speedon11

I have an 89 gt vert with moderate mods....engine sometimes idle suges while clutched and sometimes not. When it surges, it jumps between 300 rpm and 1300 rpm and eventually dies. KOEO= 33(egr not opening), 91(ego always lean)......KOER= 31(egr not opening), 81(IAC cuircut failure), 33(egr not opening),41(ego always lean), 91(ego always lean)....

The check engine light is NEVER on and the car runs abnormally rich(the exhaust smell is horrible) at all times....the smog pump was removed before I bought it and cats were removed before I got it.....any ideas would help a ton....thanks guys!!!

jacostang

Sounds like a vacuum leak or breakdown of your lines...

DynamicmustangGT

I agree with the vacuum leak theory.

speedon11

Ok....looked fac leaks...found none.....replaced all vac lines and still....same issue...pulling my hair out here.....if its any help, when I set the cruise....I surges up and down 7 miles per hour in a constant patern....disconnected and blocked it from the tree to rule it out....same issue, just now no cruis control

jacostang

Throwing that many codes, I would swear your vacuum tree is mal functioning or its not pulling any vacuum at all, make sure all your intake points on the valve cover and plenum are not sucking any air..

speedon11

So I replaced the tree, and pulled the upper plenum...gaskets new...check...vacuum ports sealed or properly used....check. checked vacuum on the tree and it idles at 13 in hg......give it gas...dropes to zero.....on the decel shoots to 20ish. Timing maybe?????

speedon11

Shouldn't idle and normal cruise in hg be around 20 in hg???

mizritv2

Did you recently add a CAI?

speedon11

Not sure what a cai is

DynamicmustangGT

cold air intake- if you changed the air tube and filter or the mass air sensor it could act like this. Could be the mass air sensor slowly going bad as well. Its an issue with the air somewhere though. I am still leaning toward a vaccum leak, did you check the hoses that run through and under the intake?

jacostang

Man, thats what it sounds like to me.. But if the Mass air sensor is bad then disconnect it and see if it makes a difference... But it sounds like its searching for a sensor is the TPS working? Throttle Position Sensor right on top of the throttle body..

speedon11

Has a cold air...but its been there for few years.....yea...all the hoses are brand new now....anyway to test a maf??

speedon11

Tps is working...don't have an analog volt meter to properly test it.....but that's 1 thing I was thinking....the loop to me is= why would it be intermittent??

DynamicmustangGT

Have you cleaned the maf lately?

speedon11

Let's go try and see what happens

Higgy120380

I have 90 GT vert and mine was doing the exact same thing and it was a pain in the butt to figure out since there are like ten different things that could affect it. I'm not sure what you have already done so I will just tell you everything I was told that it could be and what I fixed. First check your mass air sensor. Now I checked mine and it seemed to be working so that is why I ended up going through what I listed below. But what ended up happening to mine was my mass air sensor was faulty because when i fixed everything below it still idled bad, the moment I put my buddies mass air sensor in it idled amazing I couldn't believe it. However the things I listed below are the majority Idleing problems and in my opinion should def fix your prob.

First I started with the IAC valve, I took it off and cleaned it and put back on it did help slightly however I was told from a number of people this fixed there prob completely. Plus it helps that fuel smell or rich smell.
- Then I checked for vacuum leaks which there where none.
- next I chained the PCV value. This is sometimes all crudded up because it's slightly difficult to locate unless you know what your looking for so a lot people forget to change it.
- I then checked all my plugs and wires. Since I was due for tune up I went ahead and replaced it all.
Now when I did all this it significantly helped the situation but didn't fix it. I have a bunch of friends who only had to just one of these I have listed and it fixed theres. So basically it's process of elimination unfortunately.
-check all your connections like your salt and pepper shakers which are right above intake. Again I'm just listing as if you may not know so I apologize if l am explaining things you already know.
- another possible prob is your TPS sensor I think the voltage should be set between .95 - .98 you may want to check that figure but I think it's right.
- And lastly i changed the EAC valve and sensor. It runs amazing now. So long story short cause I know I put slot of info in here which may be useless to you if you have already done these, if not I really hopes this helps, but check your mass air sensor first and iac second. I think your year is like mine and if it's different and if I can help in any way please let me know. Oh I forgot to mention make sure you don't have an exhaust leak either like at your headers. Good luck

jonb

Did you ever get it fixed, I'm having the same issues. i replaced the air flow, throtle control sensors.. new plugs.. was told it was distributor, we adjsuted a little higher and kind of runs better.. so now going to try a adistributor.. fortunately my dad runs advance so i get a discount and can take back if thats not it.. did you ever fix yours

speedon11

YES...finally fixed my issue this weekend.....believe it or not it is quick easy and free......a buddy of mine told me about "clocking" m& MAF. I was hesitant at first but tried and it worked. I had the cold air with a 90 degree bend, then MAF, then into my throttle body.....what happened is the incoming air from the 90 degree bend was disturbed and missing the MAF some...while the car is running, losen the clamps on both sides of the MAF....when its running messed up turn the MAF housing towards the engine or fender....my fix was about 55 degrees towards the fender and 275 miles later, no more surging......sounds dumb and irrelevent, but it did work.....decided to omit my 90 degree bend and fix the air filter directly to the MAF housing and no matter where I turn the MAF now, it is perfect....reinstalled the 90 bend and the idle issue was back....so for mine, that was the fix, took a total of 2 mins

jacostang

Glad you found it, it def. sounded like an setting issue.

jay90

I too have idle issues, I'm going to delete my 90 bend and see if that works for me aswell!!