[menedu]

I have a few problems with my newly acquired '99 Gt. I would like your feedback on how to approach them in a methodicaly manner. I do not have a MIL and the MIL turns on when engine starts and then shuts off a few seconds later. The following are the conditions:

1. The engine when revved takes a long time to return to idle, meaning when revving in neutral or in between shifts the revs suspend themself high at the point you left off the throttle and then slowly come down. It also does this when slowing down in gear.

2. When driving, if I depress the throttle hard , especially when it gets close to 3k RPM, the engine starts to sputter/miss. I've changed plugs and air filter and condition persists. once you get this condition, the only way to restore the engine performance is to shut down wait a few seconds and then restart it, then it will behave normally until the engine load gets higher and condition returns. I did get a MIL one time when it was sputtering in the HWY and I could not afford to turn off the car until I pulled over, but it cleared after like 3 or 4 driving cycles.

What is wrong? Are this two conditions related? Which problem do I deal with first.

Any help from a Ford Tech('s) would be greatly appreciated!!



Regards,
-Ed

[Casper98GT]

4.6 Gt motors have problems with the rev's floating on these cars. I bought a gasket on ebay for this. You can make youre own. The holes in the gaket are diff. size than the FORD gasket for the IAC. So it lets them drop much faster during shifts and rev's.

The miss/stumble problem... i cant help online. If i had the car i could tell you for sure. But you have 8 seperate coil packs for youre motor. So you would need to perform a powerbalance on youre motor to see if a coil pack is missing every so often. You may be getting a ranodom misfire from a coil pack.

Hope it helps.

Matty

[menedu]

I guess I will have to go to the dealer for service, Man that is going to be expensive!


Regards,
-Ed

[Casper98GT]

Shouldnt be.... usually 1 hr of diag time for a check engine light.

Just let us know what it is before you have them fix anything. Im a ford tech. So let me know

[menedu]

I'll post diagnostic results prior to repair. Thanks for your time!


Regards,
-Ed

[menedu]

Well, this evening I replaced all 8 coilpacks with brand new ones. I put new plugs and air filter last week. Problem is still there . Stumbling/missing when pushed hard over 3K Rpm.

I have a better description of the symtoms: Car performs well when cold all the way up on the Rpm range, but once warm the stumble/miss is encountered when pushed over 3Krpm. Once the condition is set in the only way to return to normal is shutting it off for a few seconds and restart.

Today I also left the car idling for a while and got the stumble/miss problem. The strange thing is that while the condition was apparent it seemed a very rough idle, like 2 or more cylinders were out . Eventually the car stalled. I let it sit for 30 sec or so fired her up and problem is gone!

I guess I'l have to bite the bullet and go to the dealer, If I only had one of those diagnostic computers the dealer has...

Any suggestions?


Regards,
-Ed

[Casper98GT]

Hmmm. only thing that really comes to mind right now is maybe an 02 sensor. But without a CEL its hard to say without guessing.

And with 8 new plugs and coil packs... rules out ignition. lol. And if it happens after its warm. Like i said maybe 02.

good luck brother

[menedu]

Today the car ran good for a longer period even after warm up but the stumbling/miss returned almost as I reached work and it shifted to @ 3,5K rpm's instead of 3K. Obviously we are heading in the right direction even though the problem is not resolved.

I know that the previous owner (female) did not take care of maintenance with this car. The car has only 55K miles but it has been neglected.

Further inspection revealed a colision in the rear passanger bumper. This explains the inconsistent fuel gauge reading. Could the Fuel pump have suffered any damage because of this? Could it be related to my symptoms?


Regards,
-Ed

[ChrisJ]

It very well could be fuel related...

[Casper98GT]

Could very well have, but why would it act up when warm? I actually had a Ford windstar.... customer says it doesnt run right? Ok...checked codes found 02 code. replaced. test drove after letting the 02 warm up in my bay. The thing wouldnt go over a certain rpm or mile per hour. pulled over and brought it back... if i let it sit in my bay over night i could cold start and it would be find. Ended up checking fuel pressure and it had all of 20 psi. Checked fuel filter and was ok, so i installed a new fuel pump and was ok. Im not saying this is youre problem.

Check fuel pressure..

[menedu]

Will do!


Regards,

-Ed

[lemon]

engine is good cold start. engine misses/sputters when warm. another, but less likely ( because some p011x codes should have been thrown, or maybe a manufacturer specific code), the mass air flow sensor. just a thought - not a tech like a good chunk of the members are

[menedu]

Thanks Lemon, I'll check that as well! Your input is very much welcome!!!


Regards
-Ed

[tarik916]

Does the car have any fuel system mods? I have not had the rev problem with this car, but my '95 GT revved high between shifts and stayed at about 2k for about 3 seconds after I stopped at a light or put it in neutral. This was because the car was running very rich.
Good luck!

[menedu]

Well, I have not been able to check the fuel pressure due to my rear end quitting on me. It seems that the drivers side carrier bearing decided to break. When I took the cover off it was pretty evident since there were neddle bearings loose in the carrier. I took it to my buddy's shop. He disassembled the axles, LSD, ring & pinion and discovered that this might have not been the first time this car had this problem because the seat for the bearing appeared to be ground by the axle, therefore the seat would not accomodate the new bearing perpendicular to the axle. It was more or less tilted creating major stress on the race from the ackward angle.

I have to decide if I take the housing and try to weld a build up and then grind a new seat or find a new to me axle. I guess finding a gt axle assy might be more costly but if I could find an affordable one I might just replace the thing and be done with it.


Regards,
-Ed

[menedu]

Update:

Well I got my rear end problem squared away. Bought a used 04 rear with 34K miles. Swapped them and Done!


On another note:

I finally got a fuel pressure gauge, the one by Jegs that installs under the pressure sensor on the drivers fuel rail. I Imediatelly noticed that the fuel pressure was oscillating between 27 and 30 PSI while idling. Is this normal?

When reved, the pressure does climb.

Today, I got the infamous miss/stumble. I pulled over and checked the guage, the pressure was at ZERO . Of course the car was idleling like sh@##$.

Any Ideas wether it could be the pump or the pump drive/amplifier? How do I test them.



Regards,
-Ed

[purplepony96]

im haveing the same problem with my 96 gt


but you see i just pushed it harder and it stoped

for some reason my seams to fix it self

[mayday]

My 01 GT has been doing the samething except mine is from 1000 to 1500 RPMs, and seems to fix itself when I push it harder. I too have replaced the coil on packs and spark plugs. I have noticed on the programmer I have that when it sputters the timing is falling off. My car normally is 16 to 18 degrees advanced and when it misses, it falls to 3 degrees. When you find the answer please let me know.

[232stang]

my car had the same problem and i changed the oil (3000 miles overdue.... i read on the sticker change at 73000 i thought it meant it was changed at 73000 lol...) but i did that and fixed my exhaust problem and my 02 sensor was out but now its fine.. maybe its got some old gummy oil in there? doubt it but who knows. also clean the maf and iac

[menedu]

Update:

Took a chance and changed the fuel pump assy. for a new one, Problem is gone!!!!

Now the car runs like silk, Smooth!!!!!

With the old pup the pressure oscillated from 27 to 32 PSI at idle, with the new pump it oscillates from 29-30PSI. Also when revved the gauge indicated a max of 45 PSI with the old pump, now it reads almost 60psi.

This is great news!!! My car has around 62K miles, I never suspected a bad pump, but there it is.

Casper, Thank you for your input, I would have been running around wasting money, chasing this isssue.


Regards,
-Ed