7 stops. Possible ECU problem? HELP!!!

[PaulBaker]

Hi there,

 

This has been a bit of an ongoing problem. But with the 7 only recently going back on the road it was forgotten over the winter months!

 

The problem is as follows: The 7 suddenly backfires, coughs and splutters a bit, and the engine dies. Turn the ignition off and it starts straight back up, while i'm still freewheeling! The problem seems to occur when i've been driving fast, and then stop fairly suddenly, so no throttle, changing down through the gears.

 

However the fact it starts straight up again is a bit strange. Could this be an ECU problem, or any other suggestions. If it is ECU (MBE systems) how do you go about checking out an intermittent fault?

 

The engine also gave a great big backfire when I was out last night, and switched from standard to full beam lights!! Possiblt some sort of electrical glitch causing the problems.

 

Help!!! Please.....

 

Paul

[EFA]

MBE ECU's are sensitive to ignition leakage.

 

First point of call will be to check the condtion of your HT leads. Not possible visually, you will need to swap them with somebody elses.

 

Is this an Race SLR/R500 or a VX??

 

Fat Arn

Visit the K2 RUM siteid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[PaulBaker]

Car is an 1800 Zetec. Road car.

[EFA]

OK, Do you know what model of MBE ECU you have??

 

Check the ignition/injection loom ground (normally onto the rear brake line brake tee by the pedal box)

 

If this looks clean and OK, a set of new HT leads are your best option. The fact that things go totally dead and a power cycle to the ECU clears this problem is very indicative that you have an HT fault upsetting the coil drivers in the ECU.

I have had this problem on my VX with an MBE 912V3 a few years back. Took ages to find this was the problem.

 

Magnacor leads are expensive but will ensure you don't get a repeat performance.

 

 

 

Fat Arn

Visit the K2 RUM siteid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

 

Edited by - fat Arnie on 10 Apr 2002 17:34:39

[TorAtle]

Sounds exactly like the problem I have, although it's a K with a GEMS box. Easiest way to provoke the fault is full throttle or high rpms...or both :-)

 

Usually there's only misfires, but once in a while it just dies. Ignition off and on cures it as you say.

 

I've changed the HT leads, swapped the coil, flywheel sensor, disconnected alternator, doublechecked ground connections etc etc.

 

Any thoughts would be much appreciated, I've had this problem for over a year and don't want to spoil another season.

[Mick Day]

I had a similar problem: 1.6K & GEMS ECU: persistant misfire at 6000 rpm in 5th & 6th. Mapping was OK as was the alternater, battery, leads, coil, dis. cap, rotor arm, plug gap as all were checked/changed! It was completely cured by changing from Bosch FR7DC(new plugs) to NGK BCP7ES plugs.

 

Mick

 

[peterg]

Magnacor leads definitely a good idea, I put them on my 1800 Zetec after the neighbours complained that their TV picture broke up every time I started the car - no more complaints and the car runs more smoothly as well since

 

It's still not fast enough!

[ROC]

The problem I was/am having is a little different but some of the symptoms match. It was suggested to me that it could be a block in a breather from the fuel tank. I was told to drive the car till I got the prob and then remove the filler cap. If there was a vacuum sucking the cap on then that would be the problem. As luck would have it I messed around with the HT leads and the problem has almost gone. I am going to put a meter on mine to check the ohms on each lead. should be 5K I think on the rover leads.

[Peter Mears]

Check the breather on the tank, when I converted to a Zetec and an aero filler the cap needed a small hole to stop the tank pressurising. Sounds kind of similar!

[ROC]

Peter, are there better places than others to locate a hole ;) Seriously though I guess I will be doing this on my aero cap just have not got to that point yet.

[PaulBaker]

Surely if it was a fuel tank pressure problem then it wouldn't just start straight up again, would it?

 

As for the ECU it's MBE model 956i if that helps.

 

First thing to check is the HT leads I guess. Without just swapping them for someone elses, or buying a new set. How can I tell if they need replacing or not? And if so. Anyone recommend some decent, but not expensive ones!

 

Paul

[ROC]

Paul: I think is the tank has a partial block then after a rest the tank will settle down to equal internal and external pressure - hence no problem after a rest.

 

To check the leads I was going to try two techniques. One: put a multi meter on them and check that all have the specified resistance. It should be written on them. (I think about 5K Ohms). Two: wait till night falls and see if I can see a blue spark running over the top of any of the leads.

 

I have never tried this but I also thought I may wipe the leads with a damp cloth first to exacerbate any problem. I don't know if this is a stupid idea and could cause any other problems but I cannot see what.

 

[CHRIS CLARK]

In regard to the fuel feed/tank thing My ex mother-in-laws (1983) Metro did this stop/rest a while/ start again thing from brand new. It turned out to be a poor PDI that had left a plastic sleeve over the tank breather!The reason I know is that she took me out in it and it happened a couple of times. I took a look, found the sleeve (by the filler neck) and with difficulty pulled it off. The noise of the tank getting back to its original shape was an incredible bang. All ran fine after this.