ragni

Brothers:

Need some feedback on this.

94 LT1, 70,000 miles, check engine light came on and started thowing code 36.

Starts, but only after extended cranking. This is totally abnormal. Normally the engine starts right up.

It runs fine at idle and on very short runs around the neighborhood. I didn't want to test it further from home.

I checked and cleaned the connector to the Opti. No visible corrosion. I cleaned it with CRC electric parts cleaner and blew it out with compressed air. Disconnected the battery to clear the codes and got the same results; ie, started only after exteneded cranking and it threw the code 36 again with the check engine light illuminated.

The Opti was replaced approximately 10,000 miles ago in December 2007 with an AC Delco unit that according to the invoice, I was charged $690 for.


I have to drive it tomorrow for a 20 mile round trip, 10 miles each way.

Question: (1) Is this for certain a bad Opti and (2) even though it runs fine at idle and for short runs is it likely that it will die tomorrow when I drive it 10 miles each way?

Thanks for your input,

Rich

Jon Hekking

Pretty sure that's a mass air flow sensor issue, should be alright but I would replace the MAF if the leads look good.

ragni

Jon:

Boy that would be great. Btw, It's a 94 with 70,000 miles.

I think the code 36 linked to a MAF problem is for previous years/models.

But God, I hope you're right.

Thanks, Rich

Jon Hekking

Could be wrong, there are many people here that are better techs than me, but that's the case for my 93 LT1.

ragni

Cool, thanks.

I hope they chime in.

Rich

Cdn UFO

found this

If you get a Code 36, MAF... read full caption

If you get a Code 36, MAF burn-off malfunction, it should immediately reveal itself at startup and it won't affect performance. '85 Corvettes will never show a Code 36, only '86-'89 Corvettes. You can check to see if the ECM is calling for an MAF burn-off by running the car for at least 5 minutes, and checking the black wire at connection F (circuit 900) on the gray connector. It should be grounded for approximately 30 seconds. This is the ECM grounding the wire to actuate the relay. If there is no ground, the ECM is at fault. If you have ground, check the power to the relay. If the relay is sending power to the MAF, check that the dark blue wire (position D) on the MAF sensor connector has power.

Cdn UFO

Try this site it has a lot of info

http://www.corvettefever.com/techart...ems/index.html

ragni

UFO:

Once again, I hope you're right but according to the trouble code list I pulled off this forum code 36 is: Distributor ignition system High pulse.

For the life of me, I can't find the proper section in the FSM to verify this.

Can anyone verify this code (36) for a 94 and if yes, where is it listed in the FSM?

Thanks, Rich

ragni

UFO:

Thanks. I'd seen this link before but thought it pertained to pre-94 models. I'll read it in it's entirety.

Thanks, Rich

powerpigz-51

Dtc36 is the lack of a hi res pulse from the opti. This pulse is used for calculating timing advance, and is not needed for the car to run, but there is another thread on here where someone is having the same problem you are. You will need a troubleshooting flow chart to determine where the problem is, I can help with that if you have a good DVM.

ragni

Power:

Thanks. That may be beyond my capabilities since like most people, electronics are my weak point.

Plus, I have a digital volt meter but can't say it's a real good one.

So I take it from what you've written that I can drive without fear of it dyeing?

Any help or info you can supply is appreciated.

Thanks, Rich

powerpigz-51

What I mean by a good Digital Volt Meter, is one that has a internal resistance of 10 megohm. This means that when checking integrated circuits, it will only sense a small load on the circuit. Some cheaper DVM's put to much of load on these sensitive circuits. Walmart sells a 10 meg DVM for about 20 bucks. I think your car will live for your trip (as in it will get you there and back), but I do not know the consequences of not having the proper spark advance. It may be running in limp mode. When you mean extended cranking.....is it around 6 seconds?

ragni

Power:

OK, thanks.

For what it's worth, power and performance seemed normal when I drove it locally.

Rich

ragni

Correct, about 6 seconds.

ragni

I drove the car today a combination of highway/city driving for about 30 total miles with no performance issues other than the extended cranking, about 5~6 second. (And a CEL throwing code 36.)

Power was fine, no misses. According to the driver's info center instant mpg was normal at all times.

I don't think it's my Opti since it's a relatively new AC/Declo unit but a mechanic suggested to me it could be the crank position sensor that, according to him, is part of the Opti.

Any opinions or advice appreciated.

Thanks, Rich

ragni

Will do but, I'm still stumped.

If it's the Opti, I don't understand why it runs fine once it's started.

KARR

Code 36- Distributor ignition system. Faulty high resolution (360X) pulse or multiple low resolution pulses detected. Check pigtail connector from distributor to main harness for any opens or shorts. Verify wiring is okay before replacing distributor.

frank1973

Had same code on my 92 with 16K miles. After testing all the usual suspects finally changed the OPTI and it's been clear for 3K miles so far.

frank1973

There are parts that can be replaced but I put in a new Delphi OPTI, sealed the edges with RTV and added a weep line to the water pump.

powerpigz-51

There is an open thread on here with someone having the same problem. He is lacking the hi res pulse, (DTC36) and it is delaying the starting by 6 seconds or so. This is only when his car is hot. This pulse is not required for starting or running, what caused the starting delay is anybodies guess......his pulse shows up after the car fires up. You should have the wiring checked, but low mileage on a opti is no guarantee that it is not malfunctioning.