3100 Malibu running rough

[cardana24]

Hey guys. We have a company car, 2003 Malibu. I assume it has a 3100 in it. It started running rough so be bought the salesman another car. The car has high miles (over 200k) but mostly highway from a traveling salesman. Does these engines have common problems that would cause the to run rough? The salesman said it was running fine one day then the next day is started running rough and was down on power. I may be able to get this car for cheap, and I was wondering if you guys have any input on what the problem could possibly be ( I know I did not provide much info., but I am just looking for common problems, that I could possibly troubleshoot before I make a decision on the car.) If the engine is toast I would not want the car other than to use the top end parts on my 3.4L in my Jeep Cherokee. Please let me know your thoughts. Thanks.

[robertisaar]

kinda sounds like the O2 or MAF could have died overnight.... something to look into at least.

[cardana24]

would an 02 really cause it to run rough? I can understand the maf. The car is about 4hours from me. I was going to take my compression tester with me when I go up there, to see if that shows up a bigger problem. Can you access all of the spark plug holes with out removing the manifold on these engines?

[robertisaar]

if the O2 gets skewed, the motor could be running lean or rich in closed loop and the PCM not know it.

yes, you should be able to reach all of the plug holes without removing anything other than the plugs themselves. i'm not sure if the n-bodies can be rocked forward like in a W, but that always gave a ton of extra room.

[bszopi]

What about a bad coil pack? Did he say it was acting any differently besides just being down on power?

[cardana24]

What about a bad coil pack? Did he say it was acting any differently besides just being down on power?

he said it is running rough. He said it's driveable but it is not fun. I guess if one coil pack fails it would take two cylinders out of the loop. I was going to bring an extra map sensor, coil pack, OBDII scanner, and my compression tester. Any other sensors that would swap over from a 94 3.4 camaro engine to a 2003 3100? He said it never got hot. Just started running real rough out of the blue.

[cardana24]

Bringing this back up. It looks like I should be able to see this car next week. According to one of the guys I am talking to he says it is running on 5 cylinders. Any common things to look for? I will take my ODBII scanner and compression tester. Just looking for advice before I actually see the car.

[Azrael]

Also check under the oil fill cap and coolant resevoir and make sure there's no cross-contamination of oil and coolant. That's the only real common issue for these motors.

[cardana24]

Also check under the oil fill cap and coolant resevoir and make sure there's no cross-contamination of oil and coolant. That's the only real common issue for these motors.

What are you refering to? Blown head gasket or blown intake manifold gasket. I am guessing if it is the head gasket that would show up on the compression test, but if it's a blown intake gasket the compression test should check out. Thanks for the input.

[pocket-rocket]

Azrael would be referring to LIM gaskets, although head gaskets could do it, LIM gaskets is way more common and almost expected depending on mileage.

[cardana24]

Azrael would be referring to LIM gaskets, although head gaskets could do it, LIM gaskets is way more common and almost expected depending on mileage.

Gotcha. It has over 200k miles. What would be the best way to troubleshoot a blown LIM gasket as opposed to a head gasket, am I right in assuming a compression test will point to one or another? Assuming the problem really is a blown gasket?

If it is a blown LIM gasket what work would need to be done other than replacing the gasket?

[robertisaar]

hmm.... compression test can determine a bad headgasket, and using a little pressure tester for the radiator might be able to check LIM integrity.

[Azrael]

The LIM gasket issue really only affects the sealing around the coolant ports between the head and the manifold. A pressure test of the cooling system and/or a visual inspection of the oil is the only way of knowing for sure. If it's the cause of the rough running then the engine is already far gone enough that just looking under the cap will be enough. It will end up looking like a milkshake.

If it doesn't then continue diagnosing. I agree that the coilpack is a likely suspect.

[cardana24]

What I am getting at about the compression test is that it compression checks out then it could be the LIM gasket but not the head gasket. I think we are all saying the same thing. Do these newer engines still use the same coil packs that I would have on my 94 camaro 3.4 engine? I have spares of these and I was planning on taking one or two.

[robertisaar]

any GM engine with the "twin post" coil packs, the coils are the same, so go for it.