Saturday night, I'm driving home with no issues. I've been having some stumbling at lower rpm's lately and a consistent miss in the higher RPMs (over 5000), but on this night everything was working as intended and kept under 5000 rpm (I suspect a wearing fuel pump, and thus have not been taking it so high in the RPMs lately to extend its life). Less than 2 miles from home, I do a 2nd-3rd gear pull (shifting around 4500 - nothing crazy) when the engine suddenly died on me. No warnings, no power drop, just the "check gauges" light to comfort me. I pulled over and checked out under the hood and under the car, and everything looked okay. Upon trying to restart the car, I heard the fuel pump prime, but the car wouldn't start. There was a decent amount of backfiring though.

The following day I returned to the car and read 43psi at the fuel rail with a pressure gauge (good, I've got fuel). I then pulled a plug and held it close to the header to check spark, and I did. I had a buddy use his timing light to check spark on all cylinders, and sure enough they're all firing (good, I've got spark). I lastly checked the intake for any blockage, and all was clear (good, I've got air). Suspecting that all that could be left was timing, I used that same friend's data tool to scan for codes. A few older codes popped up, but after clearing them no new ones were triggered. We did notice, however, that the scan tool read 45rpm with the engine off.

Here is my working theory: I think my opti is tapping out. A nonzero engine speed with the engine off indicates a crank position sensor failure to me, though I've found my car doesn't have one - rather the optispark has a cam position sensor internally that it uses to read engine speed. Additionally, I'm considering the possibility that I may have misidentified my 'fuel pump' problems (stumble at lower speeds, consistent miss at high RPM's, occasional slow start) for opti problems. Blend this with the sudden death on the road and the backfiring, this is my current best guess. My opti is 70,000 miles old, so it may just be it's time. I wanted to get some additional opinions and alternative perspectives before I go through the rigamarole of sourcing a new opti and changing it in the Lowes parking lot!

 

It's normal to get a 45 RPM reading when the key is on/engine is not running. Shows up that way in every data log I've ever looked at.

My guess is the rotor in the Opti either came loose (not unusual for the mounting screws to come loose over time, need Loc-Tite before installing), or the tip of the rotor (contact) came loose.

 

You might be lucky and only have a rotor/cap issue, which is common with a sudden engine stoppage scenario. 70k is not a death sentence for the other internals of the opti, if it looks clean inside.

 

Thanks for the feedback you guys!

Injuneer, it's good to hear he 45 RPM reading is normal when the key is off, but I'm wondering why that is? I would assume the engine speed is read by the optical sensor in the Optispark, but it sounds like that isn't the case. Curious, quite curious. In any case, that's good to know for future readings!

You make a good point Shoebox - I can't be sure whether this is a death sentence or not, and I won't know really until I take it apart (which I do plan to do). However, with this being my only car, I've got to get it back on the road quick! I did some research and ordered a Petris Enterprises Optispark, and plan to diagnose the failed Opti once the car is running again. Hoping to fix that one and have a spare ready to go should any new problems arise!

Are there any tips/tricks to doing the job, or it as straightforward as I think it is? (Disconnect battery, drain coolant, remove belt, remove crank pulley, remove water pump, remove distributor, change seals and reassemble). Never done this job before so if you've got any advice I'll gladly take it!

 

Shoebox has a procedure for camshaft swap. The removal of the Opti is included. The removal of the radiator is optional if just removing the Opti. But it covers things like removing the AIR pump, because it is held on by one of the water pump bolts.

4th Gen LT1 F-body Cam Removal

Scroll down to “Disassembling The Front of The Engine”.

You don’t have to remove the crankshaft hub.

Reinstall is covered in a separate guide:

4th Gen LT1 F-body Cam Install

Obviously you have to skip steps that are related specifically to the camshaft. If unclear ask here.

The factory service manual will also prove useful:

https://www.mediafire.com/?40mfgeoe4ctti

The water pump driveshaft seal in the timing cover is easy to mess up.

It's so long ago (24 years) that I did anything with the Opti I can’t remember all the details.

 

Thank you for the resources! Fortunately, the job isn't too difficult given my dad deleted the Air Pump and has previously swapped to an electric water pump. I got about halfway through the job before realizing I'll have to remove the crank bolt to install the pulley! I've read the crank bolt is torque-to-yield, so I've ordered an ARP bolt and will finish the job when it comes in!

I'm looking forward to getting back on the road. The Petris website and delivery has given me confidence in a quality part so I'm hoping for the best from it! I've been driving my friend's Miata as a loaner car in the meantime and I'm missing the power from the Z

 

You don’t have to remove the crank bolt to remove or install the damper/pulley. Only if you remove the crank hub and there’s no reason to remove that.

http://shbox.com/ci/balancer_hub.jpg

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

If you’re lucky and things are not too rusty you may not need the claw puller. The pulley is not an interference fit.

 

I have the same situation as Rob mentioned you and it was the case from the first after all inspection. It was the rotor and cap problem, as rotor usually fells off because of mounting screws get loose.

At your place I would try with the new Standard Motor Products or VWE cap&rotor kit and fix a problem within $100.

Also, I would inspect for the any undesirable cam movement, because it can trigger this situation also to rip off this plate from the rotor picture. Try to figure it out that first.

This is the common problem. First time when I had this problem was last winter and the second time was 2 months ago. This is best to be fixed like on the another picture where is presented MSD rotor.

The MSD rotor brass solution with the screw attached on these two sheet metals, don't know precisely how do you call it

 

Update:

Thank you all for your advice and resources! My issue was indeed my optispark. I've gone with a Petris Enterprises Optispark to replace the old part, and thus far it's been running great! Fingers crossed it continues to do so Friendly reminder to all those doing this job to put thread sealant on the Water Pump bolts. Can't believe I spent as much time as I did hmm-ing and ahh-ing trying to decide between a FelPro or OEM Water Pump gasket when after all that deliberation I almost forgot the thread sealant!

Take care everyone - I'm certain I'll be back on here next week when my fuel pump finally kicks it!

 

Thanks for following up with resolution of the problem. Wish everyone would do that. Glad you got it fixed.