I bought a custom tuned chip from pcm of nc a while back for my 88 auto corvette. I thought it would help the hard starting problem and the severe power loss problem I had, based off the selections I picked. I tried the chip and it did nothing for those problems. It turned out my cold starting issue was because my new fuel pump didn't have a working check valve. And my severe power loss was due to the engine timing being way off.

Fast forward to today. I have a few issues that stand out such as: fluctuating and fluttering idle, a thud from engine bay at idle (only started to occur after I corrected timing), and intermittent power loss on the highway. I don't have much time or troubleshooting abilities to look into it especially since this is my daily so I planned on taking it to a corvette shop and getting it diagnosed. Before i go through with that and lose $150, i want to see if my tuned chip helps. I plugged it in and it drove great. It idled smooth, it drove smooth, and there was no thud from the engine bay.

I data logged a before and after. I was wondering if anyone could tell me if the chip did good or bad for my car. Only thing i was able to notice was that on the "after" wot, i saw a large increase in knock counts. Usually the knock counts only go up by maybe 1-3 when i wot.

To me, drivability definitely improved, but knock counts increased. Is it worth it and is there more that im missing?

Before chip:
https://datazap.me/u/elijah/chip?log...9&zoom=167-339

After chip:
https://datazap.me/u/elijah/after-chip?log=0&data=9-28

I appreciate the help.

 

Do you have a chip burner? Any chance we could just see what’s in the chip? It’d be dead simple to check the changes against the stock ‘88 BIN.

 

all I have is a scanner and ALDLdroid. There is a section that says "chip programming" in ALDLdroid though

 

The (after looks like an 89 $6E arap based bin) 13.37 Target AFR at WOT is rather lean and is likely contributing to the knock counts/knock retard. Spark advance does not appear to be excessive (32-34 degrees).

https://datazap.me/u/elijah/after-ch...8&mark=288-298

 

Is there something i can do to make it not so lean at wot? If not, then would you reccomend that i keep the chip and just refrain from pushing the car too hard?

And im curious as to why the chip fixed all my drivability issues as opposed to the factory tune. Before this, i was positive that something mechanical or electrical was failing like a sensor or vaccum leak. Now im just lost. But if i have to daily drive with this tune for now, i guess i can do that.

 

The after tune appears to be a bit leaner (based upon the fuel trim behavior), significantly leaner at WOT (which can be risky), has greater idle rpm (725 vs 550) and appears to have less aggressive spark advance at WOT but increased idle advance. I don't know how this solves any of your issues. Maybe the greater idle rpm and increased vacuum is masking some little things or causing a placebo effect.

To en-richen the WOT target AFR, you can complain to pcm of wherever, tune it yourself, or find a new tuner.