Fuel Problem??

[Mach]

Ok I am having a problem with my cars start up and idle. The car will turn over just fine but then the rpm's drop substantially and then will finally equalize. It also requires a good 5-10 mins to warm up, if I drive right away after it sitting all not it will lug extremely bad from about 1k-3k rpms. Sometimes even got a bit of a pop or back fire.

As well as when I am driving when I push in the clutch the rpms drop to roughly 400-500 and acts like it almost wants to stall. Then sitting at a light the rpms after will bounce around by about 500-650. My idle is set at 750-810 I believe.

Its going into the shop next Friday but was wondering if anyone had any ideas?

Also, just starting yesterday the fuel gauge and digital read out of the miles til empty was way off. It would start out reading a fuel take and then drop over the next 10-15 to be where it should be at (about 3/4 of a tank right now).


Any ideas?

[Rev'n Kevin]

When I read the first part of your post, I thought about the 02 sensors, but the last part of your post sounds to me like 1: Could be a weak battery or 2: You may have to go in and have the computer reprogrammed. I had a very similar problem with my Hemi Commander, they reprogramed the computer and all was well again. Sometimes those doggone things just go haywire and the gremlins cause all kinds of weird little problems.

[IMSHAKN]

Originally I answered this as if you had a Mach 1...oops.

I'd check your IAC and your EGR. Not sure how problematic the TPS or PCV are on the newer mustangs but they may be worthy of checking as well.

[Mach]

When I read the first part of your post, I thought about the 02 sensors, but the last part of your post sounds to me like 1: Could be a weak battery or 2: You may have to go in and have the computer reprogrammed. I had a very similar problem with my Hemi Commander, they reprogramed the computer and all was well again. Sometimes those doggone things just go haywire and the gremlins cause all kinds of weird little problems.

It has a brand new batter. The oddball idling started right after changing the battery when the previous one died.

[99WhiteGT]

It has a brand new batter. The oddball idling started right after changing the battery when the previous one died.

in that case id take it to where you got it and have them check it, couldve just got a bad battery...has happened to me before

[Rick Shopmier]

Sounds like your engine is fuel starved, check and replace your fuel filter if you have not recently. Also your fuel pump could be going bad, not building enough fuel pressure and with the false readings you are getting on the guage/mpg comes from the fuel pump flow and fuel level sensor. If you are not getting any trouble lights then your problems is mechanical (nee fuel pump) and may not show up on a OBD check which is recommended. I would check with the guys at Stage3, they are knowledgable on this and could make the proper fix.

[Rick Shopmier]

Just as a follow-on, I did not mention that the fuel pump is electric and located in the left side tank (I think). You could have another problem and this is just a possible solution to add to the others.

[fazm]

check the alternator?

[MOTANGT]

Out of curiosity have you pulled your pump out and make sure nobody put anything in your tank.