My 88GT has been running perfect for so long now I haven't had to ask for any help here in quite a while but I need some direction. I had a code 35 about 2 weeks ago. I did notice the idle jumping up and down every time I had the defrost on. I checked for vacuum leaks with a water bottle spray but found no fluctuation in the idle. So I swapped out the idle air control valve. That seem to fix it but the jumping idle remained when I used the defrost. No codes though till finally this morning I got a 44 (oxygen sensor). I doubt it could be the O2 sensor because I just had it changed about 10,000 miles ago. Both codes also say check for lean injectors but I just installed a freshly cleaned set by Cruzin Performance around 16,000 miles ago. Both codes also say to check for vacuum leaks but I checked and re-checked unless I'm missing something? It's hard to check the egr tube with the metal sleeve around it. I wonder if the leak could be around the exhaust manifolds? 44 also says it could be the MAP sensor which I've never replaced. If it's original I wonder if it's past it's life span? Thanks for any input to narrow down my problem.
Marc

With the idle issue changeing with the defrosters on I'd think you might have an engine to frame ground issue.

https://www.fiero.nl/forum/Forum2/HTML/043240.html

Here is a way you can find out if your EGR tube is leaking. It's cut from a pop can. No need to pull the bolts, just loosen them. 10mm heads on them.

quote Originally posted by phonedawgz: With the idle issue changeing with the defrosters on I'd think you might have an engine to frame ground issue. https://www.fiero.nl/forum/Forum2/HTML/043240.html Here is a way you can find out if your EGR tube is leaking. It's cut from a pop can. No need to pull the bolts, just loosen them. 10mm heads on them.

I don't think grounding is an issue. I'm on page 4 of that thread started by $Rich$ showing a picture on how I added mine. Could you explain what you did with a can and the egr tube to trace a leak please. I cannot make it out in the picture you posted.
Thanks, Marc

Cut a strip of aluminum 1 1/2" wide and slip it between the bottom of the upper plenum and the EGR tube. Then re-tighten the EGR-manifold bolts. That blocks off vacuum from the tube. If your idle reduces than there is a leak in the EGR tube or EGR. (Most likely tube) If the idle doesn't change look elsewhere.

[This message has been edited by phonedawgz (edited 11-06-2010).]

Got it. I'll give it a shot. Thanks!
Marc

Anyone else have any idea what could be causing these codes?
Marc

Have you checked your fuel pressure?

quote Originally posted by phonedawgz: Have you checked your fuel pressure?

No not yet. My pump is likely original so I guess it could be the culprit. Would low fuel pressure send off codes to the ecm though?
Marc

Like an O2 reading lean? Sure it could.

Remember the codes don't mean you have a bad sensor. It says the sensor is reading outside of what is a tolerable norm. It does NOT mean the sensor is bad. It could be bad. It could also be that something is causing the reading to be outside of the norm.

btw there is no sensor to measure the fuel pressure to be sent to the ECM.

Also if your fuel pressure does test low, that doesn't mean its the fuel pump.

[This message has been edited by phonedawgz (edited 11-08-2010).]

I did some searching for "erratic idle" in the tech archives and noticed the alternator was the problem for some too.
This will be allot of fun tracking down. The joys of owning a 20+ year old car

[This message has been edited by Gokart (edited 11-08-2010).]

Unless your voltage is wacking out up and down, I don't see it being an alternator.