C4 ignition issue
09-06-2015, 11:44 PM
#1
Instructor
Thread Starter
C4 ignition issue
I've been reading the other threads about a similar problem that I have. I've noted the bad grounds problem, and the Opti problems.
My 1994 C4 LT1, is throwing "Pulse codes". I initially decided to change the OPTI since it has 70K miles on it and it still had the original. I replaced it with the MSD distributor. That however, didn't fix it.
Here's my question, before I start to dig into it.
When it fails, the RPM rises and then drops as the check engine light comes on. This is always a momentary thing. It acts like the timing is advancing raising the RPM. If I am right the ECM module has some timing control functions.
I no longer have the facilities and equipment to do much work on my own cars, other than simple things, so I will be taking it to my mechanic (reluctantly).
- Does the RPM change point to anything in particular?
- Where is the best place to obtain a service manual?
Thanks,
My 1994 C4 LT1, is throwing "Pulse codes". I initially decided to change the OPTI since it has 70K miles on it and it still had the original. I replaced it with the MSD distributor. That however, didn't fix it.
Here's my question, before I start to dig into it.
When it fails, the RPM rises and then drops as the check engine light comes on. This is always a momentary thing. It acts like the timing is advancing raising the RPM. If I am right the ECM module has some timing control functions.
I no longer have the facilities and equipment to do much work on my own cars, other than simple things, so I will be taking it to my mechanic (reluctantly).
- Does the RPM change point to anything in particular?
- Where is the best place to obtain a service manual?
Thanks,
09-07-2015, 02:48 AM
#2
Intermediate
I just got done with the same problem. Old opti left me on the side of the road and in need of a tow, so I bought a MSD, mostly due to fear of a DOA OEM.
Vette started stalling and dying at stop lights. I got a code 16 if I remember right. I trusted what the car was telling me and called MSD. Of course it was all my fault, I must have contaminated the unit.
They wanted to do all kinds of testing that would take weeks. So I just sent it back to Jegs and they sent me a new one.
The code and the problem went away for a while, but recently came back, this time no code. After about a week though the SES light came on and it gave me a code 22, which according to the service manual is a open circuit on the TPS. Popped the hood, and sure enough the blue wire was half broken at the connector.
Ran to Autozone to get a new connector and it died on me twice in traffic. Wired it in out front of the parts store, and no problems of that nature since.
All in all, the first MSD opti was ****, but just in case, check your TPS connector before pulling the opti again. Do stick with the MSD if yours is bad though, it gave mine some noticeable pick up and go, especially paired with new wires and MSD spark plugs. Just beware the hellhole if you put new wires in.
As far as the service manual, look on ebay or just let me know what you need to know. Mine is a '93, but beside a few computer changes like OBDII it should be almost the same. I hope this helps man. I seriously get sick when mine goes down and I never seen to find satisfactory answers online.
Vette started stalling and dying at stop lights. I got a code 16 if I remember right. I trusted what the car was telling me and called MSD. Of course it was all my fault, I must have contaminated the unit.
They wanted to do all kinds of testing that would take weeks. So I just sent it back to Jegs and they sent me a new one. The code and the problem went away for a while, but recently came back, this time no code. After about a week though the SES light came on and it gave me a code 22, which according to the service manual is a open circuit on the TPS. Popped the hood, and sure enough the blue wire was half broken at the connector.
Ran to Autozone to get a new connector and it died on me twice in traffic. Wired it in out front of the parts store, and no problems of that nature since.
All in all, the first MSD opti was ****, but just in case, check your TPS connector before pulling the opti again. Do stick with the MSD if yours is bad though, it gave mine some noticeable pick up and go, especially paired with new wires and MSD spark plugs. Just beware the hellhole if you put new wires in.
As far as the service manual, look on ebay or just let me know what you need to know. Mine is a '93, but beside a few computer changes like OBDII it should be almost the same. I hope this helps man. I seriously get sick when mine goes down and I never seen to find satisfactory answers online.
09-07-2015, 02:51 PM
#3
Race Director
We need an optispark sticky......
Another one replaces an OEM quality optispark, with mitsubishi opticAl sensor, with a russian roulette MSD optispark (known to have issues).
Here are some facts:
1. Oem optisparks, with mitsubishi optical sensor, were the best quality ever made as long as a sinple flaw is corrected.
2. Oem optisparks gen 1 optisparks arent available anymore. You may get really lucky and find one that someone had as a spare....
3. The flaw is on 92 thru 94 units... They need a custom vent harness added like on gen 2, with the appropriate air inlet, vacuum line, and flow reducers.
A simple cap/ rotor change, clean up of the optical area, and adding a gen 2 (95 thru 96) vent harness would have been all i would have done. I would have also checked bearings and sealed up everything with rtv silicone.
To add the vent harness, use a gen 2 opti cap (it has an air inlet fitting) as the air source and drill out: use one of the 3 weep holes as the vacuum source. Block off /seal up the other 2 weep holes.
Lastly, i would have added a weep hole mod to the waterpump to route any leaking coolant away from the opti for if/ when the water pump fails.
Good luck!!!
Another one replaces an OEM quality optispark, with mitsubishi opticAl sensor, with a russian roulette MSD optispark (known to have issues).
Here are some facts:
1. Oem optisparks, with mitsubishi optical sensor, were the best quality ever made as long as a sinple flaw is corrected.
2. Oem optisparks gen 1 optisparks arent available anymore. You may get really lucky and find one that someone had as a spare....
3. The flaw is on 92 thru 94 units... They need a custom vent harness added like on gen 2, with the appropriate air inlet, vacuum line, and flow reducers.
A simple cap/ rotor change, clean up of the optical area, and adding a gen 2 (95 thru 96) vent harness would have been all i would have done. I would have also checked bearings and sealed up everything with rtv silicone.
To add the vent harness, use a gen 2 opti cap (it has an air inlet fitting) as the air source and drill out: use one of the 3 weep holes as the vacuum source. Block off /seal up the other 2 weep holes.
Lastly, i would have added a weep hole mod to the waterpump to route any leaking coolant away from the opti for if/ when the water pump fails.
Good luck!!!
Last edited by dizwiz24; 09-07-2015 at 04:05 PM.
09-07-2015, 09:19 PM
#4
Instructor
Thread Starter
Today I ran her up on ramps and found the ground strap between the rear engine bolt and the frame by the battery. Though they look good, I cleaned the connections on the frame. I cannot get to the bolt on the engine block. After looking at the strap, one could question whether the crimp on the ends are still good after 21 years, or is there corrosion where it can't be seen.
This car has not seen rain in over 14 years, so things looked pretty good.
I am going to get a new strap and install it on the frame end and have my mechanic connect the other end on the block.
Anyway, after this, I drove about 15 miles and no hickups. Though that doesn't mean much.
This car has not seen rain in over 14 years, so things looked pretty good.
I am going to get a new strap and install it on the frame end and have my mechanic connect the other end on the block.
Anyway, after this, I drove about 15 miles and no hickups. Though that doesn't mean much.
09-07-2015, 09:28 PM
#5
Instructor
Thread Starter
OK,
I'm not clear on the fault codes and how to measure them.
What is the right way to check for fault codes? Use an ODBII and use it as a 1996?
I suspect that the new MSD is OK, as I have exactly, to a fault the same symptoms and conditions of fault that I had before, except I have not had it miss at idle.
Thanks,
I'm not clear on the fault codes and how to measure them.
What is the right way to check for fault codes? Use an ODBII and use it as a 1996?
I suspect that the new MSD is OK, as I have exactly, to a fault the same symptoms and conditions of fault that I had before, except I have not had it miss at idle.
Thanks,
I just got done with the same problem. Old opti left me on the side of the road and in need of a tow, so I bought a MSD, mostly due to fear of a DOA OEM.
Vette started stalling and dying at stop lights. I got a code 16 if I remember right. I trusted what the car was telling me and called MSD. Of course it was all my fault, I must have contaminated the unit. They wanted to do all kinds of testing that would take weeks. So I just sent it back to Jegs and they sent me a new one.
The code and the problem went away for a while, but recently came back, this time no code. After about a week though the SES light came on and it gave me a code 22, which according to the service manual is a open circuit on the TPS. Popped the hood, and sure enough the blue wire was half broken at the connector.
Ran to Autozone to get a new connector and it died on me twice in traffic. Wired it in out front of the parts store, and no problems of that nature since.
All in all, the first MSD opti was ****, but just in case, check your TPS connector before pulling the opti again. Do stick with the MSD if yours is bad though, it gave mine some noticeable pick up and go, especially paired with new wires and MSD spark plugs. Just beware the hellhole if you put new wires in.
As far as the service manual, look on ebay or just let me know what you need to know. Mine is a '93, but beside a few computer changes like OBDII it should be almost the same. I hope this helps man. I seriously get sick when mine goes down and I never seen to find satisfactory answers online.
Vette started stalling and dying at stop lights. I got a code 16 if I remember right. I trusted what the car was telling me and called MSD. Of course it was all my fault, I must have contaminated the unit.
They wanted to do all kinds of testing that would take weeks. So I just sent it back to Jegs and they sent me a new one. The code and the problem went away for a while, but recently came back, this time no code. After about a week though the SES light came on and it gave me a code 22, which according to the service manual is a open circuit on the TPS. Popped the hood, and sure enough the blue wire was half broken at the connector.
Ran to Autozone to get a new connector and it died on me twice in traffic. Wired it in out front of the parts store, and no problems of that nature since.
All in all, the first MSD opti was ****, but just in case, check your TPS connector before pulling the opti again. Do stick with the MSD if yours is bad though, it gave mine some noticeable pick up and go, especially paired with new wires and MSD spark plugs. Just beware the hellhole if you put new wires in.
As far as the service manual, look on ebay or just let me know what you need to know. Mine is a '93, but beside a few computer changes like OBDII it should be almost the same. I hope this helps man. I seriously get sick when mine goes down and I never seen to find satisfactory answers online.
09-07-2015, 11:15 PM
#6
Intermediate
Newb? Really? Maybe that's the way you would do it, but to assume that the OP and I are idiots just because we paid for an upgrade part, and you like to build your own does not make you better than us. Some people don't have the time to fabricate parts. Please have some respect.