Engine sputters and hesitates - *FIXED!*
 

I am literally praying that you guys can help. (Nice forum by the way).

I've got a 4.3L 2000 4X4 Blazer with 87,000 miles on it. I've had it to two different shops without luck. Here is the SPECIFIC problem.

Once warm, under accelleration the engine sputters. If I let off the gas, it'll idle fine, once I hit the gas it sputters terrible.
If I shut it off, even if for only a few seconds, and then restart it will run fine again for about 5 minutes and then sputter again. Again, everytime I shut it off and then restart, it's fine for 3-5 minutes and then sputters again. I do this over and over until I get home or to work. Drive, sputter, pull over, shut off engine, restart, pull out again, drive for 5 minutes, pull over, shut off, restart, etc......

Mechaincs checked fuel pressure and it's fine. Fuel pump and filter are 6 months old and I was sure the pump was no good. Even when it sputters, the fuel pressure is up around 55-60 psi or so.

I thought it could be a plug or wire but both shops said it wouldn't sputter the way it does. When one cylinder is bad the skip would sound diffrent, this is definately all cylinders.

I have had a service engine soon light on for about 5 months. I don't remember the code # but it was indicating a leaking gas cap. I replaced the cap with a new OEM one, reset the light and it came back on within a week. Both shops told me this was an emissions related problem and that it wouldn't cause driving issues.

Please help. I've been renting a car from Enterprise for days now, the truck still isn't fixed and I'm stumped. My next step is to go to a Chevy dealer but I know this is gonna co$t me plenty more.

RE: Engine sputters and hesitates
 

I'd really like to know the code that it is throwing. It sounds like you have a problem when the engine goes into closed loop operation. If you were near me, I would want to take it for a spin with my scan tool hooked up to take a look at the O2 sensor graphs as well as the fuel trims. Almost sounds like a sensor is telling the engine something that is incorrect.

Have you tried cleaning the EGR valve, IAC valve (whole TB for that matter) and MAF sensor? Not that it will cure your problem, but it'll only take an hour or so to do all of them. Run searches on the proper cleaning procautions to take with the MAF sensor.

How does it drive when you unplug the MAF sensor (this will throw a MAF sensor code)??

RE: Engine sputters and hesitates
 

Thanks for replying!
I haven't tried cleaning any of those parts. At this point, if you don't even think it will help, I don't want to try.

Would you recommend trying to disconnect the MAF sensor to see if the problem improves? Would you recommend I do it now and see if I can drive home without problems or once the problem happens? It usually happens within 5 minutes or so of driving.

Like I mentioned, it will go away for 5 minutes at a time after I restart it. It runs perfectly but ony for about 5 minutes or less.

Let me know. I really am afraid I'll have to take it to the Chevy dealer. The last time I was there was for a NYSI. It failed due to inoperative license plate lights. They claimed I needed new sockets as well as bulbs..... $210 later (incl the inspection and taxes) I was on the road again. I was mad as hell over THAT one! [:@] I can't imagine the poking I'd get over this one just in diagnostic time alone.

BTW, At this point I'd travel to Waterloo to see you but the way it's running, it would take me hours and hours! [&o]
*edit*
I wish I could remember the specific code # but both the mechanics as well as the local Auto Zone said it was indicating a leaky or loose gas cap. I've got a brand new cap on there and I know it's on tight. I originally bought an aftermarket one, got the code again, then went to an OEM. Same thing there too.

RE: Engine sputters and hesitates
 

Wow.. Didn't know where you were from, but I'd take a crack at it if you could get it down to me. I'm located about 10 minutes south of thruway exit 41.

Anyway, by disconnecting the MAF sensor, you will effectively eliminate any false readings that it may be giving once the truck goes into closed loop. The same goes for the upstream O2 sensors. If you disconnect them and it runs better, then you mostlikely have a faulty O2 sensor messing up the mix. Anytime a sensor is disconnected it will trigger a code, but the PCM will go to a default, safe map to compensate for the missing sensor. Mileage and power will be down, but the engine will run.

As far as the cleaning of the sensors and other components goes, like I said, its cheap, relatively easy and not too terrible time consuming. It can only help and may solve your problem.

RE: Engine sputters and hesitates
 

check for a plugged cat.

RE: Engine sputters and hesitates
 

I gave up and took it to the local GM dealer.

It was in fact, the FUEL PUMP! Grrrrr. The one in it is only 6 months old. The first shop I took it to was the one who installed it in the fist place. They did a pressure check and said it was fine, even showed me the gauge.

Apparently the pressure was showing fine most of the time but the pump wasn't giving the engine enough VOLUME of fuel to run. As far as the restarting and having it run fine part.... they don't know that one unless the engine just get's enough pressure to run for awhile and then dies again.

Total is just over $750!
$500 + for the pump, the rest is labor.

I can get my money back on the pump in there but not the labor for the original install.

I'll be picking it up in a few hours.

*sigh* Thanks for the help. I'll try to pop in here now and then. It's a great site.

RE: Engine sputters and hesitates
 

Where did you get the last fuel pump from? If the part was under warranty, then they should be able to do a labor claim for you and at least get part of the money back. I know where I work, they pay a flat fee of $30 per book hour.
It won't get it all back, but at least part of it.

RE: Engine sputters and hesitates - *FIXED!*
 

It was a small local shop that did the work the first time. I don't know where he got the first pump from. I dropped it off to him a few hours ago. Now he's saying they may only give me another fuel pump instead of my money back. i explained I've already got the vehicle fixed and I don't need another fuel pump, I just want my $$ back on this dead one.

My guess, he bought the pump elsewhere (who knows where), marked it up to sell to me and now he doesn't want to give me any $$ back. He seems like a nice guy and said he'd "try" to get the money instead of another pump. I hope so or I'm gonna be a little pissed.

I'll see what happens.

BTW, I've been driving the truck for a few days now and it runs nice! It starts up faster then before, it used to crank a bit before it'd fire. Now I just turn the key and go.... best of all, it doesn't die 10 times during my ride home!