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Hi All, bought a '96 with issues a few weeks ago. fixed the airbag light and ARS, now onto the misfire. OBD2 scanner pulled P0300, engine has a miss. Put my inductive timing light on each wire at idle and driver's side 1-3-5-7 have a clean pulse, no jumping or missing. Put the light on right side wires and 2-6-8 pulse correctly 2 or 3 times then the light flutters rapidly (3 or 4 times faster than the idle pulse) and you can hear it miss. Cylinder 4 seems to pulse fine, no flutter. Checked the resistance on the wires all below 7K ohms. Never saw this happen to an HEI distributor. Plugs look fine, not fouled. Before I start spending money on parts and taking the front of the engine apart was hoping to get some LT1 ignition advice. Thanks.
Hi All, bought a '96 with issues a few weeks ago. fixed the airbag light and ARS, now onto the misfire. OBD2 scanner pulled P0300, engine has a miss. Put my inductive timing light on each wire at idle and driver's side 1-3-5-7 have a clean pulse, no jumping or missing. Put the light on right side wires and 2-6-8 pulse correctly 2 or 3 times then the light flutters rapidly (3 or 4 times faster than the idle pulse) and you can hear it miss. Cylinder 4 seems to pulse fine, no flutter. Checked the resistance on the wires all below 7K ohms. Never saw this happen to an HEI distributor. Plugs look fine, not fouled. Before I start spending money on parts and taking the front of the engine apart was hoping to get some LT1 ignition advice. Thanks.
what I'm looking for here is does anyone know what would make the spark suddenly go from a steady pulse (2 per second or so) to 20 or 30 per second at idle. I've read that when the ICM goes bad car doesn't run, same with coil. I'll buy wires first I guess and see if that fixes the issue. Trying to avoid buying ignition parts until I find the right one.
what I'm looking for here is does anyone know what would make the spark suddenly go from a steady pulse (2 per second or so) to 20 or 30 per second at idle.
A bad opti spark.
You are viewing this on a scan tool, I'm guessing?
EDIT: I read that you're looking at light flashes w/a timing light? That probably isn't a very accurate way to asses what's happening. Can you get a scan tool on there and look at "Hi res" and "lo res" signals from the distributor?
When you moved the timing and could "hear it miss", was that miss happening only when you moved your timing light?
Last edited by Tom400CFI; Oct 16, 2017 at 12:58 PM.
You are viewing this on a scan tool, I'm guessing?
EDIT: I read that you're looking at light flashes w/a timing light? That probably isn't a very accurate way to asses what's happening. Can you get a scan tool on there and look at "Hi res" and "lo res" signals from the distributor?
When you moved the timing and could "hear it miss", was that miss happening only when you moved your timing light?
Don't have a scan tool, would certainly pick one up if at a reasonable price, recommendations? Didn't matter whether induction clamp on timing light was moved or stationary on the wire, I would get a few steady idle pulses then rapid flashes, like I brought the RPM up to 2000 to 2500. That's when I'd hear the miss. Missing under light, moderate, and full load driving as well. Thanks for your response.
I would get a few steady idle pulses then rapid flashes, like I brought the RPM up to 2000 to 2500. That's when I'd hear the miss. Missing under light, moderate, and full load driving as well. Thanks for your response.
When this happens, observe the tach. If it's moving around, then it is likely the pick up in the distributor. Is there anyone in your area from whom you could borrow a scan tool to watch the distributor pick up signals?
thanks. I replaced the wires (which) I was going to do anyway and no change, still getting erratic timing light on cylinders 2-6-8. 4 and drivers' side seem to be fine. Interestingly enough the fitting on the intake snorkel that's supposed to be a line into the opti is plugged with a screw. Will tear it down this weekend and order a new distributor. Just want to be sure the ignition module and coil are okay also. Usually when they go bad its a no start, no run condition? just basing that on other vehicles I've had.
here's some pics, air inlet hose was cut like mtw's. maybe the same idiot worked on our cars. the connector had broken and been "silicon glued" together. that orange stuff in the optical sensor section isn't paint. surprisingly the rotor and cap looked pretty good. i have no idea if this is original or aftermarket. hopefully this is whats causing the mss.
just wanted to update this thread for users that may be in search of a solution to the same problem or problems. Finally got it all bck together. Looks like the optispark was the main problem, no more miss, no more obd2 code p0300, cleared and did not return. I should mention that this is/was "while you're there" job. Also replaced ICM, coil, crank sensor, opti seal, water pump seal, front crank seal. I found replacing the opti a tough job. Could not get it to line up properly. Did not want to pull the new cap and rotate the rotor so i pulled apart the old opti down to the hub. plugged that back in and rotated the shaft to where she would drop. Pulled it out while holding in place and marked the back of the housing. Transposed the mark onto the new housing and after a couple of tries got it to seat properly. I've done a ton of "normal" SBC & BBC distributor pulls and installs with no problem, this opti BS however was a big PIA. Hope that helps.
Glad to hear it's all back together and healthy again. Just out of curiosity, which Opti did you end up getting?
i used an AIP optispark ordered from sac city corvette, a supporting vendor here I believe. 2yr warranty. Was one of the "lucky" ones that had to modify the connector, but no big deal.
i used an AIP optispark ordered from sac city corvette, a supporting vendor here I believe. 2yr warranty. Was one of the "lucky" ones that had to modify the connector, but no big deal.
That's where I got mine, as well. I hope it ends up being a decent unit. I cleaned and saved my Mitzubishi sensor out of the stocker for backup but now, I got a bearing for it so I'm going to rebuild it and save it on the shelf in case the AIP unit takes a dump. A person can get pretty fast at changing Opti's but I'd rather not have to.
My connector needed to have the little tab snipped out also. Like you say, not a big deal.
I did hit my entire motor with Gunk and a hose yesterday. The AIP Opti fired up without a hitch after the drowning....but I did run a bead of RTV around it prior to install.
'96 P0300, random misfire, ignition issues.
