Idle stumbling

Mileage?

Should be 50-60 psi

Appreciate your quick response! Mileage is 66,000. Even though my fuel pressure is low, the car runs great at highway speeds where more fuel is needed. Do you think that low pressure is causing my idling problem?

Since you say there are no other symptoms and no engine trouble codes...

First, given the mileage I'd replace and properly gap all of the spark plugs to see if that helped. Next, I would do a good throttle body cleaning using TB or combustion chamber cleaner (not carburetor cleaner), an old toothbrush, and soft cotton rag. Next, I'd check or replace the PCV to make sure it is functioning properly and verify there were no vacuum hose leaks anywhere. Next, I'd replace the air and fuel filters assuming these were not done recently. Lastly, if all of the above still did not help, then I'd go ahead and replace the Coolant Temperature Sensor since it is cheap and easily swapped and a known issue in these engines.

I'd estimate the total cost to do all of the above would be around $50 and an hour or two of your time. Look at the plugs carefully when you have them out as they will tell you a lot about if all cylinders are firing properly and if the engine is running lean or rich. Good luck and post what you find.

Bob

Very likely. 30 psi is rougly half of whats called for. It could be a failing fuel pump or a faulty Fuel Pressure Regulator.

He's probably got another 10k to go on his plugs though he can inspect them.

Carbon build up isn't likely to be an issue with an Ecotec that has 66k miles on it.

No its not a S-series 1.9L, its a L200 which has a 2.2L Ecotec. The ECT sensor isn't known to be an issue. He could diagnose that with an Ohm meter and save his time and money.

I did check the spark plugs. They were a nice light tan color. All 4 were the same. No evidence of fowling.

Next, I would do a good throttle body cleaning using

I first tried some cheap injector cleaner in the gas tank. I then tried Lucas injector cleaner in the tank figuring a better brand is... better. I then tried Seafoam. The directions said it was O2 sensor safe. I slowly poured it directly into the throttle body and added some to the gas tank.

I couldn't find the PCV. I found a hose from the valve cover to the plastic tube that goes from the air filter to the throttle body. There doesn't seem to be a PCV in that hose line.

Both air and fuel filters were replaced.

I always associate stumbling with a rich condition. That's why I didn't think it's a fuel delivery problem. I associate coughing with a lean condition. That's why I don't think it's an EGR problem. Without any error codes, I'm trying to troubleshoot it as if it isn't computer controlled. I might have to invest in a shop manual to find out where all the sensors are and the voltages and/or resistances are. Do you know of anywhere on the net to find this info without buying the manual?

Thanx again for all the help and idea's

Tinker

A failing fuel pump rarely sets codes.

You might find some information at Saturnfans.com

You could also purchase a yearly subscription to alldata

The pcv is what one end of the hose connects to, inside the throttle body (pull it out?)

Well I bit the bullet and took it to the dealer for diagnosis. They said one of the ignition coils was bad. Here's the disturbing part of the story. This dealership is where we bought the car and had the ignition recall taken care of. Other then oil changes, they've handled all maintenance on the car. They have the complete record of service on the car. They said the car had after market plug boots on it. These boots were low quality and caused one of the coils to go south. If they were aftermarket boots, they would be the only ones to put them on. I can believe the coil is flakey but these have to be OEM boots. They also want $350 to repair the car. Definately inflated price. I found the OEM coil assembly with boots on the internet for $168. One connector and 4 bolts hold it on. Working blind folded with one hand tied behind my back, it could be replaced in 5 minutes. If my math is correct, their shop rate must be $2184/hr. I will replace this myself and report back to the group.

Thanx again for all the insight and ideas everyone passed along. I hope this info will help others out.

Tinker

We are having this same issue right now. My husband took the car to our mechanic because the dealer always charged us at least 30% more and he told us to take it to the dealer because of the recall.

We had the recall fix done in 2003, so it shouldn't be an issue, but of course they have no problem charging us 100 bucks for a diagnostics test.

Is there anyway to prove that even though they fixed it at the time of recall that this could still be a result of a problem on their part?

Thanks.