HELP! My car isn't making any power, poor idle.

[BlackBadGT]

I was on my way to class this morning, and I had to turn around and come home. My car isn't making any power, and it idles like it's got a set of cams. BIG cams. It even stalled out a few times. I managed to coast (yes, coast) to Autozone and get the codes read, all it said was a P0401.... ERG valve. That's just because of the LT's and it's been like that since july, so that isn't the problem. What could cause it to run like this? Spark plugs? I have about 47K on the stock plugs...I know i need to change those.
Any other ideas?

-Jason

 

[99SilverGT]

IAC Valve...................

POS goes bad on ALL mustangs and takes your idle with it when it goes.
Does it idle at or below 500 RPMs and does it dip down that low when you put the clutch in? Die if you brake hard or turn the AC knob quickly? Its the part attached to the front of the plenum.

 

[BlackBadGT]

I've had the IAC replaced once, under warranty. That would explain the poor idle, but what about the lack of power?

 

[mrvax]

I've had the IAC replaced once, under warranty. That would explain the poor idle, but what about the lack of power?

I thought my car seemed to be a bit slower out of the hole but chaulked it up to getting used to it. Then my IAC went, I replaced it and it made a big difference in low end grunt!

It's the most likely culprit, then your gas filter.

 

[99SilverGT]

I've had the IAC replaced once, under warranty. That would explain the poor idle, but what about the lack of power?

It can make it feel really hesitant to want to go. Almost like the car isn't getting gas. At least it did with mine. I had to rev it up pretty good to get it moving.

 

[Sam98]

I thought my car seemed to be a bit slower out of the hole but chaulked it up to getting used to it. Then my IAC went, I replaced it and it made a big difference in low end grunt!

It's the most likely culprit, then your gas filter.

That or a clogged injector or maybe a bad coil...

 

[BlackBadGT]

Car isn't slow out of the hole... The damn thing barely moves. Even once i get up to speed, i can feel it jerking, like it wants to die, but the momentum of the car is keeping the engine turning. Never really experenced miss-fires.. suppose it could be doing that, but the PCM isn't reporting a miss.

 

[Jason2000GT]

I am having some of the same problems with my 00GT. I changed the plugs to Autolite 764s last monday and it has ran like crap since last wednesday night. This morning it was pretty cold out, 38-40 degrees and the car ran like crap this morning on the way to work. It had really bad hesitation and felt like the car was misfiring. I am thinking about putting all my stock plugs back in to see what the does. If that doesn't fix it, I will need to check my coil-on-plug packs.....

 

[BlackBadGT]

Well.... I changed my plugs and put in a set of NGK TR6's that I had lying around. (I was going to spray earlier this summer) And they seem to have smoothed ot the idle issue. Still having some problems with misfire/hesitation tho. It's running pig rich when it does it. I am starting to think it's just too damn cold and the comp is freaking out, because it seems to have worked itself out on my way home from work.

 

[JonJon]

My car kinda does that when I first start it... stumbles and hesitates when I give it gas. 10 minutes later though, it's fine.
Cold as crap here in MA.