RTLee

Hi all, Rob here. This is a great site, but I've been searching this forum for a few days, and none of the situations are the same as what's happening with my truck.

2001 S10 4.3L Vortec, approx 130,000 km on it - Needed a crank sensor, so replaced that. Would start but not run, found that the cat was plugged. New cat installed, then did a tune up and replaced the distributor because the housing was broken.

Here are the current symptoms/issues:

Truck starts, but always on second try, never first (almost as if you have to hit it once to prime, starts right up the second time). Idles great, has lots of power, but I can only drive a few hundred feet and it shuts off - no warning, no bucking, coughing, sputtering - just shuts off, as if you turned the key.

At this point, it won't restart - it's giving me a MAF sensor code P0101. Clear the code with the scanner, truck will start.

Here's the trouble....I have a Blazer with the identical engine that works fine, so I swapped out the MAF. Getting the same problem.

Also tried unplugging the MAF - the truck STALLS. I'm seeing a lot on here that if the MAF is bad and you unplug it, the truck runs better.....so what does it means if the truck stalls?

ThatChevyGuy

if the MAF sensor is uninstalled the vehicle will run to "stock" settings. it appears like your mass airflow sensor is trying to correct a problem that another sensor is missing.
I have an hombre which is basically the same car. if i remember, there is an air charge temperature (ACT) sensor and a Throttle Position sensor (TPS). maybe one of these has gone bad.

ThatChevyGuy

maybe vacuum leak?

RTLee

Thanks ThatChevyGuy....I thought that it might be an issue with another sensor, but no idea which one it could be - this is a great help! I'll try swapping out the sensors - good thing I have another truck I can take from instead of buying all new parts!! Re vacuum leak, I've checked and can't find one, but if the sensors don't pan out, I'll have another go. Will update on progress!

ThatChevyGuy

awesome let me know how the sensors go. as far as vacuum leaks (I know checking them is the worst), are you using the "carb cleaner method"?
the worst part is only a few pinsize holes can have devastating performance affects.

RTLee

I swapped out the TPS, ACT and IAT (might as well, while I was in there). A few runs up and down the road to the house, no stalling, it seemed to be working fine - I thought the problem was solved. Took it for a bit longer run, and it stalled out AGAIN!!! Kicked out the P0101 code; cleared that, started it up, got it home.


I've checked for vacuum leaks, and can't find anything. Wouldn't the truck run poorly overall if there was a leak? It idles and runs great, when it will stay running lol


Any more suggestions would be greatly appreciated!!

ThatChevyGuy

you are correct, If it's not running poorly at all, that should rule out vacuum leaks.
now is your engine getting fuel? the MAF sensor makes me think it must be a problem with air getting to the engine. however, I would expect it would have poor performance all the way around and I would imagine that it would die rough.
So I'm starting to think this could be something electrical.


very good read here for you:
P0101 Trouble Code - Mass Air Flow (MAF) Circuit Range/Performance Problem


maybe it is as simple as a wire frayed (simulating key being removed from ignition).
don't know if this makes sense, but when the circuit is opened, everything will shut down, when it is closed, everything gets power. so my question is: is everything electric shutting down? or just the engine?

ThatChevyGuy

also check the EGR valve. this might be what caused your cat converter to go bad.
might be sticking or something

RTLee

Thanks for the reply!


To answer the question re electrical - when it dies, it's just the engine. Radio, lights, etc all keep working.


As far as fuel goes, haven't done a fuel pressure test yet....may have to check that. A bit more detail on exactly what happened on my last test drive: truck never starts on the first turn of the key, always the second, then starts and idles great. doesn't run rough, purrs along like a cat. I drove around close to home for about 10 minutes, working great up to 30 mph. Went a bit further, when I got to about 50 mph sporadic loss of power, I slow down a bit, it went back to working fine. Drove for a another 10 minutes or so, and was going up a steep hill at about 30 mph, and it just quit, cold. At that point, kicked out the MAF sensor P0101 again (thanks for the reading material on that one, will check it out). I've got half tank of fuel and new fuel filter.


EGR sounds like a good thing to check (even if just for maintenance, anyway). What do you think about PCV system?


As far as wiring problems, I keep coming back to that myself, but I've wiggled every bit of wiring trying to get it to stall out, can't make it happen.

ThatChevyGuy

It's not overheating is it? I'm pretty sure you would have mentioned this if you noticed. haha
I guess you could change the PCV valve (only like 5 bucks or so), but doesn't sound like it's the problem. the PCV valve is designed to reduce blow-by gases and keep them out of your crankcase.
maybe it is something we are overlooking...
was going to say crankshaft position sensor, but you already replaced that.
I'm really thinking you aren't getting spark


things we haven't thought of:
1. Ignition coil
2. ignition module
3. bad ground


I hate option 3, so try the other two first. haha