Phaedrus Posted May 31, 2007 Report Share Posted May 31, 2007 Hi guys! I just bought a very nice dark greeen 1994 Pontiac Grand Prix GTP. However, it no longer has the 3.4 liter motor. It has the standard 3.1 liter engine and 4 speed auto transmission. The powertrain has about 90K miles on it. It runs great and seems to shift fine, but I think the transmission has a big problem. If I am crusing down the freeway, say between 60 and 70 MPH and the transmission is in 4th, the car does not want to accelerate in this gear. If I get on the gas just a little bit, the car will noticeabley surge and shudder, but not go any faster! If I punch it and make the transmission kick down, then it will take off like a rocket. It also seems to me like the transmission sometimes floats between 3rd and 4th gears, or perhaps the torque converter is locking/unlocking. Is this a common problem for these transmissions? Is it fixable, or will it require a replacement? Could an engine problem be causing this? Thank you! Quote Link to comment Share on other sites More sharing options...
89GP_SE Posted May 31, 2007 Report Share Posted May 31, 2007 try unplugging the TCC (tourque converter control?) it will be a big round plug on the front of your tranny, right under the airbox. take it out for a spin and see if it does anything. if it changes then you know its the selinoid for the torque converter Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted May 31, 2007 Author Report Share Posted May 31, 2007 That's the 7 pin plug right above a vacuum solenoid? I just unplugged it so we'll see how that goes. Thanks for the advice! Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted May 31, 2007 Author Report Share Posted May 31, 2007 I unplugged and it and drove to work, it mostly makes the transmission act weird! Accelerating from a dead stop, the torque converter slips a ton, and I really have to punch it to get going. During this time, the car kind of shudders and vibrates. Also, with this disconnected, the car will not shift into 4th gear. It's taching about 3K at 65 MPH, and I can move the shifter between 3 and D with no effect. The bonus side is though, that I am able to accelerate gradually now. Does it sound like I need to replace the TCC solenoid? Thanks! Quote Link to comment Share on other sites More sharing options...
Brian P Posted May 31, 2007 Report Share Posted May 31, 2007 Yeah, actually plug that harness back in. You have the electronically controlled transmission. Unplugging it will basically put it into limp mode and have I believe 2nd and 3rd gear only (maybe just 3rd?) Anyway, though it may seem like a transmission problem, any kind of minor misfire will show up more pronounced under load. Accelerating on the highway in 4th gear w/ the converter locked puts a lot of load on the powertrain. I'm willing to say you may just need a tuneup, or worst case, have a fuel problem. Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted May 31, 2007 Author Report Share Posted May 31, 2007 How is the torque converter supposed to function? Should it remain locked as you accelerate a little, or should it unlock itself every time? I've noticed that even at somewhat constant speeds in 4th, the converter will lock and unlock istself, but will stick locked when I push the gas.... It really does seem to me like the car is running fine, but I will go ahead and tune it up a bit. Maybe it's a cracked distributor cap or something. Quote Link to comment Share on other sites More sharing options...
Pontiac6KSTEAWD Posted May 31, 2007 Report Share Posted May 31, 2007 One way to test the TCC on a electronicly controlled tranny is to try your accelerating like you normally would, once it starts to shutter, try tapping on the brake pedal and holding. Just enuf for the brake lights to come on, and not actually cause any brake drag. By pressing on the brake pedal lightly, it turns off the TCC, and you should be able to tell from that. For this to work thou, you need to have that harness plugged in. Try it and see what happens. It might solve the problem by giving you a better RPM. But for some reason, I am thinking its something in the plugs or wires, but I could be wrong.. Quote Link to comment Share on other sites More sharing options...
Brian P Posted May 31, 2007 Report Share Posted May 31, 2007 How is the torque converter supposed to function? Should it remain locked as you accelerate a little, or should it unlock itself every time? I've noticed that even at somewhat constant speeds in 4th, the converter will lock and unlock istself, but will stick locked when I push the gas.... It really does seem to me like the car is running fine, but I will go ahead and tune it up a bit. Maybe it's a cracked distributor cap or something. It's supposed to unlock when over a certain % throttle, usually 25% or a little higher, depending on speed. So you CAN accelerate with lockup applied, but push it further and it's supposed to unlock. My mother's old '95 Cutlass developed a similar problem. Engine otherwise ran fine. Turns out there was arcing occuring at one of the ignition coils, which got progressively worse. Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted May 31, 2007 Author Report Share Posted May 31, 2007 Yes, tapping the brakes while the car is shuddering in 4th causes the TCC to unlock, then the car accelerates better. I'm not sure I'd expect the engine to be able to pull 4th with the transmission locked from 2K rpm. Maybe whatever sensor is supposed to unlock the TC is not working when I hit the gas? Quote Link to comment Share on other sites More sharing options...
Pontiac6KSTEAWD Posted May 31, 2007 Report Share Posted May 31, 2007 I dont think thats the case. The TPS is what tells the computer what % of throttle the car is currently at. So the computer can retune for spark, fuel injector pulse, etc. So I think that it is working. Just whether or not you have a cracked crown on one of your plugs, or coil, or if the TCC is just faulty, I dont know. I would start with a really good tune up. Plugs, wires, PCV valve, and a fuel filter, maybe a O2 sensor if it hasnt been replaced. Since this stuff is all the low price stuff. Then work your way to the coil packs. You can buy one, try it, if it doesnt work, swap that coil down the line to the other locations. The reason I am leaving the TCC for last is that it is a involved job for the do it yourselfer. I had a dealership charge me 360 for it on a 3 speed car. and I know that the 4 speeds require alot more work. It does sound like you are throwing money at it by doing it this way, and in fact you would be on this. But I would be money, that if you took it to a tranny shop, to get a diagnostic done, they would tell you it needs a tranny. Which it doesnt sound like it does to me, and it might not even correct the problems. So the next best thing to do is a process of elimination, not to mention your motor and fuel milage would probly benefit from doing the tune up anyways. Quote Link to comment Share on other sites More sharing options...
Guest JuniorBaconChee Posted May 31, 2007 Report Share Posted May 31, 2007 Going by what I've read, it seems the 4t60e is known for the shudder. I can tell you this, when we went and picked up the Buick, the 1-4 coil was bad and I drove it home that way. The shudder in OD4 was TERRIBLE. You might pull the plug wires and check to see what kind of spark you have. Beyond that, no clue as I'm still trying to rid myself of the midget making the knocking noises in mine. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted May 31, 2007 Report Share Posted May 31, 2007 dare I ask..... if the engine has been swapped, what pcm is the engine running on? and what is the gearing of the transmission? is the check engine light on? Does is light up during startup? Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted May 31, 2007 Author Report Share Posted May 31, 2007 The engine and transmission are both from the same 94 3.1 liter car. I was told the PCM is the for the 3.1 liter engine. It's running alright, since it just passed the stringant CA smog check very cleanly. This motor/tranny's been in the car for the last 50K miles.... Any way to find out for sure if it's the correct PCM? Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 1, 2007 Report Share Posted June 1, 2007 find the 8 digit service number on the PCM. and tell us if it a black box, or a silver odd shaped case Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted June 1, 2007 Author Report Share Posted June 1, 2007 Where's it located in the car? Quote Link to comment Share on other sites More sharing options...
ns87 Posted June 1, 2007 Report Share Posted June 1, 2007 Anyway, though it may seem like a transmission problem, any kind of minor misfire will show up more pronounced under load. Accelerating on the highway in 4th gear w/ the converter locked puts a lot of load on the powertrain. I'm willing to say you may just need a tuneup, or worst case, have a fuel problem. X2 I used to think my transmission was dying every time my car acted up. Every problem in my three years of ownership has been engine related. The transmission is still in good shape Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 1, 2007 Report Share Posted June 1, 2007 passenger side front, opposite corner from the battery. Quote Link to comment Share on other sites More sharing options...
Brian P Posted June 1, 2007 Report Share Posted June 1, 2007 I dont think thats the case. The TPS is what tells the computer what % of throttle the car is currently at. So the computer can retune for spark, fuel injector pulse, etc. So I think that it is working. Just whether or not you have a cracked crown on one of your plugs, or coil, or if the TCC is just faulty, I dont know. I would start with a really good tune up. Plugs, wires, PCV valve, and a fuel filter, maybe a O2 sensor if it hasnt been replaced. Since this stuff is all the low price stuff. Then work your way to the coil packs. You can buy one, try it, if it doesnt work, swap that coil down the line to the other locations. The reason I am leaving the TCC for last is that it is a involved job for the do it yourselfer. I had a dealership charge me 360 for it on a 3 speed car. and I know that the 4 speeds require alot more work. It does sound like you are throwing money at it by doing it this way, and in fact you would be on this. But I would be money, that if you took it to a tranny shop, to get a diagnostic done, they would tell you it needs a tranny. Which it doesnt sound like it does to me, and it might not even correct the problems. So the next best thing to do is a process of elimination, not to mention your motor and fuel milage would probly benefit from doing the tune up anyways. I agree with this! Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted June 1, 2007 Author Report Share Posted June 1, 2007 I *think* I found the PCM. The housing is corroded, but it is odd shaped as you say, in a silver case. Seems to me like the problem is getting better as I drive. Before I bought it, the car sat around alot and was only used for very short trips. I'm going to put plugs and wires on it, maybe an O2 sensor and run a couple bottles of fuel system cleaner though it. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 1, 2007 Report Share Posted June 1, 2007 do that. plugs, wires, and all filters. sounds like you have the correct PCM. how about the check engine light? does it cycle/test when you start the car, and remain off while running? Quote Link to comment Share on other sites More sharing options...
Phaedrus Posted June 3, 2007 Author Report Share Posted June 3, 2007 You guys were 100% right. I should have checked the simple things first. The sparkplugs are COMPLETELY worn out! The gaps are up to about 100 thousands each, the electrodes are cracked and broken, and they're all caked in crap. I don't think they've been changed in the last 80K miles. Too bad replacing them hasn't been an easy job! I've never encountered this before, but I couldn't get the wires off the rear 2 plugs on the passenger side! I eventually had to take off 2 coil packs and the alternator so I could get my hands and some channelocks in there to pry the wires off. We'll see how my new AC plugs pay off on the drive to work tomorrow... Quote Link to comment Share on other sites More sharing options...
Brian P Posted June 4, 2007 Report Share Posted June 4, 2007 Common thing to occur when the original plugs and wires are in for so long. Hopefully all is solved (I'm sure it is) Quote Link to comment Share on other sites More sharing options...
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