'92 VX engine problem
 

OK, my trusty VX has been having some problems the last month or so.....idles and runs fine while cold, but once it warms up, starts to miss.

We took a quick look at it, the plugs were all fouled, cleaned them and it ran OK for a few minutes and went back to missing. Have to really "nurse" it on the highway, can't get up to 60mph. FE has dropped to maybe 27mpg.

It has a transplanted D15B engine, which up to now (15,000 miles+) has been trouble-free.

Any ideas VX guys?

Well, first clue is that it runs OK when it is cold, but messes up when it warms up. Look at some component which comes into play when the computer goes into closed loop mode. Check your computer codes, and see what they tell you.

O2 sensor?

Certainly could be the O2 sensor....has the old VX sensor on it. The sensor that came with it was damaged somewhere between Canada and here.

Well be sure to get that sensor tested before you replace it. I don't know if autozone can do it but it definitely can be tested. I've tested O2 sensors with a butane torch and multimeter but I've yet to try it on a wideband O2 sensor.https://www.youtube.com/watch?v=ItnKP-XKaZo

That says 1 wire o2 sensor, I was able to test a 4 wire (heated) o2 sensor as well doing the exact same procedure.

I've neve done a test like this. Does that mean that it's OK? How would one do a 5-wire wide band?
If I don't throw a code would I conclude that mine is OK?

Dave

4bfox,

Ever find your problem? My 94 has the same symptoms except my MPG was 37.6 on my last tank, even with the hesitation problem!

Dave

Still working on it. I'm getting a 4-wire O2 sensor, which should be the right one for this engine, I'll have to modify the wiring a little to get it to work, hopefully the CEL will go away then, along with my other more recent problems.

I don't know if this would change as the engine heats up, but mine was running poorly until I changed the engine grounds. The old grounds were hardly functioning. It's also a cheap project and a lot of the sensors need good grounds.

Also check the coolant temp sensor- a bad temp sensor might make the ECU think the engine is still cold even after it warms up and be making the mixture too rich for a warm engine.