94 F250 5.8L, high idle and won't start problems - Ford Forum - Enthusiast Forums for Ford Owners

Thread Tools Search this Thread
Old 05-03-2006, 04:40 AM
Thread Starter
Join Date: Mar 2005
Posts: 3
Default 94 F250 5.8L, high idle and won't start problems

Greetings all. I'm looking for some trouble shooting suggestions. I search the forum but did not really find an answer. Here's the situation. Vehicle: 1994 Ford F250 with 5.8L, auto. I just purchased the truck at an auction a week ago so I don't know much history about the truck other than what I found under the bench seat (a lot of dirt and some french fries ;') Anyway, it was owned by a concrete/construction company and has been well used with 260,000+ miles shown on the odometer. I drove the truck home ~200 miles, every time I'd have to stop you could feel the engine fighting the brakes. In park or neutral the truck would idle rather high making for a good clunk when you would shift into drive or reverse. I asked a friend for some ideas and he told me to check the Idle Air Control Valve (IACV). Sure enough, if I unplug the connector to the IACV, the truck drops down to a nice low idle. If the engine is cold you might have to feather the gas pedal a little to keep it running, but when it warms up it seems to run fine with the IACV unplugged, (well, just sitting there in park, no A/C on or turning the wheel putting a load on the P/S pump.) I tried cleaning the IACV but it did not seem to make any difference. If I plug the IACV in, high idle. If I unplug the IACV, nice low idle. So I would assume that means that the IACV is junk, not just dirty, and I need to replace it.

When the IACV fails, do they typically fail open or closed?
Can you take a measurment on the pins of the IACV to test if it is good or bad?
If you were to take a measurment at the wiring harness, what kind of a meter do you need? DMV or a Oscilliscope. What kind of reading should you be getting?

Second problem: Won't start without giving it a shot of starting fluid now. After I figured out that I could get the idle down by unplugging the IACV, I decided to degrease/clean the engine compartment. I sprayed a couple cans of GUNK Engine Cleaner under the hood, let it soak, then started it up and hosed it off. (NOTE: Did not need to use starting fluid any time before cleaning the engine.) I took the truck for a spin around the block to heat up the engine compartment and dry things out. During my spin I noticed that the truck was running like crap, I figured that there was some moisture in the distributor cap. I got home, opened the cap and confirmed my hunch. I blew the cap out with compressed air and strated the truck back up, (NOTE: No starter fluid needed.) I then proceeded to remove some of the misc. wiring that was left in the truck from the previous owners. I took my time doing this traceing the wires back to figure out the circuits. I removed the switch for a beacon light, another switch that went to some accessory that had already been removed, the power/antenna to what I assume was a two way radio, old car phone, and lastly a car alarm system. Again, I was very careful removing all the wiring, traceing the circuits making sure that I was not removeing any factory wiring. I then went to start the truck and it would crank but would not fire. I started to think that maybe something with the security system was preventing the engine from starting so I check for spark and confired that I had good spark. Then I thought maybe power to the fuel pump was being cut off so I sprayed a little starting fluid in the TB. I figured the truck would start and die as soon as the starting fluid was consumed, but to my surprise the truck keep running. I started to think that maybe the problem was due to the IACV being unplugged so I plugged it back it but it would still not start unless I gave it a shot of starting fluid.

So why do I need to use starting fluid to get the truck started now? Once started it seems to run fine.

Point me in the right direction guys, PLEASE!!!

Reply With Quote
Old 09-13-2006, 04:58 AM
Join Date: Sep 2006
Posts: 11
Default RE: 94 F250 5.8L, high idle and won't start problems

hi im new here today and i would like to help but this might be diffront from what you have going on.Ihad a 1988 ford ranger w/2.3 4 cyl and i had to eather it every time i started the thing after about 2 hours it would need it agien to start i drove it for about 1 year and alot of people looked at it and come to find out it was the brain in the truck and the only thing that gave it away was the smell of the gas if you start it in the garage the thing burned your eyes like pepper spray it was bad does yours smell bad?and mine did not run good on idol eather i bent the tab on the intake were the gas was to act like it was at a little foot speed inside and it ran good this was just my winter beater did not want to put the money into it so i hope this helps it might not this is not at all the same truck but same crap
Reply With Quote
Old 09-13-2006, 05:09 AM
Thread Starter
Join Date: Mar 2005
Posts: 3
Default RE: 94 F250 5.8L, high idle and won't start problems

Problem was resolved by replacing the TPS. Thanks anyway.
Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
RPM's go high low and high low when stoping at a signal surferjoegomango57 Ford F-150 2 12-11-2013 03:32 PM
Engine Noise and High Idle mrmancuso Ford F-250 & Ford F-350 1 06-13-2008 11:30 AM
2002 F250 V10 smooth idle to intermittant rough idle Olpapa Ford F-250 & Ford F-350 3 05-18-2008 04:22 PM
1996 Escort 1.9 eng:What sensors tell the motor to go to a "cold start" high idle? Ferd General Tech 2 01-15-2008 01:31 AM
94 F250 5.8L, high idle and won't start problems 6x6man General Tech 0 04-30-2006 04:10 AM

250, 58, aerostar, engine, escort, f250, ford, high, iac, idle, idles, moisture, motor, mustang, start, stop, wont

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Featured Sponsors
Vendor Directory

All times are GMT -5. The time now is 02:01 AM.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.