Stumped! Please Help!
 

Okay guys, I have a 2000 Blazer and has a 4.3 liter v6 (of course). A few days ago, I noticed it started bogging down when I got on the accelerator. No issues driving 30-40 mph but when I was on the interstate and needed to accelerate, fell on its face. Took it to shop and they diagnosed that the mass air flow sensor was bad. I replaced it and still the same. Replaced air filter, spark plugs and wires and still the same. It is a VERY hard start but once it starts, will start very easy and run fine until I need to accelerate in a hurry. Once the engine cools down below operating temp, hard start again. What am I missing? Thanks, Don

I would check operating fuel pressure and do a leak down check. Idk if your truck has the upgraded fuel injectors but the older style liked to leak into the mani. Or it could be a bad check valve in the fuel pump.

It does sounds like a fuel problem. Almost sounds like it could be a fuel pump. I've had the same thing happen on a few other vehicles and it turned out to be the pump.

i will jump on the fuel pump bandwagon...get a pressure check done.

What were the specific codes that were present? P0102 perhaps? A MAF specific code does not mean that the MAF sensor is bad and should not have lead to replacement of the MAF sensor.

If it was P0102 for instance, this could mean that you have a rather nasty vacuum leak that is allowing air into the engine that the MAF sensor is not sensing and the PCM is not accounting for with fuel or spark timing.

It could also be a partially clogged EGR dumping spent exhaust gases into the intake manifold. Both are relatively easy to check for and cheap too. A screened EGR gasket costs less than $10 and takes ~30 minutes for a first timer to install including cleaning the EGR valve & supply passage. Vacuum lines are cheap as well. Or it could be something as simple as a disconnected PCV fresh air make-up tube that runs from the passenger valve cover to the back of the intake hat on top of the throttle body.



Diagnosis starts with a full listing of the codes that were present.

swartlkk-Yes, the code was p0102. How do I check for a vacuum line leak or bad EGR? Thanks for the help.

You can check for a vacuum leak by spraying throttle body cleaner, some say starting fluid but I don't like catching stuff on fire, spray in one spot and see if the engine revs if it doesn't go on to a different spot. Don't just spray it every where at once cuz then you wont know where the leak is haha. For the egr you just pull it off and spray it down with some carbon off and clean up the valve really good then put it back on with a new gasket. I would do a quick fuel pressure check as well though.