1997 Gmc Misfire

[fnengineer]

Hello,

 

I have a 1997 GMC heavy duty half ton 4 wheel drive 5.7 ltr. I am struggling with a misfire...or I believe it is a misfire I am not seeing any codes.

At idle it runs fine, when I put it in gear it has a miss and poor ecceleration. It appears than when I put it in gear for the first 5 or so minutes it is fine without the miss.

 

I have pulled the plugs after 15 or so miles and it appears that #7 and #4 are running extremely rich.

 

Here is what I have attempted to date:

New plugs

New Wires

Cap / Rotor

Dist. Gear

Compression check (all good 160 psi on my gage at 5000')

Injector pressure balance test (all good)

Cat / Muffler back pressure test.

Fuel pressure 53 psi (maybe volume is suspect?)

 

Any help or suggestions would be greatly appreciated.

 

thanks

[fnengineer]

Hello,

 

I have a 1997 GMC heavy duty half ton 4 wheel drive 5.7 ltr. I am struggling with a misfire...or I believe it is a misfire I am not seeing any codes.

At idle it runs fine, when I put it in gear it has a miss and poor ecceleration. It appears than when I put it in gear for the first 5 or so minutes it is fine without the miss.

 

I have pulled the plugs after 15 or so miles and it appears that #7 and #4 are running extremely rich.

 

Here is what I have attempted to date:

New plugs

New Wires

Cap / Rotor

Dist. Gear

Compression check (all good 160 psi on my gage at 5000')

Injector pressure balance test (all good)

Cat / Muffler back pressure test.

Fuel pressure 53 psi (maybe volume is suspect?)

 

Any help or suggestions would be greatly appreciated.

 

thanks

 

Well I have solved the misfire issue and poor accelaration (two different issues).

It appears two of the new plugs I used were "bad" replaced the plugs for the second time and it cleared up the misfire. A new fuel pump resolved the poor accelaration.

 

Now the problem is I am getting the check engine light. It reads bank 1 and bank 2 rich. The light appears to come on and go off randomly.

[VR021302]

Welcome to the forum

[superjim]

Well I have solved the misfire issue and poor accelaration (two different issues).

It appears two of the new plugs I used were "bad" replaced the plugs for the second time and it cleared up the misfire. A new fuel pump resolved the poor accelaration.

 

Now the problem is I am getting the check engine light. It reads bank 1 and bank 2 rich. The light appears to come on and go off randomly.

 

 

Check the FPR for any fuel on the vacuum side.

That COULD cause the problem you are seeing.

Pull the vacuum hose and see if there is any fuel leaks there.

There should ne NO FUEL AT ALL on the vacuum side.

Smell of the vacuum hose...if it smells of fuel, I would suspect the FPR.