2000 Impala Misfiring and Engine Fan Problems

[VA Impala]

Hey guys, I have 2 problems here that have been giving me a headache for some time now. I have a 200 Impala 3.8L that will misfire whenever I accelerate to pass another car or when getting onto the interstate or just plain driving faster than 60mph. The engine light will blink a few times then stay on and in a day or so it turns back off. I have pulled the codes and gotten the multiple misfire code. I have read on a few places where possibly the catalytic converter is bad or something is making the fuel run too rich causing the plugs to get messed up, but it only misfires when I do the things listed before. Also I have taken it in before as the engine fans wouldn't turn on and it worked for a while but now they stopped again. I really don't want to overheat my engine and have it cause even more problems!! Please guys any help would be greatly appreciated.

[BNaylor]

Welcome to AF.

The CAT is a possibility but depending on the mileage have you replaced the spark plugs and ignition wires? A blinking SES/CEL light definitely indicates a misfire condition. The plugs and wires should be AC Delco only.

On the cooling fans disconnect the engine temperature control sensor (ECT). Start engine and the fans should turn on within a few seconds. That way you can rule out the output of the PCM module, the cooling fan relays and the fans themselves. That leaves the input to the PCM from the ECT sensor.

Also, do the fans turn on with the A/C in Max/Hi?

[57chevyragtop]

I agree with The old hot rodder on this. I would suspect plugs to be worn or 1or 2 of the wires. Plugs wear at the rate of 2.5 thousandths for 10k miles. Once you get past 60k your looking at a gap of .073-.075, recomended gap is .060 and if you have the iridium plugs (AC 41-101) it is not recommended to adjust the gap as the center electrode becomes brittle and breaks easily. Also be aware that AC Delco wires clip, fit tight on the plugs and the wire clip can pull away from wire if not careful pulling plug boot off. This is especially true of the rear side plug wires due to the greater heat buildup that side of engine. Yours may have heat shields on the 3.8...the 3400 does not.

The following was posted by Bigrod118 in recent post: However I did edit a little bit.
Re: Firing order of a 2002 v6 Impala

--------------------------------------------------------------------------------
1-6-5-4-3-2 (3.8 0nly)

Front bank, from left to right (passenger side to driver side) is 1, 3, 5
Rear bank, fro, left to right (passenger side to driver side) is 2, 4, 6.

The coils should be labeled, if the numbers are worn off they are:

top coil: 6 on top/left, 3 on bottom/right
Middle coil: 2 on top/left, 5 on bottom/right
Bottom coil: 4 on top/left, 1 on bottom/right

[Gems]

Originally Posted by bnaylor

Welcome to AF.

The CAT is a possibility but depending on the mileage have you replaced the spark plugs and ignition wires? A blinking SES/CEL light definitely indicates a misfire condition. The plugs and wires should be AC Delco only.

On the cooling fans disconnect the engine temperature control sensor (ECT). Start engine and the fans should turn on within a few seconds. That way you can rule out the output of the PCM module, the cooling fan relays and the fans themselves. That leaves the input to the PCM from the ECT sensor.

Also, do the fans turn on with the A/C in Max/Hi?

FYI/Question:

1.) When I had a clogged CAT I never got a SES/CEL light or any codes.

2.) Is the ECT sensor located just below the thermostat housing?

[BNaylor]

Originally Posted by Gems

FYI/Question:

1.) When I had a clogged CAT I never got a SES/CEL light or any codes.

2.) Is the ECT sensor located just below the thermostat housing?

The symptoms on a clogged CAT vary. Some have reported misfire DTCs set and a SES/CEL light. Another possible code is P0420 (Cat operating below efficiency).

Correct on the ECT.

Once of the quickest ways to test for a clogged CAT which is relatively inexpensive to run is an engine vacuum test. You compare vacuum at idle and at around 2000 rpms. The vacuum readings will be lower than normal and may even slowly drop off even to below 15 in-hg especially on the 2K rpm test. This test works in some cases not not all.

[VA Impala]

Thanks for welcoming me guys. The plugs and wires have been replaced 3 times and I've had the car for slightly less than a year. Seems no matter how new they are, if I accelerate quickly it still starts to misfire. As for the fans, they haven't come on in forever even when the AC is on (which I don't use BTW as there is a leak in the hose resulting in very soaked carpet) I'm going to try disconnecting the ECT and see if they turn on. Unfortunately I'm not the biggest mechanic there ever was so this stuff is pretty new to me. I love that car to death but man, I can only take so much

[57chevyragtop]

3 times for wires/plugs in a year!? first I would double check I have the wires routed correctly. I know you think you got em right but I seen this happen more often than anything else. Other than that, rather than suspect the cat I would be thinking fuel delivery problem from MAF, IAC, regulator to injectors. Have a fuel pressure test done, be sure the throttlebody/butterfly is clean, look for vacuum leak, make sure PVC valve rattles freely. What kind of miles on this 2000? Also could be a bad coil, I don't know off hand the test for this.

[BNaylor]

Three times? What brand wires and spark plugs did you use to include heat range or identifier/part number?

Like 57chevyragtop mentioned I would not rule out coil packs or an ICM based on his symptoms. Unless it was clarified earlier there should be other noticeable driveability problems with a clogged CAT not just a misfire that corrects itself. If he is getting a random misfire P0300 code then troubleshooting the coil packs will be difficult. Plus swapping them out with each other may not prove anything either. The ICM can be tested.

[VA Impala]

Originally Posted by bnaylor

Welcome to AF.

The CAT is a possibility but depending on the mileage have you replaced the spark plugs and ignition wires? A blinking SES/CEL light definitely indicates a misfire condition. The plugs and wires should be AC Delco only.

On the cooling fans disconnect the engine temperature control sensor (ECT). Start engine and the fans should turn on within a few seconds. That way you can rule out the output of the PCM module, the cooling fan relays and the fans themselves. That leaves the input to the PCM from the ECT sensor.

Also, do the fans turn on with the A/C in Max/Hi?

I disconnected the ECT and the fans did nothing when the engine was started. The only thing they will do is whenever the engine is first started, they begin to turn on, but not 3 seconds later they stop.

[BNaylor]

Originally Posted by VA Impala

I disconnected the ECT and the fans did nothing when the engine was started. The only thing they will do is whenever the engine is first started, they begin to turn on, but not 3 seconds later they stop.

Yeah, something is not right. The way it should work with ECT disconnected is after about a 3 - 5 second delay both fans turn on and stay on after engine is started and A/C off. There is some control problem via the PCM module. In your case the fans did turn on indicating al least the output of the PCM module to all 3 cooling fan relays in the engine compartment fuse box and the fans are good. For input to the PCM you could check calibration of the ECT sensor resistance wise with a digital multimeter.

[cmfml]

I have an 04 impala 3.8 police package that was having the same problem with missfiring when accelerating hard or going over 55 - 60 mph. I changed the plugs and wires with no change. Then I had a friend in the automotive business hook up a professional code reader to it while driving. It returned the missfire code and furter indicated that it was plugs 3and 6 that were missfiring. Since wires and plugs were known to be good my friend tested the ignition coil and found that the coil for 5 and 6 were not firing at the right voltage causing a verry weak spark. Changed all 3 coils just to be safe and now it runs perfectly. Coils were fairly cheap arround 35 a piece and a sinch to replace. Note be carefull testing the coils your self they are very powerful and will give you quite a shock you wont soon forget. As for the fan problem check your relays located right above the battery in a black fuse box. Getting your car read by a code reader would probably help identify these problems.