My '01 seems to have a slight engine miss that is affecting power. It seems to idle smoothly, but when I rev it to around 3K, the miss is very noticable. Occasionally the miss is not present and the car performs noticeably stronger. Before I start throwing parts at it, what is a good way to troubleshoot? I'm thinking it is maybe a plug or plug wire, or maybe an injector or injector connector. Its got me puzzled the way it comes and goes. Any suggestions? Jeff

 

How does it run at WOT? Any codes? Does it clear up at higher RPMs?

I fought a miss at 2k RPM and turned out to be a bad O2 sensor.

 

First thing I'd do is check for DTC. Especially look for a P0300 as that will tell you the PCM is also detecting a misfire.

Are there any "clicking" or "snapping" noises associated with the miss, or static on the radio that associates with the miss ??? Those would be signs of a badly connected or arcing plug wire. If a wire is arcing, in the dark, have someone run the engine while you (don't stick a body part into the engine in the dark) look for a bright spark from a wire or wires.

If it seems worse when the engine is "under load" that is another possible sign of a bad wire or plug.

If it seems entirely random in occurance, then I'd lean more toward a bad wiring connection either for a fuel injector, or a coil.

How old are your plugs and wires ?? Do you know what brand they are ??

 

I'm not getting any DTC codes and the random nature of the miss is what has me puzzled. I'm leaning towards a injector connector or something like that. The plugs and wires are pretty new, so I don't think that is the problem. Other issues should set a DTC code, and since I'm not getting any, i'm thinking is a connector issue?

 

Jeff

The DTC P-0300 is sometimes difficult to see as a DTC. You can sometimes see it as a FLASHING " Check Engine Light" when the problem is presenting its self. The P-0300 DTC will be reset when you turn the ignition OFF. If you check for the DTC while the engine is still running ( I check mine on the fly all the time) you may see it.

I agree with BLACKZO6 in that it is most likely a wire or plug. I too hate to throw parts at a problem without being able to find the smoking gun.

You can remove the wires and examine them. Look for tears, burnt insulation, damaged, loose, dirty boots and damaged /corroded connections inside the boots. You can check the resistance of each wire. A stock OEM black wire will read between 250-750 ohms. Most read about 350 ohms. If they read any higher than 750, theres something wrong!

The hardware inside the boots should be clean and positioned in the boot to allow the terminal to SNAP on to the plug. If there pushed back inside the boot, that too will cause a high speed misfire. If you need wires, I highly recommend the GM Performance RED wires. Best wire for the money. PERIOD! About $50 a set!

Remove the plugs and look at the gap, electrode, anode and insulators. There in-expensive enough, while there out, just replace them if theres any more than about 30k on them. Make sure that the exterior insulator is not cracked:



Once you have insured that the plugs and wires are in good shape, it easier to zero in on other components.

BC

 

Here is what I have done so far to diagnose this problem:

I pulled each injector connector while the engine was idling to try and see if I could pinpoint which cylinder had the miss. As I D/Ced each injector, it picked up a noticeable miss. This procedure did not help.

Next, I then changed out the plug wires, but they looked OK, and there was no signs of arcing in the dark. The miss is still there.

Next, I plan to change out the plugs, any recommendation on plugs?

I don't know if this is normal, but I can hear a slight ticking noise coming from the valve cover while idling (prominent on the driver side). Is this valve noise normal, or could there be a stuck or failing hyd lifter giving me this intermittent miss? I'm not sure how much valve noise is normal for this LS1.

 

Pull that valve cover and look for a damaged spring, rocker, bent pushrod ect. The noise is a dead give away that it a little more involved than a wire or plug.

BC