1996 Ford Windstar rought idle after hot soak restart

Tiny
PERRYTIME
  • MEMBER
  • 1996 FORD WINDSTAR
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 201,000 MILES
Only in warm weather, after a nice 30min or longer drive, if the van is turned off for 20min, on restart the engine idle is too low and sometimes stalls until it goes closed loop. Never happens on cold engine.
The rough idle will go away if vacume to fuel pressure regulator is removed and plugged.
injectors sent off and leak, flow tested and cleaned.
No loss of coolant, had this problem for over 1 year. Lower intake manifold gaskets done about 100k miles.
I replaced FPR and IAC. Fuel pressure is 40 when key goes on and drops 30 engine running, holds true when problem is happening. When engine is heat soaked, I can cycle key several times until fuel rail is full of cool gas, still has problem. I plugged vaccum tee on throttle body top, goes to PCV, no fix. I checked for vacum at EGR, none. Cleaned MAF, all clamps on air intake tight. I removed and cleaned dust off camshaft position sensor, no fix. I pulled connector to PCM, all contacts look clean. New plugs, wires, and coil pack in last year. I unplugged MAF and started engine, same rought idle on hot soaked engine. Long term fuel trim about 3 when driving, about 15 when idling. I don't see it trying to do anything strange when it goes closed loop and the rought idle subsides. Van drive fine in all other respects, good acceleration. I even kept my old IAC and swope a cold one on hot engine, still rough idle. No check engine light. No misfires reported. EGR ports clean. Scan tool shows air temp, engine temp, all sensors good values on heat soaked engine. I verified I can cause rough idle and set engine light when hand applied vaccum to EGR, so DFP working. I cannot read injector pulse widths, I think all evidence is pointing to lean engine.
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Wednesday, March 24th, 2010 AT 4:35 PM

3 Replies

Tiny
MECHANICS FOR DUMMIES
  • MEMBER
Check your fuel regulator or fuel pump one of them will be quitting on you at any time. My guess is the fuel pump is not putting out enough pressure. Check the psi according to the manual for your vehicle. If it is not at specs then your pump is going bad or you have some clogged screens in the tank. It is a great idea to change your fuel filter regularly. You don't know what is in the ground when you fill up your tank. My suggestion is every third oil change, change your fuel filter also

JJ
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Monday, March 29th, 2010 AT 6:48 PM
Tiny
PERRYTIME
  • MEMBER
As I said, I already put in a new fuel pressure regulator, FPR. The fuel pressures are in spec, and are not any different between a good and bad start. Any other ideas?
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Saturday, April 3rd, 2010 AT 7:09 PM
Tiny
MECHANICS FOR DUMMIES
  • MEMBER
I would suggest yu do an engine on scan and take it for a ride with the scanner connected to analyze the lean setting you are getting my guess and it is just a guess is the idle position sensor I have had to replace one on my windstar for the same reason. The cost was about 15.00 + change at auto zone and 30 minutes of my time. It solved the rough idle on mine.

Also just a note the throttle body may need a little cleaning as oil gets in there and clogs up the sensor so the readings may not be correct.
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Monday, April 5th, 2010 AT 1:45 AM

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