joeld

I had a custom chip done by a very knowledgeable gentleman several years ago, car ran perfectly for over 10 years. This wasn't an extreme change only the VATS, slight lowering of temp coolant fan, and a change of the cranking fuel injector pulse width for a quicker start. After this the car started up on the 1st or 2nd revolution and ran fine. Now, this is on a 1989 Corvette. Last year car would still start quickly, but sometimes it would die instantly. Re-start good and all was good. Then it started intermittently having a sharp quick "dead" bump" while driving at any and all conditions. After several months of checking and replacing some parts I removed the Moates adaptor and the chip. Put it back to stock configuration and have been driving some lately with no issues. Is it possible this chip has something degraded inside?
Thank you
Joel

GeneralDisorder

iTrader: (1)

Unlikely to be the chip itself - more likely a bad contact between the chip and adapter, or the PROM socket on the board, etc. Try re-seating everything and checking carefully for poor connections or cracked solder, etc.

GD

joeld

Thanks for the reply. I forgot to mention I did try a new adaptor a few weeks ago with the same results. I have re-seated everything several times and tried another ECM I have as a extra. Still the same issues when I use the piggyback chip and adaptor.

Joel

GeneralDisorder

iTrader: (1)

Still - I have never seen a bad 27SF512 like that. Doesn't seem likely. It could be that the difference in the tune is exposing some deficiency in the ignition system for example - simply because the timing and fueling are different between the two. If you lean out the mixture it might not ignite as easily and an enlarged plug gap, or poor wire/cap/rotor connection might become evident where it wouldn't with a richer mixture. You just can't rule out the tune changing the behavior of marginal components like that - especially when it's been in place for 10 years. Everyone is always too quick to blame the computer and it's usually not the problem.

GD

joeld

Actually, the ECM/chip was the last thing I thought the problem was. I've been working on this for over a year when I had some spare time. It very well could be something I've missed. Other than the problems I described the car does run very well. No codes ever, nothing. I'm going to look around and try to find someone that will copy this chip, I assume that is possible? I do appreciate your time and replies. But I will take another look at all connections and the ECM's .

Thanks
Joel

Tuned Performance

iTrader: (92)

I have had a few sst that go bad after the first use but very rare.
I never got the chips back to examine but the car went from running good to limp home and code 41 or 51.
Never seen data erase on a sst but have on a uv prom.
original multecs? Sounds like another issue other than prom.
your current chip can easily be read and saved to a bin and reburned.

joeld

No, I installed a new set of Delphi injectors last year along with a boat load of new parts. It's getting real annoying to find the cause of this. Thanks for the reply

Joel

GeneralDisorder

iTrader: (1)

Send the chip to Tuned Performance and have him copy it to a new one. He's closer to you than I am and I don't know anyone else doing it these days.

GD

joeld

Thanks, appreciate the replies and help.

Joel

89onlyZ51

iTrader: (3)

I've seen this happen a number of times now, from a few Callaways to my guldstrand gs80. A few bits drop off the bin and read 'ff' or '00', I forget which. The way I've fixed them is to do a compare with a known stock binary that the chip is based off of, look for the dropped bits and substitute until the checksum doesn't change. Then you know you've gotten it right.

joeld

Thank you for that info.

Joel

Tuned Performance

iTrader: (92)

I’ve seen uv erasable flip a bit but not to blank FF.
good information

RBob

iTrader: (1)

This is a good reason why the checksum function of the firmware shouldn't be disabled. A lot of folks still do it.

RBob.

Tuned Performance

iTrader: (92)

Thread update: got the chip did a read and recreated changes made to arap . Checksum looks fine.
dont think there were any bit flips . Flow rate was slightly changed single and double fire but if edited with tunercat this happens not a drastic change in numbers. Did a fresh tune close to the one read fingers crossed solves issues.

joeld

Just a quick update: Received the new chip from Brian today. Very quick service from him. Car has been sitting for the last 3 weeks, temp today was approx 50*. After less than 2 revolutions engine fired right up with no problems. Had a good idle with no stumble. Drove car around for about 5 miles with no issues, but still need to get some more drive time before I put it all back together. Many thanks to Brian at Tuned Performance

Joel