Hello YOTATECH this is my first post. After doing days of research on the forums I still cannot find a clear direction on what the potential problems I am having can be.

Just a quick history on my 1992 3vze.I bought it for 249k miles, new heads, ecu rebuild, all new vacuum hoses, new MAF, and little things here and there that should affect my current issue.

My issue is when initial cold startup, it drives great. There is lots of smooth power, good idle and everything is kosher. The problem is when it starts to warm up about 1/4 on the temp gauge, the car starts to idle rough like those muscle car V8's with a sick cam then stumbles during acceleration and a loss of power. After a good warmup and the engine is in good operating temp the idle slightly get better but the power is not as good.

It has a CHECK ENGINE Code 25. Now before I go changing all kinds of parts like 02 sensor, coolant temp sensor, MAF, TPS and so on an so fourth, do you guys have any experience in with this issue?

What steps in chronicle order do you suggest I start?

Thanks

RNSK

 

1. Look at the manual http://www.ncttora.com/fsm/1990-1995...e/diagnosi.pdf
2. Use a voltmeter on OX1 to see if the O2 sensor output is low all the time, or just too often, or only under certain circumstances.
3. Visually look for vacuum leaks.
4. Use an unlit propane torch to look for vacuum leaks.
5. Look at the manual.

 

I'm going to try this and see what happens.

Anyone else ?

 

A wonky O2 signal can certainly cause the engine to run strange. Any smoke out the exhaust when running rough? How does your oil and coolant look? Using coolant? How many miles on the new heads?

 

There is about 1000 miles on the new heads, coolant levels are perfect and oil is clean and fresh.

 

The diagnostic scope103 provided in post 2 is good as the FSM (Factory Service Manual) lists the things to test for code 25.