acceleration issue at high speed
12-09-2018, 12:31 PM
#11
Senior Member
True Car Nut
Whay rjolly87 said ^^^^^^
I'd start by connecting to the PCM and (with the engine off and ignition on) watching the PCM'* opinion of the throttle position as you slowly move the throttle slowly across its range both directions. If it jumps around or pauses along the way then you've found your problem. Or one of them.
And yeah, the TPS is sealed and unserviceable.
I'd start by connecting to the PCM and (with the engine off and ignition on) watching the PCM'* opinion of the throttle position as you slowly move the throttle slowly across its range both directions. If it jumps around or pauses along the way then you've found your problem. Or one of them.
And yeah, the TPS is sealed and unserviceable.
12-09-2018, 09:51 PM
#12
Senior Member
True Car Nut
Get the car to normal operating temp........
From a dead stop, safely lay into it.......does the transmission shift ok, and get up to speed quickly?
Or does it rev out at 3K, and doesn't shift? But if you lightly accelerate from a dead stop, it shifts ok , and gets up to speed?
If that'* what happens, I would be leaning towards a blockage in the exhaust(cat).....
From a dead stop, safely lay into it.......does the transmission shift ok, and get up to speed quickly?
Or does it rev out at 3K, and doesn't shift? But if you lightly accelerate from a dead stop, it shifts ok , and gets up to speed?
If that'* what happens, I would be leaning towards a blockage in the exhaust(cat).....
12-22-2018, 10:45 PM
#13
Junior Member
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To confirm the Torque converter clutch (TCC) is behaving properly, you can hold throttle still at cruise, and then start dragging the brakes slightly. Once you start to engage the brakes, the TCC should release, causing engine speed to jump. Once you release the brakes, the TCC should reengage soon after, and engine speed should lock back down.
I am also curious what the service history is. If the vehicle is down on power because it needs a tuneup, or as a result of another mechanical or electrical issue, it could cause what would appear to be a deadzone in the power band. When the TCC is locked at cruise, this is typically the weakest point, because the engine is locked with essentially a solid connection to the drive wheels, and often at a speed low in the power band. Think of trying to accelerate a car with a manual transmission up a hill in top gear. Just about anything is going to seem weak at that point.
I am also curious what the service history is. If the vehicle is down on power because it needs a tuneup, or as a result of another mechanical or electrical issue, it could cause what would appear to be a deadzone in the power band. When the TCC is locked at cruise, this is typically the weakest point, because the engine is locked with essentially a solid connection to the drive wheels, and often at a speed low in the power band. Think of trying to accelerate a car with a manual transmission up a hill in top gear. Just about anything is going to seem weak at that point.
12-22-2018, 11:18 PM
#14
Senior Member
True Car Nut
Unless it is making bad noises it'* probably not the problem.
Last edited by CathedralCub; 12-23-2018 at 08:53 PM. Reason: Removed redundant question.
12-23-2018, 12:52 AM
#15
Senior Member
True Car Nut
I am still thinking it'* down on power.
Honestly, my first reaction was exhaust restriction, and I haven't seen anything to discredit that possibility. Just because a car can pass emissions doesn't mean the catalytic converter isn't clogged.
Without a scan, or proper diagnostic, I believe everyone is just throwing guesses out at this point.
12-23-2018, 08:49 PM
#16
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True Car Nut
I agree with rjolly87 . We're guessing. Can you post a video of the behavior?
12-26-2018, 02:09 AM
#17
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Sorry for the delay. I tried your suggestion. I was cruising on 95 doing about 60mph @2000rpm and as soon as I dragged the brakes it jumped to 2500 or so (just like you said) and then went right back to 2000.
12-26-2018, 06:37 AM
#18
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Thanks again. Your suggestion that its an exhaust issue jogged my memory. When I first got the car, the muffler (which had already been replaced at least one) was split almost completely down the seam. I patched it and honestly forgot all about it. I was only concerned about the noise. I feel kinda dumb tbh. So since I already need a new muffler I'm, going to get me one and I'll let you know if it fixes the issue. It can't it any worse.
12-26-2018, 07:59 AM
#19
Senior Member
True Car Nut
It would only matter if the repair was done in a way that causes a restriction. I would be more concerned about why the muffler was split. If it took a back fire to the exhaust that blew the muffler out, it would have likely damaged the catalytic converter.
12-26-2018, 10:15 AM
#20
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I've been putting off getting a new muffler for a while anyway. But I'm still trying to figure out why the car doesnt accelerate. I understand the lock plate and how that works but if I press the gas, the engine RPMs should go up. Is it normal to hit the gas and the RPMs not go up unless I let off the gas completely and reapply gas? What would cause that?