Good thing his car has a computer controlled ignition system, that would and does increase the timing directly proportionate to the RPMs.

 

Check to see what RPMs the engine is turning over when cranking with the key,and see what they are when it fires while slowly increasing speeds pushing it off ,but the backwards running is very screwy.This problem needs to be fixed I feel for you man.

 

I agree with the others i believe it has to do with something ignition or timing related because im having similar problems. I decided to replace my whole optispark about 2 weeks ago due to a diagnostic test from chevy saying the optispark was cutting out. It was having the same symptoms as yours, backfiring etc. I replaced the opti with a new one from Jegs and same thing that happened to you, happened to me, Car would not turn over, would backfire from the intake, etc. I troubleshooted the crap out of it checking ignition, wires, plugs, making sure the pin was in correctly and it was. The only wierd thing is I put the old opti in just to make sure i wasn't going crazy, and sure enough it started right up. I figured it was a defective opti. Well i had them sent me a new one, put it in and same thing won't start. I figured 3rd opti's a charm so i tried one more and again wouldn't start, backfiring from the intake, engine cranking backwords after starting. The only thing i haven't checked yet is if would start if i jumped it. I will try that tomorrow when i go for another round with this thing trying to figure out whats going on with the thing. I know you mentioned when you did the tune up you replaced the opti with it. Ill post back tomorrow and let you know how it went.

 

alos is your opti vented or not? what year is your car?

 

`95, my opti is vented.

 

Lets clarify this, the car runs and IDLES perfect after you give it a rolling start?

 

yes.

 

lol well let me join this group. just got my motor back in and have removed the following. ac, heater, anti lock brakes, emission items. i think that is all. i have got good spark, new msd opti. i replaced the icm and coil today ( they were over 2 years old anyway). i can pull the coil wire and get fire ouot of the coil, pull a plug out and lay it on the header and get fire. i am going back outside now and spray some gas down the intake, even though i could swear i have plenty of fuel, by the smell. i will also put a gauge on it and see if i have enough pressure.

 

Reluctantly I pulled the timing cover off, and although the chain is a bit sloppy, it`s dead on for the timing.

 

I dont think it has anything to do with VATS(security) because your car shouldnt turn over at all if it was disabled.

The rolling start thing is odd. The only issue that should really make a difference with is if you had a bad battery. Thats or if the starter cable was internally burned/corroded creating excessive resistance. The starter turns the engine over at a normal speed, correct?

If the engine and optispark are timed correctly, the only thing that would cause the engine to rotate backwards would be the engine detonating/dieseling.

It doesnt really go along with the rolling start bit/then running fine, but are you sure you dont have bad gas? Since they've switched to the Ethanol blends, Ive seen countless cars come into my dealership for fuel related issues. Disconnect the fuel line and put a clear empty bottle up to it and crank. Look for visible seperation, debris, or an odd smell, although even then theres no guarantee its good.

 

You stated in the earlier posts that the car actually moves backwards from the engine rotating backwards. That means only one thing, the engine is detonating early. Maybe only a little bit, but it's still prior to TDC.

There really is no other situation that could generate enough toque to move the entire car backwards.

Just to make sure, disconnect the ignition coil. See if just turning it over with no spark causes the same thing to happen.

 

Is it possable at all for the VATS to manipulate the timing at all?? Is it possable for it to be turning over, but screwing with the fuel and timing? Seems something is causing the timing to be off and no to weak injector pulse durring crank but everything is normal when push started.


I`ve eliminated the possability of a bad battery(voltage drop) by installing a second battery for the starter. Plus I have a 60 amp charger which would/should provide pleanty of voltage. The starter turns over at normal good speed.

Opti must be timed right as it runs when pushed, and there seems to be only one way it installs.

 

Yes, I agree the spark is at the wrong time during crank. The car cranks fine, it`s only after you release the key from crank and let it go to the 'on' position does it then pop and roll over backwards. When it does, the injector pulse goes to full bright like it should be when cranking. It does not pop off over backwards with the coil dissconnectecd.

 

Well that narrows everything down a lot. We can rule out dieseling (which was a long shot at best anyway).

At this point the possible culprits are OptiSpark, Opti wiring harness, PCM, ICM, ICM wiring harness, ignition coil.

I would visually and rigorously inspect all of the wiring harnesses. Make sure they are immaculate.

Next I would troubleshoot the rest of the ignition system by following this guide:
http://shbox.com/1/4th_gen_tech2.html#opti_test

That should eliminate the ICM from the list. You said you replaced this, so I suspect it's good, but check it anyway. It'd be nice and cheap if it were the cause.

Finally you'll be stuck between the Opti and the PCM. My guess would be the Opti, because it sounds like you replaced the optical sensor and cap & rotor seperately.

If you have access to a friends PCM you could swap that in to do the final check.

Most likely you'll just have to buy a whole, fully assembled, ready to go, idiot proof opti.

 

I would buy a whole new GM opti, i don't know what brand opti you have on there now but if it is jegs brand then that might be your problem right there. I don't mean to bash jegs in any way but i think they have a defective "batch" of optisparks or something because i ordered 3 from them and they all made my car do the same exact thing as yours (except for the push start because i never tried it). I threw a new GM one on and it was fine. good luck.