Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Intermediate rough running

Good Afternoon
Vehicle is a 1995 Plus 8. It has a total of 9,600 miles on the odometer. As far as I know the engine and electronics are as factory and untouched. Headers have been added.

3 of the past 4 times I've had it out I've experienced a short period (1/4 mile or so) of rough running. It acts as if one spark plug is not firing. Two of the three times the engine was warmed up. Today it started cold. In fact, for the past three trips it happened on trips 1,3 and 4. Trip 2 was not a problem.
Also seems as the problem doesn't happen until about 1 mile passes. Misses for about 1/4 or so miles, and then runs normally. When it happened on trip 2, I drove another 30 miles with no problem. Just during that 1/4 mile at the beginning. Today it happened from cold engine start. About 1 mile and it started missing. Lasted about 1/4 mile and went back to normal. Drove another 5 miles to get home with no problem.

Thoughts?
Suggestions?

This is a "where do you start" problem.

So it's either fuel or spark.

Fuel could be old? or there may be water in the tank from condensation, which is getting drawn through occasionally.

Spark might be an intermittent fault such as HT leads, plugs, or anything electronic in between. Experts will tell you that electronic systems either work or they don't, and yet I had an intermittent fault on a module which drove me mad until that was the only thing left untouched.

Thomas, I had some similar troubles last month on my Plus 8 (97). Misses and rough running, to begin with just for parts of the journey then continuously. I initially put it down to fuel however that did not solve it. I spoke to BHM and replaced the distributor cap, rotor arm and all plug leads, This solved it, and all is now well. BHM supplied the parts

Run the engine in the dark and look for electrical discharges around the distributor. (assuming it’s got one)
Change the rotor arm anyway, often an issue on these units.

Sounds like the ignition amplifier breaking down

My guess too.

A 1995 +8 should have 14CUX fuel injection and distributor ignition.

The ignition module is normally mounted on the inner wing valence , left side looking forwards, just in front of the engine. This is a relatively cheap part so is probably worth replacing anyway. If someone has replaced this with a so-called "superior version" throw it away and revert to standard

Appears that the ignition module has been replaced with a unit called an A&R PowerAmp II, by RPi Engineering. It is located just aft of the distributer. It looks to have been wired into the system, so I have no idea what the original configuration looks like. I did see one purple wire at the distributer, and it had been cut for some reason.

I also found the vacuum line to the distributer laying loose. Fixed that and put back on. Doubt if that has caused the problem tho.

I have the Discovery manual, so HOPEFULLY it will provide me with the wiring and a few pictures of the original configuration.

Sure wish I had another 95 +8 around here for comparison!!

I might have guessed as much . Throw that RPi unit away and rewire back to standard.

With luck the ignition module will still be on the valence, but without the top lead connector (? terminology) in place . Also with luck the RPI unit will just be spliced into the wiring and its removal should still give you the possibility to connect everything back up as standard . If this is not the case I can start by taking a few photos of my set up for you so you can get a general idea

PS I too had an RPI amplifier, and it threw up all sorts of issues , so was eventually ejected from my car and garage with some force.

Here is a couple of shots just taken from my 1999 3.9 and standard I believe, they are a bit limited but might help.
Everything you have said in the way of symptoms seems to point to the amplifier and Andy's first hand experience of the RPI unit endorses that I think. Be wary of even new one's as I know someone that spent hours searching and in the end the new one was faulty, not too helpful but don't rule it out of your analysing.

I would appreciate ANY help you can give me.

I did not see any ignition module on the valence, but will look again.

Thanks for the help. Have to leave home in just a bit, but will get back to you.

As I said before, the only cut wire I could see was a purple one.

Took a pic of the Distributer info. HOPEFULLY it will show!!! Not real up on posting pictures.