Miss Fire - need advise

[Yosh]

Hello all,

this is my first post on here and I would have introduced myself in the right section but I need help desperately. My FTO (95 GPX Tip) has a seriouse miss fire problem that no-one seems to be able to trace.

Plugs, leads and coil packs have been checked back to the ecu with no fault. The ECU has been swapped with another FTO and worked fine and the feed into the ECU from the sensors have been checked and seem to be in working order

The miss fire is on 2 cylinders and it seems as thought the signal from the ECU that feeds these cylinders is 1/10th of the strength it should be. Has any one had any similar probs? If so what was the cause?

Any help would be much appreciated.

Cheers.

[CJ]

Hi Yosh

Can I assume that a full diagnosis has been undertaken in terms of reading error codes off the ECU? If there is an electrical problem of some description, it should show up a fault code. When you say "Plugs, leads and coil packs have been checked back to the ecu with no fault", have you tried using another set of leads and plugs?

CJ

[Yosh]

Hi CJ,

It looks like an electrical fault but there weren't any fault codes on the ECU when they checked (wasn't from a MUTII though). The coil packs and leads have been swapped around to. The mechanic has said that they have taken readings from the three outputs from the ECU and it seems as though it's the signal coming from one of these which is low, however they tried my ECU on a different FTO and the car worked fine.

The car has been to 3 garages now and out of action for over 2 months with no progress. Have you ever heard of anything like this?

Plus they've also removed the de-limiter and alarm to rule these out of the equation.

[/quote]

[kevinod]

I guess if the plugs, leads, coil packs and ecu have all been checked they're probably ok...

could you describe *exactly* what happens, do the 2 cylinders not fire at all? Which 2 cylinders?

how about looking at the fuel supply side of it - are the injectors, etc. ok? Since its a GPX the tappets are adjustable, could 2 have worked themselves into a position that they don't do their job properly?

The leads are supposed to be hooked up in a certain order, tbh I'm not 100% sure what would happen if 2 were in the wrong order, would the car start at all, but it might be worth checking that.

Did the car just start misfiring one day or was something done to the car around that time?

You said they didn't use a MUT-II to diagnose the problem, what did they use?

[Dave]

i'd take it to get it MUT-II'd first, it's only a few quid to get done and that should show something up.

[Yosh]

could you describe *exactly* what happens, do the 2 cylinders not fire at all? Which 2 cylinders?

The cylinder on the front far right (as you look at the engine) isn't firing and it's the other cylinder fed by the same lead that isn't firing. There is no current coming down the lead that feeds these plugs so they aren't firing at all.

how about looking at the fuel supply side of it - are the injectors, etc. ok? Since its a GPX the tappets are adjustable, could 2 have worked themselves into a position that they don't do their job properly?

There's a strong smell of petrol and the odd faint pop from the exhaust, I'm assuming this is unburnt fuel from the cyclinder so I think the fueling side of things is OK.

The leads are supposed to be hooked up in a certain order, tbh I'm not 100% sure what would happen if 2 were in the wrong order, would the car start at all, but it might be worth checking that.

Did the car just start misfiring one day or was something done to the car around that time?

Immediately prior to the problem, when I started the car the idle hunted slightly and settled down after about 30 seconds. The next time I started the car the engine was miss-firing. Don't know if this is related or just the stepper motor?

You said they didn't use a MUT-II to diagnose the problem, what did they use?

Not sure he didn't say, I'm assuming he used the method where you earth one of the connections and the code flashes on the engine management light.

I think the problem lies with the weak pulse signal from the ecu output, but it's the cause of this that the guy just can't seem to find.

i'd take it to get it MUT-II'd first, it's only a few quid to get done and that should show something up.

I think this might be the next step, but would a MUTII show errors that wouldn't show up from the checks they've done?

[NobbyV4]

I know you said the coil packs have been checked, but it's simple to swap them over (I think, not 100% sure) and see if the problem move to the other cylinders?

[Yosh]

Hi Nobby,

They tried this and the problem didn't shift. The guy is certain it's down to the low pulse signal coming from the ECU, but he can't figure out why the signal is low. To tell you the truth I'm a bit fed up with the situation and I'm thinking about throwing the towel in. Don't want to but it's been nearly 3 months now and I need a car.