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Rough start

Tiny
JASONMICHEL
  • MEMBER
  • FORD F-150
I have a 1992 F-150 4x4 with 5.8L, when starting up when cold, it won't stay running unless I step on accelerator immediately after starting and pump it a few times to keep it running, even then, after that and it sits at idle its very rough running until warm. Any ideas? Or does this sound like simple tune up, and if that is the case what do you recommend changing during tune up?
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Sunday, November 11th, 2007 AT 11:02 AM

13 Replies

Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
If yours has a MAF sensor clean it with qd cleaner. May be making engine run lean.

Check coolant temp sensor and sending unit.
Can be making engine run lean also, causing it not to have enough fuel to stay running when cold.
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Sunday, November 11th, 2007 AT 11:50 AM
Tiny
FORDFAN
  • MEMBER
  • 9 POSTS
Check your spark plugs. Does it almost miss when you are driving it from a stop to 60mph? If it misses some I would definetly check your plugs. If not your MAF sensor or O2 sensors on the exhaust might be bad.
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Sunday, November 11th, 2007 AT 2:36 PM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
Well the check engine light is on but haven't got the code, and yes it runs and kinda misses at low speeds
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Sunday, November 11th, 2007 AT 3:06 PM
Tiny
FORDFAN
  • MEMBER
  • 9 POSTS
So I would pull the last 2 spark plugs and see if they are black, if so then pull them all and replace them. My buddies truck did the same thing and we pulled the last 2 plugs and they were jet black. We replaced and the sucker runs smoooooooooooooth
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Sunday, November 11th, 2007 AT 4:08 PM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
Pulled plugs and they were all white, and a couple were gapped wrong, still runs rough as hell at idle, seems to run a little smoother under power though. I found that the idle air control motor was unplugged, I plug it in and it idles smooth, but at about 1500rpm and won't come down, unplug it, idle comes down but rough and check engine light comes on. Any ideas?
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Friday, November 16th, 2007 AT 8:28 PM
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Good good, can you take a picture of your IAC if you can post it here and I can tell you if you can clean it or if yours is not the cleanable type model.

The cleanable one is striaght with a plug at the end, the uncleanable one is like the straight one only the plug at the end comes out at a 90 degree angle.
Hope this helps
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Saturday, November 17th, 2007 AT 9:45 AM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
It's the 90 degree one, but why can't it be cleaned?
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Saturday, November 17th, 2007 AT 1:09 PM
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Certain ones have the removable inside parts, but the one you have I belive may have parts pressed in, and it may not be able to be put back together properly.
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Saturday, November 17th, 2007 AT 10:10 PM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
You are correct, but I took it off anyways and cleaned what parts I could see with throttle body cleaner. The mounting surface to the intake and the throttle body itself. The IAC looks almost new. I changed plugs, wires, cap and rotor, cleaned airbox and new filter. Still runs rough at idle, idles about 1k-1.2k surging like, kinda runs rough under power in low rpms and at stand still in gear. Is there anything else I can try, this is driving me batty
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Saturday, November 17th, 2007 AT 10:14 PM
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Well I still would like you to replace it, never would hurt, they can be tested at autovalue.

Scan for trouble codes while your there also.

Only other thing I can think of is MAF and coolant temp sensor, but im almost certian it is the IAC
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Saturday, November 17th, 2007 AT 11:00 PM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
You think autozone can test it? Don't have an autovalue around here. And can they test it still on the trucK?
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Saturday, November 17th, 2007 AT 11:56 PM
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
If you can get the truck there then yes, they should be able to test it seing they are a auto parts store!
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Sunday, November 18th, 2007 AT 9:22 AM
Tiny
JASONMICHEL
  • MEMBER
  • 15 POSTS
Is it possible the PCM is bad? Or the wrong one? The orginal engine was a 302, it now has a 351. How can I tell.I took it to a repair shop and the PCM wouldn't power up their scanner
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Tuesday, November 20th, 2007 AT 10:55 AM

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