mxracer1618

haha i didnt think the intake was the issue but wanted to throw it out there anyway. im going to def clean the maf sensor and if that doesnt work i will buy a new one. just still trying to figure out why my car runs good when it is cold, but starts runnin like crap when it warms up

Deannostang

When your engine is cold, your computer is in start-up mode where the only regulation being done is basically fuel/air where much of the sensors are off. Once your car is up to heat, the O2 sensors among others are activated. It is much the same thing as when a carburetored engine has its choke on when cold. If anything, you are probably running rich when your engine is cold to prevent stalling such as can occur in the winter months. You may have a very lean situation when the engine heats up. Some sort of electronic tuning may be necessary to alleviate the problem.

I have a similar problem where I can't go much above 1/2 throttle when the engine is up to temperature without my car bogging down and the exhaust making a fluttering noise. If I gently ease off the accelerator, the problem stops. No way right now to go WOT......real bummer! It is possible the computers in this era Mustang (I have a '98 GT vert) can not properly compensate fuel/air mixture on its own when many mods have been made to the intake system. Again, an electronic tune may be required to properly dial in the engine to fully accept its new mods. I think we should all send e-mails to places like SuperChip, Diablo Sport, etc. that supply the aftermarket tuning systems and see if they have anything to say on the subject. I wouldn't doubt for a minute that they may say much the same thing about proper dial in of the computer with extensive intake modifications. Just my feeling.

Now, if your car is exhibiting the exact same traits with a bone stock set-up, I guess much of what I have said could be thrown right out the window. In that case, I vote for some sort of sensor going haywire. There is a "throttle position" sensor on the engine that may possibly effect the running of our engines. I would think it would be located somewhere around the throttle body. Another possible cause......stuffed cats. If you do not have any cats at all and your Mustang is still acting funny, so much for that theory. I do know O2 sensors can cause a whole host of problems if one or more of them are malfunctioning. But, my car still sucks (or should I say "pushes") and I have 4 new O2 sensors, a new MAF, new throttle body, new IAC, new plugs, new fuel filter and two new coils! WTF are we supposed to do if there are never any codes being emitted from our computers? Sounds to me to be a way too common occurance for there not to be some sort of common denominator here. The aftermarket tuning mfg's may be one of our only good sources for additional info on this subject.

I hope more people chime in on this thread with additional input. I think we all could use some new opinions on this annoying subject. Thanks to anyone who can offer additional help.

mxracer1618

good information, your problem sounds much like mine. i really hope that someone with a 96-98 stang has had the problem and found out the solution and can help us out. im going to clean my maf sensors tomorrow but if that doesnt help i dont know where to go from there. dont have the money to take it to a shop and have them do a bunch of **** that doesnt work because they have to guess at what it could be

04BlueGT

I'm not in any way, shape, or form, an expert.

You said it starts out fine when cold, then starts acting up. Seems temp may be an issue. What about the IAT sensor? Could that be the problem? My car has the integrated MAF, but I think it's still in the intake tube up to '01 or '02. Just a thought.

Are you getting a MIL? Most O2 failures cause the light to illuminate, don't they?

02StanGT

Anything having to do with the emissions acting up will give you a check engine light.

04BlueGT

I thought so. mxracer1618 never stated anything about the light, so I doubt the O2s also. What do you think about the IAT sensor idea?

BCisme

mine has done the same thing your car is doing.


fix? i switched fuel brands. no more base gas, shell V power 93 octane is the only thing i put in now. runs like a top.

what brand/octane fuel you using now? i was getting ready to start replacing parts, but this action fixed it for me.

mxracer1618

what Deannostang said about why it might run ok when its cold kind of makes sense.....

" When your engine is cold, your computer is in start-up mode where the only regulation being done is basically fuel/air where much of the sensors are off. Once your car is up to heat, the O2 sensors among others are activated. It is much the same thing as when a carburetored engine has its choke on when cold. If anything, you are probably running rich when your engine is cold to prevent stalling such as can occur in the winter months. You may have a very lean situation when the engine heats up. Some sort of electronic tuning may be necessary to alleviate the problem. "

no my check engine light is not on, and i also have no error codes being detected


EDIT: im at less then 1/4 tank full of gas so i will definatly put 93 in it as soon as i run low, i currently am using 87 octane so we will see how that goes

02StanGT

That might make sense, but I see that he just said he has no codes. If the IAT failed it would make the car run too rich or too lean (not sure which) and the O2 sensors would pick that up and throw a code. He'd probably get a code for IAT failed I think.

98gt0311

My 98 vert does this bone stock. I have changed many things and they just don't seem to do ****.

It acts the same way, good cold, sh1tty warm. The sensors or computer are my best guess, but no check engine light.
Deanno hit the nail on the head as far as describing the way my car acts. Ive changed the throttle position sensor and it didn't do jack.

I just can't believe with as many people saying that their car has done this, that it hasn't been investigated or Ford techs don't know what the problem is.

Deanno is right on about getting together to figure out what the problem is. Im going to call SCT tomorrow and see. I want to get this resolved before I bolt my Procharger up. Keep the posts and advice coming please.