8.1L still stalling after crank sensor replacement

[Waffeey]

Hi all Just replaced the Crank Sensor on my 02' 2500HD 8.1 and it still stumbles occasionally and stalls the same as it did before. It will start right back up and run for hours fine after. I got the OEM ACDelco part and it looked identical to the one that was in the truck. No codes are being set however I have two intermittent codes when I read it with my scanner P0101 and P0107 MAF and MAP codes. My wiring harness all looks intact and I wiggled every connector and plug wire while the truck was idling, still nothing. I also viewed the RPM signal and MAF signal when it was stumbling and they both were working no spikes are drops in the signal.. What else could cause the truck to just die? Cam sensor? Throttle body? Fuel pump/relay?

[Waffeey]

Replaced the MAF sensor and still experiencing stumbling, no stalls though. Now have a pending and intermittent MAF code P0101 after clearing codes and installing new MAF.

[davester]

Could be the MAF, could be wiring, could be connectors.  If you google for that code, generally the diagnostic procedure involves checking everything first to figure out what the problem is, rather than just say "replace MAF".

[Waffeey]

On 6/6/2020 at 12:39 AM, davester said:

Could be the MAF, could be wiring, could be connectors.  If you google for that code, generally the diagnostic procedure involves checking everything first to figure out what the problem is, rather than just say "replace MAF".

I did check everything I was able to with my scanner at home for the intermittent MAF and MAP codes and wasnt able to find anything. Another user on a different forum suggested I check the intake manifold bolts as they tend to come loose and sure enough the front 4 out of 8 bolts were loose. Torqued to 10ft/lbs spec and Truck is running much smoother now.

[davester]

"Vacuum leak" was listed as part of the diagnostic procedure for the first result I got when googling "gm p0101 code"...

[Waffeey]

 It didn't stall or stumble for awhile but their both back now unfortunately. I just threw a check engine light when I was towing so depending on what that code is I will likely follow what it was set for. Shame as the truck runs great otherwise. I'll get back to you with the code.

[sefiroxx]

Try

Cleaning the throttle body and butterfly.
Monitor STFT to rule out any lean/rich scenarios

[Waffeey]

P0101 confirmed code for the MAF again, going to check intake manifold bolts again and check for a vacuum leak. If I dont find anything I'll check the MAF wiring.

[Waffeey]

10 minutes ago, sefiroxx said:

Try

Cleaning the throttle body and butterfly.
Monitor STFT to rule out any lean/rich scenarios

I have already cleaned the throttle body and IAC but I will monitor fuel trims next thanks for the tip.

[Waffeey]

So the stumbling issue has gotten worse with the truck throwing a new CEL yesterday P0342 for Cam sensor after the truck wouldn't start after a longer drive. Checked wiring harness and installed new sensor today and its still stumbling and not starting first try! Threw the CEL again too... The only other thing I can think of is a bad fuel pump causing the stall and stumble but why am I still throwing a cam code?

[Waffeey]

My fuel trims are -0.8 - 1.6% for bank 1 and 0.8 - 3.2% for bank 2 while idling.

Edited August 11, 2020 by Waffeey

[Jac365]

I had to replace the cam sensor in my 01 8.1. 2001 cam and crank sensors were a known issue. I did both at the same time. The crank sensor was a "new, update design". The symptom of my bad cam sensor was hard starting and a backfire that blew the exhaust manifold gaskets.

 

  The only other sensor issue was knock sensors that has to be replaced. I will caution on one thing that I have learned. These motors are great, but they DO NOT like aftermarket sensors. Replace them with A.C. Delco only.

[Waffeey]

16 hours ago, Jac365 said:

I had to replace the cam sensor in my 01 8.1. 2001 cam and crank sensors were a known issue. I did both at the same time. The crank sensor was a "new, update design". The symptom of my bad cam sensor was hard starting and a backfire that blew the exhaust manifold gaskets.

 

  The only other sensor issue was knock sensors that has to be replaced. I will caution on one thing that I have learned. These motors are great, but they DO NOT like aftermarket sensors. Replace them with A.C. Delco only.

 

Thanks for the reply I will try swapping back in the original cam sensor since mine is standard brand. My new crank sensor is the updated acdelco one and MAF and MAP sensors are the originals. I tested my fuel pressure at the rail with just key on and i got 48psi instead of spec 55-62psi so i am thinking about replacing the fuel pump but the truck now will not start again. With that confirmed fuel pressure and audibly hearing the fuel pump I am thinking something else is causing the no start. So now I'm lost.

Edited August 11, 2020 by Waffeey

[Waffeey]

Progress! Tried the starter fluid trick to find out it's not fuel. Replaced the NEW "standard" brand cam sensor with my OLD one and the truck now runs like before.. Wow. So I still have a hard starting issue, ocassional stumbling, and P0342 Cam Sensor CEL but have figured out the no start was the new cam sensor. Also I have a harbor freight special fuel pressure tester so its probably not accurate. Thanks for your tip I will try to find an ACDelco Cam Sensor!

Edited August 11, 2020 by Waffeey

[Waffeey]

So I tested the voltage at the cam sensor connector with a multimeter and got 11.6V (Checked battery at 12.5V) a voltage drop of .9 volts could this be it? I looked inside the loom up to where it meets the rest of the harness couldn't see an broken wires. Confirmed still throwing the P0342 Cam Sensor code. Skeptical of the accuracy of the harbor frieght fuel pressure tester so I rented an OEM tools one and tested it in the parking lot. Got 50 psi this time, harbor freight reading was 48psi. Truck started and drove fine the 5 miles there and back.