2003 Sunfire Rough Idle

I have a rough idle, RPMs look okay and stay steady at around 800 at idle and at stop light. No engine codes and new spark plugs.

I only saw one vacuum leak which was the hose coming from the rocker cover to the resonator. I replaced the hose and still have rough idle. I thought it was a vacuum issue... maybe a fuel issue??

It could be a a fuel issue, possibly the fuel pump or the filter. It could also be an ignition issue. Spark plugs, wires, coils, etc.

It could be a a fuel issue, possibly the fuel pump or the filter. It could also be an ignition issue. Spark plugs, wires, coils, etc.

Update: Throttle body cleaned replaced IAC, MAP sensor, Fuel filter, Fuel pressure regulator.

When I check fuel pressure I get 50psi.

Spark plugs were changed there are no spark plug wires in 2.2L Ecotec.

No vacuum leaks.

I'm at a loss.... :frown:

I did a compression test today and came out with 149 on all cylinders with dry test. But I came out with only 150 wet. Did that come out right?? I put a cap full of oil in each cylinder... :confused:

Condition getting worse!
Car is stumbling more when I stop, today on my way to work it almost concked out on me...

Surprised a code is not set.......

Check the vac line, on f/p regulator, for fuel?

Could be a misfire.......bad coil or ICM....

Surprised a code is not set.......

Check the vac line, on f/p regulator, for fuel?

Could be a misfire.......bad coil or ICM....



I tested the ICM AND Ignition coil per this video. Since I had a new coil and the old coil I ruled them out. They both showed 2 ohms. And the ICM passed the circuit test.

https://youtu.be/7PK6r3HbjkU

Actual physical test is midway in the video.

Someone in another forum said it might be crank position sensor??

AS you say, this is coil module on top of plugs, no wires.....

I think a road test is in order, with a scan tool, to pinpoint which cylinder(s) is/are misfiring....if spark and compression are ok, we could have an injector problem....

AS you say, this is coil module on top of plugs, no wires.....

I think a road test is in order, with a scan tool, to pinpoint which cylinder(s) is/are misfiring....if spark and compression are ok, we could have an injector problem....

I tested the ICM AND Ignition coil per this video. Since I had a new coil and the old coil I ruled them out. They both showed 2 ohms. And the ICM passed the circuit test.

https://youtu.be/7PK6r3HbjkU Actual physical test is midway in the video.

compression test came out with 149 on all cylinders with dry test. But I came out with only 150 wet

I replaced the crank position sensor and still the same. I listened to the injectors and all 4 were consistent with each other. Still not throwing any codes...

I ran a live data from my scanner today, maybe u can help me read it.


https://www.youtube.com/watch?v=JErzJa01G6o

O2S11 is staying high and not switching, meaning the vehicle is running rich.......

If the car is idling badly, try running the vehicle with the injector harness disconnected and spraying carb cleaner into the intake.......if it smooths out, could be a bad injector(s).....

I just saw ur post and will try it.

Meantime here is an update:

Update:

Someone had said to check tranny fluid level, I did notice a little seepage at the pan so I went ahead and dropped the pan and change the fluid.

When I drained the fluid it came out to almost 9 quarts and the specs say 9.5. So anywayz it got brand new fluid and a new gasket.

Here's where it gets interesting. I drove the car around went grocery shopping etc... Still a little rough at the lights but not so much.

As soon as the weather changed and the car started acting like it wanted to turn off at stops again... maybe coincidental but it happened to me twice when the weather changed (raining)... kinda reminded me of the days when your carburetor would close up.

:shakehead

Update:

I cleaned off some of the wiring yesterday and the idle actually improved.
Today coming off the stoplight the engine stumbled and finally threw a code.

P0171

SYS TOO LEAN (BANK 1)

FREEZE FRAME DATA

TROUB CODE P0171
FUEL SYS 1
CL, USING HO2S
FUEL SYS 2
N/A
CALC LOAD 46.2%
COOLANT 88 C
ST FTRM1 42.9%
LT FTRM 18.7%
MAP (Kpa) 82
ENGINE (RPM) 2410
VEH SPEED (Km/h) 41

So injector or O2 sensor??? I replaced everything else, Dammm!!

:crying:

Update :

Turned out being the timing chain. No warning, tried to start the car last week and just heard a backfire and spinning sound... So when it backfired the valves got bent.

Got the cylinder head back the other day no damage to the head and replaced the valves. Got most of it put back together and turned the key. Motor sounded good.

Just a matter of putting the rest back together, weather hasn't been too kind...