Question : first problems on my 94 GP

[jwakamud]

first off, thanks for reading.

so i bought the car a couple of days ago, i needed a car quickly to go A to B, for cheap. so i bought this one. and since you get what you pay for, it has problems.

maybe you guys can help out. i hope so. ill describe the problems ive found.

1: when im driving above 20 mph (roughly), theres no issue. but in city traffic, ive noticed that the temperature gauge begins to go up dramatically (it WILL reach the red, in under 5 minutes if idling, at a stop light or stop sign for instance). i can stop the rise in temp if i shift it into neutral and hold the RPM's around 3, if i do that then the temp drops about as fast as it rose.

2: when i start the car, it starts. but if i dont immediately give it gas, the rpms drop below about .8, then the car shakes a bit and dies. also, once at a stop light, it shook [i noticed RPMs below 1, so i gave it a bit of gas and it was fine]

so . . . any ideas guys?

1994 Grand Prix [badged GTP] with the 3.4L DOHC, 128000 miles.

[GTP091]

first off, thanks for reading.

so i bought the car a couple of days ago, i needed a car quickly to go A to B, for cheap. so i bought this one. and since you get what you pay for, it has problems.

maybe you guys can help out. i hope so. ill describe the problems ive found.

1: when im driving above 20 mph (roughly), theres no issue. but in city traffic, ive noticed that the temperature gauge begins to go up dramatically (it WILL reach the red, in under 5 minutes if idling, at a stop light or stop sign for instance). i can stop the rise in temp if i shift it into neutral and hold the RPM's around 3, if i do that then the temp drops about as fast as it rose.

2: when i start the car, it starts. but if i dont immediately give it gas, the rpms drop below about .8, then the car shakes a bit and dies. also, once at a stop light, it shook [i noticed RPMs below 1, so i gave it a bit of gas and it was fine]

so . . . any ideas guys?

1994 Grand Prix [badged GTP] with the 3.4L DOHC, 128000 miles.

invest in a haynes repair manual and check out some of these things::

1. For your temperature problems I would check the car at idle and see if you fan kicks in to cool it. The fan is controlled by the ECM so if it is having problems there may be your trouble. If the fan doesn't come on check the fan relay in the electrical centre; should be in front of the coolant resevoir replace it if not working (you'll need a voltmeter). Your gauge works ok it seems but before you replace the ECM maybe try the coolant temp sensor and it's wiring. Also check the fan wiring itself if the relay is working fine. I assume you've done the obvious and checked the coolant level.

If your fan is coming on but the car still gets hot then maybe your thermostat is shot and needs to be replaced. Check the rad hoses to see if they are hot this will show if the themostat is opening.

2. This could be a lot of things. The book will tell you to start replacing sensors but test them first the price will add up quick.

I would check the Idle air control valve first. You have to take it out and see if the pintle is free to move. (turn the key on and off) if it comes out too far just push it back in with your thumb.

There could be an intake leak as well spray the intake plenum seal with carb cleaner to see if there's a leak and if the engine surges or dies that's probably whats going on.

The throttle position sensor tells the ECM where the throttle plate is at and then adjusts the air fuel mix. Not likely this as the engine would usually surge instead of sputter and stall. but still ok to look at.

Theres lots of vacuum lines to test to so check these out to for leaks.

[SappySE107]

Headgasket is blown between the cylinder and a waterjacket? Is your coolant overflow full or the radiator low (both?) This is my guess for both problems.

[pocket-rocket]

As much as I hate to suggest the store, go to Autozone and rent a Cooling system pressure checker. I did and I ended up keeping it because on two cars, it helped me a ton. Put it on with the car cold and see if it drops over time. If it does, try to listen to where your leak is. Warm it up to the point where it starts overheating. Then test it again. If the gauge stays up when cold, but drops fast when warmed up, I agree with Sappy. That's exactly what it did on a 95 Sonata I worked on. Also when warmed up the car would spit coolant back out at me as I added it (compression leaking into the cooling system). Tore the top end down despite a "25 year ASE certified master mechanic" telling me he didn't think it could possibly be the problem because the person I was doing this for just had me change the head gasket on their other car, and they couldn't possibly both go out within a week of each other. Well, cars don't talk to each other and plan stuff like this, and it was indeed a head gasket. I kept that one for a momento :P

[jwakamud]

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thermostat was glitchy, so i replaced it. shortly after i replaced it, i took it for a test drive (after filling the coolant again), i noticed when i pulled off the highway the temp gauge spiked again, about halfway between 210 and red (thermo i put in was a 195*). started going, and the temp dropped. for awhile longer, it hung around 210*, and a couple times i noticed it went down to about 170* and hung around there. then went back to around 210*.

could the fans be the issue? i checked them once, and they came on.

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forgive the stupid question, but how do i check for leaks in the vacuum lines?

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[pocket-rocket]

If you didn't purge the air out of the system, the spikes could be from air getting to the sensor since it can't read steam accurately, just coolant. There are 2 bleeder screws in the coolant system, one by the brake booster and one by the t-stat. Try opening them till you get good coolant flow out like you do for brakes. Also idle it up from time to time (ei. rev it to 2-3k rpms) to help blow air out. When I do a t-stat in my car I also drill a small hole in it and point the hole towards the top to help bleed air out. I only drill about an 1/8" hole so it doesn't let too much coolant bypass the t-stat, but will help tons with bleeding air. Hopefully that fixes the temp spikes your getting while going down the road. I suggest this over looking at the fans for the spikes while moving issue because after 45 or 50, the ECM won't even turn the fans on because they will actually block airflow while spinning at those speeds. Oh, I also squeeze the top radiator hose while filling it back up to help blow bubbles out of the system as well, lol.

[GTP091]

Did you get this figured out yet??

[jwakamud]

nope, still havent gotten it figured out. heres the problem so far:

replaced head gaskets on my way to the oil pump drive seal (oil leak) and replaced the thermostat. it no longer seems to want to die when i cold-start, so im assuming they were related. coolant is fine.

i checked the fans. the motors are fine in both fans, and i tried it with two new relays. fan 1 seems to be getting a constant signal to turn on as long as the car is on while fan 2 never gets the signal (temp above 210* or max ac, neither work to send it the signal). interestingly, while fan 1 is constantly getting the signal to turn on and the relay does work, the fan does not turn on.

like i said, both fan motors work fine.

jeff

[55trucker]

Have you tried bypassing the relay altogether by removing the relay and jumpering the the hot side of the terminal socket from battery to the line side of the fan supply to bring on the fan motor?...

[GTP091]

nope, still havent gotten it figured out. heres the problem so far:

replaced head gaskets on my way to the oil pump drive seal (oil leak) and replaced the thermostat. it no longer seems to want to die when i cold-start, so im assuming they were related. coolant is fine.

i checked the fans. the motors are fine in both fans, and i tried it with two new relays. fan 1 seems to be getting a constant signal to turn on as long as the car is on while fan 2 never gets the signal (temp above 210* or max ac, neither work to send it the signal). interestingly, while fan 1 is constantly getting the signal to turn on and the relay does work, the fan does not turn on.

like i said, both fan motors work fine.

jeff

Weird, The fans are controlled by the ECM through a relay that you have already replaced. If the ECM is telling the fan to always be turned on then maybe there is a problem in the coolant sensor wiring (short) or the coolant sensor is bad itself. There is a way to test the sensor; though I can't remember how (do a search). Hopefully your ECM isn't bad.

[55trucker]

Only the *coil* side of the relay is controlled by the ECM circuit, The line side is directly off the battery. I still feel Jeff needs to double check the line side circuit to the fans and after the fans (common ground for both) to see if there are any problems in that wiring at all. Remove that possibility then start looking at other control items on the *coil* side of the relay circuit. Here, this diagram should help.....

[GTP091]

[QUOTE=55trucker;377028]Only the *coil* side of the relay is controlled by the ECM circuit, The line side is directly off the battery. I still feel Jeff needs to double check the line side circuit to the fans and after the fans (common ground for both) to see if there are any problems in that wiring at all. Remove that possibility then start looking at other control items on the *coil* side of the relay circuit. Here, this diagram should help.....

Would have been my guess to except he said the fan turns on as soon as the key is turned on which shows the wiring is grounded and not shorted from the relay. Also since the fan is turning on the wire from the ECM should be good as it's hot in run. This still isn't normal the fan should only come on when the ECM says to.

[55trucker]

Multiple and a bit confusing problems here....[quote] interestingly, while fan 1 is constantly getting the signal to turn on and the relay does work, the fan does not turn on.[quote] ...I was under the impression that Jeff's fans (the primary fan) still will not engage.

[mn95gtp]

the GTP problems

yeap had something similar check ur thermostat replace if needed, top off your radiator fluid. also have your o2 sensor checked along with your fuel pressure regulator. those sound like they could be the problem.

first off, thanks for reading.

so i bought the car a couple of days ago, i needed a car quickly to go A to B, for cheap. so i bought this one. and since you get what you pay for, it has problems.

maybe you guys can help out. i hope so. ill describe the problems ive found.

1: when im driving above 20 mph (roughly), theres no issue. but in city traffic, ive noticed that the temperature gauge begins to go up dramatically (it WILL reach the red, in under 5 minutes if idling, at a stop light or stop sign for instance). i can stop the rise in temp if i shift it into neutral and hold the RPM's around 3, if i do that then the temp drops about as fast as it rose.

2: when i start the car, it starts. but if i dont immediately give it gas, the rpms drop below about .8, then the car shakes a bit and dies. also, once at a stop light, it shook [i noticed RPMs below 1, so i gave it a bit of gas and it was fine]

so . . . any ideas guys?

1994 Grand Prix [badged GTP] with the 3.4L DOHC, 128000 miles.