Was wondering if anyone can help me narrow this down. Its my cousins car. Its a 1996 z28 m6. It got scanned for codes and p0174, p0101, and p0300 came up. I know different codes or issues can throw more than 1. He hasnt done much to his car since hes gotten it. Its just clicked 100k on the mileage.

Now it runs a little rough, and misses. Sounds like crap through exhaust and pops a lot. i was thinking having him replace o2's anyway cause mileage. He just did plugs and wires. I was thinking if he had the money i was gonna tell him just to do opti, and waterpump for piece of mind. I know that might not be the issue but its 100k miles and always just nice to have a new opti when mileage gets up. Ive seen them go 170k+ though so i dunno. I can hook it up to laptop if need be to read anything. Let me know what you think i should go about

 

Assuming your codes are correct, the 300 should be dealt with first. A 300 is a missfire. if you have the equipment to see that, you should be able to also see what cylinder it is from. OBDII shows both. Now focus on that cylinder.

If you don't use the scanner, pull injector clips until you find the one that doesn't change the idle when you pull it. That would be the cylinder that is the problem.

Since you have a 174, chances are the problem is on the passenger side of the engine.

Once you have the missfire addressed, see what codes remain. 101 is MAF, 174 is right bank lean.

 

Using the scanner, check the long term fuel corrections for both banks of the engine. P0174 set for running lean the passenger side, but it would be interesting to see if the driver's side is also lean, but just not lean enough to set P0171. One bank lean leads to a problem that affects only that bank, both bank lean indicates something that affects both banks.

P0101 is the rationality check on the MAF sensor flow readings. When the PCM compared the MAF reading to the mass air flow calculated using the speed-density method, there was a difference of more than 40% at low flow, or more than 25% at high flow. Could be as simple as a dirty MAF, or a tear in the rubber inlet elbow allowing air to bypass the MAF sensor.

Sequence of the codes setting would be of interest, since P0174 can not set if there is an MAF code.

The lean code may be causing the random misfire, or the random misfire may be causing the lean code.

 

Excelent info from both....cant add to that!

 

i agree. both these guys always help me. ill be looking into the car this weekend i believe. thanks guys