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Dying LT1

kfehling

Well-known member
Joined
May 8, 2001
Messages
83
Location
Santa Rosa, CA
Corvette
1996 Collector Edition
My 1996 LT1 (automatic, 67K) has been hesitating upon startup but eventually recovers. Following a long period of driving (>1 hour), it sometimes stalls but usually starts right back up. Yesterday, however, it started then stalled 5 seconds later not to start again. I had to be towed home. I originally thought it was the optispark as the symptoms were the same as what I experienced last time the optispark had to be replaced. That is, a couple of hesitations here and there, then no spark to the engine but with fuel pressure. The dealership does not believe that it is the optispark, rather, they believe that it may be the computer module as they are getting the codes B0054, P0118, and P1115. Only the first is indicative of a computer issue as far as I can tell. Their theory is that the computer is failing to read the key code (even though B0054 is not this specific error) and cutting the spark to the engine. Thus, it goes into anti-theft mode. Obviously, replacing the computer is time consuming and money consuming so I thought that I would reach out here to see if someone can confirm or deny that computer replacement is the best course of action. What do you guys think?
 
Most computers that go back as a core....they don't find anything wrong with them. Most of the time....not all the time. Voltage fluctuation can make a computer act erratic as well as a bad connection. Battery, battery cables and all ground connections should be checked out first and confirmed.
 
Not ECM

I just went through what you are describing in May. Do this check for fuel and spark. If you have them then remove the rubber intake tube and have someone crank the engine while you spray choke cleaner past the throttle body. Be careful not to spray to much directly into the throttle body. All you are trying to do is see if the engine will fire or backfire. I had the same codes on my 93 and replaced the ECM only to still not have power to the injectors. My problem was the TPS it was telling the ECM to shut down because the engine was flodded and needed to crank and clear itself. The backfire reset the ECM and it then allowed power to go to the injectors and the car would start. In my case when the car started it then idled at 2000RPM again a funtion of the TPS. Took the parts store TPS off and put an OEM AC Delco unit on and everything was good again.

Throttle Position Sensor

The scan tool displays throttle position in volts. The voltage should display between .23 - .59, with throttle closed and ignition “ON,” or at idle. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT) about 4.6 volts.

The ECM has the ability to Auto-Zero the TP sensor voltage if it is between .23 and .59 volt. This means that any closed throttle voltage between .23 and .59 volt will be determined by the ECM to be 0% throttle angle, and should display 0% when the throttle is closed. A failure in the TP sensor circuit should (MY OPINION MAY NOT )set a DTC 21 or 23.

Copied from the service manual for a 93 model

I ended up buying an ECM I did not need because the core had to be turned into the parts distributor in order to get the Rebuilt ECM, and they would not take the Rebuilt ECM back and put it in stock. This cost me about $300 that I did not need to spend. At least the garage doing the work only charged me what he payed for the ECM.

Please report what you find out and how you fixed it.:beer
 
Thanks John. I will pass this along to the technician and post the result.

Kurt
 
John,

We tried your test and no luck. I think I have no choice but to replace the ECM at this point.
 
I would be plugging in a used one if possible. These PCMs (in '96 they are the powertrain control, both engine and tranny) are available with upgraded tunes and trans shift firmness and shift point change. The fan temps are set lower. I have one from Bryan at PCMFORLESS and it's a different, better car.

Is there nobody local that can drop one in to see before plunking down retail dealer cost of $350? I KNOW they won't take it back once it's deflowered.
 
John,

The TPS voltage checked out as normal.

TLong,

Good suggestion but I decided to go with a stock ECM. I am hoping that it will be done today or tomorrow. I will let you all know the result.
 
Yeah, let us know. I have the same car within 1000 of mileage. It's called a PCM for our year. I hope it squares you away. I just had mine reprogrammed by PCMFORLESS, and it turned out great. It takes 3 minutes to install with 4 plugs. Can't imagine what the dealer charged.

If in the future you wnat to save some $ try a DIY with our help!

Cheers
 
I guess I still have some time here as the dealership does not have the part yet.

Because the issue is intermitent, I am inclined to believe that there must be something physically wrong with the ECM (or PCM?). Thus I do not believe that a reprogram would help.

I doubt I could do any DIY'ing as much as I would like to due to the amount of time required to get at the device.

But, if there are any other suggestions, please pass them along.

Thanks for the help thus far.

Kurt
 

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