Hey guys I have a 2007 Tahoe 5.3 and it threw a Crank Position Low Voltage code a couple weeks back, never run funny. So I replaced it this past weekend and now whenever I give it gas in park or under load while driving it backfires through the intake and stutters until it gets above 1500 rpm. If I give it full throttle at any speed it backfires, hesitates and and then ramps up the rpm's. Then when it gets above 4000 rpm goes to backfiring again. No codes.....where should I start?
07 Tahoe stuttering
- Thread starter sarge77
- Start date
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I think you need to do a relearn when you replace those
iamdub
Full Access Member
^^^ What the Doub said- you need to have a CKP relearn performed. Call around to a few shops and, if they don't know what a CKP (or "crankshaft position sensor") relearn is (some may call it a CASE learn), move to the next one. They shouldn't charge more than a half hour of labor. It's a process initialized by a bi-directional scan tool that sets the PCM in a learning mode to calibrate itself to the new sensor. Basically, you initialize it, then rev the engine to a specified RPM as directed by the tool, then it's done.
Relearn completed and didnt fix anything and then on the way home from shop lost all oil pressure. Shut off truck and crank it back up and pressure goes back to normal and then slowly drops to zero. Shop said anything from timing chain to fuel pump to lifters to wiring issue.....
I would re-inspect the areas you worked in when you did the CPS replacement. You may have not gotten everything plugged back in or remounted correctly. How old are the plug wires and plugs? I would look for a ground wire or two that need attention. Hell, check all ground connections under the vehicle and around the engine and firewall.
Ok so 250000 on motor had the dreaded lifter issue at around 180000. Everything up top replaced with new AC Delco parts...all upgraded parts required by GM. Only part that wasn't changed was camshaft. Heads were also redone. Lifter tap was back at less than 5000 miles after repair. Been driving it since with no issues. Repaired oil pressure sensor tonight and screen. Pressure used to be around 28 to 30 at idle and between 50 and 60 at high rpm. Now around 15 or 18 at idle and 40 to 50 at high rpm. Drove a couple miles and left idling for a good 35 minutes with no loss of pressure. Still seems low though. And still have the studder and backfiring. Checking fuel pressure tomorrow if thats good im at a loss. Maybe stretched timing chain? I can look at real time timing, rpm, tips, etc with my programmer so anything I should be looking at especially the timing?
swathdiver
Full Access Member
At 250K the oil pressure is bound to not be as high as new when the bearings were less worn. Oil pump can wear out too.
I would be looking at misfire counter on scan tool, looking to see which cylinder is the offender for starters. But first I'd view the GM troubleshooting guide for this symptom at AllDataDIY.
iamdub
Full Access Member
Whale, hale. With your timeline of events and following symptoms, I thought for sure it was a simple CKP relearn.
Moving forward...
First off, I agree with James- use your scanner to see where the misfire(s) is(are). Getting any codes?
Try unplugging the MAF to see if it improves.
A weak fuel supply and a clogged cat both present very similar symptoms, possibly very similar to what you're experiencing, if I'm understanding you accurately.
To clarify, it ran fine before but just threw that CKP low voltage code? Then, after replacing the CKP sensor, that's when all the other stuff started? You may have a defective sensor and the code that you originally got doesn't necessarily mean the sensor was bad. What brand of sensor did you replace it with?
Moving forward...
First off, I agree with James- use your scanner to see where the misfire(s) is(are). Getting any codes?
Try unplugging the MAF to see if it improves.
A weak fuel supply and a clogged cat both present very similar symptoms, possibly very similar to what you're experiencing, if I'm understanding you accurately.
To clarify, it ran fine before but just threw that CKP low voltage code? Then, after replacing the CKP sensor, that's when all the other stuff started? You may have a defective sensor and the code that you originally got doesn't necessarily mean the sensor was bad. What brand of sensor did you replace it with?
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