Pre-detnotation saga cont.

[mike2020]

By now everyone must be sick of me. I am still batteling the predetonation problem and computer not communicating. I was on line with a parts store and they have a super-chip for Reattas. They are $175. My mechanic says this could solve the problem because the programmed paramaters are greater. i.e. according to his computer it is only retarding the timing 3 deg. He thinks that the competition one would have greater paramaters hence solving the predet. prob. Is there anyone out there reflashing EEPROMS that could add more timing int my old one or should I start fresh with the Super Chip one. What do ya think?

<img src="http://forums.aaca.org/images/graemlins/confused.gif" alt="" />

Some people learn by other peoples mistakes, its just too bad the rest of US have to be the other people! <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />

[jonlabree]

OR, You could have YOUR chip reprogramed.

sinisterperformance@dtcc.cz2...

E-mail Address(es):

sinisterperformance@dtcc.cz28.com

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[padgett]

Do you have a stock PROM now ? Are you sure ? If you insist on buying a chip anyway there is this bridge for sale...

[mike2020]

Just talked with the parts guy at local Buick dealership. He can get a new EEPROM from GM for $85.00 but I am not sure that will solve the problem since my old one is retarding -3deg when engine is under load. My mechanic thinks that is not enough. Ideas? <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> </div></div> Some people learn by other peoples mistakes, its too bad the rest of us have to be the other people! <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />

[padgett]

I show an attack rate of about 1/2 degree per millisecond. Retard is not a fixed amount but rather a continuing decrease in advance until knock stops. What is your mechanic measuring the -3 degrees against ?

For load above about 50% TPS (approx over 2v)you are supposed to go into "Power Enrichment" which boosts the injector pulse width to richen the mixture. This also is necessary to control detonation.

The entire program is not trivial and uses many factors to control advance and mixture according to tables.

I would look for a mechanical problem first. Has the mechanic verified that what the ECM "thinks" is TDC is really TDC ? That is the place to start.

[mike2020]

Padgett,

I will certainly check with him on this, however, I had the timing gear sprocket, chain and interrupt changed out about 20k miles ago and didn't have any problems until a couple of months ago. Wouldn't the cam chain have to had slipped a tooth or something for the timing (TDC) to change?

[2seater]

You can read your own timing retard in diagnostics. Is it showing knock counts also or just retard? It normally will take a continuing increase in knock counts to start getting retard, in other words it isn't an instant retard for a single ping. If it is registering knock counts, not the spark retard number, then what is causing the knock? False knock from something rattling around, or the knock sensor installed improperly, too tight will increase sensitivity? Heavy deposits in the combustion chamber, low octane etc.. The chip itself shouldn't do anything to the timing without an external input telling it something is in need of adjustment. It simply operates in cells based on rpm, load, temperature and other carefully programmed parameters. That in itself doesn't change, unless the chip is so far off it causes the engine to do something that activates its protection protocols. The only spark retard that I know of in the diagnostics is caused by knock. All other changes, such as reduced timing due to high inlet air temperature, shouldn't show as retard, it simply reads a sub-table to adjust timing based on the operating condition. I am guessing the question is if the threshold for knock retard can be changed or not? Padgett is better qualified and I do not know if that setting is in the chip or hard programmed into the ECM?

[2seater]

Oops, I should have reread all of the previous posts, not just relying on memory. You said it is showing intermittant communication? That could certainly cause the timing to change, although I don't know if it would show up in diagnostics as retard? His scantool is probably more in depth in that regard. If you lose the EST circuit between the ECM and ICM, so the ECM loses control of the timing, it will protect itself and go into limp home mode. Possibly the loss of other sensors or control may do the same thing? Three degrees of retard isn't really a lot, at least not if it is in limp home mode, which will drop timing way back to maybe 10 degrees of fixed timing, which is a large change. Do you get a check engine light or stored codes? It isn't really unusual to get some retard under some conditions like high load with low rpm like pulling a small grade with the trans. in high gear and the converter locked up. I see that fairly often, although it has been a long time since my setup was stock, so I do not know if it did it many years ago or not. I know my old Saturn work car does it constantly. I have watched it with a scantool and it will show a few degrees of retard, up to 5-7 degrees, and will gradually come back to zero as it adjusts. It doesn't take much change in throttle to make it do this, even on a flat road. Large throttle changes don't do that. It is more like the programming is designed to keep it "on the edge" so to speak, under cruise conditions, for maximum economy. I am not implying yours is doing this and is normal, since from what you have said, this is a new condition. Usually I would suggest you go back to the last change before the problem occured, but it has been a long time since the timing chain was changed? The needs of the engine can change over time, as I suggested previously. Have you tried higher octane to see if anything changes? If it is a communication issue, then that won't help.