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car runs fine until it warms up.. then.. GARBAGE!

6K views 13 replies 9 participants last post by  bgjohnson 
#1 ·
Car runs fine for the first 5 to 10 minutes then like clockwork the CEL comes on and the car stutters and wants to die sometimes at a stoplight... acceleration is fine but at steady cruising speeds its studders sometimes..

only when warmed up though..

here are the codes I pulled:

81 o air divertor solenoid fault/intake air control circuit fault
82 o air divertor solenoid circuit fault
34 c insufficient EGR flow or EVP voltage high
41 c HEGO (HO2S) sensor signal out of range/always lean
63 c throttle position circuit fault/below minimum voltage
66 c VAF/MAF sensor fault - below minimum voltage
91 c HEGO (HO2S) sensor signal out of range/always lean

anyone think they can tell me where to start?

thanks corral!
 
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#2 ·
Well, the codes you pulled pretty much tell ya where to start....

Do the Free, or close to free stuff first:

Check all wires and connections to the MAF, TPS, O2's, EGR, and air diverters for loose , corroded, broken, or worn wires and connections.

If that checks out, check and set the TPS voltage around .99 volt, and clean the wire in the MAF sensor with CRC or similar electric cleaner. You can also clean out the EGR with carb cleaner and ensure the valve moves freely.

Clear the codes and take her for a run, n see where your at.

If you still have the same symptoms and codes, it's prolly time to start replacing parts. The MAF, TPS, and the 02's are the most critical.

The EGR and air diverters can wait if they have too. just be aware that they will have to function correctly to pass smog.
 
#3 ·
Car runs fine for the first 5 to 10 minutes then like clockwork the CEL comes on and the car stutters and wants to die sometimes at a stoplight... acceleration is fine but at steady cruising speeds its studders sometimes..

only when warmed up though..

here are the codes I pulled:

81 o air divertor solenoid fault/intake air control circuit fault
82 o air divertor solenoid circuit fault
34 c insufficient EGR flow or EVP voltage high
41 c HEGO (HO2S) sensor signal out of range/always lean
63 c throttle position circuit fault/below minimum voltage

66 c VAF/MAF sensor fault - below minimum voltage
91 c HEGO (HO2S) sensor signal out of range/always lean

anyone think they can tell me where to start?

thanks corral!
erik, my car had almost the same problem and I fixed it last week :joy:. Let me tell you a little more about my car's problem: it wasn't limited to only warm engine problems. It did it even when it was cold. The codes that I pulled were 34, 41, 91 (which I've had for the last yr and a half) and finally code 63.

When I tested the TPS, it was giving funky voltages.....like 0. I probed the power wire from the EEC and it showed 5V so I knew it was getting good voltage but it's output voltage back to the EEC was bad.

I bought a new, USA made TPS from Advance Auto parts on New Year's Day and installed it. I also reinstalled the original, Ford TFI back onto my distributor. I had replaced it last summer when I had another problem. I was suspecting that it was causing my recent problems so I decided to go back to the Ford TFI.

Anyway, the problem is completely gone. Throttle response is so much smoother with the new TPS. I haven't seen the CEL since last year! I'm sure it was/is the new TPS that fixed the problem so, since you've got the code, check your TPS carefully. Good luck.
 
#5 ·
When I see that many codes, my first step is to clean and tweak the 10-pin connectors at the back of the manifold. All the sensor signals run through those connectors, and when they age, bad things happen.

Also, on a fox-body, if you get a lean code on the O2 sensors, it means they're either totally dead (not likely) or there's a wiring or connector problem (very likely).

Look at all those "below minimum voltage" and "out of range" descriptions...the EEC is not getting much, if any, voltage back through the harness from these sensors.

So also check your grounds, including the O2 harness ground at the back of the drivers side cylinder head.

I would do all this before I spent a dime throwing any sensors at it.
 
#6 ·
+1 on checking the 10 pins and the O2 grounds. I'd also make sure things are all plugged in and plumbed properly. The MAF is present and in the air tube, stuff like that.
 
#8 ·
If none of these things fix your issue, I just got rid of most of the problems with my '86 by replacing the distributor because of a suspected stator issue. Used the same TFI on a spare distributor I had laying around and it's running better than it has in a WHILE.
 
#10 ·
thanks all..

I checked the TPS voltage and it read 1.17 so I jiggled it back to a healthy .98

that seemed to fix it... It runs great now but after warming up still throws a CEL so Ill pull codes again tonight and see whats listed now..

adjusting the TPS definitly helped a LOT, my dist is a new MSD unit so I dont suspect that.
 
#11 ·
haha, I would suspect the MSD still. They are junk, I have one.

But anyways, I would open the pins up on the salt and pepper shakers ( 10 pins ) to help with connection. Multiple codes like that usually means a connection issue, or your MAF is reading incorrectly that is making it run lean.

Your EGR diaphram is probably bad, or you have a bad solenoid.

TPS voltage read too low, not too high. Check the sweep, slowly open the Throttle while monitoring the voltage and made sure there is not dead spots and you getting a clean sweep from 1v to 4.5V+-. Usually happens where the throttle is the most...cruise.

Also I assume that you removed your smog pump?
 
#12 ·
I am going to open up the S+P shakers and clean em up for good measure.

I pulled codes again and the only ones left are the 81 and 82... so EGR it seems.

I also DID remove the smog pump a LONG time ago..

so I should probably replace the EGR stuff?
 
#13 ·
ok UPDATE - for the good!

So after MFE posted up about the 10 pins with the car running I grabbed the harness connected to them and as I moved the harness the idle changed and the car DIED!!!

So I push down on the 10pins to seat them firmly and WAH-LA!!! car runs like a dream.
This weekend I am going to open them up, clean them and also do the little mod to them which is nothing more than tightning the female side and spreading the pins on the male side before reconnecting.

Thanks everyone - yet again - when MFE comments my problems get fixed. Love the Corral.
 
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