Ok so I put my 99 obs Tahoe up for sale after 3 years of flawless ownership for 2 years. Never had an issue, all maintenance done on time, took good care of it. Two days after posting it, it starts to misfire.
Never threw a code but, clearly misfiring.
Sprayed the plug wires in the dark, no sparking.
Changed pcv, hose, and grommet- no change
Changed plugs - no change
New cap and rotor - no change
Wires- no change
Fuel filter - no change
Fuel pressure 50-55 at start, increases when u rev it, holds 50psi when u shut it off for a long time, I stop timing after 30min.
I don’t have a smoke tester but all vacuum hoses look good.
I had never bought a new mpfi bcuz it ran so good, but I figured what else could it be? So I bought a new mpfi-, turns out it already had one! Changed it anyway. No change! Gonna keep the old one for my next obs.
Pulled off the passenger side valve cover, no broken valve springs.
Distributor isn’t loose.
Exhaust temps are all pretty close.
The cat temps are about the same as well.
Soooooooo what the hell?
I have a coil to try, and need to take off driver side valve cover, just ran outta time today.
Thoughts? The misfire doesn’t change no matter the load, rpm or throttle position.
Never threw a code but, clearly misfiring.
Sprayed the plug wires in the dark, no sparking.
Changed pcv, hose, and grommet- no change
Changed plugs - no change
New cap and rotor - no change
Wires- no change
Fuel filter - no change
Fuel pressure 50-55 at start, increases when u rev it, holds 50psi when u shut it off for a long time, I stop timing after 30min.
I don’t have a smoke tester but all vacuum hoses look good.
I had never bought a new mpfi bcuz it ran so good, but I figured what else could it be? So I bought a new mpfi-, turns out it already had one! Changed it anyway. No change! Gonna keep the old one for my next obs.
Pulled off the passenger side valve cover, no broken valve springs.
Distributor isn’t loose.
Exhaust temps are all pretty close.
The cat temps are about the same as well.
Soooooooo what the hell?
I have a coil to try, and need to take off driver side valve cover, just ran outta time today.
Thoughts? The misfire doesn’t change no matter the load, rpm or throttle position.
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