Morning y'all,

I'm after a little assistance with my poor '93 RRC. It passed 250k miles about two months ago, and it's been behaving like a grumpy old woman ever since. It starts fine, idles fine, and goes fine... until it's been running for 15-20 minutes. It... stutters. For example, at 55-60mph it'll be smooth one minute, and the next the revs are all over the place. It feels a lot like fuel starvation to me, and there's no fault lights to speak of

So far.. I've cleaned out the IAC and replaced the IAC valve itself, changed the coil, replaced the fuel temp sensor, inspected (and replaced) the plug wires, checked every ground I can find, checked the dizzy gap, and replaced the fuel pump and filter (hey, it's only a ten minute job!). The alternator is virtually brand-new, as are all the belts and spark plugs.

Any ideas where to check next very much appreciated. I'm not really sure where to go next - except perhaps the TPS (again) or a fault in the wiring harness rather than a sensor itself.

 

after it happens take the battery cables off the alternator and bolt the b+ wires together
insulate them so they don't short on anything and roadtest. if the problems gone it's the alternator.
Other than that I can only suggest you make sure you have a factory distributor cap and rotor installed,
or poss tps problem. you can check the tps with a volt meter by back probing the blue and green wires.
the voltage should be from approx .3v closed to 5v at full. an open circuit or 0v anywhere in between would indicate a bad tps.
That should keep you busy for a little while..

 

Well.. after a day of teeth gnashing and hitting things with hammers, it turns out that the issue was my (newly-rebuilt) alternator. I put the original 1993-vintage Marelli alternator back on it out of sheer desperation, and it runs like a champ. Well.. a champ with an (optimistic) 50A alternator installed. At least I know where the issue is though

 

great glad to hear that. 50 amps is better than no amps. lol

 

My indy alternator shop forman drives a Rangie. He told me the rebuilt by mass producers use China parts, poor quality control, lots of failures. He rebuilds a Rover alternator (regulator, brushes, etc.) for under $100. I suspect this is the going rate in many places. We pay the price for the quick service of the corner box store.

You sure on the 50 amps? The 88 version had a Lucas 80 amp, perhaps yours has a bad diode and is only pushing out 50 amps.