I bought a 92 f150 1.5 years ago, 137k. Many EFI/Emissions parts had been changed. About 2 months later, it began to flash an occasional CEL. The valves rattled on pulls and it has idled very fast 3 or 4 times, usually during cold weather. I stopped and removed the spout connector one time and the idle returned to normal. I repaired a vacuum leak and the CEL came on more. I took it to a dealer to go through diagnostics. The tech said that he found only some EGR codes. I repaired another vacuum leak and the CEL came on within 10 minutes every time I drove it. Dealer tech said it looked like the ECM. Bought a salvage one, nothing changed. Codes showing 33,34. EGR position sensor resistance tested low. Changed it and got codes 31-34. CEL still came on. Checked vacuum on EGR solenoid, disconnected. It did not hold vacuum. Took it apart and cleaned diaphram. CEL does not come on, but it still reads 33, 34 KOEO using a scanner. Ordered a new solenoid and waiting to try it. Truck runs okay, but not quite right. Any suggestions?

 

Fast idle problem - check the Idle Air Control valve for any crud buildup. These are bad about fouling and sticking, causing idle swings, etc.

Also, check for vacuum leaks - manifold, hoses, intake gaskets, etc. - another good cause of fast idles.

Confused by your description of the EGR solenoid not holding vacuum. If the EGR valve leaks down, it needs to be replaced.

There is a control solenoid supplying the vacuum control signal to the valve - just follow the vacuum tubing from the EGR valve back - mine is located on the driver side of the engine, on the intake manifold, near the rear of the motor.

Have had an instance on mine and one on a similar truck where a small foam filter inside this control solenoid plugged up, not allowing proper control of the EGR valve and throwing codes. It looks that this can be taken apart and cleaned - however, be careful, I ended up breaking things and had to replace the solenoid.

Also, check the integrity of the vacuum lines. I'm not a big fan of the nylon or whatever tubing Ford used - gets brittle with age. Can replace with suitable rubber vacuum hose if needed.

If the EGR valve is suitable - check the valve seat so that it can seal properly. Also, inspect the exhaust tubing to the valve. Have experienced an occasion where this tubing split, allowing fresh air instead of exhaust gas to be sucked in - messed performance up greatly.

 

Haynes manual gave check for applying vacuum to EGR solenoid. If I understood correctly, it said to apply vacuum to the input connection, bottom hose, with electrical disconnected. I did that, and it did not hold vacuum. One of the clips that held the solenoid together was broken. Seems someone had been into it. There was no foam filter. This probably let the grit into the solenoid. I guess I need to just replace it. Got a good deal on ebay.

Do you have any idea about the check engine light going off, but still reading a code?

I put the old EGR position sensor on and the first set of codes KOEO no longer showing. It was 34 before.

I believe I found a small hole in the vacuum can. I may have made it taking it off to check. I am plugging hole, and going to try it on the road.

 

First, is the 'check engine' light still working - does it self-test when you start the vehicle?

May want to clear any stored codes to avoid confusion. IIRC, stored (historical) codes are read in KeyOnEngineOff mode, active (current) codes are read in the KeyOnEngineRunning mode.

If faults are still present, they will pop back up. The scanner should have a function to clear historical codes, or the main negative battery cable can be disconnected for about 20 minutes.

If I understand what you did - there is a leak either in the hose or the EGR diaphragm, or perhaps the device used to pull the vacuum is not sealing properly. The EGR valve should stay in a given position for a given vacuum level.

 

CEL comes on at startup. I got a hard code 34 with the KOEO test(the first set), after I changed the EGR position sensor. When I cleaned the EGR solenoid, the CEL stopped showing, but I still got codes, KOEO and KOER. Same codes 34 first set, and all others showed 33. The vacuum test I did was for the solenoid not EGR, following Haynes. I started at the EGR and worked my way back.

I plugged the hole in the vacuum can, cleared codes, removed the battery terminal and put my old position sensor back on. No codes showed on KOEO. Hard code was gone. I drove about 10 min, no codes on KOEO or KOER. I put the new position sensor back on and got all the codes back. I think I got a bad sensor. I'll try with the old one for a while and see what happens. I may try my old ECM to see if everything works the same. I am still puzzled by the CEL not on but codes present. I believe it showed both 33 and 34 on KOER until I cleaned the solenoid. The extra code may be the difference.

I think I had a problem with the EGR solenoid all along, but it did not get vacuum to make it operate. When I fixed the vacuum leaks, probably cause of the valves rattling, it made the EGR function, resulting in codes. The fast idle may have been unrelated to the codes, or connected in some way to the vacuum leaks. Thanks, for your help.

 

did you ever get this figured out? I've got the same truck and have been having the exact same problem for months. I've done everything you've done and changed everything you've changed and still no luck. I've also fixed a couple of vaccum leaks and nothing is working.

 

I thought I had it fixed, but the CEL flashed on again. I got codes 35(EGR) and 41(oxygen sensor) on key on engine off test. I took back the EGR position sensor a few days ago. I got all kinds of codes when it was installed, but I did not with my old one, after I replaced the EGR solenoid. I replaced the position sensor because the resistance tested out of range. The store gave me a second new one and it did the same thing. I got lots of codes. The resistance tested out of range on it once, then tested ok. I am suspecting my test meter is not working well.

The only things I am sure of at this point is that my EGR solenoid (had grit and not closing) and vacuum leaks were a problem. It may be that the new position sensor is working correctly and pointing out more problems than the old one.

I am going to check out the O2 sensor and the actual EGR and wiring, as soon as I can. I may need to get a new meter to try as well. I notice a stronger exhaust smell. Any suggestions?

92 F150 4x4 AOD 146k

 

I have no idea at this point. I'm telling you I have the exact same issues. I'm dead serious. Everything you've described is exactly the same on my truck. The occasional high rev, the intermitant CEL, strange exhaust smells, poor engine performance, etc. I wish whatever it is would just freakin' break so I could find it easier. I've replaced the exact same parts that you have. I don't think there is a sensor related to the exhaust/fuel system that I haven't replaced. I'm with you - I think I'm going to replace the EGR valve even though my vaccuum test shows that it's okay. I also haven't changed any of the O2 sensors due to the fact that my scanner isn't showing those to be bad. I've also got a post on here regarding the possibility of yanking the whole computer and losing the CAT's. Not sure if that's a good idea or even doable, but I'm tired of this. There's a guy on here, Steve83. I think he's a ford tech. He knows his stuff. Maybe see if you can get him to troubleshoot it further. I would do it, but he helps me out too much already that I hate to bother the guy. Keep my posted. -Al Nobles, Fort Mill, SC

 

I took off the EGR valve today and nothing obvious showed up. It held vacuum and seated well. I cleaned it with carb cleaner. I put back on the new EGR Position sensor. Same codes 33 on the KOEO self test, then 33, 34 with the engine running. I believe I still have a bad position sensor based on the codes.

Selbona,
Where did you get your replacement parts? I got my EGR Position sensor at Advance Auto, GP Sorenson. My EGR Solenoid came from EBAY. It was a new factory Ford part.

I am going to test these out better with another meter when I get time. I will also try to go through every detail of the Haynes tests. I am very short on time and it takes a while to go through everything at once.

By the way, I found 3 vacuum leaks one on top of the throttle body in a red vacuum tube, one in the white tube that goes to the heater control, and one in the vacuum can, on the bottom, under the mounting bracket. The transmission shifts rough in high gear and overdrive, I looked for a modulator valve to check that line and didn't find one. Any information there?

After the vacuum leaks, and the solenoid mine is running a little better, long time since fast idle, only ocassional valve pings. I will check out the position sensor so that I can try to get my money back, if it's bad and then may try to make it till Spring. I'll keep posting.

 

That's the spirit, red-truck! Keep after it!

If you are still getting faults - the computer ain't likin' something.

The colored nylon (or whatever it's made of) tubing is a problem - it likes to get brittle and crack. General wisdom is to replace it with standard rubber vacuum tubing.

Did you get the correct sensor? I mention this as when I replaced mine, there was a big deal made about the color - grey or black (eh, maybe white instead of black, but there were certainly different parts in question for my application) - to be the correct part.

Just asking - how do you know that the control solenoid is working correctly?

I suggest that the 'bad position sensor' fault could be due to any reason that the EGR valve isn't where the computer expects it to be - whether it be due to a bad control solenoid, leaky vacuum tubing (both supply to the control solenoid or between the solenoid and valve, or the exhaust circuit of the solenoid), a faulty sensor, or a problem with the EGR valve itself (bad diaphragm, mechanical binding, etc.)

 

Thanks. It's my understanding that the initial codes in KOEO tests indicate fauts that are present at the time of the self test. This is why I think that the problem is not exclusively vacuum, even though there may still be more leaks.

You are right that the computer is not happy. Given this, the codes show that the voltage read on the signal return indicates that the EGR is not in a closed position. The resistance on my old part was about 40 ohms on a closed test. The Haynes manual said that it should be about 100, and that if it is less, replace the part. The new one reads about 200 ohms that may explain why I get codes that indicate an open EGR on the self test. However, I have gotten inconsistent readings with my meter. One time the open reading was 15000 ohms with the new sensor then about 4500.

My position sensor was white or light gray, the new one is dark gray. They did not ask about the color. I will check online for the part to see.

I have not tested the new solenoid. Maybe I should. It is obviously a newer version than my old one. I believe the Haynes manual was wrong on the vacuum test for it. It said to unplug the electrical contacts and to connect vacuum to the inlet connector and a gauge to the outlet. The vacuum should hold on the inlet and no vacuum be indicated at the gauge. I thought the vacuum bypassed to pull outside air from the top (sponge) when no EGR was called for, and closed to pull from the EGR when called for by the computer. If this is the case, it would not hold vacuum when open. The old and new both vented, but I did not do an electrical test on the new one. The old one tested okay, only physical damage to the sponge filter and fastening clips were a problem. No codes changed with the new one.

I'll keep trying. Thanks for the encouragement.

 

Just another thought - are you confident that your meter is correct?

You are obviously being very thorough. And if this stuff were easy, monkeys could be hired to serve as mechanics.

I applaud your efforts thus far - many others would have just said, "screw it" and let things ride.

 

I haven't had tranny problems(yet), so I've never looked for a modulator valve. Apparently, removing the computer and everything related to it is not an option as it has been pointed out to me by a couple of smart asses on this message board, so I'm going to get back on it next weekend. I've also noticed some oil usage. I have no idea how that could be related, but it wasn't using oil before. So anyway, I plan on removing the intake, replacing all of the injectors, seals and fuel filters so that I can rule that out. Then, I'm replacing all of those brittle vaccuum lines with rubber lines. I'm also replacing the EGR. I'll let you know what I find if anything. I never got questioned about the color of my sensor (white or grey). Maybe I need to start buying motocraft parts. I've been getting everything from Advance or Autozone because they're open late and are close by. That very well could be part of the problem.

 

ive always had a problem with those places. and get rid of the egr! just delete it! you dont need it! hahhaha

 

I checked out the different Egr position sensors (colors, numbers etc). I found one online at Advance Auto that matched the OEM number. They can't get it at the store and only have the one I bought listed.

Called my local NAPA and he had one that cross referenced to the OEM. My wife picked it up and it was made by the same company as Advanced, just different box, same color and everything. It had a different number stamped on the side of the part. I tried it and no codes. I unhooked and to try the Advance part to make sure (I got the codes back), and one of the pins pulled out of the Napa one. They are ordering another one.

I found one at another store that was light gray like my old one. Same number but had a "B" on the end in stead of an "A."

I always wondered why my dad kept all his old parts. This is one time I'm glad I did. The local ford dealer couldn't match it without the OEM number from the part.

I hope I'm winding this one up.