P0301 Buick -

Question

Code P0301: 1997 GM 3.8 Buick Super charged Riviera

Slight rough idle Miss fire in drive while stopped, more so at normal operating temperature.

1.) changed coil
2.) changed plugs and wires
3.) Removed injectors, cleaned, tested and replaced, (not in same position)
4.) Cleaned EGR valve and reinstalled
5.) Checked fuel pressure 45 psi
6.) Checked compression #1 170psi other five 180
7.) No fuel at regulator at vacuum line
8.) Replaced all vacuum boots, lines and hoses
9.) replace intake and supper charger gaskets
10.) tested ECM with ECM tester, (good)
11.) Replaced fuel filter
12.) 02 sensors looked good on scan tool
13.) Replaced air filter
14.) New battery
15.) checked spark with spark tester (good)

Code returns after warm restart some times day in between

Answer 1

P0301 Misfire number 1 cylinder.

With the super charger if there is a misfire at that cylinder there tends to be a lifter noise at that area. and it is usually caused by coolant seepage into the intake manifold. If the compression of number 1 cylinder is showing 170 and the rest 180 even though this is a small difference this would be mechanicall condition. Also listen for a engine rocker noise the rocker arm bolts tends to loosen itself out .