Compression test, then you know its not a major part. Have you done the grounds refreshing all over ? 67GMC touched on the subject a bit. If compression is good then your computer is only adjusting to what signals it is getting from sensors, voltage and grounds can effect those inputs.

 

A little bit of new info. It's been hard starting cold. It just gave me a hell of a time. Dying at idle. Had to give it throttle to keep it going. Violent shaking. It did not like running. I let it die then turned off ignition.

This thing really doesn't like a cold start.

What causes really rough cold starts?

 

How does this O2 sensor look? Normal? This tell anything?

 

I just measured 4 ohms of resistance on the heater wires. Heated the tip up with a mini torch and had a hard time reaching 1volt. Best reading I saw was around 1/10 volt with the tip glowing. Not sure if this is a reliable test.

 

Did you look into scanning it? I don't know about 1994/1995 years as that was about the time things were changing to OBDII I believe. Most of the equipment can read the codes being set (or you use that paper-clip method to make the light flash out the codes). Does your check engine light come on while starting to see if the bulb works?

 

Usually white deposits on an O2S indicates coolant contamination. But it might be lean mixture.


Regardless, change that O2S.

 

Have you noticed the coolant level in your overflow reservoir going down? Having to add a little bit of coolant?


You may have coolant leaking in to a cylinder from a bad head gasket.

 

Bulb works. I've seen it on. I need to clear the codes as I have had multiple things unplugged while running during testing. The info stored is useless. Mines obd1. I don't think the scan tool will tell me any more than the key trick. I could be wrong though.

 

I am changing the sensor tomorrow when it arrives. No, I believe the cooling system is solid now. Previously, yes. Had a pile of leaks including head gasket. This has a new motor. Only about 5 miles on the new motor. 8-10 hours of idling time.

This is not a daily driver at the moment. Just a project. That I really want finished. Ha.

I pressure tested a year ago after the new motor was installed, flushed, and filled. Coolant still nice and green.

 

Ugh. I can't win for losing. I replaced the O2 sensor and now I'm getting a no start condition. The first attempt to start seemed to almost start, but, was going to be very rough. Battery was weak so I threw a 10amp charger on it and waited 15. Tried it. One revolution it tried to pick up then nothing. Have tried 10 times. 2-3 times it tried to pick up on a revolution but nothing. Strong crank.

I pulled ignition coil wire and verified strong spark. Spark is coming through distributer. I checked two terminals and both are sparking. Had a little fuel in the rail. I pushed in shrader valve and it didn't get a quick stream like I thought. It trickled out. Next time I checked it didnt do much at all.

I'm not hearing the fuel pump kick on. It's brand new. It's airtex...I know. I verified 6 ish volts to the fuel pump. Thoughts? I returned the fuel pump pressure tester last weekend when I knew fuel system was good. Ugh. Should I go get it?

Fml

 

Replced fuel pump with Bosch. She purs again. However, I think I see a problem. Just re-did my compression test. Results below. Got her almost up to operating temp to start the test. Guage was broke so I had to rent another one. I already pulled the plugs and wires before I noticed this. By the time I got back, motor was warm but no where near operating temp. Did test anyway. All plugs removed and foot on accelerator to the floor (for WOT). All number at 5-6 revolutions based on listening to starter.

1. 123
2. 129
3. 120
4. 130
5. 135
6. 113

All of these look a little low to me. At the bottom end of acceptable. The problem one is number 6. 22 psi below the highest reading and 8psi below the bottom threshold. I know from previous testing, putting oil in there does bring compression test up to about 125 or 130. I know the rings are failing.

Is this causing my rough idle? A better way to describe it is a shake at idle. It sounds fine, but, there is definitely a shake and hesitation.

 

"New" junk yard motor?
If it has never run properly I would strongly suspect a wiped cam lobe.

 

That's correct. New to me JY motor. It came with a warranty, but, a 30 day one. About 120k miles or so.

Would that cause low compression?

 

Try new transmission fluid and replace governor pressure sensor/control valve for the transmission ...work for me only after replacing everything else

 

My baby has a bad wire to the injector. Caused what you are saying. Sometimes worked great. Others... not so much.