My Herky Jerky Cav!

[QCubed]

Yesterday morning, my 2.2L 99 Cav automatic seemed to misfire and was driving jerky. When idling, the engine seemed to surge, then almost stall, then surge, then almost stall, etc. I was on my way to an appointment and did not have time to stop so I kept going. Once the engine got warm, and I got on the highway, the problem went away. After my appointment (which didnt take long so the engine should still have been warm), the car drove fine. Then, starting up the car this morning, the problem started again, but was worse. This time it seemed to sputter as well. And soon the "check engine" light came on. I had to give extra gas to keep it going at normal speeds and I thought I could smell gas (probably because I was giving extra gas.) Once again, once the engine got warm, and I got on the highway, the problem seemed to disappear. I did a cursory check of the spark plug wires, and they all seem fine. Does this seem familiar to anyone else? Any ideas on what the problem might be?

[QCubed]

P.S. I should add that I have had to use the car several times today, and so it has not had a chance to cool down. It has not been jerking, and this last time I went out I noticed that even the "Check Engine" light had gone out! So the problem, whatever it is, seems to be prominent when the engine is cold, and "silent" when the engine is warm. Any body know what the problem might be?

[PlanetDude]

Cars run in a "closed loop" mode when cold, meaning they only receive info from a certain amount of sensors. Once the car warms, it goes into "open loop" where it receives signals from all sensors, and the computer tweaks everything to perfection.

I could have the loops backwards, but you get the idea.

Something in the "cold run" loop seems to be out of whack. That`s where I`d start.

Can anyone help me expand on this?

[joeuser742]

I have a 2002 cavalier that was jerking while I was driving, no engine light. I cleaned out the intake, MAP sensor, and Idle Air Control Valve and the problem went away. When it gets warmer out, I'm going to take the intake apart and do a good cleaning, and replace the valve and sensor.

[QCubed]

Update: I got a chance to look under the hood, and found that the air filter cover had not been screwed on, probably from when I last got the car serviced about a month ago. Could that be the source of the problem? I screwed it back on tightly. However, I'm sure stuff needs to be cleaned "downstream" after sucking dirty air for about a month. Can I find instructions on the net about how to clean the intake, MAF sensor, MAP sensor and Idle Control Valve? The problem seems to be getting worse though, as the car seems to sputter and miss ocassionally even when the engine is warm now.

Thanks to all who read and reply!

[joeuser742]

Not sure if there are instructions on the web to clean the intake. There are 3 things screwed into the throttle body; the MAP sensor, IAC valve, and the throttle position sensor. I took them all off, cleaned them out with carb cleaner, then sprayed the carb cleaner into the intake. I did notice alot of buildup when I took off the MAP sensor.

If your engine light is on, then I wonder if they forgot to plug in the air charge temperature sensor or maybe even damaged it. That is located on the rubber part of the intake.

[QCubed]

Hey Joeuser:

I cleaned them with the carb cleaner as per your suggestion, and it did help give the car a little more power. The problem however, did not get resolved. So I bit the bullet and took it to the mechanic. The OBD code told him there was misfire. Turns out I needed new spark plug wires! He replaced them and the spark plugs and the car is running great again. And thanks to you, I do feel a little more pep in the car! And, yes, I did notice a fair bit of carbon on the MAP sensor. So its gone now.

My thanks to you, and to PlanetDude for his earlier posting. I learnt from both of you, and I'm sure future readers of this thread will find your postings useful also.