stormsracing10

i have a 99 ls1 that stumbles when u give it more throttle without the rpms building, and i have a rattling noise that sounds like valves rattling. you can make it down shift and it runs perfect, no engine codes. do you ave an suggestions?

LS6427

iTrader: (2)

02 sensor(s)

You'll need to get it scanned with e dealership type OBDII scanner.....NOT the ones at auto parts stores that just tell you the codes. You need to see how the sensors are switching with the engine running after its up to operating temp.

If this just started out of the blue suddenly..thats my guess.

But man..it can be a bad battery, fuel filter, dirty injectors, failing fuel pump, loose spark plug wire(s), broken/cracked sprak plug, water in the gas, etc.....and a dozen other things.


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stormsracing10

i have had it hooked up to scanner and no codes present. changed plugs fuel filter and battery. have had the car for 2 years and it has always done it. as long as you keep the rpms built up its fine

stormsracing10

also have cleaned throttle body maf sensor and seafoamed the car

LS6427

iTrader: (2)

Failing 02 sensor(s) WILL NOT always give you any codes till one totally fails. Mine doesn't.

2 years...its been doing this for 2 years??? WOW. Maybe something mechanical inside the engine then.

Dirty injectors can cause problems at low-mid rpms if they are dirty.

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stormsracing10

can i unplug them and see if thats what it is or will that make it run worse

LS6427

iTrader: (2)

No, you need them otherwise the engine...I think...will dump massive amounts of fuel in there as a safety limp-home mechanism. Not positive on that...but you must have them or the engine will run HORRIBLY.

If its been like that for 2 years, I doubt an 02 sensor can hang on that long in a failing type of state. They usually start failing and the car keeps getting worse and worse over a matter of days until its just terrible.

SO......if you're cruising steady at say 45 mph and you nail the pedal down hard it will accelerate fine.
BUT...if you give it more throttle slowly from say 45mph it will stumble as the rpm's increase?

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stormsracing10

exactly that way. say ur going up hill at 45 and nail it its fine. but if you smoothly give it more fuel with letting trans down shift it stumbles and jerks and wont quite until you make the rpms build

stormsracing10

changed plug wires added seafoam to gas and changed fuel filter still doing it what next