Sportrak Running Rough


I've been having a problem with my engine over the last couple of weeks.

When the engine gets hot and its idling, it only runs on 3 cylinders, with unburnt fuel pouring out of the exhaust.

After revving it a few times it fires on all 4.

I changed all the plugs, leads and distributor cap.

It ran fine for about a week, and then it started playing up again, but not as bad.

I took one lead off at a time, and found the 3rd cylinder back was the problem.

When I took the lead off it, it made no difference whatsoever.

I changed the lead with the old one and it ran fine again.

Another week later, its running rough again. Could it be the old lead is breaking down?

It only happens when the engine is hot. It's getting fuel, its all going out the exhaust.

Any ideas would be much appreciated.

Spark plug's cap.

Problem must be electrical. Since its firing on three cylinders the fault must lie between the distributor's rotor and spark plug electrode. Check the high tension cable again and renew the spark plug cap which might be faulty.
When the 3rd cylinder is not firing, have you tried detaching the problem spark plug and connecting a spare spark plug ... then ground the plug to earth on the engine and look for a spark at the plug's electrode? Use insulated pliers to hold the spark plug! If spark is intermitant/none then detach the spark plug cap and repeat the proceedure for the bare wire .. or push a nail into the cable to act as an electrode. [The spark plug gap is 1mm.]
If there is no spark then renew the high tension cable and try again.

Finally sorted

I found it was the HT lead which was faulty. I borrowed an electrical meter off an electrician at work which clips on to the lead and measures the frequency of the sparks.

When it got hot it just broke down.

The car shop I bought the leads from gave me a whole new set today, and its running fine now.

Thanks for the help.

I think I spoke too soon.

The engine has once again started playing up. The thermostat got stuck again, so I took it out and ran without it. Everything was fine, just running cool. A couple of days later, after driving 15 miles or so, it started to run rough when idling again, and the temp went up to over half.

When I started it from cold this morning, it started on 3 cylinders, and went to 4 after revving.

I changed spark plugs over, leads, checked dizzy cap, rotor arm and still no different.

It is still the 3rd cylinder playing up.

I am thinking it is either something to do with the timing, ie. the distributor itself, possibly governor weights or vacuum advance or something, or I was thinking possibly problem with a valve or the injector letting to much fuel in.

I think that the problem with the engine is probably causing the engine to overheat, but I can't work out what is causing the problem in the first place.

Has anybody got any ideas about what the cause could be?

Thanks for any advice.

Think I've found the problem

I think that the problem is the fuel injector. When the engine is running rough, I can disconnect the injector cable, and it makes no difference whatsoever.

Also, when I started it this morning, it seemed to be flooded, so I think the injector is constantly leaking fuel into the cylinder without atomising it, hence no detonation, as there is only air in the cylinder.

It would also explain the strong smell of petrol from the exhaust and the very poor fuel economy I am getting.

I am going to call the AA out tomorrow, and see what they think, and if it is the injector, send it off to be tested and ultrasonically cleaned, which I hope will solve the problem.


CD guide suggests checking all wires and connections between ECU and injectors. Also remove and clean the earth connections.


I checked all the wires with a multimeter, and they all came up with the same reading - 3.5v.

I'll check the earth connections, and the AA man will probably be able to put some diagnostic test equipment on it.

If it turns out to be the injector, I'll send them all to be cleaned.

I'll let you know what I find out. Thanks


The AA man also thought the injector could have been the problem, so I took them all out.

They were all extremely dirty and its not surprising they weren't injecting properly. The injector in #3 cylinder was the worst, which explains the problem.

I have sent them off to be ultrasonically cleaned and tested, which costs around £12 each including delivery, which I don't think is bad.

They should be back by Tuesday, and I can get the car back on the road.

Thanks everybody for the help and advice.