Hi everyone. I'm new on here and was wanting some input.

I have a 2001 Blazer 4.3L automatic with 103k mi. My blazer seems to loose power almost as if I were running out of gas once the engine temp reaches around 210 degrees. It never exceeds 210 but when I pop the hood it does seem pretty hot under there. It wants to stall at times but mainly just bogs down under acceleration. I replaced the fuel filter and air filter today, cleaned the MAF sensor and EGR valve with no change in performance. I am getting a fuel pressure reading of 60 psi with engine off/key on and loose around 5 psi after pump shuts off. While running motor with fuel pressure gauge attached the pressure jumps around and drops to around 50 psi and vehicle stalls at idol. I had to store the vehicle for a deployment so the other day when I tried to start it I had to replace the battery. Prior to storing it the check engine light was on, but upon installing a new battery the check engine light went off and no codes are showing up. Another oddity is when the transmission is in Park, the gas gauge bobs up and down constantly.

Any input that you may have to offer would be great. In the mean time, I will continue to search the forums for help.

Thanks,

Bill

 

Hmmmmm....I had a similar issue. I too cleaned the MAF, but still bogged down. Found another thread on this site where someone had unplugged the MAF and the bogging down issue went away. So, I tried that and the bogging down went away. Of course, the check engine light came on while it was unplugged. I purchased a new MAF and all is well. I can't say this is the problem with your vehicle, but it might be worth a try.
Good Luck

 

Thanks man for the reply. I will give that a try tomorrow. What is stumping me is the fact that the problem only arises after the engine heats up. I'm also going to try and take it over to a local exhaust shop to get the the exhaust pressure checked out and see if its a plugged CAT. I've also considered the O2 Sensors. I'm not really sure how to test them since my service engine light isn't on and it's not throwing codes yet (just put a new battery in and it reset ECM). I'm finding a lot of great advise on here but I'm not always able to find the follow ups to see if the problems others have had were solved. I guess I'll just continue with the old process of elimination.

Anyhow thank you for your advise,

-Bill

 

Well, in regard to it only happens after warming up, generally the computer runs in "open loop" mode until it's warmed up. That means the computer runs the engine at a default settings, then, when warmed up, changes to "closed loop" mode and receives data from all the sensors to run the timing, fuel mixture etc...
So, it could be related to the O2. Sounds like you're on a good process of elimination. I think a bad cat should set a code, but as I have found out, they codes don't always set. Please come back and let us know what you find out.

 

I just unhooked the MAF sensor and am going to take her for a drive, fingers crossed. If its not throwing codes, is their a way to test the O2 sensors? I admit I haven't performed a search yet on that subject but I thought I'd ask anyway.

I'll let you know the result of the MAF sensor when I get back.

Thanks,

Bill

Update:

Unhooking the 02 sensor is a, NO GO. My Blazer instantly idols poorly and sputters when sensor is unhooked. Any ideas?

 

Problem solved:

Well, thanks to some info I found on this website I realized that I not only needed to check my fuel pressure but also my fuel volume. Found that the volume was normal under cold start but it seems as the pump had to work harder under a load (acceleration) after 15min or so drive time the volume would drop considerably. I replaced my fuel pump today and she's running good as new.

Thanks for all of your help 1998MSO. This website offers a wealth of knowledge to those who understand the "Search Feature." I will continue to frequent this site with any future questions or concerns.

-Bill

 

Did you disconnect it with the engine running? This should not be done.

When you disconnect a major sensor like the MAF or O2 sensors, the PCM will default to a safe map for fuel and spark once restarted. If this causes the engine to run better, then the problem is likely at with that sensor.

Damn, one minute too late. LOL

Glad you fixed your problem!

 

I have similar symtoms to 134LRS. When I unplug my MAF sensor, the engine dies. Is that normal or a sign of the problem?

Thanks,

Kevin

 

The gas gauge being wonky is a design flaw in the fuel pump. The contacts wear out. It should stop for a while now that you have a new pump.