Hey all, I'm trying to t-shoot a hard start problem on my '88 LB9 IROC, (see: https://www.thirdgen.org/messgboard/.../010748.html), and in playing with my Diacom, I came up with a couple of questions.

1) when the cooling switch is listed as ON, does that mean the ECM is looking for the fan to turn on? If so, why is my ECM looking to turn the fan on at 185, OFF at 190 and back on again at 187? Especially when the fans are turning on and off at just about any time they please.

2) Does the EGR Diagnostic Switch truly reflect passage of EGR? If so, why do I have 10 minutes or so of an ON condition, followed by about 10 minutes of an OFF condition? EGR Duty Cycle is doing its thing, but EGR switch seemingly isn't. Could it be a bad solenoid?

Thanks for the time, and if you have a chance, please check out my other post. - John '89 L98

 

You might try re-posting this on the PROM board. You might get more answers there.

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1989 IROC-Z 5.7L
NOS 5151 150HP kit
ProBuilt 700R4, PI Vigilante 2800 stall lockup
Baer Brakes 12" Sport System

 

Consider it done...

 

All right... I tried posting this over in the DIY PROM section, but it didn't seem to help. So, here it is again. Thanks. - John '89 L98

 

Anybody?

 

Dont you just love how useless the prom board is? You do know that nobody there ever uses diacom to tune their cars to change their chips, right? That or they never get outside of their little box over there to read other boards...

1) when the cooling switch is listed as ON, does that mean the ECM is looking for the fan to turn on? If so, why is my ECM looking to turn the fan on at 185, OFF at 190 and back on again at 187? Especially when the fans are turning on and off at just about any time they please.

2) Does the EGR Diagnostic Switch truly reflect passage of EGR? If so, why do I have 10 minutes or so of an ON condition, followed by about 10 minutes of an OFF condition? EGR Duty Cycle is doing its thing, but EGR switch seemingly isn't. Could it be a bad solenoid?

The ECM does not receive information that the EGR is working on your car aside from the temp sensor, and from what I have experienced it doesnt do anything either.

Just looking at the way your fans act, the ECM variously deciding to check if the EGR is working or not, and your fueling problems, something sounds wrong with the chip or ecm. Check the grounds and power supply to the ecm, and just as a guess if thats not it, check the TPS and make sure its set right and doesnt do anything funny when you open up the throttle. I think (although I am not positive) that the EGR diagnostic switch stuff that Diacom is reporting to you is just the error logging BS, and for some reason its turning off.... the only time I know of it doesnt check it is if the coolant temp is low.

 

Cool. Thanks for the reply. I guess I'll stop looking at the more complicated things with my problem, and get back to the more simplistic possibilities. Thanks again. - John '89 L98