My car is cutting out, almost off at part throttle driving. It is only occasional that its doing it. Sometimes it will cut out a few times and stumble around and come back. Other times it blurps and comes back. Could this possibly be the MSD wires?

 

The symptoms you describe could be related to a number of issues...fuel and/or ignition. Sometimes, they're hard to tell apart.
Are the MSD wires new? Have you tested them for resistance? Have you confirmed they are securely snapped onto each coil/spark plug?
Some say that oem GM wires (red or black) are the best to use...

 

I recently had a similar engine stumble issue. If you have been on the forum long, you will see that I have had a number of C5's an a C6 and have been working on engines since I was 6 yrs old When I first noticed my problem, I was hammering the car on the TRACK and giving a WRX hell. All of a sudden it seemed as though I hit the rev limiter or ran out of fuel at 6500 rpm.

I instantly let out of it thinking WOW, I just toasted something. First thought was a valve spring. Nope, it still running good when I'm not hard on the throttle. I hammered it again and it starts breaking down, this time at 5000 rpm. Checking gages,, everything is fine. Temp=195, oil pressure 40, Volts 14.1, fuel 1/2 tank. So, I down shifted to third, slowly bring the rpms up to red line and when it started to fall flat on its face at 5500 rpm's the "CHECK ENGINE LIGHT" starts flashing, indicating that I have a cylinder miss. I nursed it to my buddies house 5 miles away and let it cool down and checked each spark plug wire.

Checked 2, 4, 6 & 8. All were on tight and looked good. Checked wires 1,3, and then found plug wire #5 just resting on the plug. Plug wire 7 was fine also. Reinstalled #5 and went back out WRX hunting! ONE LOOSE WIRE caused all those issues.


Long story short,, LSX engine problems can be difficult to diagnose at first, even for seasoned mechanics. You just need to start with the basics and cover each leg of internal combustion engine operating formula.

Do you have:
- Compression
- Fuel
- Spark
- Correct Timing

As for spark plug wires, they MUST fit tight and read the correct resistance from end to end. For OEM wires, there suppose to read 250-750 ohms. The wires and rubber plug insulators (BOOTS) cant allow any electrical leakage (arcing) and the plug gaps need to be the correct gap and the internal insulator tips cant be soot black!

Do you know how many times that forum members have replaced wires, coils, wiring harnesses etc... only to find out that the spark plug ceramic insulator was cracked??? Don't forget to check that.

BC

 

Great advice Bill ...

 

Well Bill isnt that interesting. At the track a week ago I couldnt understand why I was 15% down on power. No codes. Like P300. Next day I saw the # 5 WIRE hanging off the plug end. Maybe vibration i guess. As a DD hard to tell if youre running on 7 or 8 cylinders

 

If this problem started shortly after installing the MSD wires then I'd ditch them for something else, I bought a set of MSD wires and had all kinds of problems with them arcing to the headers so I went back to the GM performance (red) wires.

Checking the wires is very easy just wait until it gets dark outside, raise your hood and start the engine then physically watch both banks while someone else revs the engine, in the dark it's real easy to see bad wires arcing.

 

The GM Performance wires are part #12495519 - it is a kit of 8 wires - so only order one kit. The wires are red, so they look and they work great.

 

Not that I know for sure, but you may want to see if one of the Air Check Valves are bad. (Do you get any "shotgun" blasts or backfires out of the exhaust?) It's a ~$12 part from Advance Auto, ~$14 from NAPA and ~$26 from GMPartsDirect. (Looks like I have to replace one or both of them myself right now! )

 

Air check valve??? I have removed the AIR system and PCV system

 

I just spent some serious time with Bill C last night on a similar issue. Car threw P0300 misfire code, MAF code, and a few others like a P0500. I've checked all the wires and they seem fine. I ran an infrared thermometer along the intake runner and I found one cylinder is much hotter than the other (on intake) so there is a chance my intake valve spring is broken. Time to yank the valve covers and see what's up. I'll do a quick compression test on #1 and #2 before yankingthe covers however.

 

Small world. I have been chasing an idle issue. I had MSD wires on , almost newa nd the GM metal plug sleeves. I ended up going back to GM plug wires only because they fit so much better than the MSD's.

I also went out and bought some basic Champion plugs and try them as well to see if idle cleans up. When I ran a misfire test using EFILive, it seemed like the same cylinders keep showing up.

 

I guess it was about 5 years ago, I was going around a neighborhood corner when the engine in my '99 suddenly stumbled, but came right back. It happened several times after that on the same corner, but no where else. Not finding anything wrong that I could determine, I changed the plug wires. Problem solved. Still not sure how that could have done it, but it did.

 

I've had some issues with the MSD as well.

first .. the boot design makes it difficult to know if the wires are fully seated; poor tacticle feedback when trying to feel the "click of completion"

second, the LS1 set seems to be about 1 inch too short. This puts right angle stress on the boots... making it even more difficult to determine if thet're fully seated or not.

Further complicating the friction needed to keep the coil end from slipping off.

Although I use the provided diaelectric grease on the spark plug end.. I learned to not use it on the coil end... as they were being slowly pulled loose due to vibration and the already mentioned shortness of the wires.

 

similar problem -- result was weak valvesprings