Well it’s not the Map sensor, i replaced it and it still threw a CEL after about 10 min. I do know now that it’s not temperature related necessarily. I thought the light would come on then the truck went into closed loop. But after the light came on one time, i stopped and turned off the truck and quickly restarted it. The light went away and didn’t come back for about the same amount of time. So I’m not sure what this means.


The egr is working. I can see the valve move up and down. It appears to only lift at around 2000 rpm and it will close as the engine gets into the higher rpm ranges.

 

Well im starting to get the hesitation and light switch effect that i had last year. It must be temperature related. When i say light switch i mean, i start to accelerate from a dead stop and you can feel the truck hesitating and underpowerd and as the rpms slowly climb, (not porportionally to throttle) all the sudden the truck will come to life like a switch is flipped or sombody hit the nitrous button...(haha jk) but seriously.

The light switch effect happens when the truck is in the same gear, no down shifting. It also has a slight miss at idle still and sometimes going down the road it will miss, especially when your at constant speed/throttle going up hill. It reallly starts to cut. Seems to related to engine load as far as the missing.

 

How old is the O2 senor again?

The light switch effect seem ignition related to you?

 

O2 could be original for all I know. It's either injectors or ignition

 

Do you still have the codes we were talking about a couple weeks ago? If you do, I'm under the impression that there is an O2 senor issue.... Unless it is truly running lean and that may be related to the lack of power you are experiencing now. You said fuel pressure is within spec, so it may not hurt to pull the spark plugs and see if they can tell you anything.

 

Truck seems to hesitate before 2500 rpm when cold. But when i stand on it, it will run fairly good. Still have the light switch effect as i described.

 

Oh and the engine sometime idles way way to low. LIke 600 rpm, it will start to miss/knock at that low. Other times it will idle smooth at 750 rpm. Not sure why it does that.

 

Hey Burnstough,

did you ever figure out what's going on with your truck? I just bought a '95 F150 w/5.0 and I'm getting codes 172 & 332 also. Mine runs fine (cold start & after warm-up), but after about 10 mins the check engine light comes on (no change in performance) and I can shut it down then start it right back up and no light for another 10 mins.

 

Code 332.
You have an EGR valve problem with the valve not opening after the engine warms up at mid throttle while driving.
The code 332 will not cause the engine to run bad.

The book:
Continuous Memory DTC 332 indicates the EGR valve did not open with the engine stabilized and the EVR solenoid duty cycle present sometime during vehicle operation.

Possible causes:

-- Obstructed or cracked hose to EGR valve.

-- Icing.

-- Damaged EGR valve.

-- Damaged EVR solenoid harness.

 

I'm ready to pull my hair out!
I'm STILL getting codes 172 & 332

I've put NEW egr, NEW egr tube, NEW egr vacuum solenoid, NEW carbon canister, NEW purge solenoid, NEW O2 sensor, got rid of ALL the crap plastic vacuum lines and replaced with rubber ones. Found 2 pin holes in the "coffee can" vacuum reservoir and replaced it as well.

What could I be missing?

 

I was getting KOEO Continuous Memory code 172 (HEGO {HO2S} sensor fault/lean) and KOER code 311 (Thermactor/air system fault during engine run self test) and my truck was running exactly as described although I didn't have the check engine light come on. Missing or hesitating at stop lights, while driving and especially when pulling up hills. My Catalytic Converter and the O2 sensor are brand new and so is my exhaust system from the manifolds back to the muffler so I had no leaks or other actual Thermactor issues. I have no vacuum leaks and my fuel pressure was fine. While checking the ignition system I discovered my #6 spark plug boot was split. I changed the wire and all of my codes went away and my truck is running great again.
I hope this gives you another place to look. For me it was not obvious that I would get the codes from a faulty plug wire.

 

Well, I'm willing to try anything at this point. I just ordered new cap, rotor, plugs and wires from RockAuto. EVERYTHING (including shipping) was only $33. My truck has 132K on it and hasn't had a tune-up since I bought it back in January. So it surely couldn't hurt.

 

Almost forgot, I DID get rid of the 332 code. I found that when the plastic vacuum lines were replaced, a couple were routed wrong and also found a hole in the vacuum reservoir (coffee can), it was underneath were it couldn't be seen unless removed.
One step closer.

 

Interesting about the stumbling at constant load/speed issue cropping up. My '95 does that very thing and its annoying the crap outta me!

 

Mine runs like a scalded cat, no stumbling, no hesitation. But that check engine keeps coming on and it's driving me crazy. Keep getting code 172 which is an O2 code, I've replaced the sensor 3 times, this last time I went with the "Motorcraft" one.
Somebody else (in another thread) had said he had the same code and it was a bad plug wire.
I figured it sure as hell couldn't hurt, my truck has 132K and no tune-up since I got it January.
I played hell getting rid of code 332 (insufficient egr flow), replaced ALL the crap plastic vacuum lines, the egr, egr solenoid, egr tube, carbon vapor canister, canister purge solenoid everything I could think of. Come to find out after all that my "coffee can" had a hole in it. I sprayed the nheck out of it with stuff similar to that crap they sell on TV (where they put a screen door in a rowboat). IT WORKED.
So now I wait for the tune-up parts and cross my fingers.