Matt3855

Hello All

I’m having some very random issues around the ECM, Drivability, Starting, and randomly activated outputs. After scouring the pages for the last few weeks I am at wits end and looking for opinions. This will be lengthy and A LOT of detail but should cover the basis of issues…

92 TPI 5.0 / 5 Speed low milage car that gets a couple hundred miles a year at most. Every couple of months I’ll pull it out and let it get to operating temperature before putting it back in the garage and on a battery tender. The issue started two weeks ago when I pulled it out of the garage and it was idling rough with the SES light on and I noticed the cooling fan turned on with the key. I drove it to the shop, running terrible, with the intentions of hooking the scanner up to it. As I drove it there were periods of 1-2 seconds where it would clear up and sound fine before going back to rough idle and no power. This is where the chase began.

Day 1

Pull the car in the shop, hook up the scanner, and the Verus scanner won’t recognize the ECM. I double check the connections and ensure they’re correct. So, I decide to flash the codes at the ALDL and get nothing. It wont flash 12 and just doesn’t seem to recognize the jumper being installed. I take a break from the electrical side of things and check spark which is good, check fuel pressure which is good, and pull a spark plug which is fuel fouled. I get it running enough to drive it on a lift and replace all the plugs. Start it, same issues. This is when I start digging through the third gen archives.

Day 2-4

Replace ECM with Cardone Reman and original AXYC MEMCAL. Turn the Key on and things get weird. The SES light comes on for about 3 seconds, the driver side cooling fan turns on, the EVAP canaster clicks on, and the diverter valve clicks on along with some other random components. Then, after the 3 seconds, the fan turns off, the SES light turns off, and the components that previously turned on turn off for 1 second before all coming back on along with the SES light. So the car is just sitting there, key on engine off, turning the fan/SES light, and random components on and off in the same pattern. It still won’t connect to the scanner or flash codes. During this time I check ground to ECM, 5V signals, etc. I sit down on the lift, go back the forums and wiring diagrams, and leave the key on for 10+ minutes. Then, the pattern changed for a brief period before all the clicking and cycling stopped. I walk over, push the clutch in, and car starts while running perfect. No issues, scanner connects, no codes, real time data looks good, and acts like its fixed. As I go back to the passenger side and “knock” on the ECM it dies. I can repeat the malfunction by hitting the ECM. Great, “Bad Reman ECM”. In the meantime, I have ordered a MEMCAL from Hawks that I put in the second ECM in an effort to rule out MEMCAL and had the same results.

Days 5-8 and Current state

Replace Reman ECM (This is now the third ECM) and new MEMCAL, car fires up perfect, no issues, no codes, awesome. Leave it running for 15 minutes, shut it off, hook up the A/C Gauge Set because it is low on refrigerant, start the car and start adding refrigerant. After about 5 minutes of perfect runtime the car dies. Wont restart. Check spark and its good, check fuel psi and its good, security light isn’t on, no codes on the scanner, real time data looks good from a starting condition standpoint. Place a noid light on one injector plug in both banks and find that neither banks are flashing the light. The light comes on steady which tells me the ECM isn’t pulsing the ground. I then replaced the ICU and inspect the distributor cap for issues. Put original MEMCAL back in the third ECU and have the same results. Replace third ECU with original ECU and although the fans come on along with SES the injectors are now pulsing during cranking. Ohm’d out the injectors and found all were 15.9-16.1 ohms except #6 which is 1 ohm.

Summary

I would appreciate recommendations on where to order replacement injectors and any other input or opinions around the ECM issues/randomness of issues.

ECM 1 – SES light on, Fan runs constantly, idles rough, no power, wont connect or flash codes

ECM 2 – SES light and other components turn on and off sometimes. Hitting the ECM will change its behavior.

ECM 3 – Ran great for 15-20 minutes and now is in a no start condition. No codes, flashes 12, wont start, wont pulse the injectors.
Thanks for taking the time to read the novel and share any feedback you may have.

Tuned Performance

iTrader: (92)

Unplug all injectors then check for pulse with a noid light. Sounds like the shorted injector shut down the injector driver. Southbay has a complete set of injectors
for a good price.

https://www.southbayfuelinjectors.co...injectors.html

southbay08

Thanks tuned performance.....just a reminder that all tgo members still receive 10% off on all tpi injectors and parts.
Use promo code tg11 at checkout. If you have any issues with the code please let us know

TTOP350

iTrader: (8)

Im not sure about holley inj offsets or tuning but if you're looking to keep a somewhat stock look, they fit the bill.

aliceempire

iTrader: (14)

Holley provides the offsets. As far as tuning, that's still in the air as I'm working on it now.

Matt3855

Thanks all for the feedback! Replaced injectors and we’re up and running! Much appreciation to all that took the time to respond!

Chevyriderk15

So replacing your injectors corrected the ECM issues? Even tho it seemed the issue was at the ECM?

Tuned Performance

iTrader: (92)

The ecm did what it’s designed to do, shorted Injector leads shut down injector driver.

Matt3855

Just as you said it would. I do find it odd how the shorted injector caused such different issues across the three different ecm’s. Fans on/off, some times it ran rough and cleared up for a few seconds, then went to not starting at all.

Chevyriderk15

I'm currently experiencing the same issues, Brian is sending me an ECM but I'm going to check the injectors as well