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97gtp stutter at hard throttle


97grprixgtp
10-15-2010, 01:24 PM
Hey there i did an engine replacement recently and finished up this monday. car idles and runs fine under light throttle. But under heavy and hard throttle it it has multiple misses that makes it feel like i'm running a stutter box. I have pulled a few codes, p121 tp sys perf, p1406 egr pintle position sensor, p300 multiple/random misfires detected, and p0140 ho2 ckt insuff activity sensor 2. The p0140 I know what is going on with that one. I could use some help on the other ones and if either would cause the stutter. Thanks

3100
10-15-2010, 02:12 PM
check that your EGR is installed correctly (not backwards)

97grprixgtp
10-15-2010, 02:20 PM
yes the egr is on properly and I should add this happens only under load. In park I can rev it under any throttle condition and there is no miss no stutter or anything.

tblake
10-15-2010, 05:07 PM
I would start narrowing down the list of codes. Begin with the first, once that problem is solved, clear all of them and then see what comes back on. Repeat. You could try to replace the TPS Sensor.

I would see if you can find a common circuit that the TPS, O2 Sensor, and EGR Valve share. Maybe a ground wite isn't hooked up correctly.

Other than that, missfires under load are usually caused by low fuel pressure or an exhaust restriction (blocked CAT).

97grprixgtp
10-15-2010, 06:28 PM
The o2 code i know the issue... no o2 sensor. The other two do share the same ground location, that is what I am doing now, looking for that connection. Then I am going to start testing voltages to each and see if one is bad. Oh I also have a connector on the firewall side of the harness I can not find where it does. The wiring diagram I located it on says it is a data link connector. It goes to the dlc uart and dlc class 2 data pins on the pcm.

97grprixgtp
10-16-2010, 12:01 PM
ok all the grounds are good and so is the reference 5 volts from the pcm. I have noticed it happens at 4 thousand rpms in park and at 2400 rpms in gear. fuel pressure is 40-45 at idle goes up to around 50 psi under throttle. tps shows smooth increase and decrease. map starts at 10" hg and moves to 30+". egr pintle shows no open or close percentage at all. took off egr and the pintle easily opens and closes with a light push on it with a finger.

3100
10-16-2010, 04:05 PM
at 4K rpm that is normal that is rev limiter. Maybe crankshaft relearn is what you need since you replaced engine. There should be code for that, but I would do it anyway.

97grprixgtp
10-16-2010, 07:22 PM
Could a coil pack cause that at higher rpm? I am running rich when it happens as well.

3100
10-16-2010, 07:34 PM
running rich because of misfires, unburned gas enters exhaust + o2 sensor sees more air (unexploded mixture of gas and air) and is telling to ECM to rich en AF ratio even more.

-try disconnecting O2 sensor for AF mixture see how it rides then. It is possible that o2 sensor is sending confusing signals to ECM.

BNaylor
10-17-2010, 07:13 AM
Hey there i did an engine replacement recently and finished up this monday.

What year was the engine and what source?

97grprixgtp
10-17-2010, 07:51 AM
Best of my knowledge it came out of a 99 buick.

3100
10-17-2010, 10:29 AM
did you try disconnecting the O2 sensor?

BNaylor
10-17-2010, 10:39 AM
Best of my knowledge it came out of a 99 buick.

Did you use the throttle body and MAF sensor off the '99 L67 engine or use your original?


To clear the air on "case learn" especially for the 1997 model year Grand Prix GTPs with the Series II 3800 supercharged engine a crankshaft variation procedure aka case learn is normally not required unless a P1336 DTC is showing and then it becomes mandatory. If the original 1997 PCM module to include knock sensor module is used then there should be no issues regarding a case learn and doing one may be a waste of time and money.

A "case learn" does not prevent physical misfires whether random or fixed from occurring but prevents false/bogus misfires from getting picked up or setting and being stored in the PCM module or showing up on wrong cylinders. In other words it is used for diagnostics only and not performance.

97grprixgtp
10-17-2010, 10:40 AM
yes I did, no change. Went ahead and changed the coils also no change. I started running the scanner oem tests and so far my map is questionable says it is reading 30 inches hyg and should be between 12-20 inches hyg. But I am not entirely sure I am conducting the tests right.

97grprixgtp
10-17-2010, 10:42 AM
I am using the throttle body and maf from the 99. Along with the 99 map, tps, iac, egr, and O2. My original 97 pcm is also being used as I was told I needed to run that pcm because of that knock module.

BNaylor
10-17-2010, 10:45 AM
I am using the throttle body and maf from the 99.

The MAF (Mass Air Flow) sensor for 1997-1998 is different from 1999 and up. Also, the MAF/VAF programming tables programmed in the PCM module is different so one issue is you have an incompatability issue.

Do you still have your original throttle body and MAF sensor?

3100
10-17-2010, 10:46 AM
map should show outside barometric pressure withe key on engine off. It should also be about 4.7V then when engine is idling it will show 10 or 11 in Hg so you subtract from your barometric pressure for example : 30in Hg with key on engine off and when engine is idling you see 10 in Hg that means that your engine at idle is producing 20 in Hg of vacuum and that is normal. So at idle map should show about 1.3-1.5 V

97grprixgtp
10-17-2010, 10:48 AM
The MAF (Mass Air Flow) sensor for 1997-1998 is different from 1999 and up. Also, the MAF/VAF programming tables programmed in the PCM module is different so one issue is you have an incompatability issue.

Do you still have your original throttle body and MAF sensor?

No I do not still have the old stuff unfortunately. Do I need the throttle body? Or just the MAF?

97grprixgtp
10-17-2010, 10:50 AM
map should show outside barometric pressure withe key on engine off. It should also be about 4.7V then when engine is idling it will show 10 or 11 in Hg so you subtract from your barometric pressure for example : 30in Hg with key on engine off and when engine is idling you see 10 in Hg that means that your engine at idle is producing 20 in Hg of vacuum and that is normal. So at idle map should show about 1.3-1.5 V

And actually that is my reading at idle of 10in hyg.

3100
10-17-2010, 10:51 AM
how many g/sec of air MAF is showing at idle? it should be between 3-5 g/sec

3100
10-17-2010, 11:03 AM
if you experience the same problems with maf sensor disconnected, then maf is not your problem. With MAF sensor disconnected PCM takes over using its own mapping tables. You will still be able to drive, and the only problem you will notice is when ever you accelerate from complete stop engine will choke for 1/2 sec other than that it will run normal.

97grprixgtp
10-17-2010, 11:32 AM
how many g/sec of air MAF is showing at idle? it should be between 3-5 g/sec

The g/sec at idle is between 6 and 10. mostly around 6 to 7

97grprixgtp
10-17-2010, 11:35 AM
I also show a lean mixture in the 12s at idle and seems to shoot to rich under load when it breaks up.

97grprixgtp
10-17-2010, 11:40 AM
It does do it with the maf unplugged too.

3100
10-17-2010, 12:31 PM
did you have this problem with the old engine? try removing serpentine belt for and test drive it for 2 min, sometimes rectifier bridge in the alternator can go bad and some AC voltage will pass unfiltered and that can cause problems that you have. Or put your old alternator on.

97grprixgtp
10-17-2010, 01:10 PM
Did not have the prob prior. It is my original alt.

3100
10-17-2010, 01:46 PM
can you do ckp relearn on your scanner?

97grprixgtp
10-17-2010, 03:53 PM
No it does not seem to have the ability to do a case learn. I see the maf is smaller on the 97-98 so I guess i need the throttle body. Are they the same on the non sc as on the sc engine?

97grprixgtp
10-22-2010, 06:40 AM
Ok picked up another throttle body and put it on last night, the stutter and miss is not as bad but is still there. Got in it this morning fired it up and at first it would not idle and the throttle was nearly unresponsive. Finally got it to idle but it is idling at 1800 rpm. And now my scanner will no longer read the car. It keeps saying to check the key is in the on position and I have no check engine light any longer. Any new help is greatly appreciated.
Thanks

tblake
10-23-2010, 07:50 PM
Check your fuses for the cigarette lighter circuit on the scanner issue. Then you'll want to make sure all the Pins in your ALDL are lined up and not bent both in the car plug and your scanner.

The Crank Variation Learn as Bob (bnaylor) mentioned is not necessicary unless the code is present.

What year, make and model did the throttle body come from?

3100, just so you know, I was working on a 1998 olds intrigue with 3800. The car ran bad, random misses all over the place, and randomly stalled. Unplugging the MAF made the car run WORSE. Replacement of the MAF is what cured the problem. So sometimes unplugging it isn't a valid test.

Bob, do you think the knock sensors should have been transfirred over from the old motor the the new one?

BNaylor
10-24-2010, 07:48 AM
The throttle bodies between the L67 and L36 are different. The L67 is much bigger. L36 is around 65mm but obviously you use the throttle body from a L67 only and MAF sensor should be for '97-'98 only.

To bring the idle down check the throttle body butterfly stop and adjust the stop screw until the idle comes down and/or the IAC counts are correct.

BNaylor
10-24-2010, 08:12 AM
Bob, do you think the knock sensors should have been transfirred over from the old motor the the new one?

Tim,

Probably a good practice but not necessary. The knock sensors are the same for '97-'03. Plus a PITA to replace once the engine is installed.

However, I would run a check for knock retard (KR) with a scan tool that has the capability to do so just to be sure.

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