a programming dummy right now till it all gets here and I dive into it in a week or 2 . I did a lot of the same troubleshooting as you have . MAF check . TPS setting . IAC you name it . My biggest thing was I couldn't wrap my head around the engine ran like a top in my GTA , but all these gremlins in the 87 iroc. I think most of my problems are still ecm and chip related , hence the cable and chip burner. I am going to try and find an 89 bin for the enrichment since my engine is a 91 and see what the values do fo me on a new chip.
I did drive for a bit , probably 30 min at least before I rehooked the est back up . And after that it ran pretty good and continues to do so . I am still wondering if there is a learn curve for the ecm to relearn base timing before you should hook up the bypass again . It is all I really did that was different and it seems to run a lot better now.