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And to answer your question I don’t know if it’s a renix or GM ECU/ECM. I would have to pull it out and look at it but the jeep is still at the mechanic shop. These guys have been the best in our area for years and have put a lot of effort and research into figuring this thing out. But just like...

I used my timing light when trying to start it so I could see what the spark was doing. The spark would quit and then the engine would die so I decided it was related to the ignition system and not fuel related. My mechanic acquired some data ( I don’t know where from and I’m only getting this...

I’ve finally narrowed this issue down to what we (myself and a very knowledgeable mechanic who has had my jeep at his shop for over a month now) believe is the ECM. Can anyone tell me where to find one? All my searches turn up plenty for the 6 cylinder but nothing for the 2.5 liter 4 cylinder.

MAP I’m assuming is manifold air pressure? I’ve checked all vacuum lines but I’ll go over everything again just to be sure. I replaced both the IAT and TPS early on in the troubleshooting but it didn’t change anything.

I greatly appreciate your help Ecomike. I’ve posted a new thread “extremely cold natured Yj”.

I have an 89 wrangler YJ TBI with 2.5 liter 4 cylinder that is hard to start when it’s cold. It will fire rather quickly but immediately dies. Sometimes it takes 15 or 20 tries to keep it running. Once it warms up, it runs well. I noticed the electric fuel pump stays running almost constantly...

I measured the voltage on the CPS AC and it was showing .4 volts. So I did as you mentioned and enlarged the holes in the mount and moved it closer to the flywheel. It started putting out .6 volts which now allows it to fire rather quickly instead of having to crank it for 10 minutes on a cold...

I was trying to read it DC so I will go back and try it AC. I also have a better fluke meter that I will use. This jeep is an 89 so the CPS should put out voltage. I originally was thinking this cold starting issue was related to the O2 sensor but I’ve since eliminated that as a cause, but we...

The jeep has a new battery and I even hooked jumper cables to my truck but it didn’t change anything. I put my timing light on the number one plug wire so I could observe the spark. It took a few revolutions before the light would blink and then the engine would fire. I measured the voltage...

I actually just purchased this jeep and the previous owner mentioned the hard starting in cold weather. I haven’t changed the O2 sensor so I have no idea what is actually in it. I’ll have to dig out my old analog meter and see what the voltage does.

The pin on the ECU does not have voltage. I did a search online but all I can find for my year model (89) is for the 6 cylinder and mine is a 4 banger. There are plenty for 91-95 but they look different. Where would I get it repaired?

So I finally had a chance to do some more troubleshooting. I located the 5v wire coming out of the ECM and verified that I’m not getting the 5v out of the ECM. Sometimes it will read .2v but never anything more than that. Is this an ECM problem then and if so where do I get one?

I’m having trouble with my 89 yj starting in cold weather. It will fire but won’t stay running until I’ve cranked it 6 or 8 times and then it’s still very cold natured. I checked the IAT sensor and coolant sensor and they are both good. I replaced the throttle position sensor. I followed the O2...