random misfiring

[flyingewok]

I have a 96 gst. For the most part the car runs fine but out of nowhere while cruising it will start misfiring badly and it shows a lean reading on the afc o2 voltage. It will stay this way until i throw it in neutral and let it drop to idle (all the way til the iac catches it) and then it will run normal for a short time. If i simply let off the gas and keep it in gear it will NOT fix the problem. It seems to have gotten worse since the weather got a bit warmer.

I did have an intake leak recently in the throttle body screw, and also somewhere in the boost gauge lines and/or the manual boost controller...i removed all of that and the car ran alot better but this problem remains.

When this does happen and i let it drop to idle it seems to be idling a bit high..1200 or so at the highest but thats while still moving at a decent speed so i think thats normal. Any help is appreciated.

Also...this will happen continuously if it starts. Bad misfiring, i have to drop to idle, i get about 10-20 seconds of driving til it starts again. Some days its not constant but it's guaranteed every time i make a trip usually about 10 mins of driving, but sometimes sooner. Once it starts it goes on for awhile, sometimes it randomly goes away. Can't make any sense of it.

 

[flyingewok]

Someone suggested it might be the throttle position sensor but i don't want to throw parts at it unless someone can verify these are symptoms of the TPS going bad.

 

[Mitsumungst-gvr4-tsi]

So get a volt meter and test the tps sensor and see if its still in range/spec. When's the last time you did a tune up or checked the plugs and wires? How many miles on the car? Could be a clogged injector, fuel filter. How high did you do a blt to?

 

[spyderdrifter]

Like the last guy said, test your TPS before deciding to buy a new one. Here's a link to follow on how to test it. I've done it myself and it works: TPS Adjustment This test uses an anolog meter, but I used a digital and it worked just fine.

In addition, random misfire may be related to an idle surge problem if you're leaking air. Here's another link to follow to rule that out for yourself: http://vfaq.com/mods/wayback/BradBauer/engine/surge.html