94 Escort Still Won't Idle - Guess It's Time to Send it to the Shop

Well, I finally have had a chance to work some more on my 94 11.9 Escort That Refuses To Hold an Idle.
So far, I have replaced the Idle Air Control Valve, O2 Sensor, Throttle
Position Sensor. Have checked for and found no signficant vacuum leaks anywhere. Based on the erratic idle (it sometimes will but usually won't once the system goes closed loop) I was thinking sticky EGR valve.
That was ruled out today. I was going to replace the EGR valve, but could not get the exhaust gas inlet line loose from the exsisting valve. As an EGR diagnostic, I made up a small blanking plate that I was able to install between the valve and where it bolts to the intake runner. The blamk made a tight seal against any EGR leakage into the intake manitold. At the same time, I was able to blank off the fuel canister purge line that connects to the underside of the throttle body. I've eliminated all the other vacucum lines as leakers already.
Well, those two above diagnostics had no significant effect on the poor idle performance. So it looks like the EGR valve replacment would have been a waste of time.
I have been focusing on vacuum leaks from such sources since the poor idle seems to be accompanied by low manifold vacuum. The only relevant OBD code that I have been seeing is an intermittent 182: Partial throttle rich adaptive limit, system lean. This comes and goes mainly at speed with no notable coincident changes in performance.
As always, the car runs very strong once you goose the throttle and never hesitates or surges under load. Lately the idle stability has gotten worse, with the engine immeditely going into a stall while at the end of slowing down to a stop with the clutch disengaged. But at other times it will hold idle quite well for many throttle up and down cycles. I'm stumped...
Fuel filter? If it is partially clogged, why is only idle affected? There's no hesitation or surging when the throttle is booted and going through the gears, or on a steady cruise conditon.
Timing belt a little off tension/timing?
Fuel pressure regulator?
Clogged injectors?
Whatever it is, it's gradually getting worse - I'm thinking its time to throw in the towel and send it to a shop....
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Chris Bowne wrote:

the PCV? it is supposed to leak air, if it was plugged it would cause a lower idle. Is your TPS adjustable? It should be about 1/2 a volt at idle. If its adjustable find out what its supposed to be at and set it (at idle). A fuel filter sure wouldn't hurt, there cheap and often overlooked at tune up time.
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I think you're getting too much air, as you may have already guessed, thus the rich adaptive limit. Someone correct me if I am wrong, but I think the way it works is that the computer tries to compensate with fuel for the overage in air that is being detected in the exhaust stream. Up to a point, until it reaches the adaptive rich limit.
Same problem on my 1990 Escort GT, had a bad air leak that I could never pinpoint, but I think it is from a warped head or intake. I've been tearing her top end down lately and will be replacing all the gaskets from the head gasket on up.
Try a smoke pen and with the engine running see where the smoke gets sucked in. Good luck!
sleepdog
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Forgot to mention that I have also replaced the PCV valve, and put hose clamps on all the associated tubing joints. I have blanked off all lines that draw vacuum from the intake runnner and none have proven to be the source of the idle problem. I will try to listen around with a piece of tubing as a stethescope to see if I can pinpoint any other air leaks. Thanks for all your comments.
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Start with probing around the intake manifold assembly.
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Chris Bowne wrote:

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I looked at the throttle plate and it's clean ...PCV valve was the first thing replaced, along wit the IACV, TPS, O2 Sensor. As I stated in my post, I've run out of auxiliary stuff that could be causing an air leak.
I watched the engine speed on a long warmup at idle today. On initial firing, went to about 3K initially, then down to less than 1K, then up again for about 3 cycles. Then held a half decent idle about 1200 for a while. I then took off for a drive. At some points it was idling fast at stops (above 2k) during the drive in neutral (its got a 5 speed), and eventually , on full warm up, started idling slow and lumpy at about 600. Was trying to hold that, but eventually just quit like something shut off. What ever the cause is is behaving very erratically.
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Chris sometimes the valves or a valve may cause this problem. If I where you I would get this checked first before spending any more money. Have you done a compression check or leak down check? Sometimes the intake leak from the gasket to head. Possible bad plug or wire.
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Its time to call in the expert - I'll be calling my mechanic at Kars Inc. of Westerly RI to take on this case...I've gone about as far as my time and troubleshooting equipment and skills will go. I've been wondering about a bad valve issue myself...Thanks all for your help!
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Chris Bowne wrote:

Let us know what you find out.
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