jrhaus76

1989 IROC, 350

short headers
no cat
flowmaster exhaust
no SMPG pump (removed)
3.73 gears custom chip burned off dyno


OK, here is my issue. Car has been getting restored the past 2 years. I thought I was all done but apparently not. It was running fine, put maybe 400 miles on it in the past few months. Hasn't been giving me an ounce of trouble, until yesterday.

Drove it all day yesterday, probably 60 or 70 miles. Several stops, everything was great. Got home, decided to wash it. After I finished I went to go for a drive and about 5 minutes into my drive it started acting up. running very rough and missing bad. I limped it home. Couldn't give it much throttle or it just missed and shook violently. Got home, poked around a few minutes and then tried to restart it. It wouldn't start??!? At that point it was time to call it a day. I figured maybe something got wet and I'd let it dry.

This morning I go out, it starts right up. NICE, maybe something did just get wet. Made it about 5 minutes and same issue. Missing, running rough. Limped it back home and put it in the garage. Did some errands and yard work and decided to give it a quick tune up. I replaced the following items, hoping one of them was just bad and heating up and causing the issue.

-Plug wires (not the plugs)
-distributor cap and rotor
-ignition module
-coil
-o2 sensor

Got all done and it fired right up. Took it for a ride, 5 minutes same exact issue as yesterday and this morning.


So... does anyone have any ideas on where I could go next? I am thinking something is getting hot and then going haywire.

I am desperately looking to get this thing fixed. I am supposed to be going on the Power Tour in a couple weeks but I need to get this figured out first.

I know these cars are notorious for injector problems. Is this a possibility? I can't really think of much else other than a bad distributor or something... HELP!!!

truckerz

iTrader: (2)

Check the the injectors with a multimeter. If you have a bad one, or ones, they will read in the single digits. I had two bad stockers, they were reading 5.3, 4.2, vs 14ish. I bought some bosch3 injectors from south bay and my stumbling dying problem went away. No promises, but it could not hurt to pick up a cheap 15 dollar multimeter and test them. If they are bad, you'll know. And replacing them is easy.

lonestar7

iTrader: (1)

Sounds like a closed loop issue. Are you getting a service engine light? Did you spray the engine bay? I'd double check the dizzy wires inside the cap for water. Could take a while to dry out by itself if you got some in there. I'd check the CTS also.

FBOMB90

With headers on it, you can check the injector operation really quickly. Use an infrared thermometer and point it at the individual header tubes, while running. The lower temps will show you the cylinders that aren't burning efficiently. It also sounds like you could have a partially clogged fuel filter or fuel pump sock. Just a couple thoughts for you to check out. Hope it works out.

Rednecht

iTrader: (1)

Here's hoping you got your problems fixed on your car. But I wanted to drop a note on my issue as well. I own a 1988 Iroc 5.7 TPI and it basically has been doing the same thing you described. It has gone on for about 9 months now. It started where the check engine light just came on randomly. and when it did, it affected the automatic tranny shifting patterns, the temp control and caused the engine to miss. Then one day it came on and stayed on. Took it to the dealer and they hooked up to the ecm and said it was the MAF and burn off sensor. So they were replaced. About 2 miles from the dealer the light came back on. I waited a several months to go back money was tight. But fast forward to yesterday. I took it back to the dealer and they said it was the ecm was shot and there were burned wires connected to the ecm that needed resoldered. And of course the MAF and burn off sensor. but now it runs like it should. the bad thing is that no codes ever came up telling us that the ecm was shot. they found out through trial and error at the dealer. This car is a great car. And now that the problems are behind me I hope to enjoy it. It only has 17 thousand miles on it and is show room new. And one of not that many gray color cars for that year. So for those having these issues, try changing the ecm and check for burned wires connecting to it. For some reason when the ecm goes crazy it affects a whole lot of other things making one think its those instead of the ecm. Just my two cents....When I finally figure how to post pics I will post some of my baby...

tyeo098

TPI or TBI?

Violent shaking and missing means something isn't firing correctly.
Check all your plugs for spark.

jrhaus76

It was a bad ecu
Worn drive gear on distributor
2 shot fuel injectors

Runs like a top now.