Hey guys, I have been driving my car and have had any problems till now. It has been dying when idling some and is hard to crank back. Well it doesn't do it every day but today it did and set of the ses light. I pulled the code and it was dtc 36 hi res signal. Just curious if someone could give me a little more information on what causes this? Do I need a new opti?

 

Optispark or opti harness. Check the harness first for good connection and no corrosion on the terminals (especially on the opti end).

 

O.k. will do......It's not missing or anything just shuts down every now and then.....So that would make since

 

If it died before, or did not set the SES, it's not the hi res signal.

I proved the shop manual correct with my engine by cutting the hi res line and twisting it back together. It was such an intermittent signal, it continually set the SES light but NEVER DIED. I left it that way and even sold it that way and for weeks the new owner hadn't fixed it and it still never died.

I have seen quite a few folks that had a 36 and a 16 at the same time. The 16 will kill the engine and NOT set an SES. So if you were dying before and not setting an SES, more than likely, that was the cause.

The 36 always sets an SES.

 

Cthomson21, The GREAT thing about this board is that there is NO shortage of opinions on what can be causing problems with our beloved LT1 engines ...... when it comes to that darn Optispark!

Speedygonzales and I have a longstanding "agreement to disagree" on DTC 36 and what it will, or will not do to the starting and/or running of the LT1 engine. For more info on this, please refer to this post: https://www.camaroz28.com/forums/sho...d.php?t=737219

Shoebox is right on target here .... check and or replace your Optispark harness and Opti ......... and your current problem ..... will be gone!

 

I will check the harness 2moro, but after reading that post I'm gonna take a blow dryer to the opti. I have been noticing a slight miss when the car gets up to around 200 degrees. I guess this also could be due to corrosion or maybe even a faulty ICM?


Also today, I cleared the code a couple of days ago, and it came back on today but never made the motor die. I dunno if that's helpful at all.

Ha I've read a few posts about this before, and it seems that a lot of people do have some good theories of why they break. I plan on getting some time to work on it tomorrow, and I'll post what I find.

One thing I'm curious about though..... If the computer has no high res signal does that affect the timing advance any? How could I test that? I didn't see anything on shoebox's website is why I ask.....

 

The ignition timing can be refereneced to the low res signal (one variable width pulse every 90 crank degrees). But the high res signal is used to "fine tune" the timing, based on knowing where the cranksahft is within one rotational degree. This results in reduced "spark scatter", which increases combustion efficiency and reduces emissions. The difference is small enough that you probably wouldn't even notice the change between running on both signals and running only on the low res signal.

I can't think of any way to "check" the timing to see if the high res signal is being used to make tiny adjustments. The main clue to loss of signal is the DTC 36 code.

 

O.k. I guess I was just thinking maybe I could plug up free scan and maybe get an average reading of timing advance, but now that I think about it it wouldn't prove crap.....

The wires were slightly corroded......So I'm hoping that's all my problem was.......I will drive it this week, and see if my problem goes away, and if it doesn't I'll perform the opti test next weekend......

 

Back when I did my experiment, I was only looking at it from the stand point of not causing a shut down.

Had I known there could be some effect to timing, I could easily have checked what the timing was with the scanner. I had it hooked up while the wire was broke and intermittently touching the wire together. The scanner quite clearly states what the timing is. Duh

 

The scanner tells you what the summation is of the timing values picked of the main timing table and the various offsets. That tells you what timing the PCM is trying to set. It doesn't tell you what the timing actually is. Whether the PCM starts to revise the values when it loses the high res pulse would be sort of hard to determine. But who knows - when it sees DTC 36, maybe it pulls a few degrees to reduce the chance of the spark scatter causing detonation.

 

O.k........So the car ran ok for a few days until it rained again.....Now It seems to run fine for about ten minutes maybe, and then it will die....If the ses dtc 36 comes back on it will crank up and run fine always, but if it doesn't throw a code then sometimes it will and sometimes it won't......its very erratic........I had an ICM off a 93 laying around and put that on, and I still have the same problem......I guess I'm looking at a fried opti?

 

Rain or in my case, high humidity was the opti.

I could always count on mine not starting on a morning with high humidity. But the afternoon would light right up. In my case, changing out the opti was not likely to stop it from occurring since it was from condensation.

I never did scan it when it wouldn't start to see if it actually threw a code or not.

Why don't you try warming yours for a good long while with a blow dryer to see if clearing out any condensation might bring it back? A low cost way to gain more insight into the problem perhaps.

 

great advise....Thanks Speedy.......I warmed each component up individually opti,ICM,coil,etc.... The coil ohmed out weird it was around 8400 ohms cold...then, 9000 ohms and jumped to open when it was warm.....that seemed a little high from what i've read in the post about checking the opti.....I replaced it and its been raining all day outside and haven't had a problem yet...

Just curious is this a common problem? anyone heard of the 36 code with a bad coil?

 

I've never had a dtc 36 from a coil. I've gone through 11 optis over the years (I wish I was kidding. Different reasons too, one time was oil contamination for example from a bad opti seal. Or the rotor bolts backing off from high rpm. Or your usual moisture.) Almost I'd say 1/3 of the time they went I'd get DTC 36 when they were on the way out, 1/3 the time I'd get both 36 and 16. And the other third I'd get nothing. I would have said based on everything you said that your opti is in it's way out. I usually get similar symptoms.

 

The coil itself won't produce a 36 but having a high voltage wire very close to the opti harness might induce enough noise to cause a problem.

Maybe in changing the coil you moved the high voltage wire far enough away from the opti harness to eliminate the problem but thought it was the coil instead.