racin4ds

iTrader: (1)

Hi guys, I'm probably asking something thats been asked a dozen times but I'm out of ideas... I can't get rid of the idle surge/very rich idle on my 94 F150 with the 5.0, its entirely stock. I've replaced the ECT sensor, the ACT sensor, cleaned the TB, new plugs, air filter, cap, rotor, etc. I also just today swapped MAP sensors with the one on my dads truck to see if that was a culprit, no change....

What am I missing!! CEL was on for a few EGR related codes. I replaced the EGR with an old but functioning one and still have the same issues.

HELP!!!

qdeezie

Ok, sounds like an issue I had. Here's my recommendations/thoughts:

1. Replace all of your vacuum hoses with rubber hose if you haven't already done so. You will need about 20 feet of rubber hose and a few "T" hose adapters. You can use some of the tips from the vacuum lines to insert into the new vacuum hoses.

2. In addtion to #1, regarding EGR codes, once you know that the vacuum hoses are ok, disconnect the battery and check for new codes. If you still have codes, your egr position sensor is bad or your egr differential pressure sensor is bad.

3. Now, with the egr position sensor, if the egr valve is motorcraft, the only sensor that will work on it is a motorcraft. If you have a bwd or wells sensor, you will continue to get codes. Bwd and wells sensors only work with bwd or wells egr valves.

4. Make sure the hose from the egr dpfe to the egr sensor has no leaks.

Those are my thoughts on the matter.

racin4ds

iTrader: (1)

Thanks! Will definitely check those out this weekend! My dads 93 has been doing the same thing since we put the new motor in.... although he decided to put an E303 cam and do some other work when the motor was getting rebuilt... so I'm sure his is a different issue...

Oh, where the heck is the DPFE sensor on these trucks? I'm used to the newer trucks...

racin4ds

iTrader: (1)

Update:

Went over all vacumn lines with carb spray to check for leaks, none found. disconnected EGR and pulled vacumn on it to ensure function, all good there. Pulled the 02 sensor out and hosed it off with CRC cleaner and it was definitely better so I went ahead and bought a new 02 sensor and threw that in and VIOLA!! problem solved! Seems to be running much better and idle is pretty steady, still not perfect but way better!

I've been a mechanic for most of my life and have never really seen an 02 sensor cause this many issues on a vehicle... I guess you learn something every day...

Just call me Sean

iTrader: (1)

I didn't see IAC on that list.

Travis_CO

what about TPS? I thought these fords were notorius for malfunctioning TPS sensors and not throwng a code?

Warlockk

X2 one of the most common problems.

racin4ds

iTrader: (1)

Yea IAC was one of the first things I swapped out. I am going to check the TPS today.

ftrucktough

I had a 2.9L bronco 2 once that had a nasty idle surge that drove me nuts. When I finally checked the O2 sensor, it broke off when I touched. For grins... I went and drove it with the sensor completely broken off and it ran the same as always. No check engine light or anything... Replaced and problem solved. I'm glad you thought if it, I was going to suggest it otherwise!