best OBD1 scantool?? Misfire/backfire ? at cruising speeds 65-70

[TylerZ281500]

start ohming your computer connectors, check grounds, etc.

 

[SkyHighColorado]

Clogged fuel filter? intake air leak or bad fuel pump and egr malfunction is where I would start.


I have a very strong feeling its the fuel pump now I think about it.

 

[jrollings]

Skyhigh, that's the way I'm leaning as well. New Fuel filter was installed Saturday night. Once my gauge and adapter get here I'll either find the culprit being low fuel psi or rule it out. The EGR valve does look brand new.
Also to rule out the intake leaking I took starting fluid and sprayed all around the intake and vacuum lines while she was running with no change in idle whatsoever.

 

[SkyHighColorado]

yeah check the fuel pressure. Problem is that the pump is probably running fine at idle and acceleration but cant maintain a consistent flow at cruise and it would be hard to replicate cruising while taking a psi reading.

 

[jrollings]

Only thing is why wouldn't it fall on its face at wot? Does it only at a cruise on slight decel

 

[SkyHighColorado]

I honestly don't really know, probably to do with the pump failing at different loads.

I have a 94 1500 350 so we are somewhat on the same page. I got an ac delco fuel pump through autozone, but they had to order it in $40. If your gas gauge is working fine then you don't need to spend $300 or whatever they charge for the entire assembly just swap out the pump and filter sock. 454 pump might be bigger and more money im not sure.

 

[jrollings]

I already have a pump and sock for it in the tool box just in case. I bought the airtex unit. Think I paid $90 for the pump sock and fuel filter.

 

[SkyHighColorado]

ah just saw your a suburban, what a biznatch. Might want to look into making an access hole in the floor pan for the future to make life easier.

 

[jrollings]

Yep 42 gallon tank. I'm thinking I'll try that route but I'm not sure where to cut.

 

[SkyHighColorado]

honestly if it were my truck I would drop the tank this time and cut an access hole with the tank out just incase. I wouldn't be comfortable grinding next to a gas tank.