Pontiac Grand Prix '96

Before I take my car to someone for repair, I need to have better terminology to tell the guy what is going on w/the car. Here lately, I’ve noticed that the engine seems to be running differently than normal. When I stay at 60 miles per hour, the tack stays at 2 (or 200) if it’s running properly. Lately, I’ve noticed it going to 3 (or 300) at the same speed - not running as smoothly. Perhaps sucking more gas? Also, even more recently, the tack has been jumping a bit and the engine just sounds weird (cannot even explain the sound). Further troubling is the fact that the car has died twice now at stop lights. It always starts right up upon me turning the key off & starting it again BUT I’m worried it’s going to not start at some point and I don’t really know what’s going on with the engine right now. The car has about $134,000 miles on it & it gets regular oil changes but I’m hoping this is not something major because I’m hoping to get a newer car next summer.

If your tach is showing an extra 1000 rpms over what it used to at a steady highway speed then you are looking at a probable transmission problem. (And yes it will suck more gas, but that’s another symptom rather than a cause).

If you add to that the tach bouncing up and down, and the occasional stall at a stop then I’d begin to suspect a torque converter clutch lockup problem. I hate to tell you, but that all means that I would start thinking about a worst case scenario.

When is the last time you checked the transmission fluid? Do it now. Note the level, color, and odor.
When is the last time (if ever) the transmission was serviced? How was it serviced?
If you have a regular, trustworthy shop that you use, then I would take it there and ask someone to drive it. However, I believe that you will end up at a transmission shop eventually. It should be a locally owned, independent kind of a place.

Had a new transmission put it in probably 3 years ago. But I do not know when the transmission fluid was checked. I am hoping not to spend a ton of cash on this car because I’m wanting to get a newer one next summer. If I need another transmission, I will probably not keep the car as I had hoped to keep it as a 2nd car (backup) since I knew I couldn’t get much for it if I sold it.

You probably got a remanufactured transmission rather than a “new” one and the quality of rebuilds can very a lot.

However, I’m pretty sure that that transmission still used a vacuum modulator (very important shifting input). These commonly fail, and are net very expensive or difficult to replace. You can always hope for something that simple, but either way I still think your next stop is a dedicated local transmission shop.

No argument on it being remanufactured because I know it was not a brand new transmission but it dying on me doesn’t sound like transmission problems. I’m also experiencing no problems with shifting (which is how I knew I needed another transmission before). I just called the one repair shop I do trust & they said it could be a coil of some kind or a mis-fire on one of the cylinders. No mention about the transmission but I will have the transmission fluid checked.

Well, just to help you out further then:

  • all modern automatic transmissions have a torque converter clutch (TCC). Much of the time while you’re driving the link between the engine & transmission is actually a fluid link. But when you’re at a cruising speed the TCC “locks up” and creates a mechanical connection. This has nothing to do with shifting between gears and is technically a torque converter thing rather than a transmission thing, except the origin of a problem with it can be in the transmission or even in engine controls. IF the TCC has problems & stays locked up it will stall the car when you stop. Its like stopping w/ a manual transmission in gear but without pushing in the clutch. TCC lockup problems will also set your tach to bouncing at various times as it locks/unlocks/locks/unlocks. These transmissions are known for valve body issues that will create this kind of thing.

  • You can easily have some other kind of problem - such as a problem with how the engine is running. But something like a bad coil is NOT going to make your engine run at 3000rpm rather than 2000 rpm at 60mph. If this is what is happening then you are in 3rd gear rather than 4th. If I had to pick an engine control issue that might fit the bill it would be a bad or contaminated MAF sensor. But once we’re there - there are lots & lots of possibilities, including the possibility that you have more than one problem & your description wouldn’t really allow much narrowing down.

I will share all of this info with my mechanic & ask a LOT of questions. This shop is the one my Mom uses regularly and they are honest w/people (don’t rip people off) so I will ask him to drive the car. Thanks for explaining things further. Will update you after my appt. on Friday.

Do you have any idea what it would cost to fix a torque converter clutch lockup problem? If that is what the real issue is?

These cars are know to have Solenoid issues, the part to fix your trans maybe as low as a $30-40 part (new TCC solenoid)… HOWEVER the labor to put this part in is huge, and while the trans does not need to be removed, it does need to be angled down, so we are talking at least 5 or 6 hrs to install the part at $100 an hour plus trans fluid etc, you get the picture… My Buick has the same trans and I have a problem with one of my solenoids that causes a stutter if I get on the gas too hard from a stop, I taught myself how to drive the car without the problem, and honestly I feel it maybe once every other month or so. Your problem is a little worse than that, so I don’t think re-learning to drive your car will help. Worst case its going to actually be your torque converter which is going to cost about 100-150 for the part plus lots-o-labor to install, as in this case the trans must actually be removed

Mitsy12 wrote:
But I do not know when the transmission fluid was checked.

If you neglect your car like this, be prepared to throw away money at one point or another on major repairs that could have been prevented.

It’s been changed. I just can’t tell you when. I am not neglecting my car if I take it in for service which I do, but pardon me all to hell because I can’t tell you the date.

And where I live, even the highest priced mechanic doesn’t get $100 per hour.

Your transmission fluid should be checked every few weeks at a minimum. Do you take it in for service every few weeks and pay someone to do that? I assume the answer is no. In that case, feel free to run your fluid low and kill your transmission. If you don’t like having that pointed out to you, it doesn’t really matter to me.

I know NO ONE who checks their transmission fluid every few weeks. Give me their names. They don’t live in my town.

My son drove a small school bus for a day care center. He had a check list that he had to perform every morning before he started on his route. This included checking all the fluids including the automatic transmission fluid, coolant, oil, brake fluid reservoir and power steering fluid. He had to check all tire pressure and all lights.

I could understand if someone drove a bus with kids in it everyday. The average person doesn’t.

I agree, nobody checks their fluid that often, but you should check it occasionally. Unfortunately, few people even check it occasionally. But the reason to check your fluid is that if a problem or a leak DOES develop, you’ll catch it before it can manifest itself as serious damage.

Cig “nailed” is as a malfuntioning tranny. He also mentioned the vacuum modulator. If it has one, it’s a diaphragmatic device that should the diaphragm fail can allow engine vacuum to pull tranny fluid from the tranny and can affect the operation of the tranny itself.

One other thought is the radiator. I believe your car uses a radiator wherein the top portion cools the engine coolant and the bottom portion cools the tranny fluid. If it forms a breech between the two portions, and that has been known to happen, coolant can mix into the tranny fluid (the cooling system is under greater pressure) and mess up the tranny.

As much as I appreciate your desire to have correct terminology and more knowledge before going to the shop, the best approach is to clearly describe the symptoms to the tech in your own words and let them do the diagnosis. Many a $100 bill has been wasted by someone telling a shop “my XXXX is acting up” when in fact the real problem is coming from somewhere entirely different.

I’d recommend going to a good tranny shop rather than a generalist.

Misty, a lot of people do check their transmission fluid regularly. It’s just another dipstick, although you need to pull it when the engine is hot and running. My old 91 Buick was, I think, mechanically similar to your Grand Prix, and checking it gave me a clue that I had a leak and was going to burn up the clutches. I caught the problem early enough and managed to keep that heap running just fine until I got rid of it two years ago.

My new Jeep’s transmission is supposedly sealed, so there’s not a proper dipstick. The owner’s manual says have it serviced at 50,000 miles or something stupid like that. It failed at 30,000.

It’s also true that lots of people don’t maintain their cars well enough. Some of them get lucky and the car keeps ticking despite that. Others aren’t lucky, and have big repair bills. You might not be lucky here.

Thanks for everyone’s comments. I have an appt. today. I will do my best to describe the issues going on to the guy. Hopefully, it will last until next summer. If not, then I’ll have to re-think what I’ll do. Thankfully, I have a Mom who is well off enough to help me buy something newer now or next summer.

I took my car to the one shop in town I trust. They hooked it up to the computer & could not find anything wrong w/it. They had the car for half a day but only drove it once. That was on Fri. so I took the car for the weekend and on Sun. it again acted up (tack acting weird, jerking at times). I took the car back yesterday & they had the car for pretty much the entire day. Told the guy to drive it a ways this time and it did act up for him. He said that I needed new spark plugs (torque/transmission not the issue). He showed me the bad spark plugs. I had these replaced about 2 years ago but he said unless you got the platinum tipped kind, that they did not last that long. He also said that my thermostat was shot & wondered if I’d had heating problems (which I had noticed but thought that it was just taking longer to heat up because the car was old). So, I’m hoping that the repair bill will be a lot less than I originally thought. I was aggravated that they did not figure this out the first time the car was there but several people speak highly of these guys & that they have a reputation for not ripping people off. My Mom goes to this shop & trusts them, so I’m hoping to have my car back by noon today. Just FYI.

Oh, and that torque problem one poster mentioned? I showed the mechanic a copy of his “diagnosis” and he said that the '93 & older models DID have that issue but that it was also a different engine size that experienced that problem so the best advice is really to let the mechanic drive it & see for himself what the car is doing. Sometimes, unfortunately, the car will “behave” and they can’t fix what they can’t see for themselves.

The torque converter lockup problems are not a '93 and older thing at all. The entire family of transmissions that yours belongs to have this as a common problem up to the present. It was also not a “diagnosis” - it was a first guess based on what you reported. There’s a big difference between a “diagnosis” and a guess based on scattered and unclear information in an internet posting.

That said, if you had 1) old plugs + 2) a thermostat sticking open - then you could easily have had the symptoms that you describe - except the running 1000rpms over normal at highway speed. That might be expected - sometimes, but if its a regular thing it just means that the transmission has not hit 4th gear. It is plausible, however, that the engine problems you were having would have interfered with normal transmission function.

In any case, engine misfires and transmission problems can often feel the same. So the bad plugs + thermostat is perfectly plausible.

Diagnosis was just a way to describe what the poster thought the problem was. There was no contract by anyone that said exactly what the problem was. No one could know without seeing & driving the car themselves. And the “misfires” was a term that I would not have come up with on my own but that is what the mechanic called it. That sounds a bit more descriptive than what I told him. As I said, it’s sometimes very hard to communicate what is happening to a mechanic in layman’s terms. Sometimes they really do have to drive it to see what is wrong. I hope that this will fix it and there won’t be anymore major issues until I can get a newer car.