RPM Surging Between 2000 - 2500 RPM


Enzy
10-15-2007, 10:21 PM
2000 Grand Prix GT 3.8.
I have had an annoying problem with this car for quite awhile.
When travelling at betwen 2000 - 2500 rpm and the load increases, either by gentle acceleration or climbing a hill, the engine continuously surges up and down about 500 rpm in about 1 second cycles. The only way to stop it is to let off the accelerator or shift down either manually or by pressing the accelerator. Otherwise, the car generally runs well.

I have replaced EGR valve, PCV valve, throttle position sensor, mass airflow sensor, fuel filter, plugs and wires. Fuel pressure tests normal.

I would appreciate any suggestions.

Thanks

richtazz
10-16-2007, 05:48 AM
Welcome to AF

Does it do it only in OD while cruising at a steady speed? If so, it sounds like a TCC solenoid locking and unlocking the torque converter. If it does it in lower gears at lower speeds, I'd say you have a vacuum leak somewhere.

Enzy
10-16-2007, 10:26 PM
Vacuum tests OK, with consistent 17-18 in. at idle and at 3000 rpm. I thought of the TCC solenoid, but the surging can happen in OD and 3rd for sure. Anybody know if the TC would normally lock in 3rd?

BNaylor
10-17-2007, 07:12 AM
Engine vacuum looks good. The TCC will lock in 4th - OD only above 45 mph. When was the last tranny service? ATF and screen filter? What brand spark plugs to include heat range/numbers and ignition wires?

Also, it would help to post your mileage.

goldberg_52403
10-17-2007, 03:58 PM
Wow, I just logged in to start a thread about the same thing. I have a 99 GTP, and it is basically the same situation. Under gentle acceleration, the revs will hop up and down about 250 rpms (maybe it will soon be worse and 500 rpms like yours), just enough to be incredibly annoying. Now I am worried from what is reported so far, as when I first got the car (~2 months ago), the check engine light came on regarding the TCC something. The shop replaced a wire for the TCC, and the light went away. Anymore input on this case would he highly appreciated. Other than this issue, the car runs great and continually does with this problem if I just give it a little more gas.

Thanks for starting this thread!

BNaylor
10-17-2007, 07:10 PM
Wow, I just logged in to start a thread about the same thing.

The fishbite or chuggle effect is caused by two possible problem areas. A bonifide transmission problem related to the torque convertor (TCC) and control circuits which could include throttle body components such as the TPS, etc. Or a secondary ignition problem not severe enough to be detected as a true misfire condition by the PCM module. The proper spark plugs and good quality ignition wires is critical or you'll get these anomolies.

As suggested to the OP always post your mileage.

Enzy
10-17-2007, 09:47 PM
Wow, good suggestions! And nice to hear someone else has the same problem.
Mileage on the car is 142,500 miles. I have 71,000 on the plugs and 43,000 on the wires. ATF and filter were changed 31,000 ago.
The plugs are Bosch platinum #HR9DPY. They are the number recommended by the Bosch book. The wires are Niehoff Premium Silicone.
I see a fuse in the main fuse box labelled TCC. Tomorrow I will pull this to try and isolate the TCC as the cause. I'll also ohm the coil secondaries.
I'll report the results.

BNaylor
10-17-2007, 10:02 PM
Wow, good suggestions! And nice to hear someone else has the same problem.
Mileage on the car is 142,500 miles. I have 71,000 on the plugs and 43,000 on the wires. ATF and filter were changed 31,000 ago.
The plugs are Bosch platinum #HR9DPY. They are the number recommended by the Bosch book. The wires are Niehoff Premium Silicone.
I see a fuse in the main fuse box labelled TCC. Tomorrow I will pull this to try and isolate the TCC as the cause. I'll also ohm the coil secondaries.
I'll report the results.

Pulling the TCC fuse will not do any good. You will lose the 12 volts to all shift, PCS, and TCC-PWM solenoids. The shifting will default to second gear and it will feel like the brakes are applied when trying to accelerate.

Do you have the same symptoms? The best plugs to use if you are stock are the AC Delco double platinum or Iridium or NGKs like TR55IX and AC Delco Premium Silicome 7mm igntition wires. Good idea to check coil resistance. .05-.09 ohms for primary and resistance 5K to 10K ohms for secondary.

goldberg_52403
10-17-2007, 10:43 PM
Thanks for the input BNaylor. I just rolled over 103k, and actually just put in new TR55IX's last weekend, the wires seemed to be near new. Driving home today I realized that the surge is really only 100 rpm at the most, just enough to notice it. Could that perhaps be a symptom of a faulty TPS? I will continue to search the forums.

Thanks again.

BNaylor
10-18-2007, 08:31 AM
Thanks for the input BNaylor. I just rolled over 103k, and actually just put in new TR55IX's last weekend, the wires seemed to be near new. Driving home today I realized that the surge is really only 100 rpm at the most, just enough to notice it. Could that perhaps be a symptom of a faulty TPS? I will continue to search the forums.

Thanks again.

TPS is possible but you can check the output with a DMM at ignition to ON not START. The input which is PCM reference is around 5 volts dc. On the output you'll get around .4 volts at idle and 4.5 volts at WOT. While moving the accelerator upwards the voltage should progress up linearly and smoothly. No erratic indications.

goldberg_52403
10-18-2007, 10:04 AM
I will try to check the output of the TPS for any erratic behavior. I suppose I am leaning against this because the car runs very smooth up until I get to highway speeds. Let's say the TCC solenoid is bad, would that cause the car to shift bad, or just have trouble accelerating in OD?

Once again, thank you BNaylor for you valuable advice.

richtazz
10-18-2007, 10:32 AM
The most common symptom of a bad TCC is sluggish acceleration/hesitation in OD, and if they get worse, bucking/stalling as you slow down due to the torque converter not releasing and the trans not downshifting.

goldberg_52403
10-18-2007, 01:59 PM
Ok, that explains exactly what is occurring, only under gentle acceleration in OD. Would it be recommended to have a tranny shop scan the transmission? I read somewhere that transmission issues dont alway flag the SES light, and a tranny scanner would be needed.

Thanks again to both richtazz and BNaylor, and sorry for all the questions.

richtazz
10-18-2007, 04:27 PM
The TPS could still cause this too if it's erratic, as the PCM wouldn't be getting a signal you're rolling on throttle thus commanding the TCC to release the torque converter. If the TPS checks out, then it would be advisable to have the car scanned with a trans capable scan tool. Never apologize for asking questions, that is why we're here and we're glad to help.

You can also do a resistance test on the wires. Acceptable resistance is 500 ohms per inch. Just because the wires look new doesn't mean much. Misting them with water at night and watching for cross-firing would also be a good test for the wires.

69ELCamino
10-19-2007, 06:29 AM
I have same symptoms/problem. guess what? it's the TCC and a rebuilt 4t65e.........

goldberg_52403
10-19-2007, 09:54 AM
69ELCamino, can you list what motor you have and miles? Also, is this the diagnosed problem, what is driving you away from the tcc solenoid? Is the problem more severe?

Thanks.

goldberg_52403
10-19-2007, 09:57 AM
I should have looked at your post a few threads down, I see you have the 3.1 and put the rebuilt in yourself. Did the rebuild come with new solenoid?

Thanks, just trying to get an idea about my solenoid/tcc.

Krule
10-20-2007, 08:44 PM
Hello, i purchased a 1999 grand prix Gt about 6months ago, and it seemed like i had the exact same issues, the surging but only when climbing hills, the rpm would be surging up n down at 2000 up n down by about 200, and just recently today while i was driving back home something in the front of the engine started clugging like metal on metal very very loud and i was only 1km from home so i drove it and then i parked the car at my place. tryed to start it up and the engine made the crazy sound and then hit the gas just a tad and that was it, no more shifting! it just gave out. Even when the cars off i can pull it into Drive and push it around. When i try to start the car now it wont even start, it doesn't even turn, the lights dim it makes the electrical sound like it's right about to crank and nothing. Wont start. just hit 394K it's well used i suppose. Recently had the oil pan gasket repaired (2months ago) at dealership. I have no idea what to even begin looking for, i've got a buddy coming over tommorow afternoon to take a look.. not much to see though. Any suggestions on what i should do?

Thanks, kyle.

Krule
10-22-2007, 04:40 PM
Timing chain snapped, and wrecked everything with it. At 394k the engine is offically toast. dealership wants 1500$ labour for an engine swap (89$ n hr at 16 HOURS LABOUR) 700$ at a backyard mechanic i know give or take a couple dollars. picking up a 200k engine for 400$ tommorow, from a 98 prix to my 99 prix, best bets to get a compatible engine, 96 le sabres 3800 i looked at had the heating pipes coming out different + wiring harness is different + mounting. So if your swapping an engine try n get a decent prix one for your prix. so 400$ + 700$ x 1.14 = 1300$ roughly. Also a refurbised or remanufactered 3800 from the dealership is 3100$! LOL! i could buy another prix for that.

Enzy
10-23-2007, 07:09 PM
Well, I've now replaced my tired old plugs with AC Delco irridiums and the coil resistance checked out OK. The car starts better with the new plugs, but still the same surge problem. I also did a little more road testing and confirmed that it still surges when manualy shifted into 3rd (D). I assume this would rule out the TCC solenoid since the TC only locks in OD?
I'm holding off on replacing plug cables since mine aren't that old.
Any chance the MAP sensor could cause this?

goldberg_52403
10-24-2007, 01:32 PM
I am pretty much in the same boat, although I am pretty sure its my TCC solenoid. My question is, could a bad wire cause the TCC solenoid to occassionally act up? My car runs beautiful 75% of the time (I drive on the interstate 60 miles a day), but sometimes acts up under gentle acceleration in OD (about 1/4 of the time). When I first got the car, the SES light came on and a wire had to be replaced at the TCC, and the light went away. Ironically afterwards I am having temperamental issues with the TCC, but no SES. Could this be related?

Thank you.

goldberg_52403
10-24-2007, 08:09 PM
I actually just found a very in-depth website that has a lot of detail about the 4t65e transmission. Take a look here:

http://www.tripleedgeperformance.com/4T65E_Transmission_Info.php

Has anyone been here before? They do have a section in regards to my issue:

Tach bounces up and down a few hundered rpm while cruising in lockup:
Another common problem / concern of this transmission and more pronounced with added engine power or higher mileage. This generally happens when the valve body has excess wear in the TCC valve area. Excessive fluid leakage in this area of the valve body causes TCC apply pressure loss and can lead to uncontrollable TCC operation which causes the engine rpm to bounce up and down a bit. This problem is noticed most after driving a while and speeds between 42 and 70mph and in 4th gear. There are other causes to this problem that can be from worn or shrunken teflon seals on the input shaft, a bad o-ring on the input shaft that seals in the torque converter, a faulty torque converter clutch, and even a bad pressure control solenoid. Another common occurance is a worn out sleeve in the channel plate that supports the input shaft. When this sleeve wears the input shaft will get chewed up where the sealing rings are and cause problems. Commonly code P0741 will be found in the pcm memory as a stored code and is described as Torque Converter Clutch Stuck Off. When this happens adaptives shifts are disabled, TCC operation is disabled, and 4th gear can be disabled. Generally a new or reman / repaired valve body will correct this condition and a new EPC solenoid is always suggested as well. The TCC/PWM solenoid is rarely ever at fault and I am yet to find one bad. Again the valve body is the common cure BUT not always the culprit and certainly not the whole problem after this has been happening for a while. Any time a torque converter fails there will be debris going back into the trans. There is a pressure relief valve in the channel plate that will collect debris from a bad torque converter and reduce cooler flow, cause trans to run hot, and greatly effect TCC operation and can destroy a new converter in a matter of miles if this isnt carefully inspected or upgraded. The best way to verify proper operation as commanded by the pcm is with a scan tool by viewing TCC slippage rpm, TCC duty cycle, EPC data, and checking any codes and making sure the engine is running properly and a misfire is not a false sense of a torque converter problem or shudder.

I think I am going to take the car to a transmission shop tomorrow and see if they can scan my transmission. I would hate for it to be the internal parts, but that would actually be covered under my warranty.

yakman
12-30-2007, 12:41 AM
Any solution on the car ? I would really like to know !
Mine is exactly the same !!

goldberg_52403
12-30-2007, 12:40 PM
Unfortunately I have not been able to fix my car yet, just financial reasons. My issue isnt incredibly bad, just annoying when driving on the interstate. If it begins to get worse, I will definitely have to take it to the tranny shop.....

Good luck!

Enzy
12-31-2007, 09:10 PM
I have not proceeded further and am currently 'putting up with it', manually shifting down when the engine starts hunting. I will follow Goldbergs advise and have a scan done when I get a chance.
Please let me know how you make out.

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