Hard Engine Miss

[88m53453]

03 Tahoe , 135,000 miles, performance tune several years ago 5.3 ltr. When going to transitional throttle such as beginning up a hill at highway speeds using the cruise control , the engine misses hard, several times, until the trans kicks down and the engine pulls hard and the miss goes away. The miss does not happen if the throttle is eased off when not using the cruise as if to save gas when going uop hill or if the throttle is aggressively used. I tried premium fuel to see if that made a difference ( knock sensor problem ).It did not help. Otherwise the engine pulls and runs great otherwise. No CEL.

[jrrod2004]

03 Tahoe , 135,000 miles, performance tune several years ago 5.3 ltr. When going to transitional throttle such as beginning up a hill at highway speeds using the cruise control , the engine misses hard, several times, until the trans kicks down and the engine pulls hard and the miss goes away. The miss does not happen if the throttle is eased off when not using the cruise as if to save gas when going uop hill or if the throttle is aggressively used. I tried premium fuel to see if that made a difference ( knock sensor problem ).It did not help. Otherwise the engine pulls and runs great otherwise. No CEL.

 

did you do any of the recommended maintenance? Change plugs, clean up various items (air filter/throttle body/maf sensor etc), Checked fuel pressure?

[txab]

Check your codes

[88m53453]

no codes , if it was fuel pressure, it wouldn't not run well at high fuel demand ( full throttle), same with air filter, I have been a prof tech for 20 plus years on imports, was hoping this might ring a bell with past problems with someone, Plugs and wires with oem parts replaced in past 30k. Intake gaskets replaced in the past 6 months

[frdfandc]

Did you see if you had any pending codes? Or just guessing because the CEL isn't on.

[jblakeney]

Sounds like a weak fuel pump, clogged fuel filter, or bad fuel pressure regulator....

 

Check the pressure.... The fact it comes back makes me think fuel filter........ Sudden throttle movements and engine load are cause?

 

Also, you say no CEL, so no codes,.... Fuel would be a good place to start....

 

Jbo

[88m53453]

ok, but let me ask this, if it was a low fuel pressure problem, wouldn't the problem be worse under WOT ?, Problem goes away under heavy throttle, in addition if it was fuel pressure, wouldn't the engine just go "thin" on power ?, instead of the feeling of a quick on off switch, which is more what it feels like.

[frdfandc]

In stead of guessing, hook up an external fuel pressure gauge to the schrader valve on the fuel rail. Then go for a drive. You will see if you have a fuel pressure problem

 

Some vehicles use a fuel pump that only requires "X" number of voltage to run the pump at idle. When engine load is increased, voltage is increased to the fuel pump to pump more fuel. If fuel pressure is ok at idle, but falls off or isn't enough under load, then you get a stumbling issue. Could be a voltage problem.

 

As a "Professional Tech for over 20 years" (your words not mine), you should always start with checking the basic stuff. Air, Fuel, Spark.

[jblakeney]

ok, but let me ask this, if it was a low fuel pressure problem, wouldn't the problem be worse under WOT ?, Problem goes away under heavy throttle, in addition if it was fuel pressure, wouldn't the engine just go "thin" on power ?, instead of the feeling of a quick on off switch, which is more what it feels like.

 

WOT you would have a lul until the pump catches up........ FPR wouldn't thou.

 

You got it fixed yet?

 

Jbo

[88m53453]

not fixed yet, and the power is instant when you go WOT, I'll ck pressures, wife's vehicle and difficult to get to the shop at times

 

no codes when scanned

[oldmann]

I'd check the fuel pressure. You are overdue for a pump.