Newly Cammed LT1 Runs Poorly In Closed Loop
 

Recently I installed my CC503 cam with all the supporting mods, (Ultra Pro Mag rockers, hardend pushrods, Comp 918 springs, etc). For now I have a tune from MadZ28. Initially the car started right up and idled perfectly. However on my first drive I noticed that it suddenly took a turn for the worse and started backfiring, and popping and would barely want to move. I brought it back and scanned it while running and noticed an insane amount of knock, which I presumed was being detected from the new rockers and valvetrain noise, which in turn was retarding the timing. So I ordered a LT4 knock module and adjusted the valves correctly.

I put the module in and it started right up again and seemded to run better. I went to go around the block after it warmed up and it started popping and backfiring once again, exactly like it had. I scanned it again and noticed there is a constant 4 degrees of retard at idle and slightly less but still alarminly high knock count (7k now 22k before).

The Opti in the car has maybe 5k miles on it and it 2 years old. The ICM, anc coil are both relatively new as well (last 2 years). It is a night and day difference between open and closed loop tough so I am figuring it has to be some type of sensor that doesnt activate until its in closed loop. I am not sure where to go from here so any help would be appreciated. Thanks guys.

Heres a screen shot of me datalogging in before the lt4 knock module http://i623.photobucket.com/albums/t...94lt1/log2.jpg

o2 sensors are a likely candidate but the screenshot doesn't really tell you anything.

Isnt AF gallons per second at idle supposed to be around 6-10?

I do have a datalog as well. I was thinking o2 sensors as well but I'm not sure

If it idles fine, and runs "fairly well" under light throttle, and you have the rockers adjusted properly, then I'd bet on you either have plug wires crossed, not clipped into the opti well, or even a burnt wire. Crossed wires is so easy and so common. Check them very closely!

I set the 918's set at 180 install height, and at 1/4 turn past 0 lash.

I'd also suggest you check for a vacuum leak and check the injectors are properly wired - didn't swap connections. Also check the wire to the knock sensor itself. I had a burnt wire that was arcing to the knock sensor and the car had fits as soon as it went into closed loop!

Scan the car while driving and post the file, or send it to me and I'll look at it.

If you email it to me I will post it here.

I take it this car is a 'Vette?

It's a 94 Z28

Datamaster is not using the right variables then. Won't effect the scan too much on certain things but it's set for a Y-Body.

Yeah I saw that it was for the wrong car. I did check the plug wires and connections and they're all good. It is a night and day difference from open to closed loop though and something like that wouldnt be so different. I'll send the file to your email

I had a similar problem and it seemed to be discovered that i crossed a set of injector wires.

I have checked the injector wires and they seem fine. I just did another datalog of the car. I unplugged the temp sensor and the car didnt start so I plugged it back in. I then got code 15 (coolant temp low, expected) and code 16, the code no one ever wants to see.

Heres what I dont understand. 1. I cleared both codes and both went away and didnt come back so was it a hiccup? 2. If this was an Opti problem, why would it only happen in closed loop (literally a night and day difference). 3. Did me unplugging the temp sensor cause the code 16 possibly? 4. If I did have an Opti problem wouldnt the code stay there? I sent the datalogs to WildBillyT so he can put them up here for me because I dont know where to go from here.

http://www.njfboa.org/WBT/log1.uni

http://www.njfboa.org/WBT/log2.uni

Thanks Bill, I'll try to look at them when I get home tonight.

TEMP sensor should not prevent the car from starting? Is the opti harness in tight? how about the ign module connetions and ground?

You are getting KR even in open loop so something is defiently up.

Is your MAF clean? Does it still have the screen?

MAF is clean and stock. I cleaned it when I had it out for the cam swap.

It started (kinda) but it didnt want to be running thats for sure. When I unplugged it the reading the PCM was getting was -44... Ignition modules and grounds have all been checked when I first experienced the problem. ICM isnt old as well.

PamperedZ have you gotten the chance to look at the logs? I'm dying want to drive this car so badly

Sorry got sent out of state, will try ASAP to get to it.

PM sent. Initial file doesn't look too bad, but I would like more data if possible.

Yeah the car wouldn't start if the the ECM is seeing -44d. It will just dump fuel into the motor trying to start and wont.

what program did you guys use to view those logs. I can't get them to open

TTS Datamaster

used to have that on my other computer.

Well I took it to a shop and unfortunately I don't think he got it. He thought it was because I have a bad plug wire on the p.s. This wouldn't make sense to me because it changes to drastically. I was talked into bringing it home and checking the timing which me ans I have to remove the front cover again...crap. Either that or an opti problem im guessing now.