Ericc

Hello all,

So here is my current situation. I just put in a new engine in my suburban (Stock L05) and kept my previous Edelbrock 3502 MPFI system. Gas mileage has been low since the engine was replaced.

Went to smog the truck and failed with high CO%. Swapped out EBLFlash for the stock ECU with the edelbrock supplied chip and the truck still producing the same high CO% conditions. All sensors are new with less then 1000 miles on them.

All the data looks good, good O2 signal etc.

So this lead me to believe that the issue is on the passenger side since the O2 sensor is in the stock header on the driver side. It wouldn't see a rich condition on that bank.

I pulled the plugs and they all looks white and clean except for cylinder 8 which was noticeable dark brown. These plugs have less then 1000 miles on them.

I put my wideband sensor on the exhaust and it was showing 13.8-14.2 at idle with it going more rich as I increased RPM in neutral.

The BLM's are sitting around 126 in this case.

I haven't checked the compression in that cylinder yet. Does this sound like a leaking fuel injector or one flowing too much etc?

Thanks for any input.

-Eric

RBob

iTrader: (1)

Swap that injector (#8) with another and see if the issue follows the injector.

RBob.

Ericc

Thats my game plan for today. I'm going to swap it to the other bank with the O2 sensor.

I figure if the truck suddenly starts trying to lean things out that would be a good indicator that injector has issues.

The other idea that came to mind was I replaced all 8 injectors when I put the new engine in and I wonder if that #8 injector was the incorrect size, and it's flow rate is too high compared to the others.

Thanks again for you help.

Ericc

So after replacing several "new" fuel injectors things smoothed out nicely and I can finally get a 14.7 AFR while cruising on a flat.

I've been trying to simulate the 50% load @ 15MPH test and the 25% 25mph test by climbing hills of various grade.

I have no idea though what 50% load is for the engine. What would that correlate too in terms of MAP/RPM etc @ speed.

I do notice that on steeper grades I'm back down at 13.8-14.1 AFR.

Is there anything in the 7747 that would enrich AFR as load increases? My BLMs are dialed in and they're 128 +/- 1 in those regions.

Thanks all the help.

Ericc

So I moved the O2 sensor from the stock header on the driver side to a bung I welded up a few inches past the Y pipe junction and amazingly the truck is now at 14.7 where it belongs.

So for some reason the passenger side of the engine is running richer then the driver side. With the old O2 position the ECM had no clue. Now it does and it pulled some fuel to get the commanded AFR.

Not sure why that is but it is.

RBob

iTrader: (1)

Power enrichment (PE) mode goes open loop and commands a richer AFR. Adds spark advance too.

RBob.