GMH94Z28

I was on my way home from work and my car just died on me. After doing some testing we determined that it was the opti so I replaced it with a napa reman unit (I know, I know but it was convenient) that resolved the no crank issue but now I have a bad miss. I swapped it out again and now it cranks fine and runs fine no miss at all. Now if I park it for about 10 to 15 minutes and try and crank it again it spins over and it will hit but not run but if I hold the key over it will eventually crank after about 15 seconds and I get a MALF 36 high res fail. It seems to only crank over easy when it is cold. I am pretty sure it is the opti but I would like know if maybe I am overlooking anything.
Thanks in advance

Injuneer

Have you examined the short Opti harness that runs from the gray connector on the bracket on the passenger side of the intake manifold, to the Opti? Damaged pins, bare wires or corrosion can cause problems.

DTC 36 is strictly for the Opti. Code sets when the PCM does not see a high resolution signal from the optical cam position sensor in the Opti, while it sees 40 low resolution pulses (10 crankshaft revolutions).

GMH94Z28

The opti came with a sealed pigtail already on it. I have some spare ones i can try though. Would the code 36 cause the no crank when the motor is warmed up?

Injuneer

Make sure your splices are good, and the wires are well insulated from each other.

In theory, the engine can run on the low res pulse only. There will be a mino loss in timing accuracy, causing increased spark scatter. But not anything you should notice, or prevent the engine from starting. In practice, an erratic high res signal can throw the timing off. You are better off with no high res signal, than you are with an erratic high res signal.

By "crank over" I assume you mean "start". Starting cold and not starting hot can possibly be related to the coolant temp sensor. If the CTS is telling the PCM the engine is cold, when it's actually hot, it's going to richen the mixture too much, anticipating a cold start.

GMH94Z28

Thanks Injuneer! Is there a way to test the CTS?

Injuneer

The best thing to do is use an OBD-1 scanner (not just a "code reader") to read what the CTS is telling the PCM. Alternatively, there is a link to a free download of 1994/95 OBD-1 scanning software in a "sticky" on the "Computer Diagnostics....." forum. There is also info in the thread about the required cable, which can be built for less than $20.

To test the sensor and see if it is accurate, Shoebox has a writeup:

4th Gen LT1 F-body Tech Articles

GMH94Z28

Can anyone tell me where everyone is buying their ac delco optisparks from now days? Last one i bought was from thepartsladi on ebay but i see they aren't around anymore.

moparman

Check Rock Auto. You'll probably have to get the Delphi which is the same as the Delco.

GMH94Z28

I tried that already and bought the 1 delphi they had left, then they called me and told me they couldn't find it and delphi doesn't make them anymore.

moparman

The only other place I can think of to look is Amazon.

GMH94Z28

I was a little unsure about buying one from Amazon.

shoebox

Why? Got something against Amazon?

GMH94Z28

Nope just wasn't sure about a acdelco optispark from amazon.

GMH94Z28

What do you think about a acdelco remanufactured optispark?

shoebox

Haven't seen much feedback about them. I would hope they would be better than most reman units. I do notice that they come with a new pigtail attached, which is a good thing.