Engine stutter and other problem

[PhilKing]

I have two very annoying problems that developed during my recent trip to Le Mans, could be that they are both unrelated but asking if anyone has an idea for either or both.

 

I recently fitted a 1.8k series eu3 engine with roller barrels and MBE ecu changing from a 1.6k EU2 roadsport carusing the loom from the EU3 engine. Everything has been running well, but on the trip after about 1 hours motorway running it starts to develop a misfire or engine stutter better way to describe it. This clears if you accelerate, but if you try runnning at constant speed the engine starts to stutter. This developed into a constant problem unless accelerating, making driving it quite difficult. Was fortunate enough to find a MG / Rover dealer near Le Man and changed the coil packs, HT leads and Spark plugs. Seemed fine driving around, no stutter or mis fire, until started driving back and the same problem developed. The tick over has also changed it seems to be searching for revs varying from 1000rpm to 1500rpm and feels lumpy.

 

Second problem is the lights now seem to pulse as do the interior switch lights and brake lights. I changed the alternator over from old engine onto this engine, stupid question are the alternators different.

 

If anyone has any ideas on these problems very much appreciated.

 

Thanks

[Myles]

Did you have the engine re-mapped after your changes?

[PhilKing]

No the MBE was mapped to the engine so just plugged it in and went with that.

[Clousta]

Your problems might be related.

 

With heat soak on the motorway and after a while running the rectifier (diode) pack/voltage regulator in the alternator could be breaking down. The voltage output will not be stable, hence the pulsing of the lights. If the voltage fluctuation of the alternator is significant enough that you can see it in the fluctuation of the lights it must be quite major and not smoothed out by the battery. So the ECU and more importantly sensors such as the the TPS and the MAP, which rely on a stedy voltage will not be getting a steady reading and hence their inputs to the ECU will be erratic. Hence when you are trying to maintain a steady speed the air fuel mixture and the throttle input will be continuously changing - causing the stutter. This will be more pronounced at idle when small differences in TPS and MAP will affect the revs significantly (the idle speed).

 

Find a proper alternator specialist who will put your alternator on the bench and properly test it rather than just sell you another one (otherwise you might not find out whether the alternator was the problem until you are in to another long trip).

 

I had a similar alternator failure but the impact was minimal (manifesting itself as a faintly glowing ignition light and reluctance for the ignition light to extinguish until 3,000 rpm after starting) as the crossflow hasn't got any electronics!

 

Good luck.

[PhilKing]

Thanks for the advise, will look at getting the alternator checked, make sure it is working properly. Have heard that failing batteries can effect ECU so makes sense with alternator, it felt like the engine was not getting a spark hence the changing of the coil packs etc.

 

Cheers

[Mick Day]

Also check your engine earths...................

[PhilKing]

Thanks Mick, will do that first,

 

Cheers

[Racingshoe]

I am experiencing a very similar problem on my 7. Had my alternator checked today and it seems to be fine (although it was cold).

 

Will look at my EU2 coil next.

[PhilKing]

Thanks for all your help, i have now changed the alternator and that was the cause of the pulsing on the lights it was fluctuating between 14.5 and 16v, appreciate your help with that would not have considered that as an answer.

 

The car appears to be running better but it still has the engine stutter. On the short run I have given, although the car was at proper temp, the stutter was not as pronounced but that could just be that I have not had an opportunity to get the car running really hot as it was on the long motorway trip. The output I have checked and it is running steady 14v now, but could the coil packs have been damaged with the alternator issue and so need changing again. Any suggestions appreciated as I really want to get this sorted for what might just be a nice summer and a few track days are in order.

 

Thanks

[Clousta]

Glad to have been of service.

 

I would agree with your way ahead. Take it on longer trip and see if the stutter is the same. Then go down the changing the coil pack route.

Always one step at a time. This makes a nice change for a systems engineer from fixing submarines for a living *cool*

 

[Racingshoe]

I'm in exactly the same boat as you Phil.

When cold the car is fine. After about 15 minutes when it is fully warmed through, it is undrivable on a light throttle. If you go to accellerate, it is instantly ok however.

 

Have had alternator checked on a bench and it was ok. Changed the regulator just in case. Also changed my throttle pot and coil, plus HT leads and coil king lead. No improvement.

 

Will check plugs tomorrow. Other than that the only thing I can think of is the Emerald map as it is a borrowed one while i've been running the engine in.

When cold I don't get any pops and bangs from the exhaust, but the misfire starts when hot, and I get pops and bangs on the overrun. Could there be a coincidence? Anything to look for on my ECU map?

[Racingshoe]

Am now considering a couple of options to investigate:

1) o2 sensor. My car is not running a lamda sensor as it is EU2, so it only has o2 readings to go off when adjusting fuelling for emissions.

 

2) ignition timing in my Emerald map. Could try playing with this a little, but i'm no way near qualified enough to know what i'm doing. Any advice?

[PhilKing]

Hi Racingshoe

 

like you I am finding the whole thing very fustrating it runs really well when cold only to drop in the stutter when hot. Will check the TPS next to see if that makes a difference, but like you I am no way qualified to look at a map and work out if that is the issue. After that I can see if the lamba sensor change helps, all worth a try. Also possibley check the coil packs again as the HT leads and plugs have all been changed, so maybe got damaged with the varying voltage.

 

If all this fails I am guessing a trip to road and race to get them to check the map, but they mapped the engine originally and it has just been a drop in with the same engine and MBE so will try that last.

 

Clousta having got stuck with no hood on the motorway for two hours in the pouring rain as the closed the motorway on the way back from Le Mans your skills with submarines could have been useful.

 

Thanks for the tips will try these and update the results.

[Clousta]

Clousta having got stuck with no hood on the motorway for two hours in the pouring rain as the closed the motorway on the way back from Le Mans your skills with submarines could have been useful.

 

Keeping water out of the 'people tank' is a fundamental maxim for a submariner.

 

Ooh, that's not fun. May I recommend a SBFS half hood. It goes with me on each blat and the full hood is consigned to the back of the garage. The hood bag now contains a tonneau, but having seen the shower cap rave reviews I am tempted as it will take up less space.

 

If the motorway was totally blocked and everything was stationary you could have fitted the half hood very quickly indeed. The rear straps of my half hood are already connected and furled into the roll cover and so its very quick to deploy. If there is some movement on the motorway you could dash to the hard shoulder or hide under a motorway bridge and pretend that you are a motorcyclist. They all do it here when it rains heavily.

[Racingshoe]

Just did some live diagnostics by running the car with my laptop giving readings from teh Emerald. Am suspecting the air temp sensor as it was reading 12degrees. Not today, no way.

 

Battery on the laptop didn't last long, so will try another run with it plugged it tomorrow just to confirm & then order a new sensor.

[Racingshoe]

FIXED !!!!! 😬 😬 😬 😬

 

Swapped out my Air Temperature Sensor for a new one, and the car runs perfectly. Just been out for 2 hours on a blat with GeoffW and the car didn't miss a beat. It even feels quicker

 

Suggest you change the sensor - on a K series car it is the green sensor & plug in the airbox or in the inlet manifold (depending on engine model). CC want over £40 + vat + postage, but I got mine from Emerald for £10 + postage. Emerald sensor is an M12 thread, but if you're comfortable with enlarging the hole, give them a call.