ruben jr 94z28 lt1
12-02-2010, 06:35 PM
#1
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ruben jr 94z28 lt1
i have a 94 z28 camaro. service engine lights comes on, then the car stumbles for about 3 seconds and still drives.i took it to my school in the automotive dept. they said i have low fuel pressure so they replaced the fuel pump.codes lead them to replace the pcm and had it flashed. but car still misfires, hesitates, and when they trouble shoot comes back with code 16. now the car will not start at times. i can drive it a few miles and when i turn it off. it doesnt turn on.The instructor said i am losing fire to the injectors after the car gets hot.the instructor believes it has something to do with the viper alarm system or the original anti theft system causing posible low voltage. he also hinted possible distributor. so far i have put in new fuel pump, pcm, ecr, pcv, o2 sensor, cleaner for fuel injectors, cleaned throttle body, and about a year ago a tune up plugs and wires..please help and if it is opti..should i go aftermarket or just by a GM opti..or msd 6a that everybody talks about..thanks 
Last edited by ruben jr; 12-02-2010 at 06:54 PM.
12-02-2010, 07:37 PM
#2
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Re: ruben jr 94z28 lt1
Sounds like an opti could be the coil getting heat soaked but my money would go with the opti check the coil before you shell the cash for the opti as far as which opti to buy I would go with gm but thats your choice
12-02-2010, 07:56 PM
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Re: ruben jr 94z28 lt1
Forget the MSD 6A..that won't fix anything.
Try removing the ICM and having it tested at the local Autozone. Test it both at room temoerature and after you heat it up with a hair dryer (since it fails when it's hot).
Before you replace the OPTI, go to the sticky at the top of this forum and do a thorough diagnosis.
Try removing the ICM and having it tested at the local Autozone. Test it both at room temoerature and after you heat it up with a hair dryer (since it fails when it's hot).
Before you replace the OPTI, go to the sticky at the top of this forum and do a thorough diagnosis.
12-03-2010, 05:08 AM
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16 would appear to be the problem
They did
The 16 is the low res signal from the opti. When it is lost by the PCM, it shuts down the fuel system. This is probably why your "instructor" saw the loss of injector pulses.
Your problem could be the opti however, it should be easy for a class with a scope to view the signal from the opti to the PCM on the red/black wire. Incidentally, many MANY times the problem is merely corrosion on the connectors. Since the feedback signals from the opti have to go through 3 different connection points between the opti and the PCM it's easy to see how the signal could be lost. Don't forget the wiring is 16 years old.
Since your problem is intermittent, it would lead one to believe the problem is wiring. Heat soak while not uncommon is less likely. Especially if we read into your post that it won't start from a cold situation.
On another note. You may want to ask your instructor if he has actually seen a GM OBDI PCM go bad. I have never seen one. Where peeps go bad in wrongly diagnosing the PCM is they see the loss of an output, such as the injector pulses. Then they jump to conclusions that the PCM is not outputting the signal to the injectors so the problem must be the PCM. When the whole time it was a missing input signal from another device.
Your problem could be the opti however, it should be easy for a class with a scope to view the signal from the opti to the PCM on the red/black wire. Incidentally, many MANY times the problem is merely corrosion on the connectors. Since the feedback signals from the opti have to go through 3 different connection points between the opti and the PCM it's easy to see how the signal could be lost. Don't forget the wiring is 16 years old.
Since your problem is intermittent, it would lead one to believe the problem is wiring. Heat soak while not uncommon is less likely. Especially if we read into your post that it won't start from a cold situation.
On another note. You may want to ask your instructor if he has actually seen a GM OBDI PCM go bad. I have never seen one. Where peeps go bad in wrongly diagnosing the PCM is they see the loss of an output, such as the injector pulses. Then they jump to conclusions that the PCM is not outputting the signal to the injectors so the problem must be the PCM. When the whole time it was a missing input signal from another device.
Last edited by Guest47904; 12-03-2010 at 05:40 AM.
12-03-2010, 11:34 AM
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Re: ruben jr 94z28 lt1
i read up on info for heat soaked referred by GRIDERMAN87 and SPEEDYGONZALES. my low coolant light is also on..but i have changed the sensor, waterpump, radiator, thermostate, and the $225 hose kit from gm..light still on..dont know if that will be the issue or why light still on.checked parked and after driving..coolant is full
12-03-2010, 11:44 AM
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Re: ruben jr 94z28 lt1
@ SPEEDYGONZALES..yeah my instructor told me he wasnt sure if it is the pcm but that is the only thing he believes it to be and is not sure..since he couldnt fix it. he gave it back to me. he had classes only on mondays for 2hr with other vehicles and said not enough time for his students to fix..@ MY1994Z28 was right..moneypit..i will try all the things you guys had referred to..but for now it will have to wait till income..because the rest of cash for college
12-03-2010, 12:09 PM
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Re: ruben jr 94z28 lt1
@ SPEEDYGONZALES..yeah my instructor told me he wasnt sure if it is the pcm but that is the only thing he believes it to be and is not sure..since he couldnt fix it. he gave it back to me. he had classes only on mondays for 2hr with other vehicles and said not enough time for his students to fix..@ MY1994Z28 was right..moneypit..i will try all the things you guys had referred to..but for now it will have to wait till income..because the rest of cash for college
Check the harness that runs down the passenger side of the intake manifold and plugs into the optispark. You're looking for corrosion or bent terminal pins. That wouldn't be a heat related issue but it one potential cause of signal loss and should be investigated.
By the way, these things don't have to be any more of a money pit than any other 16 year-old car if you follow sound diagnostic procedures. Changing parts because someone might think it's the problem will be frustrating, and expensive.
A few things to remember:
It's almost never the PCM. They just don't go bad. Don't even think about that as the source of the problem....
It's not always the OPTI although people change them out at the first hint of any issue. Always check the spark plug wires, the plugs themselves and the cap and rotor before buying an opti. My car had the original OPTI on it for 80,000 miles with only a cap and rotor change. I only changed it then because I updated to pin drive opti during a heads/cam change.
A computer scan is the first thing you should do for any diagnosis. Cables are about $100 and you can get software for your computer to read the codes. Don't believe the generic codes printed out there....LT1 engines have specific codes.
When you ask a question on here you're going to get a hundred recommendations. Obviously they won't always be right. Run them all down until you get the answer.....ignoring things and then asking the questions always yields fewer answers as people thnk you've stopped listening...
Good luck!
12-03-2010, 12:24 PM
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Re: ruben jr 94z28 lt1
i read up on info for heat soaked referred by GRIDERMAN87 and SPEEDYGONZALES. my low coolant light is also on..but i have changed the sensor, waterpump, radiator, thermostate, and the $225 hose kit from gm..light still on..dont know if that will be the issue or why light still on.checked parked and after driving..coolant is full
mine ( Low coolant light) will come on and off all the time sometimes it will stay off for days and just pop up, the sensor or wiring is faulty itsno big deal tho just a little red light
12-03-2010, 04:07 PM
#12
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Re: ruben jr 94z28 lt1
For the issue with the low coolant light.... which "sensor" did you change? The coolant level sensor on the passenger side radiator end tank is a common problem. It get dirty and turns the light on. Changing the level sensor always fixes the problem, if your coolant isn't actually low. Its seldom a wiring problem, because if there is an open circuit in the wiring, the low coolant light will never come on. It would have to be a short in the wiring.
Is it possible you changed the coolant temperature sensor, and not the level sensor?
DTC 16 is caused by only one thing - the PCM does not receive the low resolution pulse pattern from the optical cam position sensor in the Opti. As noted in posts above, its either an optical sensor problem (they do heat soak, and they can fail intermittently) or corrosion of the harness connectors.
Also as noted above, DTC 16 causes the PCM to shut down the fuel system. It seems like everyone is losing sight of the fact that you have DTC 16, and you do not have an injector signal when the car won't start.
Clear the codes (pull the "PCM BAT" fuse for 30 seconds) and see how quickly the DTC 16 code comes back. It isn't unusual to find it as a "stored" code.... I think the PCM sets it at startup, when a couple seconds go by before it can find the low res pulse signal. But if the code comes back every time the engine won't start, it would pin the problem down to the Opti.
With regard to your PM to me, if you determine it is the Opti, buy only the OEM AC Delco (now Delphi) part. Do not buy a rebuilt, a local auto shop part, a Summit brand, anything off the internet, etc. The other stuff fails much more frequently than the stocker. The MSD may match the stocker, but why pay the extra $$$'s, and then have the issue of not having any way to know it the timing adjustment screw is really in the "0" position. Whatever you buy, you MUST open it up and loc-tite the rotor screws before you install it.
Is it possible you changed the coolant temperature sensor, and not the level sensor?
DTC 16 is caused by only one thing - the PCM does not receive the low resolution pulse pattern from the optical cam position sensor in the Opti. As noted in posts above, its either an optical sensor problem (they do heat soak, and they can fail intermittently) or corrosion of the harness connectors.
Also as noted above, DTC 16 causes the PCM to shut down the fuel system. It seems like everyone is losing sight of the fact that you have DTC 16, and you do not have an injector signal when the car won't start.
Clear the codes (pull the "PCM BAT" fuse for 30 seconds) and see how quickly the DTC 16 code comes back. It isn't unusual to find it as a "stored" code.... I think the PCM sets it at startup, when a couple seconds go by before it can find the low res pulse signal. But if the code comes back every time the engine won't start, it would pin the problem down to the Opti.
With regard to your PM to me, if you determine it is the Opti, buy only the OEM AC Delco (now Delphi) part. Do not buy a rebuilt, a local auto shop part, a Summit brand, anything off the internet, etc. The other stuff fails much more frequently than the stocker. The MSD may match the stocker, but why pay the extra $$$'s, and then have the issue of not having any way to know it the timing adjustment screw is really in the "0" position. Whatever you buy, you MUST open it up and loc-tite the rotor screws before you install it.
12-03-2010, 06:40 PM
#13
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I beg your pardon?
The 16 is the low res signal from the opti. When it is lost by the PCM, it shuts down the fuel system. This is probably why your "instructor" saw the loss of injector pulses.
Your problem could be the opti however, it should be easy for a class with a scope to view the signal from the opti to the PCM on the red/black wire. Incidentally, many MANY times the problem is merely corrosion on the connectors. Since the feedback signals from the opti have to go through 3 different connection points between the opti and the PCM it's easy to see how the signal could be lost. Don't forget the wiring is 16 years old.
Your problem could be the opti however, it should be easy for a class with a scope to view the signal from the opti to the PCM on the red/black wire. Incidentally, many MANY times the problem is merely corrosion on the connectors. Since the feedback signals from the opti have to go through 3 different connection points between the opti and the PCM it's easy to see how the signal could be lost. Don't forget the wiring is 16 years old.
Last edited by Guest47904; 12-04-2010 at 05:46 AM.
12-03-2010, 07:04 PM
#14
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Re: ruben jr 94z28 lt1
i thank everyone for their views on my issues..i will have my icm checked at autozone and if needed i will by the delphi opti. maybe do another tune up..oh yeah @ injuneer..yeah i bought the wrong sensor. i got the coolant temp sensor and not he level sensor..lol..i will post again once completed and inform of my progress..thanks.
12-04-2010, 05:50 AM
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