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Lack of power


jefferie1979
05-27-2009, 08:44 PM
I have a 99 tahoe with 175000 mi and had a few general questions regarding power. I've noticed over the years a definite drop off in power especially climbing hills. Getting up to highway speeds and so on... I changed the plugs, wires last year. I know the truck is old and don't expect miracles but an improvement would be nice. I mean it still runs and shifts well don't get me wrong. Anything obvious I should be replacing after owning the truck for 100 000 mi. I've done next to nothing in 5 years. Intake, plugs, wires and that's about it. Thanks for your help.

john_6_2
05-28-2009, 09:58 AM
What about coils have you replaced them?

2000CAYukon
05-28-2009, 10:54 AM
Have the 02 sensors ever been replaced? 100,000 miles is the recommended replacement for them. The CATS also do not last forever and might be starting to plug up.

Fuel Pressure should be checked as well. Last fuel filter replacement? A weak pump can cause loss of power under a load.

Might want to have the compression tested. A leak down test can also pinpoint mechanical issues.

Any codes stored?

//2000CAYukon

j cAT
05-28-2009, 07:23 PM
What about coils/distriburator cap and rotor have you replaced them?

these don't have cap/rotor/distributor.....
most likely its low fuel pressure or bad cat's,,,,o2 sensor change out every 100,ooomi...

cleaning the throttle body and MAF would also be good idea...

jefferie1979
05-30-2009, 08:18 PM
is there any way of telling if a cat is fouled up or bad? Can these be cleaned in any way? so replacing the o2 sensors should already have been done, so i'll go ahead and replace these and look for any improvements. Also how would you clean a mass air flow sensor, soap and water? thank you

john_6_2
05-30-2009, 10:22 PM
No please do not use soap & water here is how

Thanks to j cAT for telling me how

"throttle body needs cleaning with throttle body cleaner and a tooth brush to gently remove deposits....the IAC must not be forcefully cleaned just gently brush off the deposits with the cleaner aiding this.since the air ducting must be removed clean the MAF sensor wires...use CRC MAF cleaner,,,just spray cleaner on the small sensor wires do not touch wires....let dry then reinstall."

GMMerlin
05-31-2009, 02:19 AM
is there any way of telling if a cat is fouled up or bad? Can these be cleaned in any way? so replacing the o2 sensors should already have been done, so i'll go ahead and replace these and look for any improvements. Also how would you clean a mass air flow sensor, soap and water? thank you

The only way to test the cats for restriction is to do an exhaust back pressure test.

Most likely cause for your concern is plugged fuel injectors...now before you jump in and clean them or before you listen to some self perclaimed "expert" about injecor cleaning, do some research..I have posted extensively about the injector set up on these engines and what needs to be done.

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