00 GT Lunging/bogging after shift

[jretzlaff]

My 2000 GP GT is having an acceleration problem.... It seems to act up the most when I'm getting on the on-ramp to the freeway. For the initial acceleration (20-60mph) it's generally fine, but when it shifts up (to 4th I believe) for the last moderate (medium throttle) acceleration from 60 to 70 mph, it seems to bog/lunge until it's past the 1500-2000 rpm range. I can literally watch the tach bounce 100-200 rpms at a time until it gets above 2000-2200 and then its all good. Even when this is happening, if I get on the gas, it's fine, plenty of acceleration.

Another good example is that I usually have the cruise set at 72mph. Today, I had to get out of it for a slowass in the fast lane and got down to 58-60mph. Once I got around him, I hit "resume" and the same thing happened.... It almost acts like I have a BIG trailer behind me and it's trying to get up to speed.

Anyway, a local mech. told me I need a tune-up ($100 for an air filter, pcv valve, fuel filter and plugs). Well I'm pretty cure I change all of this myself and save about half of that. But is that the fix?

Does his diagnosis sound right or is there something else I should be checking or have missed?

HELP!

J

[BNaylor]

Originally Posted by jretzlaff

My 2000 GP GT is having an acceleration problem.... It seems to act up the most when I'm getting on the on-ramp to the freeway. For the initial acceleration (20-60mph) it's generally fine, but when it shifts up (to 4th I believe) for the last moderate (medium throttle) acceleration from 60 to 70 mph, it seems to bog/lunge until it's past the 1500-2000 rpm range. I can literally watch the tach bounce 100-200 rpms at a time until it gets above 2000-2200 and then its all good. Even when this is happening, if I get on the gas, it's fine, plenty of acceleration.

Another good example is that I usually have the cruise set at 72mph. Today, I had to get out of it for a slowass in the fast lane and got down to 58-60mph. Once I got around him, I hit "resume" and the same thing happened.... It almost acts like I have a BIG trailer behind me and it's trying to get up to speed.

Anyway, a local mech. told me I need a tune-up ($100 for an air filter, pcv valve, fuel filter and plugs). Well I'm pretty cure I change all of this myself and save about half of that. But is that the fix?

Does his diagnosis sound right or is there something else I should be checking or have missed?

HELP!

J

It's probably a good starting point. Nice to know how many miles are on your GP.






Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[jretzlaff]

65K and how often should I get a tranny fluid change? I haven't had that done since I've owned it (since 22k). And is there anything in particular to make sure is done when getting a tranny fluid change?

Thanks guys...

[BNaylor]

Originally Posted by jretzlaff

65K and how often should I get a tranny fluid change? I haven't had that done since I've owned it (since 22k). And is there anything in particular to make sure is done when getting a tranny fluid change?

Thanks guys...

GM recommends a 100K mile interval but I wouldn't wait that long. Every 50K miles or less is better. Just do an ATF drain/pan drop and change the screen filter only. It uses Dextron-III and you'll need approximately 7.5 quarts. The general concensus on the forum is not to do a flush or so called fluid exchange method. Good luck!








Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.

[jretzlaff]

OK, I replaced the PCV Valce, Spark Plugs, air filter ( W/K&N) and the fuel filter. The fuel filter was obviously a problem in that you could hardly blow through it. So I thought I had definitely found the problem. I then took it for a spin and THE SAME THING! When at higher speed and you back off, then moderately accelerate again, it "jerks" forward.

Is it possible that my fuel filter was so bad (it was very plugged vs. the new one) that I damaged the fuel pump? If so how would I check that? Or is that a job for Mr. Goodwrench?

Any help would again be geratly appreciated... I'm at my witts end.

Thanks,
J

[richtazz]

Did you ever have a check engine light come on? Just to be safe, take it to Auto-Zone or Advance and have them scan it. It sounds like a torque converter lock-up solenoid or pressure control solenoid sticking, if there aren't any codes stored.

[jretzlaff]

Thanks for the quick reply... I don't have a check engine light on. I called Autozone and they said if there is no check engine light there is nothing they can do. Where is the Torque converter lck-up solenoid and the pressure control solenoid? Can an ameteur behind a wrench change these? If so, how expensive are they? Or should I just take to Mr. GR and have them charge me $$$ to find the problem?

[richtazz]

The tcc and pressure control solenoids are inside the trans, and beyond the shade tree mechanics ability (you have to drop the cradle to change them). Before giving it to the dealer, check the fuel pressure at the rail to eliminate fuel pressure as a possible cause. If fuel pressure is ok, then I'd suspect the trans is the cause.

[jretzlaff]

Okay, how do I check the pressure at the rail? And if it is bad, what does this mean? Bad pump? If so, is the pump replacement a shade tree swap?

Thanks again for you help guys.

[BNaylor]

Originally Posted by jretzlaff

Okay, how do I check the pressure at the rail? And if it is bad, what does this mean? Bad pump? If so, is the pump replacement a shade tree swap?

Thanks again for you help guys.

Hookup an automotive fuel pressure gauge (FRP) at the Schrader valve located on the fuel pressure regulator. Autozone has them for around $30.00. Actron brand.

With vacuum off the the FPR, it should read around 52 psi. With vacuum connected it will read in a range of 45 - 55 psi. There should be no more than a 4 - 7 psi difference with vacuum off and on. Initial fuel pressure with ignition on but not in engine start position will be around 52 psi or so. If the reading is below that you can suspect the fuel pump.The tolerance is 48 - 55 psi. The fuel pump can be DIY but it's tedious. We have procedures for that.

Good luck and please keep us posted.







Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 103,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials
1/4 ET: 13.210 sec. @ 104.490 mph
0 - 60 ft: 1.945 sec.