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Discussion Starter #1
Hey all, I've constantly used this forum for advise but never actually posted questions, so go easy on me, this is my first time actually reaching out for some assistance.

My car has been idling rough and stalling out, it doesn't matter if I'm sitting at a red light, or if I push the clutch in to shift. I've checked the lines and I replaced the IAC earlier today. It needed to be done; I just recently purchased this mustang and the previous owner did a terrible job maintaining the car (it was a great price, I knew it needed work). I know the IAC is pretty faulty and a common issue for this engine; I was hoping it'd fix the issue but it didn't. It's cleaned up the stalling SOME but I'm still experiencing intermittent issues. It doesn't seem to matter whether or not I drive hard or light, or what the weather conditions are (Rain/Temp).

I was considering the PCV and the EGR, but before I just start putting more cash into various replacements, I was hoping for a little direction/advise. I'm going to order a replacement PCV anyway from: Ford Motorcraft Mustang PCV Valve EV98B (80-01 V8) - unless someone has a better suggestion.

2000 GT 5spd, convertible - 133,xxx miles

Thanks in advance!

- Salvatore
 

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Just wondering. Are there any mods? Is the battery in tip top shape?

Did you dis-connect the battery? If so, the PCM needs time to re-learn new idle trim values. Even if the battery wasn't disconnected there is now a new IAC valve that the PCM will need time to re-learn.

Regarding the PCV system. Repairs to the PCV value are maintenance items. So not really throwing $$'s away.

Have you cleaned the MAF? Use only a cleaner designed for the job.

Have you checked the spark plug wells for moisture? While you are at it, what about the condition of the spark plugs?

When not stalling out, how's the power? If the power is good and the part throttle operation of the motor is good, this isn't as likely to be an EGR problem. But it never hurts to review that everything is in good repair. Especially the vacuum lines to/from the DPFE sensor.

Do the RPM's "hunt" just before it stalls or does it just die outright? If it dies outright this is less likely to be IAC related. In fact the #1 item to consider is the battery and/or alternator.

Trouble shoot IAC idle problems 1996-2004:

http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649
 

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Discussion Starter #3
As far as mods go, not really. There is a K&N intake and an SLP exhaust. I'm thinking it was one of those show off cars that the owner didn't really do anything noteworthy to except make a mess.

I disconnected the battery for a half hour when I replaced the IAC.

I'm going to do the PCV anyway, it isn't expensive and I know it needs to be done, that was more in reference to the EGR for cost/unnecessary repair/replacement, as well as just replacing the O2 sensors.

As soon as I got the car I pulled the fluids, battery, alt, fan, exhaust, searched various hoses for leaks, checked the plugs and wires, swapped out one wire for a misfire - it looks like an improper coil on boot was put back into the engine as it wasn't sitting properly and wasn't the appropriate shape, probably a junkyard screw up from the previous owner. The plugs were all sealed up, no moisture, no codes read once the one was replaced, no jumping or symptoms of a misfire now.

The battery and alternator are both solid, I checked; I chased about 40 feet of wiring back out of the car from nonsense under dash lights, a sub, and some rigged wiring, then reran what was necessary to get everything cleaned up and working.

The car doesn't have any hesitation or issue with acceleration, it seems to only idle rough intermittent. It will drop and then increase to 1,500 or so, sometimes it evens out between 900 and 1,100 and sometimes it isn't enough and stalls. I do think there might be some sensor issues going on but I haven't had a chance to hunt them down. The MAF and intake are on my to do list for this weekend for a good cleaning. Is there a specific cleaner you'd recommend, or will a part specific autozone cleaner work?

The car runs and drives without any real issue, the gas mileage is appropriate and the power is where it should be for the engine. I did have the transmission dropped to replace the clutch bearing and fly wheel, but it shifts correctly and runs like it should, I'm not encountering any questionable sounds or vibrations from that.
 

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Any codes being thrown? Sounds like a vacuum leak to me...spray carb cleaner around vac hoses, intake/tb/plenum...if it surges when you spray carb cleaner there is a vac leak.
 

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Discussion Starter #6
Thanks B.Cooper!

Sorry for the delay, I've been super busy with classes the last week. I took the car out and drove it for a few days. It didn't originally toss up any codes, however yesterday afternoon the light came on. It's now reading two codes:

P0174 - System too lean; bank 2.
P0455 - EVAP system leak detected (gross leak/no flow).

The codes weren't originally running, I'm thinking a blockage somewhere? Thoughts/advice would be much appreciated!

/edit

I also got the replacement PCV to install tomorrow morning and I have cleaner for the intake filter and MAS.
 

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Sounds like to me that there's a big (as in huge) leak in the EVAP purge system. The first place I would look is the vacuum line between the Throttle body and the Vapor management value (VMV) located inside the right hand passenger's fender well. Gas vapors are very hard on rubber parts. If you touch the line and tons of black stuff comes off, then you know that the line is rotting from the inside out.

However the leak could be between the VMV and the charcoal canister. Likely the idle gets worse when the PCM calls for an EVAP purge cycle to run. Instead of drawing vapors from the charcoal canister, it's drawing outside air.

For the 1999-2004 Model year the charcoal canister is located behind the left hand wheel.

Due to the age of the car, I would also suggest checked the gas tank filler neck for rot. Either the grommet will rot or the filler neck itself will rust through. The usual symptom is a strong gas smell when re-fueling.
 

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Discussion Starter #8
Filler neck and line going to VMV are rotting - I've purchased the lines for replacement and that *should* be done within the end of the next week. I've also adjusted the car to idle a little higher and that's assisting the issue. We'll see if that's the issue. Sorry for the delay again - I'm in the police academy and it's been ridiculously heavy on my time.
 
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