Intermittent idle probs
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From: Fl
Intermittent idle probs
My 93 van has had an intermittent problem with idle, it will occure after about two minutes of warm up but NOT everytime. It has to be electrical, when not acting up, or driving it runs like new. Until recently. Replaced EGR, wires plugs etc. Vaccum is 20 at idle, fule is 59psi (rail) but will shoot up right before it stalls (probably because vac is dropping as engine rpm drops to 350). It sets different codes on different days, and when testing whatever it sets the sensor, wiring whatever is fine! It has set nearly every code there is. Tomorrow there will probably be two or three different ones. The codes which usually return are MAP/BARO, unable to control RPM, rich bank one always came back til yesterday, now lean is the code. O2 is new, fine, wiring, vaccum lines etc. I'm goin after the pcm soon. Anyone ever had this? I have checked everywhere, replaced the MAP as well as checking it with a good spare, same for all other sensors as well as using VOM, tach etc for component testing. I've run out of places to look.
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From: Fl
It's a 94 E350 with a 7.5. 220K miles, the engine has about 40k on it.
I've been through the grounds, relays, wiring, unplugged and checked/cleaned pcm connector, same for evry wire in the engine compartment and up to the fuel pump, although the pressure is good and holds when shut off.
I know explorers were known for a bad connection in the pcm, I dont know what else it can be.
Thanks!
I've been through the grounds, relays, wiring, unplugged and checked/cleaned pcm connector, same for evry wire in the engine compartment and up to the fuel pump, although the pressure is good and holds when shut off.
I know explorers were known for a bad connection in the pcm, I dont know what else it can be.
Thanks!
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Joined: Feb 2004
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From: Birmingham, AL
Airbrush,
Check your fuel pressure regulator. Don't know about a 460 but that pressure is too high for a 351. They spec at 38 psi. Check your repair manual for correct spec for your engine. With the engine cold and the doghouse opened (and the van outside) pull the vacum line off of the fuel pressure regulator and crank the engine over. If fuel shoots out of the nipple where the vacum line was attached the diaphram is bad. Replace regulator. This can account for bad idle and the rich condition. When mine failed there was a strong oder of gas in the exhaust and the tailpipe was black and wet.
If that is ok check you IAC (idle Air Control) They are prone to clogging up. It is an electromecanical valve that controls air at idle. Some have reported success with cleaning the valve part of the device. You can't get your solvent in the electrical part though. With the mileage that you have I would replace it if it is gunked up.
Gene
Check your fuel pressure regulator. Don't know about a 460 but that pressure is too high for a 351. They spec at 38 psi. Check your repair manual for correct spec for your engine. With the engine cold and the doghouse opened (and the van outside) pull the vacum line off of the fuel pressure regulator and crank the engine over. If fuel shoots out of the nipple where the vacum line was attached the diaphram is bad. Replace regulator. This can account for bad idle and the rich condition. When mine failed there was a strong oder of gas in the exhaust and the tailpipe was black and wet.
If that is ok check you IAC (idle Air Control) They are prone to clogging up. It is an electromecanical valve that controls air at idle. Some have reported success with cleaning the valve part of the device. You can't get your solvent in the electrical part though. With the mileage that you have I would replace it if it is gunked up.
Gene
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From: Fl
Thanks guys! The fuel will not squirt out, but the pressure is about 10 psi too high. It has set "lean code" for both banks last few days, but used to set rich. It could be the FPR, it is too high... should be 30-45 for V-8's. It's about 58-59 at idle, goes to 70 WOT or as it surges to very low RPM (zero vac) I think the FPR is $60 so I may just try it and see. This is intermittent, so something inside the FPR may be sticking. I still don't understand the huge variety of wild goose-chase codes, unless they're related to the excessively low idle. (Low vacc)
I cleaned the old IAC, then replced it.... no diff but I know they are notorious. Guess I have an extra one now.
If not, PCM.
Thanks again.
I cleaned the old IAC, then replced it.... no diff but I know they are notorious. Guess I have an extra one now.
If not, PCM.
Thanks again.
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Joined: Feb 2004
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From: Birmingham, AL
Airbrush,
Have you checked the MAP sensor? The high pressure could also be from a clogged return line for the fuel rail.
Another test for the regulator would be to remove the vacum line while it is running with the fuel pressure test gauge connected to the fuel rail. Remove and reconnect the line a few times to see if the pressure indicated on the gauge is going up and down accordingly. Also make sure vacum is pressent on that vacum line. Be certain that it has passed the previous test (no gas comming out of the vacum port) before doing this.
All of the odd codes are just what you might call cascading codes. One fault causes several other things down stream to go out of spec as well. The PCM would be a last resort in my veiw. With the MAP code showing up consistantly I would test or replace the MAP sensor. It's located on top of the heater box and has an electrical connection and a vacum line attached to it.
Gene
Have you checked the MAP sensor? The high pressure could also be from a clogged return line for the fuel rail.
Another test for the regulator would be to remove the vacum line while it is running with the fuel pressure test gauge connected to the fuel rail. Remove and reconnect the line a few times to see if the pressure indicated on the gauge is going up and down accordingly. Also make sure vacum is pressent on that vacum line. Be certain that it has passed the previous test (no gas comming out of the vacum port) before doing this.
All of the odd codes are just what you might call cascading codes. One fault causes several other things down stream to go out of spec as well. The PCM would be a last resort in my veiw. With the MAP code showing up consistantly I would test or replace the MAP sensor. It's located on top of the heater box and has an electrical connection and a vacum line attached to it.
Gene
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From: Fl
Just replaced the FPR, the only change is that I'm $40 poorer.
Oh well, Im gonna order a pcm tomorrow if Im in town
Oh well, Im gonna order a pcm tomorrow if Im in town
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From: Fl
I did check the MAP, I think my post got lost. I used a tach the way the Froot of the loom manual said, and also have about 6 good ones I've switched with . No dofference unless I tested it wrong and have 6 bad maps.
Thx
Thx
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From: Fl
Other thing with the MAf, a while back the Map/baro code came up, I put one on off of another car, the code didnt come back. I bought a new Map and put the one back onto the f150. About 2 weeks later the problem came back, with the code. I took the Maf back to the auto parts guys and gave them he**.... they replaced it. I put the replced one on and same thing. Switched with other known good/used ones and the code stayed, and back then I checked all the maf wiring and vaccum lines. I then concluded theres no way its the Maf, but I could be wrong or it could be that when the problem pops up there isnt enough vaccum for things like the maf to run.
I had a 2002 Town car do crap like this and the stealership never figured it out. I had to sell the thing. I swear if my $44,000 2005 does this sh***, it will be my last ford! At least I've got years of towing out of this old one.
I had a 2002 Town car do crap like this and the stealership never figured it out. I had to sell the thing. I swear if my $44,000 2005 does this sh***, it will be my last ford! At least I've got years of towing out of this old one.
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Joined: Feb 2004
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From: Birmingham, AL
What is the fuel pressure reading since you changed the regulator? If it is still high look for another cause. Could be the return line to the tank is clogged. Vacum source may be low at the FPR. Something isn't right if you have that high of a reading. I always try to fix the stuff that I find that isn't right along the diagnostic path and I usually stumble into fixing the original complaint. With 220 K miles I wouldn't worry that I had replaced the FPR prematurely but if the pressure is still high then there is another cause.
Next thing I would suspect would be the IAC that we talked about before and then the Throtle Position Sensor (TPS) If the IAC has never been replaced there is a good chance that it is clogged up. Some people clean them I would replace it.
Have you done a complete scan with a real scan tool not just a code reader?
Does the 460 have a MAF in '94? I thought only 5.0 liter had it before late '95 or '96. My '94 351 only has MAP.
Gene
Next thing I would suspect would be the IAC that we talked about before and then the Throtle Position Sensor (TPS) If the IAC has never been replaced there is a good chance that it is clogged up. Some people clean them I would replace it.
Have you done a complete scan with a real scan tool not just a code reader?
Does the 460 have a MAF in '94? I thought only 5.0 liter had it before late '95 or '96. My '94 351 only has MAP.
Gene
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From: Fl
yes. The IAC was replaced, scanned etc. I have 20 in vacc at the fpr. Same exact fuel pressure readings. About all I could do would be replace the rtn line hoping there is physically something on the inside of it. It looks like that would involve dropping the tank. It's definitely not damaged on the exterior. TPS has been replaced but that doesn't mean it's good. It tests ok with the VOM and doesnt set a code but I've had them not set codes before. I agree about the high pressure, either whatever is making it surge drops the vaccum giving it the 10 psi increase like you would get WOT, or there is actually something inside the return line. It IS intermittent, though which seems awfully electrical to me.
Maybe I need to go drive all the gas out of it so I can drop the tank and yank the return line off. It's got $65 worth of gas in it. I have a feeling it's not the return line, though because it wouldn't be intermittent. Today I let it idle for a while and it ran perfect for about 45 minutes until it began surging. I drove it, then parked it and the surging began. But when it began, it was very bad.
Maybe I need to go drive all the gas out of it so I can drop the tank and yank the return line off. It's got $65 worth of gas in it. I have a feeling it's not the return line, though because it wouldn't be intermittent. Today I let it idle for a while and it ran perfect for about 45 minutes until it began surging. I drove it, then parked it and the surging began. But when it began, it was very bad.
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From: Fl
May be the ECT.
It spits out temperatures that are all over the place, it will go: 164, 176,182,174,182,166.... etc.
I have one on order. I shoved cardboard in the grille to get temp up to 210, from it's 188deg or so normal idle and the ECT will stabilize at around 188, still way below actual. Actual at this point is 208-210. I use a infrared handheld and the ECT won't stabilze till right about 210, but still it reads about 20 deg low. It fluctuates a lot below that. I've never seen one "hunt" like that, but up around 210, it quits hunting but is still inaccurate, and that's also when it runs the best.
It spits out temperatures that are all over the place, it will go: 164, 176,182,174,182,166.... etc.
I have one on order. I shoved cardboard in the grille to get temp up to 210, from it's 188deg or so normal idle and the ECT will stabilize at around 188, still way below actual. Actual at this point is 208-210. I use a infrared handheld and the ECT won't stabilze till right about 210, but still it reads about 20 deg low. It fluctuates a lot below that. I've never seen one "hunt" like that, but up around 210, it quits hunting but is still inaccurate, and that's also when it runs the best.
Elder User
Joined: Feb 2004
Posts: 638
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From: Birmingham, AL
Have you pulled your air and water temp sensors out and tested them? When I was Having this problem My Intake Air Sensor was all gunked up. Iwent ahead and replaced it. The water temp sensor tested ok in a pan of hot water so I reused it.
The fuel pressure may just be a funtion of erratic vacum caused by the engine not running right. If you have a vacum test pump you might try applying vacum to the regulator manualy and see if the if the fuel pressure stabilizes.
I also found several small and one fairly large vacum leak in the tubing running around the back passenger's side of the engine. The small ones were from chaffing and the large one was from a broken vacum
Gene
The fuel pressure may just be a funtion of erratic vacum caused by the engine not running right. If you have a vacum test pump you might try applying vacum to the regulator manualy and see if the if the fuel pressure stabilizes.
I also found several small and one fairly large vacum leak in the tubing running around the back passenger's side of the engine. The small ones were from chaffing and the large one was from a broken vacum
Gene