5.7L running too lean (very high NOx), won't pass state emissions

[bigmac]

I pulled the ECM and took pictures of the label and the prom itself (see attached). The BCC is an ANLW and the exact number is 86ANLW K182590103. My research says this cross references to a prom id of 66 ($42) 91-92 truck 5.7L TBI "K" LO5 w/0 4L80E. Sounds like the right computer for my setup since I have a 700R4 transmission. However, I think it does have a custom prom which is in a socket with a hand written label: HED 350 STK 4-22-04. Please see the attached pictures. I am going to load the ANLW 89 C-G-K-R-V Truck 5.7TBI 700r4 with 2.73 gears.bin file into my TunerPro RT.

Lee

[Fast355]

I pulled the ECM and took pictures of the label and the prom itself (see attached). The BCC is an ANLW and the exact number is 86ANLW K182590103. My research says this cross references to a prom id of 66 ($42) 91-92 truck 5.7L TBI "K" LO5 w/0 4L80E. Sounds like the right computer for my setup since I have a 700R4 transmission. However, I think it does have a custom prom which is in a socket with a hand written label: HED 350 STK 4-22-04. Please see the attached pictures. I am going to load the ANLW 89 C-G-K-R-V Truck 5.7TBI 700r4 with 2.73 gears.bin file into my TunerPro RT.

Lee

Definately has a reprogrammed prom chip in it. No telling what changes were made from stock. If you can get your hands on an OEM PROM, I would try running it first after double checking your base timing. I would start with ASDU myself. Does this engine have a smog air pump?

[bigmac]

No air pump. I will set the base timing later today. Any suggestions on sources for purchasing an ASDU chip? I see a 1227747 ECM with ASDU chip on eBay for $85.
Lee

[Fast355]

No air pump. I will set the base timing later today. Any suggestions on sources for purchasing an ASDU chip? I see a 1227747 ECM with ASDU chip on eBay for $85.
Lee

Local junkyard would be my first pick. Look in a 1990+ 350 TBI 1500 truck.

[bigmac]

I ordered a known good used 1224747 ECM with original factory ASDU chip (see picture below). Should arrive in a few days.

In the meantime, I attempted to check the base timing. Originally, I didn't see an existing timing pointer so I purchased the Moroso pointer and bolted it to existing timing cover bolts (pain in the butt to install). Only then did I see the existing notched pointer in the center of the timing cover (actually, I could barely see only the right end - the big V notch). I also purchased the nifty device that you screw into the No 1 spark plug hole then tightened the inner screw so the top of the piston will contact it as it comes up on the power stroke. I put a piece of tape around the damper wheel and placed a black line all the way across where the factory line is. I then turned the engine by hand and placed marks where the piston hit the special screw device. I made marks for both the original pointer and the new Moroso pointer. NOTE: the Moroso pointer is about 2 inches to the right of the original V notched pointer. Attached is a picture of the two pointers - you have to look closely to the left of the black Moroso pointer to see the rusty original V notch pointer. And now the fun part: one of the attached pictures shows the comparison of the black marks on the two tapes that were on the damper (the upper tape shows the marks for the original pointer and the lower tape for the new Moroso pointer. Not only are the Moroso marks considerably further to the right, but the distance between the black marks is about twice as wide on the upper tape (original pointer) than the lower tape (Moroso pointer). How can this be? I know the piston was hitting the screw because in addition to me feeling it with the socket wrench on the crank pulley - I had a helper put his fingers on the screw in the spark plug hole and he could feel the it tighten). Also, I marked the half way point between the black marks with a silver line that should represent TDC. Both tapes would indicate that the base timing is way off (maybe 20 degrees). Note, the battery is disconnected so this was a purely mechanical test. Can someone explain which pointer is correct? I think the silver line in the upper tape says the engine is way too advanced, and the silver line in the lower tape way too retarded. I really look forward to someone explaining this mystery to me.

Lee

[bigmac]

I think I maybe figured this out. The piston must be on the Exhaust/Intake stroke instead of on the Compression/Power stroke. I will retest today.
Lee

[Fast355]

I think I maybe figured this out. The piston must be on the Exhaust/Intake stroke instead of on the Compression/Power stroke. I will retest today.
Lee

Simce the cam turns 1/2 speed of the crank, TDC is TDC regardless of which stroke you are on.