P0171 Fixed P0300 Remaines

[l67poweredlss]

Well, I got my lean condition taken care of. The stovepipe from the EGR to the LIM was cracked, I just couldn't see it as the kidney bean shaped washer was hiding it. Replaced the TB gasket while I was at it and cleaned the TB and S/C inlet. The inlet was caked with sludge. It is very difficult to detect the misfire that is throwing the P0300 random multiple misfire. However, thanks to our advanced electronic transaxle control system, I know exactly when a misfire is occurring because the computer disengages the torque converter clutch whenever the misfire occurs. If i'm easy on the car it takes 20 miles for the condition to arise. If I go WOT it will begin almost instantly and continue intermittently throughout my 30 mile drive to work. LTFT is back down where it should be, usually ranging from 0.0 to 6.7. Timing advance is still horrible. -12 @ WOT and -30 @ between 15-25% throttle position opening. I dunno. I'm starting to think my DHP PCM is crap. There is no mechanical reason for this that I can think of. All of the following have under 15K miles on them; plugs, wires, O2s (both), & fuel filter. There are no codes other than the P0300. I'd assume if the EGR, MAF, IAT, or CPS were bad a code would be thrown.

[stevew9983]

Just a quick question what kind of plug wires did you put on it? Not always but generally a P0300 code is usually plug wires. I have ran into this code a few times with my Bonneville SSEI even after replacing my plug wires, I bought A/C Delco wires for it and they were bad right out of the box. Might be worth checking into. Also another possible cause of the P0300 is fuel pump. If the car is not getting proper fuel to burn it will cause a random multiple misfire because each cylinder is not getting enough fuel to burn to run correctly.

Maybe take an ohm meter and measure ohm's in the plug wires and check fuel pressure.

[00Beast]

Check your fuel pressure. Might not be a bad idea to OHM out the wires to make sure one isn't showing high resistance, and visually check and gap the plugs. You could also check out the coils to make sure one isn't reading significantly higher than the rest.

[stevew9983]

Check your fuel pressure. Might not be a bad idea to OHM out the wires to make sure one isn't showing high resistance, and visually check and gap the plugs. You could also check out the coils to make sure one isn't reading significantly higher than the rest.

if it were a coil issue it wouldnt come up as a random multiple misfire though. unless the ignition module had went bad but that would prevent the vehicle from even starting. i think the fuel pressure test and testing the plug wires and checking plugs and their gap would be the best options for that code.