you have the OBDII connector type on your '95(16 pin connector), but your system is still OBDI.. Jumper pin4 and pin12 and your codes will display on dash. Did you check for leaks from beneath your WP ?? Like I said, I had similar problem as you on my '94, and I had NO ERROR codes.... These PCM/ECM diagnostics are NOT bullet proof folks !!!! My car was skipping and bucking like a **** after the engine was warmed up, and no codes where ever captured.....


Follow the procedures from the link that Readeasy posted on this URL for proper error code reading(go about 1/2 down for procedure that says "Sequenced Code Recovery - 1994 through 1996" . It will also show you the location of Pin4 and Pin12:

http://www.corvettebuyers.com/c4vettes/codes.htm

 

Hooked up my code reader last night...and got the Low Resolution Ignition Circuit.

I have not noticed any leaks from under the water pump, nor any signs on the underside of the hood. But I will do a complete check this weekend to make sure.

 

Are you saying you got a code 16? That is an opti fault. Check your wiring but a code 16 usually will not let you start the car.

 

I do not remember what the code number was on my reader; just the text, it was late and dark when I did this last night. It must not be a code 16 as the car will start and drive fine until something gets HOT. I will check for leaking water pump tomorrow, but pretty certain it is not.

I will use the short the pins method tomorrow instead of my code reader.

I do want to thank everyone for the help.

 

I had no code, but she wouldnt start. This was my Optical snesor I had for a couple years. Ran fine till one pin, #4 in pic 2, broke off. So I dissected it as I have no cap/rotor as I use aDELTEQ.

 

When checking codes, the PCM and CCM monitors feedback from many parts. But that’s only a small percentage of all the parts in the car and possibilities. In military electronics it is called BIT, or built in test. It can be very elaborate and can grow as big as the things you are testing depending on how far you want to go. In the vett you will only get a code for what’s monitored. An OK system for its time. After all, it’s sold to the public and costs have to be kept down to stay competitive.

Some how at this point I do not think codes are going to be much help. You’re going to have to get more technical and find out what is missing when the engine quits. Not easy but have to be methodical and step by step.

Would like to know what codes are showing up. They of course should be followed up. Details and accuracy are important so you don’t go off in wrong directions.

So what’s the solution to the problem? Don’t know. But if you collect more specific data about the problem the forum can make better suggestions for possible answers. I think you have eliminated several items by replacing them already. Get creative in your approach. For example, connect a nod light on one injector semi-permanently. Then you can see right away if you lost injector pulses.

 

I know what you mean about BIT. I work in the defense sector and BIT is a very large part of what we produce.

I know that the OBDI is not all the complete and like you said, only those things monitored can be reported as fail. But the idea is to monitor a subsystem's operation...and report a failure of the subsystem, not an individual component. This is where more testing is needed to determine what component has failed within that subsystem.

I will be doing more troublshooting now, going from the error reported. Sure wish I had a O'scope at home.

 

Used the shorting pins method and pulled the error code. It is indeed a code 16. My code reader had it as a history code, not current. On wih the troubleshooting now.

 

Probably the low res signal not coming from the opti. Check your opti harness make sure the 4 pins are not bent in the top of opti and the female end of the wire. Unplug ignition module and check for the ac voltage at the ign module connector. If no low signal then probably bad opti sensor.

 

Duh yeah. AC voltage? Hmmm....

 

http://forums.corvetteforum.com/show...0&postcount=58

Test circuit 453 for spec current.

 

I assume you are waiting for your new Opti to show up at your doorstop from "thepartsladi". They are very reputable and you can be assured that you will receive an OEM Opti !! Meanwhile, if I was you, I would disconnect the negative terminal of the battery for about 30 seconds...this will clear your history codes. Then verify that the code16 is cleared using the paperclip trick. After you have verified that the code16 has cleared, drive your car around to induce the problem that you orignally posted....Then check to see if your error code16 re-appears. If that error code16 appears again, I would go ahead and replace the Opti. Be dog-gone sure that your WP is operable and that the bearings are good, and of course, that it is not leaking from the weep-hole. If your WP is OK, you'll need a new set of WP gaskets. Also verify that your WP and Opti seals on the timing cover are not leaking as well. I would recommend replacing them if you have any doubt....

If anyone knows how to properly hook up an O-scope, and what signal to use as trigger source to see the High and Low resolution pulses from the Opti, I would be real interested:

 

It might be explained in a link that B Cunningham posted on opti tech... I have it bookmarked on another computer.




Found it searchin...
http://www.gmhightechperformance.com...ing/index.html
Might or might not be in there - I read through once, and been a little busy wrenchin' since

 

I cleared the "History Code" using my reader, but did not go for a drive. I might take it to work tomorrow and just see if the code re-appears. I can also do another check of the WP and make sure there are no leaks.

I will need to get a set of WP gaskets that's for sure. I replaced all the front cover seals when I got the car in Dec 2006, so they should all be in good shape still.

I will probe in the igntion module connector and measure the voltage there, with the car running correctly...hopefully I can catch it when it is not and see the voltage drop out. This is not a hard, or complete failure. The engine recovers and keeps running. So the problem is most likely the optical sensor in the OptiSpark. New one is due at doorstep on Wed. Replacement scheduled for Friday, wife is going to help out too. If there is anything visable, I will post pictures.

 

Redeasy - Actually you can use a good multimeter set to AC to check this. Obviously not as good as a scope, but because the DC voltage varies due to pulse from the ignition module it looks like an AC reading to the DMM. I use this method often when going down the "what's wrong with my igniton system" checklist. I think it reads about 1.4 VAC if I remember correctly.

 

The Fluke DMM I have has a "fast" bar readout along with the nornal 3.5 digits. At 1000 rpm, that is approximately 17 revs/sec x 720 pulses/rev = 12.2kHz for the fast, and 17 x 8 = 136Hz for the slow. I know my Fluke will be able to "see" the slow signal, but not the fast one...it will give a reading, but it will be low. Guess all I really need to do is to verify that it is there or not right?

 

Okay, spent most of Friday removing parts off to replace the OptiSpark unit. Put the new unit on...no problems. Went to put the water pump back on (this was replaced less than 2 years ago) and not only was there water stains from the wep hole, but oil from around the bearing AND the bearing would turn in the pump housing as well. What a piece of $%@@#%&*(....that is.

Okay, so went and got a new pump and put everything back together. Started up pretty quickly, no leaks.....bleed some air out of the cooling system....all is good.

Took for a drive....made several stops along the way...car getting quite hot now...stopped for about an hour, took off and few minutes later...engine bucks about twice....recovers...bucks one more time..and then seems to be fine....same thing as before.

So it is not the OptiSpark, coil, ignition module, PCM. No codes were set either. Time to get really into troubleshooting this thing. If only it would just fail and stay failed.

 

Your over heating was due to air in the system. It takes a few heat cycles and burping to clear it sometimes. Re check all the wires you pulled off during the R&R. You had a code 16 a bad WP seal( I hope you replaced it if not oil will take out an opti too) and a leaky WP your old Opti was toast open it up and see.

 

Oops...slight misunderstanding....the engine did not overheat...just got hot as it will do in 100 temps and street driving.
Have burped the air out several times and will continue to do so.

Yep..had a code 16. The WP seal was replaced, along with all the front cover seals in Dec 2006. There was an oil stain on the WP, around the drive bearing. But unless oil travels inside the WP drive shaft, how did oil get there? If the WP drive seal is leaking, wouldn't there be oil on the front cover? There was not. Will continue to check for oil at the WP drive though.

I plan on taking the old OptiSpark apart and looking to see how bad it is.

Trouble is...the engine is doing the samething as before....but so far no codes set. Planning on driving it to work tomorrow, have to see what happens.

 

Yes oil can travel through the hollow shaft but I would expect to see a little elsewhere as well. Might have been the lube on the bearings you saw on the WP. Still running crappy? Codes? Are you sure all the wires are seated and right?