I need some help or advice on what is wrong with my '92 F-150 5.0. When I first start my truck it may or may not idle correctly when in Park. It surges up and down. I have replaced the throttle sensor less than six months ago. I even turned the idle up and this helped only for a little while and now it is back to not wanting to run. Once it warms up, which takes forever, the truck runs fine and idle fines. Now that it is getting colder it seems to be worse than in the summer months. I sure could use some good advice on what to do. I have a Chilton's and do most of my work because of cost, so I any help with be great.

 

Try the Idle Air Bypass. Mine is a Borg-Warner and cost like $60 from O'Reilly's.

 

I have a 1987 with 4.9 with about the same problem. Try this - Unplug the coolant temp sensor and it will probably not surge.... But it also won't fast idle until warm. Now - it sounds like your thermostat is stuck open (same as mine was) a little or a lot. Replaced mine with a 195 degree and now I'm cooked out of the cab within minutes... and warm up is real fast.

I still haven't figured out WHY mine surges - did you get that problem fixed and if so, how? I replaced the temp sensor with no change.

Good luck. If you (or anyone else) can figure it out please let me know.

 

Remove and clean the Idle Air Bypass and the ports in the throttle body as a start. When were the injectors last cleaned? Any codes? Last tune up? I have a 92 F150 w/302 also and had poor idle cleaning the IAC and the Injectors helped.


Gasman
Do you have Gas?
Propane Execeptional Energy

 

I had a problem where the idle would stay at like 1000-1300rpm. It was caused due to the coolant temp sender for the computer.

Clean that Idle Air Bypass before changing it. I did and my still didn't work as well as a new one.

Good luck

 

Well... There are several opinions on this common ford problem.
There is little to add which the above posters didn't already comment on. On thing to keep in mind is that many people believe that this problem is computer related. Several site offer to rebuild your computer which is guaranteed to cure the idle problem. My truck did this and it change about everything
1. I checked the IAC and trottle boddy for cleanliness. And replaced the IAC

2. Replaced the TPS sensor and verified that it was between .92 and .99 volts

3. checked for vacuum leaks.

4. Replaced the thermostat and temp sensor.

Still it was surging. I was planning on doing some performance changes (ie heads and about 350 horse which since has been done!). So I decided to purchase a mass air conversion kit. The minute I installed it the surge went away and has never come back.....

Is it the computer.. Could be. Just keep it in mind!

 

[updated:LAST EDITED ON 30-Oct-02 AT 10:53 AM (EST)]Also - you mentioned using a Chilton repair manual.... It would be a good idea if you're doing your own repairs to have a Haynes as well... Reason - Chilton sez about the Idle Air Bypass - "Not a repairable item - correction by replacement only" Haynes, on the other hand, goes into much detail on removal, disassembly, cleaning, and replacement of the same component..... Interestingly, my local Carquest guy sez that Haynes and Chilton have recently merged as can be seen in some of the new Chilton books front pages.... Should be an interesting situation for some of us already-confused shadetree wrenches! :-X23

 

[updated:LAST EDITED ON 31-Oct-02 AT 02:00 AM (EST)]Thanks. I will give it a look this weekend. I will try a Haynes book.
I will check out the Idle By-Pass Valve for cleanliness. My injectors have never been cleaned in the 8 years I have had it. I use injector cleaner in every second or third tank of gas. My wife does the same and we have never had any problems with either till my truck recently. So between cleaning both and lastly the temp sensor to the computer. I'll let everyone know how it turned out...

 

After reading a few responses, decided to invest in the air bypass valve - So far, so good. The truck wasn't real cold yesterday after installing it, but the idle was stable.... Today will be the real test -it's about 8 degrees F here. Thanks for all the inputs... Also found the plastic "y" in the vacuum lines from the air intake horns had a hole worn into it from vibrating against the plenum. May you stay out of the shops with what you learn on these pages. :-)

 

Also see # 8 - I wrote that before reading your latest entry.... I took that valve apart and it looked fine, so I don't know if you'll accomplish much by working on it - maybe.... I just figured at 80,000 a few critical parts probably need replacing anyway, so went for it... Hope you get it straightened out - these things are a real pain, and relying on the guyz with all the right tools and wrong brains is food for vengence when they hand you the bill and your truck still limps. Now I can go back to my lo-tech life of chopping wood...Something I can handle.

 

[updated:LAST EDITED ON 08-Nov-02 AT 01:20 AM (EST)]Well Folks, I have been slow about getting back with you on this, but have had some sickness in the house. I certainly do appreciate all of the replies with good information I have received. I want to thank everyone...

I did a possible NO NO...I put two bottles of injector cleaner into my gas tank and my truck ran fairly good, but someone sipphoned out half of my tank of gas on Halloween night so I had to fill up again. Halloween night pranksters I guess.

Anyway I have found that if I do not touch the gas pedal and let the truck start on its own and let the high idle run until it drops I get these results. On the first attempt, if the High Idle is around 850-900 rpms then more than half of the time it will die and I will have to restart. When I restart the second time and still not touching the gas pedal, this time it will usually high idle about 1200 RPMs, the truck idles fine. No stalling when load is applied. This is uncanny, because if the truck High idles at the 1200 rpm mark on the first start then the truck runs fine, no idle problem.

Now if someone could help me just a little more, but it could still be something else causing this cold idle condition. Any help would be appreciated.

 

i would have to say this is a common problem too. must have been a bad design on Fords part. my truck would idle irratically (i feared it would stop!) especially when it got cold out (MN cold). when i decided to rebuild the engine the first thing i noticed was no gasket between the throttle body and the upper intake (who, why,Profanity Removed!) also when i took the upper intake off and held it upside down oil just ran out of it, it still does even after my rebuild, just not as much. and my truck still......STILL doesnt idle right after the rebuild, better but not smooth. One thing that seemed to help on my 88 crown vic was to get some carb spray and, with the engine running, spray into the throttle body with the accelerator open. it might clean out some of the oily crap in the intake and the throttle body. it did help the stalling in my crown vic. my neighbors prob didnt like all the white smoke but i dont like the sound of lawnmowers at 8am either lol.