An update for anyone with any thoughts on this engine issue.

-This morning pulled code P0102 (MAF or VAF A Circuit Low Input).

We pulled the code early on in this process, then replaced the MAF sensor with an aftermarket, still the same issue. Pulled the aftermarket MAF sensor, replaced with an OEM, still pulling the same code.


　
　
So, we have replaced the Mass Air Flow sensor twice. Initially with an aftermarket part. We weren't sure if the aftermarket part was the way to go, so we swapped it out for an OEM Mass Air Flow Sensor. No change has occurred with either of the Mass Air Flow Sensor's being installed.
　
　
Upon start up no timing chain rattle, and doesn't seem to backfire when reving the engine.


Repairs made:


-Mass Air Flow Sensor　
　
-(2) New O2 sensors

-Timing chain was completed, and timing chain tensioner.


No change in run ability, still the same issues with the truck acting up when it is warm out.

A little more information listed below...

**We did try something different, and zip tied a bag of ice to the MAF on two occasions. The truck seemed to start smoother, and not rev and stall, or rev and settle out. Also when accelerating seemed to not ping as much and accelerated more smoothly. I don't know if this just coincidence, however I do feel the truck ran better with the bag of ice zip tied to the MAF.


Any information would be greatly appreciated as this poor running truck is driving me crazy!!


Thank you, Chris

 

Have you checked for vacuum leaks? I'm having a similar issue but far less exaggerated. I just replaced my could packs yesterday and it hasn't fixed my issue. The next most common problem I'm seeing that could be it would be a leaky fuel injector. I have a generic misfire code but it is a pending code so no check engine light and no specifics on the cylinder where it is occurring.

My suggestion is look into new fuel injectors. Rock Auto has them for less than $20 a piece for AC Delco OEM ones right now.

 

Hey @RedWings44,

We've checked for vacuum leaks, nothing. All gaskets and seals are new as we rebuilt the entire upper end. We haven't done anything with coil packs. We have two codes were pulling P0102 P0101, all relate to mass air flow sensor, nothing with misfire. We tested the leads on the mass air flow for proper voltage readings for lack of better terminology. Should we replace coil packs, and or injectors? There is like nothing else to test as far as we know...we are stumped!

Please HELP!!

 

I would vote for the injectors as well. Could diagnose with a fuel pressure drop test to see if you get inconsistent pressure drops hot vs cold and between injectors before putting in the new ones. As to why it's throwing a MAF code...possibly if the injectors are adding too much/little fuel, maybe the computer sees the rich/lean condition and assumes it's getting a bad MAF reading. Complete guess, but plausible.

 

Im following what your saying. We will look up how to do a fuel pressure drop test and replace injectors as mentioned! I have no idea what else it could be at this point. Thank you! If you think of anything else please let me know.

-Chris

 

Hello,

Just updating on my (Junk) truck! So we replaced the fuel pump/regulator assembly, no change in runability, then changed all injectors, slight improvement, however truck will upon attempting to start after warm die out, takes a second turn of the key and crank to get it running. From there generally I am backing up out of the garage or a parking stall and the truck nearly dies out. Once I shift into Drive and begin to go forward the truck seems to level out and run decently.

We are beyond frustrated and out of ideas what to do next! Any further recommendations by change?!?

Thanks! -Chris

 

I know you said no vac leaks but that's what MAF codes usually point to.

I wonder if the throttle body is goofed. Seems to mess up when hot and when it is hot the idle should be a bit slower but not be rough or die of course. Is the idle too slow when its hot? If so then maybe the TB isn't able to control the idle speed correctly when hot. Say the computer thinks it should be at 750RPM but it is actually at 500 because the TB is messed up. That could make the ECM think the MAF is reading wrong because less air flow than it thinks it should see, thus the MAF code. Know what I mean?

 

@White016, What you are saying makes sense. We replaced the throttle body about a week ago. Truck seemed to run better....we'll that was short lived and just a fluke. The truck is back to pinging upon acceleration, and nearly everytime its started it will die on the first attempt. Second attempt truck will start, tach will bounce, then it will level off. From there when backing up, or even upon accelerating going forwards will miss/sputter for lack of better terminology. Again this is generally during warmer weather.

We still have the PO102 code and we've had that throughout, which has not changed.

We checked for vacuum leaks again and didn't find anything as far as we know. The next step is to replace the ECM/ECU? Not certain if the truck has both or what they exactly are?

Again I/we aren't really certain where to go from here. Any further information would be greatly appreciated.

Thank you. -Chris

 

Do you have a scan tool so you can look at voltages, ect? Like for 5v reference to the sensors. Have you checked all the grounds that these trucks are know to have problems with? This could be a bad connection too. Man you got a bad one to deal with. I think you should do the grounds and at least unplug and plug back in all the connection to the ECM. Might get lucky.

Since it seams to be heat related get a scan tool to check readings on sensors like coolant temp, intake temp....that kind of thing.

The tach bounces with the rpm or independent of the rpm? Maybe a bad crank sensor. A scan tool would show RPM at the ECM too. If there is no signal from the crank sensor then no start, if its bad, then a miss/rough/hard to start. good luck

I'm going to look over the P0102 in the book and report back. That is the only code right?

 

@White016,

Thank you for your responses and help here! I'm sorry for the delayed response myself, I've been preoccupied the last week or so. I will look into all you mentioned most certainly! Only one code as of now. We have a scan tool, however not one that a dealer or auto shop would have, its a little more generic.

 

does the live data show the same IAT as outside air temp & is the MAF in spec post what the live data is showing . Hope your scan tool will read live data that's a must have .