Driving to work this morning, car lost power (stayed running, but failed to accelerate). Pulled over and revved the engine - it would jump to 2500 or 3000, then sputter, drop to <500, backfire (?) a bit, then level off at a normal idle. I turned it off and restarted it and drove for about 8 minutes normally before recurring. Fortunately by that time I had it in the driveway. In park at idle, I can rev it up to 2500 for maybe a minute before the same issue occurs...seems to be worsening a bit as I experimented.

I'm guessing ignition system (load doesn't seem to affect it, and I have replaced the fuel filter recently, as well as driven for quite a while with no issues); so far I've only replaced the spark plugs. Is there any way to troubleshoot the system? If not, I'm planning to replace wires, ignition module, and maybe the coil. Anything else I should take a look at initially?

Also, in regards to the coil/ballast, is built-in ballast vs external preferred? I'm seeing coils that go either way.

I'm not very experienced in this area; all counsel welcomed!

Thank you!

 

The fuel system is a likely suspect. "...I have replaced the fuel filter recently, as well as driven for quite a while with no issues" sounds like crud has restricted your fuel filter again. Rarely does an electrical problem act as you've described. Check your fuel pressure before and during when it's acting up, if you can.

Dave

 

Hmmm…interesting. If the filter was stopped up, wouldn’t it be 1) more consistent and 2) worse under load? I did notice the pump sound…seemed a bit louder than usual. Would that be consistent with restricted pump?

I thought intermittent running issues was kind of a hallmark of electrical issues, but maybe I’ll check out fuel first.

 

if you are going to change electrics, don't rush out and spend heaps of $'s replacing items that may not need to be, have a good multi meter and check items first as in ohms resistance of leads and coil Ohms values, if you need to replace the coil - replace with correct ohms value - external ballast will work, invest in a fuel pressure gauge (cheap) worth your while, rubbish in the fuel line can move giving an intermittent restriction but your description points to electrics

 

If you do spend money don't overlook the ignition (key) cylinder as a potential area that could cause problems. I've read these can go bad and cause sporadic electrical issues.

Make sure the ground on the back of the head is cleaned and tight.

Possibly upgrade the ignition module to one made by Pertronix.

And lastly, consider swapping to a Pertronix distributor that does away with the potentially problematic ignition module.

 

Sounds like the consensus is....it could be fuel or electrical.

I'll plan to start with a fuel pressure test (think I will run the gauge off the cold start injector) and see if I can recreate issue, and if fuel pressure changes when I do. Pressure should be 32 - 36psi at the rail while running, correct? How much if at all would it drop when revving to ~3000 rpm?

Have ordered new wires...those are easy and I should do them anyway, and I already have an ignition module so if I don't get love from the above I'll likely swap it out as well.

Hopefully have a solve soon!

 

Alright! It was junk clogging up the fuel filter. Replaced filter, and switch it to my left tank (which is new) and it seems to be running well. Thank you all for the thoughts, and good call Dave! @LT1 jaguar