Put a N10 exhaust on my car, no cats just a Y, now I've got a knock sensor code and it runs hot.

91 305 TBI 5 speed w/LT1 cam and TPI ign module. Ran fine before....

What have I done?

 

Looks to me like you spent a lot of money for a cheap crush-bent exhaust; one that isn't even street-legal.

What is a "TPI ignition module"? Part number? Link?

What does the data stream show when you connect the scan tool?

 

Built it myself so I'm not into it for much. The crush bend was there before, (wow it looks bad in that picture) not part of the 'new' system. The TPI ignition module adds 2 degrees of timing around 3600 rpm while the TBI module will pull 4 out. I don't have a scanner or any means to datalog, just read a code 43 with the ALDL jumper wire.

TBI D1984A
TPI D1943A

 

I remain extremely skeptical of timing changes based on the ignition module. I read the threads about the modules and the latency time programmed into the computer. And I admit that I have not done timing experiments on my own.

However, various aftermarket sources show the modules as interchangeable. If they actually changed the timing, seems to me that the EPA would be all over them for emissions and fuel-economy non-compliance.

It is very difficult to diagnose computer-controlled engines if you can't communicate with the computer. You need a scan tool. "Codes" can be helpful, but the data stream is even more useful.

"I" would erase the code, and see if it comes back. If it doesn't come back, forget it ever happened. If it does come back, FOLLOW THE PROCEDURE LISTED IN THE SERVICE MANUAL for that code.

 

Well it's fixed. Actually figured it out a couple weeks ago but wanted to drive it awhile to be sure.

At some point I had taken the custom PROM out of the car and put the stock one back in. Don't recall what I was doing at the time, haven't driven the car much the last couple of years. Popped the custom chip in, set the timing to 8 degrees and its happy. My guess is the new exhaust was just enough of a change to push stock PROM over the edge and could no longer adjust for it. The new exhaust sounds great, didn't expect this much of a change from the hard "T" of the earlier systems.

I swear I'm my own worse enemy some days!