samuraidad

05 Mustange 4.0, 80,000 miles

I am racking my brain over this. The plugs were changed, wires checked ok and snapped om plug, Throttle body cleaned. After this we get a rough idle and can hear a slight backfire or misfire in the exhaust. No codes. any thoughts or anyone have the same problem?

95SHO

Do you have the correct firing order?

zanypunk

Did you get a rough idle before doing the plugs? or is that the reason you did your plugs? What kind of spark plugs? Do you ever clean your MAF?

JimC

Clean the MAF and then double check your wires. It is very easy to mix up the wiring and get a rough running engine. The coil pack is 1-2-3 and then the other side is 5-6-4

samuraidad

The plugs are the same as factory plus and gapped per spects. We did check the wire order and thats fine. The MAF was cleaned. The car runs great at all speeds just at idle this happens. I am beginning to think a bad or plugged injector but not bad enough to thow a code. I have even checked for a air leak and that is ok. Yes it started after the plugs were changed. I do not believe in 100,000 on plugs. GRRRRRRRR do not want to take it in for a $100.00 diagonis.

Thanks for the thougts thus far

zanypunk

If it was the firing order it would throw a code :P
Thought so... It's intermittent? Ok. I have a question for you. After running the car for a while or whenever it's hot have you encounter like a high resistance whenever you crank and start the car?
If so it's fuel injection related problem.
I did a power balance test, compression test and the only thing I found was that my cyl 4 spark plug wasn't tighten to spec because I usually do mine ever 10k since I have the copper type since I'm running a SC.
I usually use my 3/8 cordless impact but I just happen to miss that one but it was just hand tighten. :P

I had a vacuum leak as well but is was so small that whenever I would set it from Drive to Park, it would stall, but it would run great except whenever I would have the hood open, engine idling It would run like it was missing but with no codes. The wind help on my diagnostics. :P

Since you're describing the problem after doing the plugs, I would check the plugs and test the wires again and compare them to spec. Keep in mind the wires on the ignition coil will come lose sometimes, making a barely contact or shorting, I would check that too.

I would recheck for vacuum as well. Spray some propane or brake-fluid cleaner that's an easier way to do it.

samuraidad

The only thing that bugs me is under load its fine, good milage, no miss or skip. I am personally going to do the recheck A-Z. I am sure it will be something very simple. Thanks

zanypunk

The simplest things make it impossible to figure out. :P

SYNY5TER

usually if u disconnect the battery and plug it bak on u will get the rough idle. this happened to me a lot. just drive around with for about 500 miles should be gone. if its not gone by then. then ur bak to ur big problem.

TangStang25

Did you ever figure out the cause of the problem? I recently did a tune up and now have the same problem I've cleaned maf sensor TB checked the plugs and wires checked for leaks only leak I found is a small coolant leak but don't think that would cause this sputtering popping while idling please help!