1991redz28ga

I have a question that I am unable to find the answer to. My car was originally a tpi 305, but at some point it was switched to a 350. Still has the tpi. When i bought it, is did'nt run, so i got the car for a steal. I had a shop put in a set of 22# injectors and it ran like garbage. Tried 19# injectors and is still ran like garbage. We determined that it could still have the factory 305 ECM, so i had a custom prom burned that changed the injector size to 22#. I also mentioned to the guy that burned my prom that I wasn't sure what other parts were not changed when the motor was swapped, because it was done like 5 owners ago. I know that the 350 & 305 have different knock sensors, so the guy who burned my prom suggested just deleting it from the new prom all together, and then it wouldn't be an issue. in retrospect I probably should not have done that and just changed the knock sensor to a 350 one (just to be sure). Well, it worked. Car runs great now with the exception of some pretty noticeable rattle in the motor when under a load (accelerating). I have run 93 octane in it, but that hasn't changed it at all. I read somewhere that the knock sensor plays a role in providing feedback to the ecm to retard timing in certain scenarios. Is this true? Could the deleted KS be causing the engine to operate with incorrect timing, thereby causing the rattle that I am hearing? The guy that burned me the prom said he has deleted a ton of them and no one has ever had an issue.

Please help me to figure this out!

Thanks

ironwill

Yes on both counts.



Of course he told you that.


You already know the solution. Restore the factory knock sensor and the programming that runs it; it's an intrinsic part of the system that runs the engine. And do it soon; that noise you hear will eventually cause severe engine damage.

Tuned Performance

iTrader: (92)

You might want to look into diy prom. Even if you just replace the knock sensor and enable the is in the tune I have a feeling the timing table still needs to be recurved.

Orr89RocZ

iTrader: (20)

^^^ what he said

1991redz28ga

Ironwill- You hit it right on the head. Thank you for straightening me out on this one. I got the correct chip for a stock L98, and the noise stopped and it runs really really good. I kind of want to put the guy that burned the chip on blast on here, but I am not one to stir up trouble. I will chalk this one up to a life lesson learned and move on. Thank you for the level headed reply.

ironwill

YW; I'm glad you got your car squared-away.

Live and learn. The aftermarket is fraught with bogus claims and poor-quality offshore parts. If something doesn't sound quite right, or goes against common sense, chances are it's not worth your time, effort, and $$$. Now more than ever, it's Caveat Emptor.