Alright guys, I have talked about this problem already and am still stumped after trying a few things. I currently graduated college and returned home and i am determined to solve this probelm and quickly as i can. Here is the story (please bare with me):

Over a year and a half ago my dad was driving home from work. The car stalled out while he was at a light (less than a mile from home). It took him several tries to get it started and when he did it the tachometer jumped up and down, the car shaked from idiling really rough. He managed to get it home with it running really rough and miss firing and the SES light on. The codes the car were throwing were:

16- low res failre
36- Hi Res Faiulure
42-EST Grounded

8,000 miles before all this i had a new water pump,optispark (GM performance from Jegs), new plugs, new plug wires, and had the electrical wiring looked at and repaired if needed.

Now 8,000 miles later the car starts running bad and has codes 16 and 36. i thought the optispark went bad again since i was told that the optispark life can be really low in some cases. i replaced the optispark ($250 from Summit),ignition coil,fuelfilter, and plugs (The plugs were carbon fouled really bad and were covered in black soot) and checked the wiring. After all this work it took 4 cranks to get the car to turn over and the rpms would be at 2grand and then slowly dropped back down to 800rpms. The car would run fine from anywhere from 5 seconds to 15 mins (depending on multiple starts) but as time went on the less time it took for the car to start acting weird. The car starts to shake as the tachometer starts to jump around sparaticaly and the engine backfires untill it stalls out. I could smell gasoline and the spark plugs (brand new) were carbon fouled so the egine was running way to rich. The SES light came on and these were the codes i got:

36- Hi Res Failure
42-EST Ground
43-ESC Failure
15- Coolant Temp too low ( think i installed the coolant wrong and have too much in there)

So after that i decided to cover the car up since i ran out of time with having to return to College in a week.

Today its almost a year later since all of this listed above and decided its time to tackle this car again. I charged up the battery and did voltage checks at the ICM. The two DC voltage readins were 10.81V and the AC voltage ranged between 1-4 V during the engine crank. I also checked the ignition system connector from the optispark to the side of the fuel rail for continuity and each terminal was good. This is what has me stumped. So i decided to start the car. After about 6 cranks i get the car to turn over, and like before the car idles at 2,000 and takes about 15 seconds to come back down to 8,000 rpms. Now with the ar started it idles a little rough and gets better over time with the engine missing every now and then while pushing down the accelerator.

With this first start i immediately got codes:

36 Hi Res Failure
15 Coolant Temp Low

and a few mins idling i got this code: 43 ESC Failure

The car ran for 15 minutes without stalling or backfiring when idling. During this time i also pushed down on the accelerator to different RPMS all the way up to red line. only a couple times the car hesitated for a sec when pushing the accelerator down. So after this 15 mins i turned the car off and cleared the codes. Then i started the car again (started first try) and the rpms went to 2,000 and back down to 800. And like before i only got codes:

36 Hi Res Failure
15 Coolant Temp Low


I let the car run for a good 10 mins and i never got the code 43 ESC Failure like i did before.

Can anyone make any sense of my situation??? Why do some of the codes just disappear? When i get the money i wanna try and replace the Summit Opti with a vented MSD one. Is it possible Summit sent me a bad opti? i want to believe it would atleast work for a little bit and not work at all and that the problem must be elsewhere. Hope you guys can give me some input. I am in dire need of help. Thanks!

 

sounds like its the opti.Get the MSD unit and as long as its installed correctly you wont have any issues.

 

multipal posts. hay again, im hoping pete will get back to u on your last post, i wanted to see what he had to say. pretty sure sumit optis are rebuilt units, in either case they are not known for there reliability.

 

you could check your wiring before you go threw the trouble of taking the opti back out. I was told a loose ground can cause problems that would seem major.

 

I'm sorry I don't have more detailed input, but I'm from the jeep world and I'm not sure about specifics on the LT1 yet, but it sounds like a sensor going bad. Maybe an air intake sensor or something like that making the computer throw too much gas in there. Sounds like you have a handheld programmer. Have you tried taking out the performance programming and putting back in the stock one?

I know on my old jeep it had a tps(throttle position sensor) that would cause problems like you are talking about. Also the crankshaft position sensor. I'm not sure if our cars have these as I just got my LT1 Z28, but hope this can help you in some way.

Also, have you tried posting on ls1tech.com? The LT1 tech section over there gets a few more hits than on here...

 

Rwing you definately have a distrubutor related EST spark timing problem. I heavily suspect the distributor. These early OPTIs were known for corrosion problems due to poor venting of the distributor. If you look carefully under the throttle body you should see a very tiny vacuum line going down to the cap and one coming from the cap to the inlet hose for the throttle body. Make sure the vacuum supply to the distributor is not kinked (Very common). Poor/no venting of the cap will result in the long connector (goes into the distributor on the r/side of engine) corroding and severe misfire/running problems. Also I would like to see you check the coil wire/tower for corrosion. Check all connectors and connections including grounds for the system. Do you know how to perform a voltage drop test? If not I will give instructions on a following post. PS I spent 25 years with GM as a Chevrolet technician and am very familar with your vehicle. Marty

 

+1

I've seen this kind of thing before, I would definately check the grounds first.