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Discussion Starter · #1 ·
Hello fellow Chevy and GM owners I have an issue with the vehicle jerking and hesitating while driving. It's a pre-owned vehicle and I purchased it at 208k miles on it. Oil change, spark plugs and wires, ignition coil pack, emission control valve all new I've replaced. I still get a p401 trouble code after all I've done. My biggest issue is it's still jerks and hesitate and sometime feel like it's losing power. Do anybody have any ideas on what this could probably be.

Thanks in advance for any information that can be given to me about these issues.
 

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What you need to find is a scan tool that can do "graphing" of various "input sensors" and "output devices".

When the jerking is going on the proper scan tool has to do a "snapshot of all those sensors to see what sensor is dropping out of the loop.

2 things come to mind with the words you wrote, one is the TPS sensor (hesitation) or the MAF sensor (jerking / hesitation) just leaving the air box. A distant 3rd place is lower than normal fuel pressure.

First homework assignment, find somebody with a "graphing" scan tool to track sensor activity, like TPS, MAF and ignition signals. Any sensor drops out, ...replace that sensor

Another action, warm up vehicle, when MAF is fully hot "lightly rap" on MAF sensor electronic module by the electrical connector with a small rubber mallet, small wood block, or some similar soft heavy object item like that. If the engine idle stumbles when banging on the hot MAF module, replace that MAF sensor ASAP with a factory OEM type MAF. Aftermarket MAF's don't have the quality control nor the reliability.
 

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Discussion Starter · #3 ·
What you need to find is a scan tool that can do "graphing" of various "input sensors" and "output devices".

When the jerking is going on the proper scan tool has to do a "snapshot of all those sensors to see what sensor is dropping out of the loop.

2 things come to mind with the words you wrote, one is the TPS sensor (hesitation) or the MAF sensor (jerking / hesitation) just leaving the air box. A distant 3rd place is lower than normal fuel pressure.

First homework assignment, find somebody with a "graphing" scan tool to track sensor activity, like TPS, MAF and ignition signals. Any sensor drops out, ...replace that sensor

Another action, warm up vehicle, when MAF is fully hot "lightly rap" on MAF sensor electronic module by the electrical connector with a small rubber mallet, small wood block, or some similar soft heavy object item like that. If the engine idle stumbles when banging on the hot MAF module, replace that MAF sensor ASAP with a factory OEM type MAF. Aftermarket MAF's don't have the quality control nor the reliability.
Hey Thanks a lot, I use Torque scan tool mobile app with a somewhat high end adapter to plug into the OBD. The only trouble code pops up is that p401 which is the EGR which I failed to add that I also bought.
 

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We will deal with the EGR code later which has no effect to the current driveability problem that needs attention now.

Find a way to start graphing those sensors when hesitation and jerking begins. It could get much worse if not caught.
 

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Discussion Starter · #5 ·
We will deal with the EGR code later which has no effect to the current driveability problem that needs attention now.

Find a way to start graphing those sensors when hesitation and jerking begins. It could get much worse if not caught.
I recently checked around since the post you mentioned on graphing the issue. Meineke, Midas, are the closest mechanic shops in the area and they both came up with the price of 200 to 300 dollars for that procedure. 3 other ASE certified mechanics I spoke with all said it sounded like failing fuel injector/s to a malfunctioning fuel pump. Also they said since the check engine light trouble code didn't indicate a failing or malfunctioning camshaft positioning sensor that that wouldn't been their best an option considering the high mileage on the vehicle without going through that expensive diagnostic test.
 

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Buy yourself an "essential" OBD2 scan tool that every shade tree wrench needs and must have!!!.

I'm on my 3rd major scan tool upgrade in 10 years. Just bought a Launch CPR 429C scan tool for $259 ($399.00 list, can find on Amazon or Ebay, also not asking you to buy this one, research heavily what you need so not to be obsolete within 5 years), ...and was given an additional baby scan tool that reads data in this $259.00 purchase price.

At least get up to 2019 standards!!!

Research cite: https://www.bing.com/search?q=Launc...s=n&sk=&cvid=fbfa890c246e4afd90158a6005de430c

Vehicles are getting way more complex by the year, so this explains the scan tool upgrade multiple times over the last 10 years. I "REFUSE" to pay 2 to $300 for scanning my vehicle codes, when I can sell my old scan tool for what I paid for it and get an upgrade for free!!!

Please don't "GUESSTIMATE" your problems!!!
DON'T slap on parts hoping for a fix!!!
You will spend way more of your hard earn cash than if you did the right procedures the first time. Find, buy a scan tool that does "graphing", not just reading data alone. Don't get "conned" into that purchase!!! Do your "research", ...and look for that scan tool option.
 
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