Join Date: Dec 2009
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Bronco 351 Cold Start Problems
My 1992 Bronco is getting to be real difficult to start when it's cold out. I've got 207,000 miles on the truck and am hoping to avoid a trip to the mechanic.
When it's warm out the truck will generally start after a couple of cranks on the starter. It'll run a smidge rough for about a minute or so and then even out.
When it's cold out I have to crank the starter 4-5 times for the engine to catch. When it does catch, generally it revs up to 1500-1800 or so then falls back down to about 400 and stumbles for about 1-2 seconds and then dies. The next time I crank it, it'll do the same thing, except that after it falls to 400 it'll rev back up to 1500-1800 again, then fall back down and die. Usually the 3rd time I try and it catches it'll rev up to 1500-1800, fall back down to about 500, then move back up to 1200 or so where it'll sit until it's properly warmed up and which point the idle will settle down to about 700 or so.
Once it's started the truck drives great. Steady idle, good power. I'd say I have a problem with the "choke" except I'm not sure how this works on an EFI motor. I did some preliminary research and replaced the IAC hoping that'd do it, but no change. No codes on the computer.
How do I troubleshoot this one?