2001 Suburban

[Tom M Kozakiewicz]

Hello, 

 

I have a 2001 Suburban with engine misfire issues.  Misfire P300 has been set at isle and usually at spped above 75mph.  Recently there has been misfire at several different speeds but no codes.  I have done intake gasket, tps, maf, crank n cam sensor, knock sensor, fuel injectors, ignition coils, 02 sensors, etc.  I thought maybe grounding issue but have done ground at rear engine.  A y other grounds?  Thought about ECM.  Any other ideas?

 

Thanks, Tom 

[Brian715]

How does compression and leakdown check out? 

[chem_man]

What is the condition of your spark plugs?  Also, have you checked your spark plug wires for physical and electrical condition?

[Tom M Kozakiewicz]

I haven't checked compression in awhile.  Spark plugs and wires are a year or two old and problem at 75mph has been around for a few years.

[swathdiver]

6 hours ago, Tom M Kozakiewicz said:

I haven't checked compression in awhile.  Spark plugs and wires are a year or two old and problem at 75mph has been around for a few years.

Is the truck losing fuel pressure at that speed?

[Tom M Kozakiewicz]

haven't checked pressure in awhile but changed pump n regulator last year or two with Delco parts.

[davester]

I would suggest re-checking fuel pressure and maybe also check that all the exhaust manifold bolts are present and accounted for.