94' Explorer Rough idle

[billycmonkey]

My truck has been idling really rough and missing when first start up. After driving it for about 5 minutes the idle smooths some but is still shaky and rough.. It seems this same problem occured last summer and replacing the spark plugs solved it. It just seems too soon to get new spark plugs again since i recently replaced them.. I have replaced air filter, fuel filter etc.. and problem still exists.. Any ideas?

 

[JDraper]

Moved to the proper forum. Please read the forum rules before posting. You posted in a forum that is meant for Technician tips only, not for having questions answered.


My bet on your problem would be the IAC (Idle Air Control valve). It controls how much air your truck gets at idle. If it goes bad or gets gummed up, it will produce a rough idle when cold, and it will improve as the truck warms up.

 

[billycmonkey]

I actually did replace that IAC and that didnt help.. Also cleaned the MAF sensor.. I'm thinking of just buying some new spark plugs since they're inexpensive and it worked last time.. Maybe something's wrong with my engine causing my plugs to go bad? I dont know.. Thank you for the suggestions!

 

[beauboy]

Your plugs are probably still good, but how's your wires? 1 bad sp wire will cause the exact same symptom.

 

[Maniak]

Another posibility is that you have low fuel pressure. The fuel pressure should stay up when you turn off the truck.

If it drops when you start the truck first thing in the morning the fuel may not be at the propper pressure for a few minutes. The easy way to test this is when you start the truck (when it would normally have issues) turn the key to the on position (not start), wait a few seconds, then turn it off, then on, then off then start it.

If priming it a few times works then you may have a bad check valve (letting the fuel pressure drop) or a leaky injector (letting the fuel pressure drop as the gas goes into the cylinder or on the engine.. depending on where its leaking).

A fuel pressure tester is the other way to test this, but not everyone has one that can read FI vehicle fuel pressure.

~Mark

 

[billycmonkey]

Yes, I did replace the spark plug wires also.. Still didnt help.

 

[rustbucketMI]

try running some injector cleaner thru this tank of gas. it may not solve the problem completely but it can't hurt

 

[walterd140]

Vacuum leak? Check your vac tree for lose / split hoses. With the truck idling, spray some ether on the lines 1 at a time. If it idles better, change that line.
Walter