Hi guys, I probably haven't posted here in 10 years or more, but I could use a little help.

I have a customer with an '02 Lightning with a built motor. Tuned by Johnny Lightning. The truck's wideband 02 gauge shows it running 17:1 A/F ratio at idle. The customer says the truck lays down under wide open throttle. Customer brought the truck in requesting we install his new spark plugs, ignition coils, oxygen sensors & fuel filter. We visually checked for any signs of vacuum leaks (none found) & a-pillar fuel pressure at idle is around 40psi. Truck reads 17:1 a/f at idle. 13:1 at light throttle. Goes back to 17:1 at WOT. We haven't really driven the truck for fear of damaging something.

My question is if the truck is really running this lean, why isn't the Check Engine Light on?

Is this something that JL has turned off in the tune or do I possibly have a stuck/inaccurate wideband gauge? I can't wrap my head around why if the truck is really running this lean there are no lean codes and the CEL isn't on.

The customer did not get a warm/fuzzy feeling from JL when he picked the truck up recently. Had a built trans installed and a race tune and supposedly new plugs. Plus we are out of state.

Any ideas or suggestions are welcome. Thanks for any help!

-Chris

 

I don't know much about Lightnings, especially built ones, but I'd suspect a few things - a bad tune and/or insufficient fuel pump capacity and/or too small injectors.

 

Lean: too much air or not enough fuel


Visually inspect for vacuum leaks, given you're also having issues off idle, I think we're looking into fuel side

Check pressure first, flow (volume output) test the pump, then look into duty cycle on the injectors etc

 

I'm guessing a vacuum leak won't cause this, because under boost there is no vacuum anyway.

 

Seems to me the 17/1 air/fuel mix at full throttle tells the tail. The engine needs about 12/1 I think. I suspect the tune.

 

Unless it's leaking boost under pressure, but that would push to the rich side..... just talking out loud I guess

 

I assume this truck has a MAF sensor? Check the intake tube after the MAF for leaks.

 

This forum is a bit weak on help for Lightnings of that vintage. I have a built 02 and recently had a fuel pump just quit. It was doing basically what you describe. I would say drop the tank, inspect the wye and the fuel lines for leaks. New set of walbros aren't real pricey and would give some peace of mind.
Before you get to that, replace all the relays related to fuel. There are three. I found that these relays tend to get corroded and sticky after the get some age on them.

Might want to try LightningRodder.com for more up to date help.

 

what Y is in the tank (where the fuel pump lines merge)? if it's plastic that'd be my guess



do the plugs show lean? if so then yes continue trouble shooting and get JLP some datalogs for review