94 Z28. Here is the problem. A few days ago the car was running fine. drove it for maybe 15min. stop the car. try to start it 30-45 min. later and it would not fire. waited for maybe 45 min. in that time i unplug the wires from the coil and the module. later it fired. Drove it home about 15 min. and it died. I try to start it and it would no. Later that night it fired. pulled the coil and ICM and tested the ohms on the coil, good. the ICM tested good but still replaced it. now the car wont start.

I have done this test. i have check for spark. None
I have check for voltage with key on at coil pink wire. 12 volts
i have check power at A and D wire connect from ICM. 12 volts
Now here is were i'm not so sure. I tested Terminal B in A/C scale for voltage from the PCM while cranking the engine.(Hayness Repair Manual says to do it on A/C) 0.03 volts is it suposed to be in A/C or DC?
Tested with volt meter one lead to battery power and other lead to C on ICM wire. 12 volts

There was a thread were injuneer said that there should be 1 - 4 volts when cranking the engine. but did not mention if a/c or DC.
https://www.camaroz28.com/forums/sho...d.php?t=685088
I have not been able to scan the car for codes.

 

Could be the opti i know thats not the right thing to do is just blame the opti but that same thing happened to me about a year ago. My car was seemed like it was running fine until it started to heat up and would stall. If i let it sit for like an hour it would start back up. I replaced the opti and no more issue. When you have it running does it stall if you leave it on? Does it turn over? When it is on is it misfiring?

 

Well if it dies and wont start after warming up it could be your coil. You should try replacing ur coil and apply thermal past to the back of it. then maybe its ur opti if ur not getting spark

 

There are several ignition parts that are subject to failure due to heat soak, including the IC Module, the coil and the optical module in the Opti. Get it scanned for codes, since these problems will set codes, and the codes stay stored for a reasonbly long period of time.

 

What brand of scanner should i try? i have tryed scanning the car with a innova scanner but it would not read it. a brand that works for someone?
Is there a way to check if the opti is sending a signal to the pcm?

 

You need an OBD-I scanner. Auto Xray made one that was OBD-I only, and is usually available used on ebay for low $$$. Do not buy the cheapie (~$30) Actron. It says on the box that it will work with the 1994, but it won't. Its just a switch that shorts the ALDL pins and flashes the codes..... basically a 5-cent paperclip in an $30 box. 93 was the last year the paperclip worked.

 

ok i will look around to see if i can buy one. Also in the mean while i'm going to check for voltage from the distributor to the pcm. see what i get. if i dont get any voltage from the high res wire or low res wire would indicate a bad opti?

 

If the optical cam position sensor in the Opti fails, you will not get the 5V square wave pulse pattern the PCM requires to set the ignition and injector timing. Loss of either the high resolution or low resolution pulse will set codes.

You could check the square wave output signals with a volt meter, but its going to read the "average" voltage, as it varies between 0V and 5V. If you can turn the Opti very slowly, you can watch the voltage on the voltmeter, and watch it switch between 0V and 5V. Or you could hook up a multi-meter with a frequency counter, and check the pulse frequency. The high res pattern is 360 equal length pulses per cam revolution (180 pulses per crank revolution) and the low res pattern is 8 variable length pulses per cam revolution (4 pulses per crank revolution).

Scanning it for codes is a lot easier.

 

thanks i'm supposed to be getting a scanner from work but until monday. Hopefully the scanner they lend me is compatible. but i will check for voltage at the opti connector. A guy sells a Tech 1 scanner for $50 dollars is that a good deal?

 

If the "Tech 1" is the OTC tool used by GM mechanics, its a huge bargain at $50.

 

http://stockton.craigslist.org/bfs/1575623950.html
is that what the scanner looks like? man the guy lives 1.5 hour away from me. I do try to buy it should i ask about up to what year it will scan?

 

If its a GM Tech 1, it will scan, bi-directionally control and modify the program in all GM OBD-I computers, with the correct software cartridges. They cost well over $1,000 new.

You might want to read this for "cautions":

http://reviews.ebay.com/AUTOMOTIVE-S...00000004909670

The Tech 1 tools typically sell for $500-600 on ebay. Something sounds odd.

 

yeah i did see one on sell for $300. darn i better be careful then. it probably dosent work

 

One question, when testing the distributor you said i have to turn the distributor real slow, i try turning the crank shaft by the pulley but darn to hard. Can i turn the engine trying to start it? will it turn to fast?

 

You will get 4 low res pulses per crank revolution. If you are trying to start it, cranking at 300rpm (5 crank revs per second), you will get 20 pulses per second, too quick for you to see. On the high res, there are 180 pulses per crank rev.

You would have to pull the Opti off, and slowly rotate it by hand.