I have a 1989 with a Hypertech Chip, 160-degree thermostat & fan switch & High Voltage Coil. I have also bypassed the throttle body heater. This was done several years ago. The ECM in the car is a remanufactured replacement. Done before I purchased the car.
My car started running rough about 10 days ago shortly after a fill-up. Then it got progressively worse and stalling. It starts and idles but the moment I attempt to pull out it stalls. The engine also stalls at about 2500 rpm without a load. The car, when running does run rich. I can smell it and it never did before. My scan tool confirms this.
Unfortunately it will not generate any trouble codes. I have checked the fuel for dirt and water and have neither. Fuel volume and pressure also are ok. I have checked almost every circuit that might cause me a problem as if I had a code to work from and have come up blank.
I believe the problem is with the ECM but cannot find a test in my service manual to confirm this and I hate to buy a ECM if I don’t need one.
Any ideas?

Thanks,
Bill

 

My car started running rough about 10 days ago shortly after a fill-up.
Looks like you answered your own question...I'd start there

 

Water makes the O2 sense a lean condition so it adds fuel which will make it rich. If lean, follow the diagnostic aids for a 44; rich a 45. Your scan will tell you what it is. If you want to check for moisture, disconnect the inlet and attach a hose. Put the other end in a Mason Jar. Turn on the key to fill the jar. Let it sit for an hour to see if anything settles out.

 

I am sure those who replied did read I checked the fuel for dirt and moisture. However, just to make sure I did not miss something I completely drained my fuel tank and checked for dirt and moisture again and again. There was nothing. I refilled with fresh fuel and purged the line before starting.
As it has been doing it started fine, idled about 5 minutes and died, as though it ran out fuel or there was no spark.
Any other thoughts?

Thanks
Bill

 

Could be the ECM or possible Injectors...WW

 

with the fuel injectors since '89 is equipped with Multechs. The Multecs were not designed to run with ethenol blended gasoline. Weak/low resitance injector coils will shutdown the fuel injector driver in the ECM....so no injector pulse....and no ECM trouble codes will be generated. You'll want to check the resitances for your injector coils but better yet just order some new ones from FIC Injectors and be done with it.

 

Help me here, you say it will not generate trouble codes, does this mean that with pins A and B of the ALDL connected the SES light does not flash?

 

On an '89 OBD1 you only get the standard flash....I think off hand its "12"....but no "trouble codes" are set with a injector driver failure....just a very low or no pulse.

 

On my 89 I had 3 multec injectors reading under 8 ohms and never got a code. Engle1147 is right, the stock Multec injectors are not ethenol complient and its not if, but when, they will go bad. A lot of people with Multecs change them out before problems start..Jon at FIC will fix you up with a set of Bosch 3 injectors at a good price and solve this known problem...WW

 

A ckeck of injector coil resitance will confirm if that is your trouble

 

My '89 recently experienced very similar trouble. After getting it checked out, it was the injectors.

 

I have an 89 also you short the last 2 pins on the right side on top row. It will blink once then twice for code 12. It will do this 3 times. After it does code 12 3 times it will give you your code ex blink blink blink pause blink blink... for code 32..

The stock injectors suck I had a similair issue and had to replace my injectors.

 

Ethanol eats Multecs I would think a lot of guys are changing them out before hey have trouble because they will have trouble. Injector failure I don't believe throws a code on an L98

 

When connecting the A/B terminals the SES does flash 12.

 

Thanks to everyone, I the injector faliure makes sense. I'll check them over the weekend.

 

One injector was way below the 10ohm minimum. New injectors are on the way.

 

Finished the injector installation. My car runs like new again, maybe better.
Thanks to everyone for their help

 

Glad to hear it!

 

I also own a 1989 Corvette with 30,000 miles and recently replaced the 3rd ECM at a GM delaership at about $400 a pop. I had an idea it was the new Ethanol gas and now you all have confirmed it. It still runs rough even after the new ECM.The most recent issue started after my last fill up with Premium grade fuel. I repalced the ECM last week at GM delaer. Now I am convinced it is the injectors that need replacement to deal with the new Etnaol gas. What make and model injectors should I order and where do I get them. Thanks cl61slg

 

Would it help to add a bottle of "Stabil" at each fill up?