Persisting P0304

[gbsharon]

Truck is a '99 tahoe, 198k miles. I have a P0304 that occurs only uphills under load. I have replaced the fuel filter, spyder injector, upper intake gasket, and distributor. The plugs, wires, coils, fuel pump, and compression have all been checked by a trusted mechanic. Based on my readings, the persisting P0304 seems to align with the crank position sensor. Ordered one to try- worth it for the cost. Mechanic just did spyder injector and upgraded to MPFI. He thouht the misfire was due to the spyder injector lines leaking into manifold and causing misfire in rear cylinder bank. After doing MPFI conversion, truck pulls harder than ever and feels great but still triggers the P0304 misfire but it is more difficult to trigger. Any other thoughts or obvious things I have missed?

 

[hawley3rdarmy]

I have a similar issue have you tried changing out the #4 spark plug wire? Also you might want to pull off the distributor cap and visually inspect the contacts. With every jump of spark the rotor tip gets smaller and the contacts on the cap grow carbon from the spark. If it's been on there like 40k or longer it probably needs to be replaced.

Sent from my SM-G935V using Tapatalk

 

[slowburb]

Sounds like a valve sealing problem, considering what you've already replaced.

 

[Biggershaft96]

Sounds like a valve sealing problem, considering what you've already replaced.

If the valve wasnt sealing wouldnt it put off a low compression reading?

 

[slowburb]

Not necessarily. Different load conditions can hide or show a valve sealing issue, and the compression test is done with no engine load. We also haven't seen the compression reading values. A leakdown test would be a more thorough means of checking for slight compression loss.