2000 Chevy express still running bad MAF code
September 17th, 2021, 11:41 AM
#11
September 17th, 2021, 11:41 AM
#12
CF Monarch
we replaced the MAF on my 07 3500 express after cleaning it , didn't cure the p0300 code . (see my posts on this forum under p0300 express random misfire for a complete list of the expensive parts we have already replaced. without success. ) my understanding is that the p0300 random cylinder misfire can only b e diagnosed by a top of line OBDII unit like the snapon with GM capability , or a dealer's GM mode 06 OEM proprietary scanner . the scanner must be one which 1/ has the ' GM software' and 2/ can do data stream and freeze frame with engine running and be attached while the dtc code is showing to analyze what cylinder is msifiring. so scanner (w ocscillosscope) must be attached and van being driven, throwing the p0300 code on the road . WHILE the MIL check engine lite is on and p0300 code are showing up, w engine running. i found out 1/ lots of shops don't buy the vehicle- specific 'gm' $100 diagnostic pack (which is a vehicle-specific add on for ach manufacturer, or bmw or nissan . at 4100 apiece...) ) some shops won't pay the the manufactirer- specific software add charge on the cheaper scanner units and won't tell you they dont have it . ) 2/ a shop won't tell you what scanner they use and whether they have the GM specific diagnostic pack unless you ask. 3/ shops will take your van in cold then tell you for a $129 fee ' and say it wasn t showing a code,' so let's then start throwing $$$ parts at it . (chevy dealers included. ) p0300 is hard to diagnose. i finally found a independent mechanic with GM diagnostic capacbility on his $4000 snap on scanner, willing to let me bring the van in while it's running hot and throwing the P0300 dtc code. then they'll be scanning and freeze framing it 'hot w engine running while it's throwing the p0300 code . data stream and freeze frame the data might show what's up.
my list of suspects is :
1/ one bad injector -- though all were professionally cleaned . 2/ cam shaft position sensor -- but it's not throwing P0340, does not rough idle, fail to start, or hesitate on acceleration . 3/ bad ECU . putting excess fuel in and out (but fuel trims checked out fine. ) (NOTE I already replaced the crankshaft position sensor twice ( #1, 1 cheapchina, wouldn't relearn . then #2 oem . still no fix. earlier models of the ckcPos Sensor developed too much clearance and GM put out a TSB on it then changed the design of the CkKPos so the OLD design should NOT be used. see my previous posts for the TSB on shimming a worn cKposS , that is no longer recommended as a fix , just replace the thing . dont know if 'old' and ' new' part no s for ckCPos S remained the same but i do now the 'shim kit' reocmmended in the 06 TSB is NOT available. just go with NEW OEM cKPos S. ) Note a a crankshaft relucter wheel problem is still a suspect but i did not ever have and do not now have its symptoms of power falling off at high rpms or low compression which are suppposed to occur for crankcase position sensor and i did NOT have that code or its symptoms. ) . replacement of crankcase position sensor with an OEM should have fixed p0300 if that part was the problem...or 4/ stretched timing chain --to replace w newisa big 12 hour job, and $500 in parts . --and why should i need this on a on an engine w only 61,000 miles on it ?
for more than you ever wanted to know about random misfires see the you tube videos on LS and LQ engine misfires. and ssannerdanner's youtubes , on how problems can be caused by a bad cam sensor.
i ll have the freeze frame and data stream data by tomorrow.
my list of suspects is :
1/ one bad injector -- though all were professionally cleaned . 2/ cam shaft position sensor -- but it's not throwing P0340, does not rough idle, fail to start, or hesitate on acceleration . 3/ bad ECU . putting excess fuel in and out (but fuel trims checked out fine. ) (NOTE I already replaced the crankshaft position sensor twice ( #1, 1 cheapchina, wouldn't relearn . then #2 oem . still no fix. earlier models of the ckcPos Sensor developed too much clearance and GM put out a TSB on it then changed the design of the CkKPos so the OLD design should NOT be used. see my previous posts for the TSB on shimming a worn cKposS , that is no longer recommended as a fix , just replace the thing . dont know if 'old' and ' new' part no s for ckCPos S remained the same but i do now the 'shim kit' reocmmended in the 06 TSB is NOT available. just go with NEW OEM cKPos S. ) Note a a crankshaft relucter wheel problem is still a suspect but i did not ever have and do not now have its symptoms of power falling off at high rpms or low compression which are suppposed to occur for crankcase position sensor and i did NOT have that code or its symptoms. ) . replacement of crankcase position sensor with an OEM should have fixed p0300 if that part was the problem...or 4/ stretched timing chain --to replace w newisa big 12 hour job, and $500 in parts . --and why should i need this on a on an engine w only 61,000 miles on it ?
for more than you ever wanted to know about random misfires see the you tube videos on LS and LQ engine misfires. and ssannerdanner's youtubes , on how problems can be caused by a bad cam sensor.
i ll have the freeze frame and data stream data by tomorrow.
September 17th, 2021, 1:16 PM
#13
i'm now cautiously optimistic that an oem crankcase position sensor and oem cam position sensor CPS rplacement have solved the p0300 random misfire , blinking check engine and steady check engine which goes on and off. MIL varies depending whether i'm at 60+ mph going up hills= steady MIL which then goes off at top of hill. somtimes the MIL would blink just occasionally then gos off. . it was told to me that CPS and CrKPos sensors age and wear and so when you 1st get P0300 , if verifying engine is tuned, plugs wires coil are all good , trying cleaning ECU ground. a oem cKPs is what to try next coupled w a oem CPS. a bad CPS won't align the cam shaft properly and will send erratic signals to ECU causing bad fuel rich mix which can burn out cat converter $$$. bad CPS likely to be a steady MIL tht goes on and off depending on camhaft position. bad CkKP S likely to be blinking and also on off. when the new OEM CKPS was put in only then it started w an occasional steady MIL especially at +65 mph going up hills. more later, my mechanic told me fuel trims good, drive it 500 miles more and let him know. it is not throwing P0300 or MIL s any more. (my advice, also buy the chiltons and the haynes manuals for your van, they have great diagrams of how to do stuff yourself...) Note my van was not throwing the dtc s for either the CPS or the CkPS, it threw a MAF code. after cleaning then total replacement of MAF, the MAF code went away but that did not fix the P0300 codes.
September 22nd, 2021, 6:11 PM
#14
update: report on the p0300: seems to be cured. my shop was standing by to put their $$$$ scan tool on it as the MIL and p0300 was flashing to get flash frame and maybe id the cylinder that might be misfiring. i drove it at speeds from 30 to 70 mph over 2 days for 4 hrs a day to a job, my 3500 engine no longer throws a p0300 code. that's good...
December 13th, 2021, 7:05 PM
#15
well my faithful p300 code is now still showing , w a steady MIL lite even on startup w/ engine cold. (before, the p0300 came on only after 20 minutes of 60 mph + freeway driving. .van hs same symptoms as before-- no loss of power, no hesitation, no hard start. it's going into the chevy dealer again on 12/20/21. (van was at the dealer 3 weeks ago . on their instruction i drove it in 'hot' and coding p0300 "so they could put their equipment on it immediately and get the freeze frames and codes. " instead, when i drove it in they turned off the engine, just put it on the lot for 2 weeks. they didn't put their scanner on it. after hearing nothing for 2 weeks they told me 'they had not worked on it ' because 'the truck lift was tied up' and they could n't lift my van therefore 'could'nt look at it. so i took van home, told them to call me when the truck lift was free. ( i'm perplexed by this because the other 2 shops i took it to didn't need to ' put it on a truck lift ' to diagnose it. ( tho it is easier on a lift if you're pulling o 2 sensors etc. ) so stay tuned...
December 19th, 2021, 11:49 AM
#16
Torque (if you load their GM PID pack) grab the *current* misfire counts per-cylinder. That will tell you which holes are misfiring but you have to catch it while its doing it because those are "current" counts and you need enough of them in the present tense for those to show up. If you have a MIL then the historical counts (which Torque can also grab) will likely show you which cylinders are involved.
Problems like this are a real BEAR to find without knowing which cylinder(s) are involved and if its moving. If its not moving then those specific holes have trouble and that points to the coil, plug, wire or injector for those holes, assuming of course there's not a serious internal engine problem (e.g. a valve that is not completely closing.)
Problems like this are a real BEAR to find without knowing which cylinder(s) are involved and if its moving. If its not moving then those specific holes have trouble and that points to the coil, plug, wire or injector for those holes, assuming of course there's not a serious internal engine problem (e.g. a valve that is not completely closing.)
December 30th, 2021, 1:34 PM
#17
the latest GM theory: per the gm mechanic: constant code P0300 and also a p0340 . new oem cam position sensor was put in. (matching it up w new oem crankshaft position sensor. ) (so now, we have both new CPS and XkKP sensors -- after spending another 2 1/2 weeks on the gm dealer lot 'waiting for the truck lift to be free'. But now, the check engine lite still comes on occasionally . local GM dealer says: GM HQ service gurus were consulted for advice and told the local GM mechanic to ' check for crankshaft whiplash.' (which means dropping the oil pan..) what is crankshaft whiplash, how do you check for it , and what would cause it on a 3500 express van w less than 62,000 miles on it ?
February 15th, 2022, 11:42 AM
#18
Yeah my van is still running bad. It's only throwing code po102! low voltage at the maf. Runs fine until you try and get out the driveway then is starts bogging down each time you left off and on th gas..then after about a minute it's almost inoperable. Removed the air intake and it seems to have more power but still running bad.
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