1998 Chevy Malibu 6 cyl Front Wheel Drive Automatic 150Kkm miles
I had my LIM gasket replaced with a good one about a month ago. Then I decided to take a trip up north to the cottage and the problem started.
Here is what happens. Usually it happens when accelerating from a stop more than accelerating while already moving so I will explain what happens when this problem occurs when at a stop light. I am stopped, the light turns green, I will go to step on the gas and the car will start to accelerate for the first second until the RPM reaches 1800 or so. Once it hits ~1800 RPM, that's it, the RPM will just want to stay there as if getting past that point is the biggest struggle ever in history. .
When this happens, the engine sounds like it is just sucking in air. You can hear the throttle responding to the gas pedal if you press the pedal a bit but the engine just won't give any "pull" or "thrust" to get moving and get going past that ~1800 RPM sticking point. It's like the engine has lost about 75% of its power to accelerate.
If you keep depressing the gas pedal more and more, the RPM gauge will usually, but not always, slowly creep up and up but it will do so more slowly than a snail. As the RPM struggles to climb up, the car gradually start to get moving but it will again be at about half the accelerating power it should normally have. Sometimes it won't speed up at all regardless of how far down you press the gas. You will just keep hearing the air coming in from the Cold Air Intake, but the car will just crawl along.
Occasionally if you slam the gas pedal to the floor then it will kick back in at full throttle. Other times if you floor it, it will creep up to full throttle RPM's but the car will take off with only a fraction of the normal power.
It is as if the engine just loses all its power on accelerationwhen this happens. But the weird thing is that if you release the gas pedal completely and press it down again, it may take 1-5 tries, but eventually you press the gas pedal and the car accelerates like normal. Also, the problem is very intermittent (happens maybe 30% of the time). As the car drives fairly decently most of the time (although I have noticed that even when performing normally the engine sounds kind of airy) There is no check engine light.
I have a fuel pressure gauge attached to the engine's fuel pressure test port and the gauge is mounted up by the windshield so I can see it while driving. Fuel pressure is totally normal even when this problem occurs. When the problem is occuring, I can press up and down a bit on the gas pedal and the fuel pressure responds just as it should.
I thought it may be the TPS. I have replaced the TPS twice in the last month with no change. I checked the wiring at the TPS and it is fine. The 5V reference wire is giving ~5V at the TPS and the TPS signal wire back to the PCM is reading 0.60V at closed throttle and ~4.5V at open at the TPS. I have replaced the IAC valve, MAF sensor, PCV valve, MAP sensor, nothing worked.
I took it to a transmission shop. They scanned it and got the code for P0122 throttle position sensor circuit low input and an O2 code. The TPS wiring though tested fine at the TPS, haven't checked it at the PCM yet. The codes did not trigger the CEL though.
The trans shop said it sounded like a slipping tranny and convinced me to get it overhauled there. After $2100 there, it didn't help at all.
This problem only happens 30% of the time but it happens at the worst times. The other day I was making a left turn in an intersection. I went to turn, pressed the gas and the car wouldn't go. Suddenly I see a tractor trailer coming right at me. The car wouldn't move. Finally, after repeatedly pressing and releasing the gas pedal, the acceleration kicked in and I was able to turn and get out of the intersection before the truck Tboned me.
What could this problem be? Nobody has any idea!
have the same problem?
Sunday, October 17th, 2010 AT 6:49 PM