RPM Suddenly Drops Off Releasing Throttle
01-10-21, 03:44 PM
#1
Rookie
Thread Starter
RPM Suddenly Drops Off Releasing Throttle
Problem is more or less exactly what the title indicates.
I'll be cruising the streets in stop and go traffic and hit the gas to get up to speed. The instant I come off the gas, the RPM drops significantly. Almost feels like it shifts into OD from 3 every time I lift off the gas.
RPM will go from 2.2 - 3.2 immediately down to 1.5 - 1.6 coasting at speed with no throttle input.
I do come off the throttle rather sharply, no 'gradual' release, so maybe that could be why, but it hasn't behaved this way before.
Some things to note: I did rebuild the ECU recently and did Lextreme's mod with the air intake. Throttle body was also recently cleaned. Also, problem does not manifest on the highway, only city speeds <50.
Is this normal and immediately releasing the gas is something I should stop doing, or is this indicative of something else wrong?
Doesn't feel like brakes dragging or anything I could easily pinpoint. I do have a badly failing power steering system but that is getting fixed soon and isn't something I would expect to interfere with engine speed.
I'll be cruising the streets in stop and go traffic and hit the gas to get up to speed. The instant I come off the gas, the RPM drops significantly. Almost feels like it shifts into OD from 3 every time I lift off the gas.
RPM will go from 2.2 - 3.2 immediately down to 1.5 - 1.6 coasting at speed with no throttle input.
I do come off the throttle rather sharply, no 'gradual' release, so maybe that could be why, but it hasn't behaved this way before.
Some things to note: I did rebuild the ECU recently and did Lextreme's mod with the air intake. Throttle body was also recently cleaned. Also, problem does not manifest on the highway, only city speeds <50.
Is this normal and immediately releasing the gas is something I should stop doing, or is this indicative of something else wrong?
Doesn't feel like brakes dragging or anything I could easily pinpoint. I do have a badly failing power steering system but that is getting fixed soon and isn't something I would expect to interfere with engine speed.
01-12-21, 08:31 AM
#2
Intermediate
Problem is more or less exactly what the title indicates.
I'll be cruising the streets in stop and go traffic and hit the gas to get up to speed. The instant I come off the gas, the RPM drops significantly. Almost feels like it shifts into OD from 3 every time I lift off the gas.
RPM will go from 2.2 - 3.2 immediately down to 1.5 - 1.6 coasting at speed with no throttle input.
I do come off the throttle rather sharply, no 'gradual' release, so maybe that could be why, but it hasn't behaved this way before.
Some things to note: I did rebuild the ECU recently and did Lextreme's mod with the air intake. Throttle body was also recently cleaned. Also, problem does not manifest on the highway, only city speeds <50.
Is this normal and immediately releasing the gas is something I should stop doing, or is this indicative of something else wrong?
Doesn't feel like brakes dragging or anything I could easily pinpoint. I do have a badly failing power steering system but that is getting fixed soon and isn't something I would expect to interfere with engine speed.
I'll be cruising the streets in stop and go traffic and hit the gas to get up to speed. The instant I come off the gas, the RPM drops significantly. Almost feels like it shifts into OD from 3 every time I lift off the gas.
RPM will go from 2.2 - 3.2 immediately down to 1.5 - 1.6 coasting at speed with no throttle input.
I do come off the throttle rather sharply, no 'gradual' release, so maybe that could be why, but it hasn't behaved this way before.
Some things to note: I did rebuild the ECU recently and did Lextreme's mod with the air intake. Throttle body was also recently cleaned. Also, problem does not manifest on the highway, only city speeds <50.
Is this normal and immediately releasing the gas is something I should stop doing, or is this indicative of something else wrong?
Doesn't feel like brakes dragging or anything I could easily pinpoint. I do have a badly failing power steering system but that is getting fixed soon and isn't something I would expect to interfere with engine speed.
My shot in the dark guess is a TPS that is on the fritz? I have read on this forum that they have caused issues before throwing a code
01-12-21, 08:39 AM
#3
Rookie
Thread Starter
I have a similar issue with my '94, and it has seemed to appear out of nowhere recently. For me its when cruising 1800-2000 RPM, let off throttle, then drops ~400 RPM instantly along with a thud noise + feeling as if it just slammed into overdrive like you say. But it is random/intermittent for me which leads me to possibly something electrical?
My shot in the dark guess is a TPS that is on the fritz? I have read on this forum that they have caused issues before throwing a code
My shot in the dark guess is a TPS that is on the fritz? I have read on this forum that they have caused issues before throwing a code
01-12-21, 08:56 AM
#4
Emissions spike up sharply when the throttle is closed abruptly so computer controlled
fuel injection systems have been programmed to gradually close the air control butterfly
valve. Perhaps your rebuild project eliminated this designed in function?
fuel injection systems have been programmed to gradually close the air control butterfly
valve. Perhaps your rebuild project eliminated this designed in function?
01-12-21, 11:15 AM
#5
Rookie
Thread Starter
All I did was change the capacitors out so I can't imagine I altered the functionality. It is possible though that the computer needed a few hours of run time to properly adjust itself to being driven for the "first" time.
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