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71 C20 gets a 5.3

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older sbc/bbc I run 2 sets of oem style with headers .

the newer ls engines use a factory multi layer style . if me I would just get a set of them from parts store . only reason I have seen them blow out is the broken/popped bolt head problem . :whistle:
 
Went with a higher end parts store multilayer, almost went with some coppers, hopefully I don't regret it. #7 was just blown out a bit, looks like it might have been a little loose. I was waiting for a couple heat/cooling cycles to tighten the headers again, guess I waited too long :doah:
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Alright I am stumped. Plugged it in and am getting p0101 (maf sensor) and p0135/p0155 o2 sensors. Checked all my voltages and they are all getting ignition hot and good grounds. Tried swapping in a new maf, same codes. The 02s have 150 miles on them. They can't both have failed already. They are not gunked up or anything.

It drives like it's not getting enough fuel. Kinda gutless. So I checked the fuel filter, a few chunks of line in there but pretty clean. Put it back together same thing.

Would low fuel pressure throw the maf code? There is no fuel pressure sensor right just a regulator?

Of course it starts acting up the day I sold my other dd
 
Check for air leaks around the throttle body and intake manifold. Spray carb cleaner around the connections and around the intake and see if the rpms come up. With that combination of codes that seems like the most probable cause.
 
That was my first thought. I broke the intake down, cleaned it all up and tightened the hell out of it. Ended up doing that twice actually with the old and new maf sensor. I am not running a map so I checked for a vacuum leak on the plug I made too. It all seems sealed.

I checked the fuel pressure. It was at 50 running 52 key on engine off. Bumped it up to 57 running and 60 key on engine off, the higher side of the factory specs I found. No change, still getting the map code. Hopefully it will be smoother once I figure this issue out though.

I think I am going to have to dive in deeper and look for vacuum leaks tomorrow
 
How's the connector and terminals on the sensor look? Also have you checked resistance of the signal wire from the sensor to the ECM?
 
Cili said:
How's the connector and terminals on the sensor look? Also have you checked resistance of the signal wire from the sensor to the ECM?
Click to expand...

The connector looks pretty good and I tested the iat and maf wires and this evening, they are both good.

Went through most of a can of starting fluid looking for a vacuum leak with no luck. I read the earlier intake gaskets dont like the ethanol in gas these days and crack pretty often. I have also read when they leak its hard to find so I swapped them out too. No change still a rough idle and a p0101 code.

After I swapped the intake gaskets I took it around the block to see how it felt. When I put on the brakes for a stop sign the engine bogged down and almost stalled. When I took my foot off again it came back up to its rough idle. Transmission was in neutral so it wasnt clutch drag
 
Also should the throttle body be completely closed when the engine is off? It seems to be about an eight inch open
 
Nope the throttle body will be open a little bit. I assume you have cleaned the throttle body too? They can cause all kinds of issues. Try plugging the vacuum line going to the booster and drive it.
 
Just tried taking the booster out of the equation. No luck. Going I try cleaning up the throttle body now.

It's weird it will bog taking off from a stop sign then something happens and it seems slightly better for a little but still unresponsive?
 
Cleaned the throttle body up, it wasn't that dirty. Anyway, still no change. I need to take it on a longer test drive so it will take a freeze frame of the air/fuel ratio data. I am stumped
 
Mine (not the same system) would act like that when I had the base timing too retarded. Might try checking timing.
 
bp71k5 said:
Mine (not the same system) would act like that when I had the base timing too retarded. Might try checking timing.
Click to expand...
The timing is all computer controlled on the lsx engines. No more distributor just an individual coil pack for each cylinder.
 
Yeah there is, I will check it out. I think it is something with the wiring, going to try to run a jumper on from the PCM to the maf tonight and see how it works
 
I finally got my hands on a multimeter that does frequency and the MAF isnt sending a signal to the pcm. Its getting the correct power and has a good ground so I am thinking its a bad sensor even though its a new part? Going to try to warranty it tomorrow and try again.

I go the bright idea to brake down the plug cause I messed up some of the wires insulation, broke a piece so now I need a new plug...:rolleyes:
 
Swapped in another MAF and rewired the plug, no change. I tried jumping the ignition hot an ground wires from the connector to the battery no luck. Broke it all down and tested the voltage on the ignition hot and ground again and they were both at battery voltage. Tested the continuity to the PMC on the output wire and it was good. There is no output coming from the MAF circuit no matter what I do. This is driving me nuts
 
How are you testing signal from the MAF? With it plugged in it unplugged?
 
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