Idle Problems???
 

I am having some weird problems with my 96 Cobra. This morning when I went to start it up, it was very hard starting, taking twice as long cranking before it kicked over. Then when it was running it was idling extremly rough, sounded like it was way to rich, but I dont know for certain. I proceded to give it some gas for a while and that seemed to smooth it out a bit. Then I pulled out of the driveway and went maybe 3 miles when I stopped it almost died, dropping to under 500 rpm's before it caught itself. After it was fully warmed up the idle smoothed out, but it was still hard starting intermitently. Also dont know if this is related or not but I noticed when I shut the car off, I hear a hissing, like a vacuum leak, dont know if it has always been there and I am just now noticing it or not. My car almost has 30,000 miles on it, and I recently replaced the sparkplugs, wires, and both fuel, and air filter. If anyone has any idea on what I should check it would be most appreciated, thanks in advance...

You didnt say if you added any mods recently or not. Just adding a K&N airfilter will cause really bad cold engine bogs, and sometimes sporadic rough idles when cold. Easy fix to that problem, but I'm not going to go into it unless you added something.

As for you hissing sound, all the 4.6 Stangs I've heard, make a simialr sound, I havent figured out yet what it is, but I havent looked to closely or hard, Alls I know is that it comes from the intake area.

Hmmmmm.....check for a vacumm leak first. Sounds to me like your problems are related to one another. Sorry, I know that sounds like lame advice, I just got home from a 12 hour day at the office and my brains fried. http://www.mustangworks.com/msgboard/biggrin.gif


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64 1/2 "D" code Red Mustang Coupe. 289, C4, 3:1 rear gear. Mallory duel point. Ported & Polished 65 heads shaved .01 with 351 windsor valves, high side of 10.5:1 comp, 1.7:1 sled rockers, blue wolverine lumpy cam, autolite 4100 Hipo 4 barrel. And to many others to list

2000 Perf Red Mustang GT. 5spd. BBK Underdrive pulleys, Flotech off-road H pipe. Hurst T-Handle

64 1/2 red 6cyl coupe. Auto. project car.

[This message has been edited by Mercury (edited 05-01-2001).]

You didnt say if you added any mods recently or not. Just adding a K&N airfilter will cause really bad cold engine bogs, and sometimes sporadic rough idles when cold. Easy fix to that problem, but I'm not going to go into it unless you added something.

As for you hissing sound, all the 4.6 Stangs I've heard, make a simialr sound, I havent figured out yet what it is, but I havent looked to closely or hard, Alls I know is that it comes from the intake area.

Hmmmmm.....check for a vacumm leak first. Sounds to me like your problems may be related to one another. Sorry, I know that sounds like lame advice, I just got home from a 12 hour day at the office and my brains fried. http://www.mustangworks.com/msgboard/biggrin.gif


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64 1/2 "D" code Red Mustang Coupe. 289, C4, 3:1 rear gear. Mallory duel point. Ported & Polished 65 heads shaved .01 with 351 windsor valves, high side of 10.5:1 comp, 1.7:1 sled rockers, blue wolverine lumpy cam, autolite 4100 Hipo 4 barrel. And to many others to list

2000 Perf Red Mustang GT. 5spd. BBK Underdrive pulleys, Flotech off-road H pipe. Hurst T-Handle

64 1/2 red 6cyl coupe. Auto. project car.

No recent mods, havent even popped the hood in like a month...

Hey Mercury,
What fix do you have for rough idle? And why does adding a K&N make the idle rough?

KingSnake.

I wouldnt believe it if someone told me it, I would think they were just Bull Sh!ttn but when people put K&Ns on there new stangs they get a rough idle and real bad cold engine bogs.

The only thing I can think of, is that the K&N ACTUALLY flows that much better than the stock filter, that the computer doesnt know what to do. Several people have come up to me and TimC and the hangout and asked us wthat the problem is, we tell them to disconnect the battery for 5 minutes, or pull fuse 21, then after 5 minues connect them and drive the car like you stole it for about 15-20 minutes. No half throttle, either full wide open, or deaccerlerating.

Guess What....No more bog. http://www.mustangworks.com/msgboard/biggrin.gif

Same thing when a cold-air or throttle body is put on.

I noticed a decrease in idle quality when I installed my cold air. I disconnected the battery but did not drive it like I stole it. After you do what you recommend, does the idle stay smooth or does this have to be done again after a little while?

King Snake

They should idle smooth, it shouldnt need to be done again. That is unless its another problem causing the rough idle.

My idle problem has gone away, seems to have fixed its self. I love it when that happens. Thanks for the input anyways guys...