46MPH hesitation
09-10-2005, 12:50 PM
#1
46MPH hesitation I have posted serveral times on different forums and can't find an answer.
I have a 99' white trans am M6. When I'm driving and I go from 4->5 at 40, as soon as I get to 46MPH the car has a slight hesitation. It is almost as if it bogs down and then everything is normal again.
It isn't everytime I hit 46 MPH and i tried to slow down from 5th with no brake to see if it would cause anything at 46 but I felt nothing. I can feel it even when I'm in 4th gear (not as noticeable). When I'm at a full WOT I can't notice anything. What would be causing this? I am getting very annoyed at feeling it bog down at this speed. Also, If I slow down but don't stop, I won't get the hesitation. It is usually when I stop and then go. I don't really feel any problems with the clutch, and I don't get any slippage especially when I slam gears.
I have a 99' white trans am M6. When I'm driving and I go from 4->5 at 40, as soon as I get to 46MPH the car has a slight hesitation. It is almost as if it bogs down and then everything is normal again.
It isn't everytime I hit 46 MPH and i tried to slow down from 5th with no brake to see if it would cause anything at 46 but I felt nothing. I can feel it even when I'm in 4th gear (not as noticeable). When I'm at a full WOT I can't notice anything. What would be causing this? I am getting very annoyed at feeling it bog down at this speed. Also, If I slow down but don't stop, I won't get the hesitation. It is usually when I stop and then go. I don't really feel any problems with the clutch, and I don't get any slippage especially when I slam gears.
09-10-2005, 11:54 PM
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woohoo, I'm not crazy. I have been trying to track down a similar problem on my '98 Z for years. I have isolated the failing condition to two points ~1800 and ~2300RPM in any gear(M6) while accelerating. The higher the gear the more noticible the hesitation. Also, using a very light throttle and going uphill while accelerating causes it to be more noticible. Very rarely(once per year), I will get hesitation so bad that it feels like the engine shut off. Here are my possible culprits:
1) false knock causing ignition retard
I suspect that the false knock might be caused by my rattling idler pully.
Rev you engine slowly in neutral from 1000 to 2500RPM and see if your idler goes beserk.
2) Throttle Position Sensor flaking out causing poor A/F ratio
3) Crank position or Cam position sensor flaking out.
4) Some weird EMC problem that only occurs when the moons are in alignment(I hope not).
I have not yet been able to track down the problem with ATAP yet.
1) false knock causing ignition retard
I suspect that the false knock might be caused by my rattling idler pully.
Rev you engine slowly in neutral from 1000 to 2500RPM and see if your idler goes beserk.
2) Throttle Position Sensor flaking out causing poor A/F ratio
3) Crank position or Cam position sensor flaking out.
4) Some weird EMC problem that only occurs when the moons are in alignment(I hope not).
I have not yet been able to track down the problem with ATAP yet.
09-11-2005, 12:00 AM
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Originally Posted by 5w20
Sounds like an EGR problem.
hmmm... anyone know what the specific conditions are before EGR kicks in. I know it is during light throttle. Maybe I'll just throw in a blockoff plate and see if the problem goes away.
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09-11-2005, 12:36 PM
#9
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Originally Posted by white99
i hope it's as simple as the egr valve. i'm going to change that sucker tomorrow. hopefully it solves the problem.
09-11-2005, 12:41 PM
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Originally Posted by white99
I get no ses lights or cel lights at all. wouldn't some of those problems throw a code?
It might not be the problem but I would give it a shot.
09-22-2005, 01:11 PM
#16
I just cleaned the MAF. It had black carbon looking dirt along the small tiny filament wires connected to the metal bars that go across. I very very carefully cleaned the filaments with a dry q-tip. The bars also had some of the dirt build up. I cleaned these very carefully (avoiding hitting the filaments).
I test drove my car for about 5 miles. Have not had the problem at all. I'll keep everyone posted if I happen to get the hestitation.
I am also going to go clean my EGR. I'm going to buy a bottle of carb cleaner.
I test drove my car for about 5 miles. Have not had the problem at all. I'll keep everyone posted if I happen to get the hestitation.
I am also going to go clean my EGR. I'm going to buy a bottle of carb cleaner.
09-22-2005, 10:08 PM
#19
As I became confident the problem was 100% gone, I found only disappointment when the damn thing hesitated at that exact speed again. I am going to clean the EGR valve with carb cleaner either saturday or sunday. Hopefully that solves the problem, otherwise I'm left clueless once again.
09-22-2005, 10:12 PM
#20
Originally Posted by denscor
I have a 2001 corvette and it does the same thing. It doesn't have a EGR system! 