Cuts out at 45MPH

[calicosun]

I have a 95 Blazer 4x4. I have replaced so much on this thing I won't even start. But the most recent is the altenator and fuel filter. I have noticed lately that at about 45MPH my blazer starts to cut out, not bad but enough to be noticed. Here the other night it is now doing it up to 65MPH. At an idle it is fine. I have noticed that the performance is a bit lagged sometimes. It has never quit or had a problem starting. Any ideas?

[TonyMazz]

Originally Posted by calicosun

I have a 95 Blazer 4x4. I have replaced so much on this thing I won't even start. But the most recent is the altenator and fuel filter. I have noticed lately that at about 45MPH my blazer starts to cut out, not bad but enough to be noticed. Here the other night it is now doing it up to 65MPH. At an idle it is fine. I have noticed that the performance is a bit lagged sometimes. It has never quit or had a problem starting. Any ideas?

In your "replaced so much on this thing" include things like cap, rotor, plugs, fuel filter types of things ?

How many miles on the Blazer and is it a 4.3L motor ?

By "cutout" do you mean unexpectedly slows down or the motor quits and refires ? Or are you experiencing a slippage in your tranny ?
Do the RPMS change ?

Are there any codes through i.e. your SES light come on ?

By performance do you mean that when you go to accelerate the truck hesitates or does it seem that the motor is running but truck isn't moving i.e. a TC lockup issue...

Guess you have tell us more.....

[calicosun]

My service engine soon light has not come on. My blazer has 123,000 miles on it with a 4.3L
What I mean by cut out is that as I'm driving you can feel it slowing down and speeding back up. Its not bad but it is noticible. A few months back I was having trouble with it running rough at an idle. I kept putting fuel dryer in it everytime I filled up. I could drive 1 mile after putting in the dryer and it would quit idling rough. After about a month it stopped completely.
I don't know if that is linked to what it is doing now. The performance issue is that it hesitates. When you give it gas it is VERY slow to take off. The other times it right on the money and gets up and moves.
We have replaced the fuel filter, the cap, altenator, battery, various lights, belts. If its not one thing, its another.

Originally Posted by TonyMazz

In your "replaced so much on this thing" include things like cap, rotor, plugs, fuel filter types of things ?

How many miles on the Blazer and is it a 4.3L motor ?

By "cutout" do you mean unexpectedly slows down or the motor quits and refires ? Or are you experiencing a slippage in your tranny ?
Do the RPMS change ?

Are there any codes through i.e. your SES light come on ?

By performance do you mean that when you go to accelerate the truck hesitates or does it seem that the motor is running but truck isn't moving i.e. a TC lockup issue...

Guess you have tell us more.....

[Kurai]

It sounds like your timing is off.

[rlith]

Originally Posted by Kurai

It sounds like your timing is off.

Doubt it, it's a locked distributor. More than likely the CPI and/or nut kit is taking a dump or the fuel pump is starting to go.

Things to start with...

Check pressure at the shrader valve. When key is turn to run position it should be at 56-60 psi. When the key is turned off the pressure should hold. If it bleeds off you have other issues.

Pull the upper plenum and check for washing

Also check that the cat converter is flowing properly...

[wolfox]

Try changing/cleaning your plugs. Fuel dryers have agents in them that can create ash-like deposits on the spark plugs. If you feel like the truck is hesitating/or not developing power at around 1500~2000 RPM, I am fairly certain that this is your problem.

Had a buddy that drowned his truck with a fresh bottle of Dry Gas everytime he topped up. Had more fuel treatment than gas in the tank, I swear. Developed a strange surging/loss of power, like a dead spot at 1500 up to about 1700 RPM, and then she would catch and run like her ass was on fire. Then once cruising at 45 to 55 MPH, it would slowly booooooog back down again, like the engine was dead between 1500~2000, but a heavy throttle would clear her up and get her moving again. We pulled the plugs, and there was this ashy stuff all over them with a light grey glaze on the ceramic and center electrodes themselves. Told him to run the gas out until nearly empty and fill up on just straight gas. Problem didn't come back.

[Kurai]

Hrm. I suggested the timing issue as I had similar troubles recently and the timing was the cause--went through a lot of differnt parts and methods before arriving at a third mechanic (who apparently actually KNEW how to do HIS job) who fixed my issues post haste. Boo on me for assuming the previous two garages would catch it--the first for not checking the timing after THEY did the tuneup (lazy gits) and the second for not even paying enough attention to think about it. >.>

[rlith]

Originally Posted by Kurai

Hrm. I suggested the timing issue as I had similar troubles recently and the timing was the cause--went through a lot of differnt parts and methods before arriving at a third mechanic (who apparently actually KNEW how to do HIS job) who fixed my issues post haste. Boo on me for assuming the previous two garages would catch it--the first for not checking the timing after THEY did the tuneup (lazy gits) and the second for not even paying enough attention to think about it. >.>

Heh, I can sympathize. It's why I do most of my own work except for internal transmission work.

[Kurai]

I try to do most of my own work but transmissions are out of the question for me, and I actually don't have a timing gun. o.O Had I actually REALIZED that it hadn't been done, I would have taken care of it immediately, since it was a rather obvious thing to check--my own fault for chasing the ghosts of lazy mechanics for so long. :P Now it runs tons better, even though it's still a bit sputtery. I'll take care of that in time.