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94 trans am no start!

8K views 25 replies 5 participants last post by  boredguy1187 
#1 ·
jumped into this nightmare a lil late started off just stumbling and dying while driving and progressed to completely not starting now, so far fuel pump and relay have both been replaced, not a vats issue security light doesnt stay on or blink at me, tested and regreased the icm, after the icm was regreased got it to start run and go back and forth in the driveway but now im back to a no start. PLEASE HELP!!!
 
#4 ·
Have you scanned it for codes? Have you checked the fuel pressure? How old is the Opti? When the ICM was tested, was it heated to simulate the heat soak the it experiences from it's mounting location on the driver's side head? Has the coil (there is only one) been checked? Did you check for a plugged catalytic converter? How old are the O2 sensors? How old are the plugs and wires? Did you check the plug and coil wire terminals on the Opti for corrosion?

Is the engine totally stock, or has it been modified?
 
#5 ·
engine is totally stock ,icm was heated during test, fuel is good i havent check spark yet didnt have the time to get into it that deep yesterday and if i had to guess the opti and coil are probably original, coil may have been replaced once and the wires look fairly new again not sure about the plugs
 
#7 · (Edited by Moderator)
Quit guessing and start testing. There's a thread on diagnosing the optispark on the ls1lt1.com forums in the lt1 engine section, sticky thread near top. I suggest you watch it and do tests. Also scan for codes, the 3 ignition biggies don't light the ses. They are dtc 16 opti low resolution pulse missing, Dtc 41 and 42 both icm codes. All 3 will leave you stranded and not light ses. If by chance you have a good spark when you test then put a fuel pressure gauge on and look for 43 psi at key on prime. Couple pounds low won't hurt but 30 psi or lower is a no no. Finally you must use an obd1 scanner to scan for codes, not one of the cheapees that simulate a paperclip across the terminals. If you don't have one you will have to find a pricey obd1 and obd2 scanner, start at around $250 + 12 pin adaptor to plug into your dlc. Or you can get a special cable to hook your car's dlc to laptop usb port and turn your laptop into a powerful scan tool. Get cable at www.aldlcable.com or www.tunercat.com Then you will need a scanner program. Freescan is such a program and it's free forever. Get at www.andywhittaker.com You can also get the trial version of DataMaster, which is a good scanning program that lets you record the scan results. Available at tunercat website as a trial. Good for 20 free scans. The advantage of these programs are they not only scan for codes but do running sensor logs also. That can help diagnose problems.
 
#8 ·
fuel is good and icm is good those are the things I have been able to test just started fighting with this thing for my roommate yesterday so I haven't been able to get to everything else before losing light and having to work today when I get home things I will be testing are the wires plugs and watching that video on the optispark, was looking for direction in where to go since this is strange how it ran after i greased the icm then a couple hours later I was back to it not starting and just trying to crank over
 
#9 ·
What does "fuel is good" mean? Did you test the pressure, using a pressure test gauge, and what results did you get? We want to help you, but you need to answer the questions in a meaningful way. "Fuel is good" doesn't mean anything without knowing how you determined that.
 
#11 ·
Another unanswered question - have you scanned it for codes?
 
#12 ·
I have not still trying to find a scanner I did say that I was trying to track one down just nobody has one anymore and I don't have the money to get one that will actually work on this thing no corrosion on the terminals but after watching that video he is almost double the mileage that it says the opti is good for, I've seen some people say theirs lasted into the 200k mark but I doubt thats common. I'm gathering energy and starting to crawl under to test spark at the plugs before I tear down to the opti
 
#13 · (Edited by Moderator)
The optical cam position sensor in the Opti sets codes. They don't turn on the SES light, as noted in a post above. But DTC 16 prevents the engine from starting, also noted in the post above. The high voltage section (conventional cap/rotor distributor) does not set codes.

I get sent data logs produced by Freescan and Datamaster, mentioned above. Often I can find problems from the data logs. Free download and 20 free uses of Datamaster is actually available directly from TTS:

http://www.ttspowersystems.com/DataMaster.html

For the cost of the cable ($50-100), and assuming you have a laptop, you would have not only a code scanner, but a data logger. Solves the problem of looking for a used Auto Xray or an Actron 9145. Freescan is good too. Datamaster just seems to have a better graphic presentation, and can also produce a .csv file that can be opened and manipulated in Excel.
 
#14 ·
ok tested at the harness for voltage that is good dont have someone here so i can check the ac current while cranking how do i test the resistance of the coil, im trying to run thru the tests in that sticky note you guys referred me to yesterday the best i can while flying solo
 
#16 ·
and I now want to light this thing on fire lol all the tests from the thread i was referred to came up as the coil being bad put in the coil still have no start, not sure where else to go with this thing now fuel pressure is still good a lil low but not way out of range getting spark at the coil, getting signal where next?
 
#17 ·
if it comes down to the Opti (and I think it is) be thankful they are less than 1/2 the price they were a few years ago, and, if need be, serviceable. You can now buy the optical portion, the distributor, or the complete unit...I've learned the hard way, don't run the motor past 6,000 rpm's... Opti's don't like that. :)also, with a 94, I think you're ok, but on my 93, the ignition wiring is slightly different, I had to locate several wire maps until I found the one that matched MY car. But the 93 is different, it's closer to a 3rd gen than yours.

if it comes down to the Opti (and I think it is) be thankful they are less than 1/2 the price they were a few years ago, and, if need be, serviceable. You can now buy the optical portion, the distributor, or the complete unit...I've learned the hard way, don't run the motor past 6,000 rpm's... Opti's don't like that. :)also, with a 94, I think you're ok, but on my 93, the ignition wiring is slightly different, I had to locate several wire maps until I found the one that matched MY car. But the 93 is different, it's closer to a 3rd gen than yours.Good luck with it!
 
#19 · (Edited by Moderator)
A code scan will tell you if the optical module is the problem. Pulling the cap will tell you if the HV section is beyond repair. Why guess? "Parts Replacement Roulette" is a very costly way to gamble.

Did you use Shoebox's guide to testing the ICM/Opti? You need to measure VOLTAGE on pins "A" and "D" of the ICM, not CURRENT. When cranking the engine, you test for AC VOLTAGE on the white wire to the ICM, not CURRENT.

http://shbox.com/1/4th_gen_tech2.html#opti_test

Did you test the coil using Shoebox's guide:

http://shbox.com/1/coil_testing.jpg

The price of a "factory" Opti has been INCREASING over the years. The only Opti's that are cheaper (1/2 the price) are rebuilt units, and units (cheap copies) that have been manufactured in China. These have terrible reliability records, often failing within a few miles, or even being bad right out of the box. Yes, some of them might last, but it's a matter of the failure rates. The cheapies fail a lot more often than the factory parts (Delco/Delphi).

Further complicating the issue is I've heard that GM is now selling GM remanufactured units, rather than new. I don't know if this is true, so there's another unknown in the equation.

I have heard rumors for years of the Mitsubishi optical module being available, but have yet to find one for sale. If you have a link, please post it.

The optical module in the Opti is good to at least 8,000 RPM. I've hit 8,000 RPM with mine, as documented in a data log (ooooppppsss... missed the 2->3 shift at the 7,400 RPM redliine). I only use the optical portion, but there are others who routinely spin the full Opti to 6,000 - 7,000 RPM. A buddy of mine also used only the optical portion, and he was spinning his 97 SS convertible (9.05 @ 156MPH at 3,850# race weight) to 8,000 RPM.

The difference in the 93 Opti/Ignition wiring is solely the PCM pinouts, and the inclusion of the tach filter.

1993 Opti/Ignition Wiring (courtesy of Shoebox)

http://shbox.com/1/93_ign_system_schematic.jpg

1994/95 Opti/Ignition Wiring:

http://shbox.com/1/95_ign_system_schematic.jpg
 
#21 ·
ok terminology was incorrect but i did the tests as they were stated in shoebox and on the video from the thread the dealership near me is selling remanufactured only is it possible the cap and rotor could be bad not the optical part of it? thats what im hoping for he threw the fuel pump at it blindly thinking thats why it wasnt starting only part i have thrown at it was the coil after doing those tests im still stuck tho so opening it up and taking a look at the cap and rotor doesnt sound like a bad idea if its corroded and making a garbage connection that could very well be my issue
 
#20 ·
ok terminology was incorrect but i did the tests as they were stated in shoebox and on the video from the thread the dealership near me is selling remanufactured only is it possible the cap and rotor could be bad not the optical part of it? thats what im hoping for he threw the fuel pump at it blindly thinking thats why it wasnt starting only part i have thrown at it was the coil after doing those tests im still stuck tho so opening it up and taking a look at the cap and rotor doesnt sound like a bad idea if its corroded and making a garbage connection that could very well be my issue
 
#25 ·
There is no way you can have 12V AC anywhere in the car, unless the rectifier in your alternator has died. Pin "B" on the ICM is the pulsed signal from the PCM that tells the ICM to fire the coil. Per the factory manual, key on/engine off you should have no voltage at all on pin "B". Then you indicated that you did have a variable AC voltage on the white wire (pin "B"). That would indicate you have an output signal from the Opti cam position sensor, but the AC voltage on the white wire is on the low side.

Then you indicate you have 0 volts on pin "D". Did you have the meter set to V-AC or V-DC? Did you check the ignition fuse?
 
#23 ·
The Opti has two major sub-components -the optical cam position sensor (back 1/2) and the cap/rotor (front 1/2). Either one can go bad all by itself. The optical cam position sensor is an electronic module. It can break down, heat soak, the optical emitters and receptors can get dirty of go bad, the optical shutter wheel can be damaged or dirty. If that happens, you get DTC codes.

The cap/rotor is no different than any other conventional distributor - the rotor tip and terminals can be burned up from high voltage discharge, the tip of the rotor can come loose, the rotor can come loose from the shaft, the cap can crack, the dielectric properties separating the routing wires in the cap can break down, there can be moisture buildup or there can be carbon tracking causing the spark to travel to the wrong terminal, or not at all.

The big problem with the non-vented Opti (93/94) is that the high voltage discharge in the cap creates ozone, and the ozone corrodes the metal internals. At 60K miles, mine was giving me intermittent codes and sudden stutters. The entire inside was full of rust, and the rust particles were blinding the tiny LED emitters and the receptors. The vented version was supposed to vent the ozone from the case. The seem to last longer. When I built the stroker, I converted to a vented unit.

On top of all that, the bearing is a cheap friction bearing, and it wears out. Oil from the timing cover can also flood into the case due to a bad seal. The rubber seal in the tower for the harness connector rots and leaks (it's right under the water pump weep hole). The ozone will then corrode the harness connector. And like any distributor, corrosion can build up in the contact terminals where the plug wires and coil wires attach.
 
#24 ·
his is the unvented one and everywhere I go has the vented ones...what kind of a nightmare am I running into replacing it with that or am I just running into parts people that are looking up the wrong stuff...which I believe could happen at an autozone or an advance or something but the dealership was even showing me pics of vented :-/
 
#26 ·
I did switch it over to v dc and got no reading and the ignition fuse is good

as in the fuse isnt broken should test at the fuse make sure there isn't a hairline fracture that I can't see and could be causing me all this grief for a 15cent part...I think I will when I get home anyway
 
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