Check engine light / rough idle

[davem]

Next time unbolt the transmission tube so that you can move it out of your way to get to #2 spark plug.





That is good that the CEL hasn't come back on yet, it could be anything that you have done to get rid of it. Let us know if it comes back.

Well, its back.

I went to run an errand over lunch. Its 31 F outside. Started engine and immediately went into the rough idle. After about 0.5 mile of driving the CEL came on. I'll get the codes scanned tonight, but assume its the same P0306.
After warmed up, it idles fine.

Not sure where to begin:

- try new wires ?
- try new IAC ? could not read ohms from IAC body, so may be bad or I need better instructions
- take coil measurements - could use some pictures
- other ?

 

[Firestorm]

Well, its back.

I went to run an errand over lunch. Its 31 F outside. Started engine and immediately went into the rough idle. After about 0.5 mile of driving the CEL came on. I'll get the codes scanned tonight, but assume its the same P0306.
After warmed up, it idles fine.

Not sure where to begin:

- try new wires ?
- try new IAC ? could not read ohms from IAC body, so may be bad or I need better instructions
- take coil measurements - could use some pictures
- other ?

It would be best to check and see what codes you are getting first. Honestly, I haven't had to check my IAC yet, but I would assume that you were checking it in the correct area. If you were touching either terminal, and touching the other probe to the IAC's body and you didn't have any resistance the circuitry is being grounded by the IAC. You should replace it. I would try to solve the misfire first.

We've kinda ruled out plugs, wires, coil, vaccuum. The MAF was cleaned. I cleaned the IAC (maybe the IAC went bad ? can it be tested ? hate to spend $100+ to 'try' a new IAC.)

How did you guys ever rule out that it was not the plugs, or wires? It wouldn't do any harm to your vehicle if you were to just replace them. They do go bad.

 

[Buffalosports]

You said it has a rough idle. Could it be more than one thing? Came accross this a few minutes ago. Could be your problem. Possibly it is not opening or closing corrently until the engine warms up. Probably would not have anything to do with the code though.

http://www.autozone.com/N,15900207//shopping/partTypeResultSet.htm

As posted before, Don't rule out that distributor coil.

http://www.autozone.com/N,16200030//shopping/partTypeResultSet.htm

 

[davem]

It would be best to check and see what codes you are getting first.


How did you guys ever rule out that it was not the plugs, or wires? It wouldn't do any harm to your vehicle if you were to just replace them. They do go bad.

I had the code read - its the P0306 again.

As I reported earlier, 2 yrs ago when resolving another P0306, which turned out to be a fuel pulse dampener problem, we tried a new plug and a different (though not NEW) wire on cyl 6. (Did not resolve the problem.) I suppose the plug/wire could have gotten bad in those 2 yrs/25K miles. During that repair attempt, the local Ford dealer charged by $450 while trying stuff, including cleaning the injectors. A local indy charged me $150 to give it a try. Then finally a 2nd indy figured it out. So I'm a little gun shy.

Part of me struggles with understanding how a wire/plug problem is resolved by warming up. Butwhat was the point of me measuring the wire's ohms - it was something like 5500. Are we saying it could STILL be a bad wire ?

 

[Firestorm]

I had the code read - its the P0306 again.

As I reported earlier, 2 yrs ago when resolving another P0306, which turned out to be a fuel pulse dampener problem, we tried a new plug and a different (though not NEW) wire on cyl 6. (Did not resolve the problem.) I suppose the plug/wire could have gotten bad in those 2 yrs/25K miles. During that repair attempt, the local Ford dealer charged by $450 while trying stuff, including cleaning the injectors. A local indy charged me $150 to give it a try. Then finally a 2nd indy figured it out. So I'm a little gun shy.

Part of me struggles with understanding how a wire/plug problem is resolved by warming up. Butwhat was the point of me measuring the wire's ohms - it was something like 5500. Are we saying it could STILL be a bad wire ?

I've exhausted what little I know about the problem, Davem. The reason we were having you check the resistance of the wire was to see if it was bad. There are so many possibilities that could be causing a misfire.
If all else fails try another fuel pulse dampener, albeit I do not know what that is.

Measure the resistance from either terminal to the IAC body. There shold be 10,000 ohms or greater. If less, the internal circuitry is grounding against the case.

The IAC would cause a rough idle, it is in use primarilly until the vehicle warms up. It allows air to bypass the throttle plate to regulate the engine's idle speed.

So if...

The IAC ohms reading from terminal to IAC body was non-existent, so I guess that good - its not grounding to the case.

It seems to me that the IAC may be bad. Also, as stated before, this could be due to an intake manifold leak. I cannot recall how many miles your vehicle had on it, and it doesn't necessarily mean that the gaskets aren't bad even after testing. The easiest, and only good way is to get a set of gaskets and replace them, even if you aren't receiving any lean codes.

Although I don't think that it would, this may get rid of your P0306 code as well, maybe unmetered air is just getting past the gasket in the rear-driverside of the motor.

At any rate I wish you luck.

-Nathan.

 

[davem]

At any rate I wish you luck.

-Nathan.

I appreciate all your suggestions. I might bite the bullet and try a set of plugs and wires.

Guess my next step would be the intake gasket. I know I have a gasket leak because my dash vents revert to the defrost vents under load, which I believe is related to a vaccum leak, too. We're never been able to find that leak, despite among other tests/inspections, some test where they spray some fluid (carb cleaner ?) around the intake gasket to see if the engine speeds up - it did not (hope I'd described the test correctly). I would love for the intake gasket to fix the misfire, dash/defrost vent issue, and the rough idle - maybe hoping for too much.

If/when I figure this out, I'll post the results.

 

[Firestorm]

Not at all, bud. Mostly I believe they check the intake manifold gaskets with propane, but carbuerator cleaner works just as good, the idle should speed up when it is sprayed.

On mine, this did not work, however I was getting P0171 and P0174.

I wouldn't really worry about the plugs, unless you want to take them out and check the gaps? Also, what kind of plugs are in it? You should run Autolite, or Motorcraft. Seemingly, these are the best types of plugs for our Fords. These fine gentlemen on the board also believe this.

I don't have any information or suggestions about the vent problem, sorry that I can't help.

-Nathan.

 

[davem]

After much doubt, I finally replaced the IAC valve. I bought it from NAPA for about $120. Installed it and reset the CEL.

Its been about a week:
- no bad idle
- no CEL

So I think its fixed.

Thanks to everyone for their suggestions. Saved me a bunch of time and money trying other potential solutions.

 

[jaypenczar]

problem like Phoenix's and Davem's

Hi gentle men,

My problem is like that of Phoenix's and similar to Davem's.

ROUGH idle but only when warm. First I had codes P0171 and P0174 but after changing the air and fuel filters I received code P0300 (random cylinder misfiring)... I have a moderate fuel problem going on and I appreciate the trail all of you have left me.

Check the 'coil pack', wires & plugs, IAC and intake gaskets. Anything else as I'm a first timer with my beloved 2001 Sport Trac (stock)?

Jay

 

[jaypenczar]

It seems to me a distributor problem or maybe even bad wire(s)? I can replace the IAC but do I have to first?

 

[kwoosley03]

Rough idle problem

I have a problem with a 03 Sport trac with a rought idle, and at 60 the cel starts blinking, i have had it run through the computer once and the mechanic changed a hose because there was running lean causeing the problem, i believe i am still having the same problem, i was wondering if anyone had a link to a diagram to the 03 sport trac engine so i can tell which hose it is cause i fount another bad hose.

 

[ThePhoenix]

MINE TURNED OUT TO BE OLD SPARK PLUGS AND WIRES AND A CLOGGED FUEL FILTER..oops, sorry for caps

I had ot look back at what I said a year and a half ago

 

[spinfisher]

Just had my code read today , CEL with a po136. This has been going on since I returned from an 8 hr. trip to orgeon in june. I'v cleaned the K&N filter, iac, replaced the fuel pump theres another sensor in front of the throttle body that I also cleaned. My ex has just under 105k, so is it time to replace o2 sensor. Thanks, this sites helps alot of us out!