bad hesitation, but it is intermittent

[benex]

buddy's 93 5.7, with 141K (blazer)

he sprayed synpower carb and T.B. cleaner

he tried seafoam in full tank of gas

we replaced O2 sensor, then coolant temp sensor.

then we replaced intake man gasket

no luck each time

he says plugs, wires, cap & rotor are less than 1 yr old.....

 

Here's the kicker, its 50 degrees today (instead of 32) , and he says its running pretty darn good!

 

I kinda thought it was still fuel delivery or vac leak, but now who knows?

 

any advice?

[ken1mod]

buddy's 93 5.7, with 141K (blazer)

he sprayed synpower carb and T.B. cleaner

he tried seafoam in full tank of gas

we replaced O2 sensor, then coolant temp sensor.

then we replaced intake man gasket

no luck each time

he says plugs, wires, cap & rotor are less than 1 yr old.....

 

Here's the kicker, its 50 degrees today (instead of 32) , and he says its running pretty darn good!

 

I kinda thought it was still fuel delivery or vac leak, but now who knows?

 

any advice?

 

<{POST_SNAPBACK}>

 

 

 

 

i don't know if your problem is identical to mine but my fuel pressure regulator was defective. I also had lean left and right codes. all problems fixed when I adjusted the regulator to spec. mine would stumble and hesitate when cold.

 

Ken

[beebow]

Having a similar problem with my 95'. I had a mechanic hook up a computer analyzer and the only things reading out of spec were the TPS and the Idle control sensor. The block learning was trying to compensate for what we believe is weak fuel delivery so I may have a weak fuel pump. I will let you know what we find this weekend.

[benex]

he didn't have any error codes...but dont know if he had it checked with an analyzer.

 

found out that in the last month, he also replaced fuel filter, IAC, new plugs (AC delco, again), thermostat,

 

can recreate by applying a load with the brack (from a stop), and giving it gas. it hesittes, and seems to chase RPM.

 

I even loosened the ditributer, and rotated it each way. it got worse, so we put it back.

 

we checked for vac leak with brake cleaner. no change either.

 

The Haynes manual does not show fuel pressure regulator. any advice?

 

Gas is spraying out of both injectors...gas flow looks ok on the throttle plates.

 

When we pulled the intake manafold to do gasket, the EGR port was completely blocked with carbon. Does that offer any clues? we are ging to test the EGR and SOL today.

Also, well try new cap, rotor, and wired as well.

 

TPS out of position...that sounds like a good one to check, thanks.

 

can you check for a bad distributer? if so, how?

[ken1mod]

he didn't have any error codes...but dont know if he had it checked with an analyzer.

 

found out that in the last month, he also replaced fuel filter, IAC, new plugs (AC delco, again), thermostat,

 

can recreate by applying a load with the brack (from a stop), and giving it gas. it hesittes, and seems to chase RPM.

 

I even loosened the ditributer, and rotated it each way. it got worse, so we put it back.

 

we checked for vac leak with brake cleaner. no change either.

 

The Haynes manual does not show fuel pressure regulator. any advice?

 

Gas is spraying out of both injectors...gas flow looks ok on the throttle plates.

 

When we pulled the intake manafold to do gasket, the EGR port was completely blocked with carbon. Does that offer any clues? we are ging to test the EGR and SOL today.

Also, well try new cap, rotor, and wired as well.

 

TPS out of position...that sounds like a good one to check, thanks.

 

can you check for a bad distributer? if so, how?

 

<{POST_SNAPBACK}>

 

 

 

 

On my 2000 5.3 the regulator is driver side on fuel rail and has a small vacuum line attached. This device is critical and its operation can be checked with a pressure gauge attached to schrader valv on opposite bank.

 

You need to test fuel pressure. a perfect pump will not work right without this regulator functioning perfectly. air conditioner gauge set will hook right up to the schrader on gm.

 

Ken