'02 GT Intermittent problem (Reward for help)

stangsdado · Aug 20, 2009

Kilgore Trout said:
Well, I would defer to one of the more knowledgable techs for the answer to that. I am just a hobbyist mechanic...

I will say that "rumbling" is usually attributed to the rear diff. Is it possible that there is a problem with your diff?

The problem is that the issue happens whether the car is idling or driving. And it also never gets worse, its always constant.

stangsdado · Aug 20, 2009

GDawg said:
My first instinct is motor mounts... Have you looked at them?

They were replaced a couple of years ago and since then, the car has been driven around 10k miles.

stangsdado · Aug 20, 2009

On my way to AutoZone right now to loan the compression testing tool so I'll post the results when I get back. In the meantime, if anyone knows the specs, please post them. If not, no biggie, I'll search the internet

trombonedemon · Aug 20, 2009

I think I overthought your problem, hmm, try higher lb fuel injectors, sounds like what you said, you air fuel mixture is funky, you have a huge intake with that intake manifold and the 90mm maf housing. It might be too much without larger fuel injectors, Darn it! You said this problem just started! Fuel, fire, or air!? Try scoping the obvious sensors or easier ones to get to. Best of luck!!!

stangsdado · Aug 20, 2009

Is it wise and is there a way to clean the IAC and the TPS? Those are pretty much the only sensors that I haven't touched...

trombonedemon · Aug 20, 2009

Higher fuel injectors needed possibly, too little. 19lbs is stock, your intake could be way to much for your fuel injectors!!?

stangsdado · Aug 20, 2009

trombonedemon said:
Higher fuel injectors needed possibly, too little. 19lbs is stock, your intake could be way to much for your fuel injectors!!?

But is it possible that this is bothering the computer after 3 years of driving?

twogts4us · Aug 20, 2009

Winters98GT said:
I'd bet it's your cold air/MAF or typhoon intake, none of which helps, but more likely hurts your performance. The Mac cold air hurts performance and gets heat soaked...

Heat Soak on a CAI is an internet myth. Sure, if you grab the tube after an hour of driving, it'll burn the ****it out of your hand, but remember the air moving through that tube is traveling so fast that it simply doesn't have time to absorb heat from the tube.

I still like the solution being related to the motor mounts. I know you've dismissed this issue, but if you are able, you should dbl ck them. Even with their replacement 10K miles ago, they may have not been tightened properly, may have been installed improperly or may have been inferior quality.

I had a 1990 Buick Century with a sideways 4 cyl driving the front wheels a few years ago. (Grandma's hand me down) It was a great lil car with very low mileage. Anyway, it started bucking and I truly thought it was a motor issue, but it turned out to be the front struts. I would have sworn it was a problem with the engine...

Best of Luck!

stangsdado · Aug 20, 2009

twogts4us said:
I still like the solution being related to the motor mounts. I know you've dismissed this issue, but if you are able, you should dbl ck them. Even with their replacement 10K miles ago, they may have not been tightened properly, may have been installed improperly or may have been inferior quality.

Best of Luck!

Do you think that loose/bad motor mounts could worsen the acceleration that much??? The car accelerates at half the rate when the vibration is occurring?

stangsdado · Aug 20, 2009

Just got the compression tester. I'm gonna wait 1-2 hours so the sun goes behind my house and my driveway is in the shade. Anyone got any last minute tips aside from unplugging the coils and injectors?

hillbilie5.0 · Aug 20, 2009

just something to keep in mind, i bad computer cannot diagnos itself. i have had cars throw all kinds of codes before and lead you in 1,000 different directions. in the end it turned out to be a bad ecm. not saying this is your problem, but you mentioned your car throwing random codes, lean then rich ect.. just something to think about. in my experience cars usually still run with bad ecms just act all weird and throw random codes and such.

tag4car · Aug 20, 2009

the TPS more than likely is ok, The IAC on the other hand can have a sticking action if it's gunked up from blowby from the pcv system, You can spray it out thoroughly with carb or tbody cleaner and see the gunk wash out. a new iac is about 75. conveniently i have one here with me i have no need for. pm if interested

stangsdado · Aug 20, 2009

OK. I've done a lot of work today. I rented a compression tester but before I got to use it, I noticed some coolant build up on top of the block that wasn't there before. I checked the level and it seems like it was little below the norm. So I found a small leak around the thermostat housing where the upper hose brings in the coolant. So I followed it and found small amounts of coolant in all four right side spark plug holes. Took out the spark plugs, cleaned the coils, replaced all 4 spark plugs and now the car is behaving a lot better. At idle and low RPMs, there is absolutely no vibration. Once you put the gas down, you feel the same vibration but its waaaaay down from what it was before.

I pulled the left side plugs and they seemed brand new (they have less than 10k miles on them) but I'm going to replace them tomorrow anyway.

blubullett · Aug 20, 2009

I had problems with my drivability on the last 5.0 I had, it would throw ramdom codes, sometime it would run really rough and sorta stumble as I accelerated. If I played with the throttle it would get better. Eventually after replacing the oxygen sensors, maf, playing with the egr, spark plugs and wires, I replaced the TPS and it fixed everything. If the tps is bad it will stumble untill you either press the gas more or release it a little bit. If they are corroded a little bit the voltage will fluctuate and your car wll stumble while it accelerates. They are cheap and easy to change too. Just make sure you have a nice multimeter so you can set the voltage when you install it. There are some good instructions on here if you search "how to set TPS" or something like that. Good luck with your car.

stangsdado · Aug 20, 2009

Forgot to say that I found the source of the leak and it was between the manifold and downpipe connected to the upper hose. I guess the thermostat o-ring wasn't enough to keep the coolant from spilling out under pressure.

Kilgore Trout · Aug 21, 2009

I was thinking about this last night and i was going to suggest check trans crossbrace to see if it was perhaps loose but it sound like you solved it. Give yourself $50 sir

stangsdado · Aug 21, 2009

So I went to buy some smokes late last night and instead of taking my daily driver I decided to give the stang a spin since it had cooled down. Got the cigs and since the stang was performing perfectly for the first time in a long time, I wanted to drive it around for a little bit. So while the engine was still cool, I got on the gas a little harder and to my surprise, there was no vibration. I did this 3-4 times and she ran as strong as ever. Once the engine came up to operating temperature, she started exhibiting a little vibration when the gas was pressed more than half-way. I'm going to go get the other 4 spark plugs, swap them out and test again. I'll post the results in a few hours.

stangsdado · Aug 21, 2009

Kilgore Trout said:
I was thinking about this last night and i was going to suggest check trans crossbrace to see if it was perhaps loose but it sound like you solved it. Give yourself $50 sir

Hehe, I've still got a little vibration going and that ABS issue to deal with before this car is in good condition again.

twogts4us · Aug 21, 2009

Kilgore Trout said:
Give yourself $50 sir

+1

Mizark347 · Aug 21, 2009

As I stated earlier I had the same problem with my 02 GT. I installed a set weapon X COP's and problem solved. How many miles are on it? Have you washed the engine recently? My car didn't throw any codes at all. I also pulled each connection to all 8 coils and each one made the engine stumble. Sounds like a weak Coil.

'02 GT Intermittent problem (Reward for help)

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