Riddle For The LT1 Guys
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
Likes: 0
From: Northern Kentucky
Well TPS sensor's will allow fuel pressure an spark, but wont let the injector pulse so if it's pulsing its probably not that. Try disconnecting it though for ***** and giggles since that takes all of 10 seconds, try disconnecting the MAF sensor too. Aside from that, PCM maybe? Something isn't adding up, the motor will fire if it is getting fuel in the cylinders, it might run like **** but after fuel builds up spark will ignite and noise shall happen, haha. Just double check the injectors pulsing.
Just because the opti is new dont rely on it, I installed a brand new one from the GM dealership, did exactly what you are describing, I even pulled the plugs, put my finger over the hole, cranked it over and checked for spark on the compression stroke on several cylinders, looked to be firing exactly at the time it was suppose to, Got stumped, replaced the opti,..............Cranked right up..
Thanks for the suggestions guys. Keep them coming.
Teching In
Joined: Apr 2008
Posts: 5
Likes: 0
won't start and possible cure My 94 Z wont start. I can crank all day and it wont fire. It sounds like the timing is WAY retarded. It sounds like it's trying to fire but it just wont start. I'm looking for suggestions. This originally started as an intermittent no-start issue when it rained. The car wouldn't start, but after it dried out a couple days it would start. When it ran, it ran great. Now it wont start at all. This is killing me cause this car has been dead reliable for the first 103,000 miles.
Here's what I know:
I have fuel. It maintains 42-44 lbs of fuel pressure during cranking and the injectors are firing (I pulled the rails and watched).
I have spark. The spark is very strong at all the plugs.
I have air. No obstructions of air flow.
I have plenty of compression.
What's new:its your opi-spark, i had the same problem, i have a94 transam. now no problem..go JEGS.com. Good prices, (cap&rotor is a option)also,check your coil. i bought a new MSD coil, it blew the next day.i put the original back on,it started right up. hows your performance? between 50-60 mph mines acts like it wants to stall, after that 60 its normal. i live in seattle, its wet here alot.
Optispark
ICM
Spark plugs
Spark plug wires
Ignition relay
Head gaskets
Heads just milled
Intake gaskets
What's tested good:
Opti (reference voltages tested good)
Opti pigtail connector
Coil
Coolant temp sensors (both)
PCM (swapped with another good PCM)
Does anyone have any ideas? It has everything necessary to run but wont. Why would timing be so far retarded?
Here's what I know:
I have fuel. It maintains 42-44 lbs of fuel pressure during cranking and the injectors are firing (I pulled the rails and watched).
I have spark. The spark is very strong at all the plugs.
I have air. No obstructions of air flow.
I have plenty of compression.
What's new:its your opi-spark, i had the same problem, i have a94 transam. now no problem..go JEGS.com. Good prices, (cap&rotor is a option)also,check your coil. i bought a new MSD coil, it blew the next day.i put the original back on,it started right up. hows your performance? between 50-60 mph mines acts like it wants to stall, after that 60 its normal. i live in seattle, its wet here alot.
Optispark
ICM
Spark plugs
Spark plug wires
Ignition relay
Head gaskets
Heads just milled
Intake gaskets
What's tested good:
Opti (reference voltages tested good)
Opti pigtail connector
Coil
Coolant temp sensors (both)
PCM (swapped with another good PCM)
Does anyone have any ideas? It has everything necessary to run but wont. Why would timing be so far retarded?
I had the exact same symptoms you are describing and it was the coil. I still had spark at the plugs but it was not strong enough. I tested the ICM, TPS, MAP and even tried with a different PCM. Then replaced the ICM and OPTI too and still no fire. As a last resort, I put a crappy, rusted stock coil on from the junk pile and it fired right up!! This was on an MSD coil with less than 100 miles. 
If you don't have another coil, i think they are like $15 bucks for stock replacement ones at Autozone. Might be an inexpensive way to see if thats your issue.
If you don't have another coil, i think they are like $15 bucks for stock replacement ones at Autozone. Might be an inexpensive way to see if thats your issue.
Last edited by TX20D; May 1, 2008 at 04:06 PM.
hmmm.. I wonder why they are easier to install wrong? As long as you get the cam pin in the right slot.. the slot thats not rounded off but more rectangular. Thats the only way it goes in if I'm thinking correctly.... sorry I hijacked your thread but I know what your going through and I'm trying to find answers too lol
The only reason why it is "easy" per se is because those who screw this up think it's necessary to force the opti on. There should be absolutely no resistence whatsoever when sliding the opti into place. It should go on like it was meant to be there.
More courtesy of shoebox:
The only reason why it is "easy" per se is because those who screw this up think it's necessary to force the opti on. There should be absolutely no resistence whatsoever when sliding the opti into place. It should go on like it was meant to be there.
The only reason why it is "easy" per se is because those who screw this up think it's necessary to force the opti on. There should be absolutely no resistence whatsoever when sliding the opti into place. It should go on like it was meant to be there.
Had a 95 car give me crap like that. Everything was correct. Started checking connections and found the terminals on the harness itself to be corroded. Replaced with a new one from Caspers (goes from opti to main harness) and the problem went away.
On a 93 car, there was corrosion on the terminals that plug directly into the opti... Replaced the terminals and problem solved... This car would fire and immediately die... Or it would sit and do nothing with the tach going crazy at key on.
On a 93 car, there was corrosion on the terminals that plug directly into the opti... Replaced the terminals and problem solved... This car would fire and immediately die... Or it would sit and do nothing with the tach going crazy at key on.
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TECH Fanatic
Joined: Jul 2007
Posts: 1,420
Likes: 0
From: long island new york
i had the same problem, where did u get your opti. the little shaft was shoved in the wrong way ruining everything. the car would almost sound like it would fire and then just crank. the little shaft was forced in wrong. no rebuilt optis.
I had the exact same symptoms you are describing and it was the coil. I still had spark at the plugs but it was not strong enough. I tested the ICM, TPS, MAP and even tried with a different PCM. Then replaced the ICM and OPTI too and still no fire. As a last resort, I put a crappy, rusted stock coil on from the junk pile and it fired right up!! This was on an MSD coil with less than 100 miles.
If you don't have another coil, i think they are like $15 bucks for stock replacement ones at Autozone. Might be an inexpensive way to see if thats your issue.
If you don't have another coil, i think they are like $15 bucks for stock replacement ones at Autozone. Might be an inexpensive way to see if thats your issue.
I 2nd that. It depends on what type of spark tester you use, I was using one that was very sensitive and i thought i had spark, then i used a tester that you can set gap on and it could not fire it.
also, i've seen some cars have the same syptoms and the EGR valve was stuck wide open.
Thread Starter
On The Tree
Joined: Mar 2002
Posts: 171
Likes: 0
From: Northern Kentucky
Forgot I had this thread open, but it turned out to be the coil afterall. I had tested it, my dad tested it, and autozone tested it and all came up good. Turns out the coil was firing, just weak.
I found it when I disconnected the MSD ignition. I noticed the coil would only fire with the MSD connected, that sent up a big red flag so I decided to swap out the coil and it lit right off. The car's been running great.
I found it when I disconnected the MSD ignition. I noticed the coil would only fire with the MSD connected, that sent up a big red flag so I decided to swap out the coil and it lit right off. The car's been running great.
we just recently had to pull an MSD opti off, brand new install and it was bad, sounded the same as your problem. sent it to msd and they sent a new one back because it was defective, it does happen,
TECH Fanatic
Joined: Jan 2004
Posts: 1,157
Likes: 1
From: Kingfisher Oklahoma
The color of the spark means more than people think, You figure if its just an orange or yellow in regular atmospheric pressure imagine how weak it will be in 10 times atmospheric pressure, needs to be blue or white !!!
