Ok so recently I just noticed my car is taking a noticeably longer time to start, to the point where my GF who doesn't usually pay attention to those things, said is your car going to start? Now before someone says it, no it's not because it's getting colder out, the engine turns over just as fast as normal. Also this only happened for a few days and then it went back to starting normal today.

Now randomly since I've owned the car it will get a weird rough idle and jump from 500-900 RPM or so trying to steady the idle. This happens sometimes when the car is sitting parked warm idling away, then out of the blue sounds cammed as hell and has a very jumpy idle for 20 seconds or so and then it smooths out all on it's own. I always just ignored it since it never really gave me problems, I could snap the gas and it would rev up and then kind of just smooth out. I wrote it off to a messed up IAC or something since our cars are known for that.

That being said, I think I was wrong. This weekend I was sitting idling an all of a sudden it starting doing the usual idle thing, but worse to the point where I thought it was going to stall. I tried snapping the gas and different throttle positions but got nothing, no response, the car just continued exactly as if I had the throttle plate closed and idling like all hell, the computer had full control. Again after about 30 seconds this time, revved up (I had my foot on the gas trying to get it to stop) like a bat outta hell... I let off, idle came down and all was well.

The car runs fine, pulls hard, no issues other then idle and this new starting issue. What can this be? It sounds like a faulty came sensor to me, or maybe crank, but what do you guys think? I just don't want to get stuck somewhere or have this happen in an intersection because this time I had no control and couldn't get the car to come off idle.

This is all on my 2000 GT by the way, minor mods, nothing crazy.

TIA

 

bump. No one?

 

Have you tried cleaning the IAC? I know it's a different car, but on my sisters boyfriends lancer it was doing the same thing and getting worse and hard to start. I cleaned the IAC for him and now it runs like new.
Just a suggestion.

 

My 1995 mustang gt has been built a little I just got it a few days ago and it won't idle it idles up and down and than it dies I put a new IAC and a new fuel pressure regulator on it and checked everything I know to check and can't figure out what the problem is.

 

Welcome to the forum Morgan. I don't personally know much about the 5.0 that is in your car. Id suggest asking your question in the 5.0 section. You'll probably get more responses there.

 

Tried that already; tt didn't change a thing. I cleaned the MAF a little while ago too but maybe I should try cleaning it again. I'm not sure if I cleaned it after I last oiled my air filter. It just doesn't make sense that it wouldn't respond at all to throttle. I know the MAF can do some funky things, but I don't think that's my problem but I guess it can't hurt to clean it.

 

Run compression and vacuum tests before you start changing parts make sure the engine is mechanically sound then look to fueling and spark.

Does it start any better with the throttle cracked a bit?

Neither the MAF or IAC are crucial to starting...

 

The issue is, the problem is intermittent. At this point in time, the car fires right up. But every so often it has this idle issue. Sometimes it's fine, other times it's not. So I don't think its anything to do with the engine mechanically (compression test) or could it be? The car was very well taken care of so I doubt there is any damage or carbon buildup in that respect.

You might be on the mark with a vacuum leak though. What kind of a vacuum leak could cause a hard start and the occasional rough idle?

 

We're kind of having the same issue on my buddies 2000 Mustang. It's a GT body, with a Saleen engine. I'm a Chevy guy, but told him I'd help him get it running. (He's one of my Sailors). Anyways, It was having a hard time starting, alt and battery went bad, so we replaced them, fire right up no problem, idled a little rough, but it ran. Then when you give it throttle, it wants to cut out and die. (I was thinking fuel filter at first).
Now, we can't even get it to restart. It turns over just fine. We took off the fuel rail and primed the pump... nothing, even tried starting nothing, no fuel. When you turn the key to on, to prime it, I can't hear it prime back near the tank, but for some reason, the "priming noise" comes from under the hood. Is that normal? (not big on these cars again). we were going to try to remove one of the fuel lines to the fuel pressure regulator to see if it's at least getting there, but these hoses dont want to come off, and I don't want to ruin them. There are no hose clamps, it's like there's an inner liner holding it on or something. Can anyone help? Much appreciated for any help and advice, we just got off of deployment and it sucks that he doesnt have a ride to go anywhere.

 

Have you found the problem yet? I would do a scan to see if any codes are popping up? At this point I'm leaning towards a bad fuel pump. Let me know?