Finally got around to putting my rebuilt engine in my truck. It ran ok at first, struggled to idle until the computer caught up but after a day went by it started to backfire under load. It was originally an EGR truck but since I have the Hughs intake the EGR isn't hooked up anymore. Throws code 32 because of it. Also has a small cam upgrade.

I'm kinda stumped at the moment and from doing some research online the closest thing Ive read was a bad crank or camshaft sensor. I also have an A/F ratio gauge that would read rich on start up but slowly come up to around 14.7 and when it would backfire the gauge would spike to 16 or 17 which would be leaning out right? Spark plugs are white which mean either to hot or lean conditions but I'm thinking to hot since the gauge has been showing its been running rich until it backfires. Any help would be appreciated.

Edit- The truck is actually leaning out when giving it gas which is then causing it to backfire.

 

From what I've read a cam upgrade requires computer tuning along with the EGR delete I would expect. If you havn't messed with the computer at all I'd start there. Also if teh distributor was touch the fuel sync needs to be set back with a mid to upper level scan tool

When I installed my cam it did run and drive some what ok, but i didnt feel much gain over it, But I set the distributor with a multimeter so I was somewhat close I believe on fuel sync, I've got my truck out getting the sync set and the computer tuned right now so I'll find out when its done how much better it is.

 

The issue i have is the truck is obd1 so tuning is limited. I guess I'll try the multimeter set to see if it helps it out until i can figure out what im going to do

 

I guess I hadn't considered the OBD1 part as far as tuning. Im not sure what there is available. With the amount of donors around I would imagine you could OBD2 swap it, with custom tuning anyway you could tune out the CEL for the trans side, not sure how the PCM would play the original dash though might have to swap everything

 

Obd2 swap or somthing like a Holley Sniper might be my best options

 

I've looked at teh sniper talked to a couple guys, sounded like a little bit of an electrical nightmare to keep the factory drivability of the truck, cruise and such, kinda depends what you're after

 

Did you set the fuel sync?

 

I did go in and turn the distributor towards the firewall making putting it at more of 3 and 9 o clock position which is what i read on a few post and i video i watched to put it at, but what I think really helped was moving the intake temp sensor from down below to up above. Where i had it originally was down in the Hughes intake where you would put a vacuum hose but it was getting covered in fuel and most likely getting to hot so I moved it into the hat of my intake hose right above the throttle body and i haven't had any problems since. If it reads cold more fuel and if it reads to hot it leans it out, at least that's what i gathered from others doing the intake temp mod. Also swapped back to stock injectors which helped the idle not be so rich.

 

Really needs to be set based off your engine, if you still have the factory harmonic balancer there should be a mark with V8 next to it, line that up with TDC, verify you're on #1 TDC compression/ignition, then the rotor should point at the mark on the distributor, but this is only baseline so the truck with run, then you need a scanner to set the fuel sync, I just had mine done as I don't have a good enough scanner for it. I thought the truck was running okayish but once we hooked up the scanner it was +12*, got it dialed back to a solid -1 to +1 bounce, I had set mine using a multimeter, but my guess is I was on the wrong side of the voltage change on the pickup

 

I dont have the original harmonic balancer old one was dry rotted. I'll have to start looking around for a shop then that can reset the fuel sync.