Help diagnosing a truck
Help diagnosing a truck My buddy has a 99 silverado with the 5.3L in it, 4WD, and it runs like complete crap. The transmission refuses to shift, it idles poorly, has no power or acceleration at all, and gets about 6-8mpg average. It sputters and hesitates like no other. He has replaced the knock sensors since it was coming up with a code for that, and done plugs and wires and that kind of crap. It comes up with p0300 which is misfire and a code that says t1000 or something communication with ABS module, the ABS light is on and it hasn't worked since he bought it.
I logged it driving around a block with hptuners tonight, but I'm new to using that kind of software and don't really know what looks right or wrong. If anyone can look at this log and tell me what might be amiss that would help a lot, since we are trying to narrow it down without replacing all sorts of stuff.
EDIT: forgot to say that we tried unplugging the MAF, and it runs 10x worse with the MAF unplugged. It can barely move under its own power with the MAF disconnected.
I logged it driving around a block with hptuners tonight, but I'm new to using that kind of software and don't really know what looks right or wrong. If anyone can look at this log and tell me what might be amiss that would help a lot, since we are trying to narrow it down without replacing all sorts of stuff.
EDIT: forgot to say that we tried unplugging the MAF, and it runs 10x worse with the MAF unplugged. It can barely move under its own power with the MAF disconnected.
Last edited by Arc00TA; Jun 4, 2010 at 01:45 AM.
Can't see the log (at work), but what about O2 sensors? Try unplugging the front 2 and see if it runs better (that will put it in open loop). Does it have any exhaust leaks? Is the coolant temperature reading correctly (bad sensor will make it super rich)...
I'll bet you have a plugged catalytic converter or 2. If you can access the misfire counter data check which cylinders are recorded as misfiring. If they are all on the same bank i.e. 1,3,5,7 then your driver side cat is more then likely plugged.
Okay, there is no specific cylinder listed like 0302 0304 etc, just the general misfire. I forced OL and it doesn't run any better. Is there any way to tell if the cat is plugged other than removing it?
I know there is no specific code that doesn't mean that the pcm hasn't counted misfires on those cylinders. If you can access the misfire counter data it will give you a better idea. You can do a backpressure test on the converter if you have the tools. Short of that drop the y-pipe and try it.
Well, the misfires were all bank 2, 2-4-6-8 so we pulled the Y pipe and the cat was clogged as hell. We had a test pipe put in and it runs like a champ now besides a slipping 204k mile transmission. Thanks a lot for the responses.
