RPM drops, then returns to normal when coasting
10-10-14, 04:00 PM
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RPM drops, then returns to normal when coasting
Hey guys! Got a prob with my '95 GS300... It operates perfectly, except when I'm between about 37-44mph.. In this mph range, when I let off the gas, the RPMs will start to lower as they should, then, about a second or two later, the RPMs take a ~500RPM dip, then return to the normal RPM levels. This only happens during thi 37-44mph range.
Even if I get going 50+mph and let off the gas, RPMs drop fine until it hits the 37-44mph range, then the dip/return-to-normal happens.
This isn't a huge issue when I'm just normally cruising, but if I, for example, switch lanes, speed up, then have to slow down quickly/unexpectedly, this dip has caused the car to stall a couple of times, and not be able to restart until usually the next day.
I've almost pulled all of my hair out over this issue. It's an on/off occurance since I've owned the car the past 3 years. It doesn't seem to matter what the outside temp is, or the engine temp.
I've done extensive research and have found fixes ranging from MAF(which I know mine has the Karman Vortex version), TPC, IAC, throttle body gasket, O2 sensors, clogged cats, torque converter, vacuum leak, fuel filter, fuel pump, temp sensor, PCV(or PVC?) valve, etc... Basically, I've seen everything but the power antenna being blamed... And, on the other side of that, I've also heard that this is a normal thing, and it's nothing to worry about.
I've recently replaced plugs, wires, distributor/rotor, ignition coil, cleaned the throttle body, changed the oil, replaced valve cover gaskets, added seafoam to the gas, scratched my head, and invented a few new cuss words...
Like I said, other than this one issue, the car is perfect.. It shifts great, has decent acceleration, doesn't stutter or shake with rough idle, etc.. I tried to pull codes about a week ago, and although my CEL wasn't on, I was throwing an O2 code. Off the top of my head, I can't remember if it was up or downstream (or if there's a difference in the codes), but I know my upstream sensors are less than 3 years old.
Can anyone offer any guidance? Or should I just pull out the rest of my hair, so I'll at least have a uniform look? lol
Even if I get going 50+mph and let off the gas, RPMs drop fine until it hits the 37-44mph range, then the dip/return-to-normal happens.
This isn't a huge issue when I'm just normally cruising, but if I, for example, switch lanes, speed up, then have to slow down quickly/unexpectedly, this dip has caused the car to stall a couple of times, and not be able to restart until usually the next day.
I've almost pulled all of my hair out over this issue. It's an on/off occurance since I've owned the car the past 3 years. It doesn't seem to matter what the outside temp is, or the engine temp.
I've done extensive research and have found fixes ranging from MAF(which I know mine has the Karman Vortex version), TPC, IAC, throttle body gasket, O2 sensors, clogged cats, torque converter, vacuum leak, fuel filter, fuel pump, temp sensor, PCV(or PVC?) valve, etc... Basically, I've seen everything but the power antenna being blamed... And, on the other side of that, I've also heard that this is a normal thing, and it's nothing to worry about.
I've recently replaced plugs, wires, distributor/rotor, ignition coil, cleaned the throttle body, changed the oil, replaced valve cover gaskets, added seafoam to the gas, scratched my head, and invented a few new cuss words...
Like I said, other than this one issue, the car is perfect.. It shifts great, has decent acceleration, doesn't stutter or shake with rough idle, etc.. I tried to pull codes about a week ago, and although my CEL wasn't on, I was throwing an O2 code. Off the top of my head, I can't remember if it was up or downstream (or if there's a difference in the codes), but I know my upstream sensors are less than 3 years old.
Can anyone offer any guidance? Or should I just pull out the rest of my hair, so I'll at least have a uniform look? lol
10-10-14, 04:18 PM
#2
Lexus Test Driver
I had a similar issue with my 94 but it never stalled. It turned out to be my TPS sensor. The sensor itself wasn't bad but it was out of adjustment. It was out of adjustment so the car thought I was completely off of the throttle before I actually was. I used the data list option in my scan tool to watch the signal input and output. Hope that helps! Good luck!!
06-05-21, 11:21 AM
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same issue here
although mine didn't start doing this until after this one incident...as I was leaving the house (after a big argument) I was so mad and I punched on the gas hard...really hard...then when I got on the freeway it was kinda ok until I exited then my car started to do that rattle like it was gonna turn off but it never did then I noticed while at stop idle would drop to 500rpm...I'm gonna get it checked...right now.
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