I have a new problem now - what seems to be a missfire...

The original problem was noticed when the car was taken for its MOT on load the car missfired and emitted whiteish smoke. When the car is idling if you suddenly depress the accelerator. If you quickly stamp it to the floor the engine tries to stall. Less severe throttle applications causes the engine revs to dip and then it visibly shakes as it missfires.

It would also hesitate and try to stall on you if pulling away at under 2000rpm.

Dissy cap, rotor arm and plugs are as new. HT leads are new. Plugs electrodes are a tan colour and correctly gapped at 0.8mm. Coil connections are clean it was good power.

Spark from king lead is good, spark from plug leads is visibly weaker but still reliable (will jump approx 5mm).

This morning we checked the timing and found it to be out - close to 0* BTDC and adjusted it to read the appropriate 10* BTDC at 1000rpm. The vacuum advance was disconnected as per the manual, although this doesn't make any difference.

The mechanical advance works as the advance increases if you rev the engine. The vacuum advance works if you suck on the tube.

After this the car started a bit easier and revved better. It was then driven 5 miles to the MOT centre and was 100%. No missfiring, no smoke and good performance.

After the MOT it was hard to start and driving it home it got progressively worse. It would not rev above 3000rpm- the power just faded away. It strugled to climb the hill up to the house, slowed right down and was smoking and backfiring (small flames from exhaust).

All lead connections were checked and no problem found. The only thing seemingly amiss was that the coil was very hot. Aha! Makes sense - the longer the car ran for, the worse the missfire got. Problem solved?!

Replacing the coil with an identical cold ford one (stock of old ford spares!) didn't help. The car was hard to start despite a good spark at the plugs. It just wound over with no firing at all. Eventually it resumed the normal hard-to-start procedure and spluttered into life.

The same problems were still present when reving at idle. Removing the vac advance tube has no effect. The nipple that goes into the plenum is clear but is obcured by the edge of the throttle plate when the throttle is closed. We adjusted the throttle stop to open the throttle slightly and then reduced the revs back to 1000rpm by winding the idle screw right in. Plugging/unpluging the vac tube now had an effect on idle speed, but didn't cure any of the problems.

When the leads were replaced a few days ago the car wouldn't start as only a couple of plugs were seeing a reliable spark. Replacing the leads with the old ones got the car started (just about). The new leads were tested and were ok, but the resistance was 2-3 times higher than the old ones, but not excessive (max. 60kohms). Seems like a marginal ignition system to me?

The new leads were caery carefully refitted the next day and we now have the same performance as on the old leads.

"Cleaning" the rotor arm and distributer doesn't help. Nor does hoseing it with WD40. The only thing obviously wrong with the distributer is that the anti-flash gaurd is cracked.

I'm not sure what voltage the coil is supposed to run at. Ours is getting 12v with ignition on. The Haynes book-of-lies mentions a ballast resistor. The only ballast resistor I know of is the fuel pump one - which I have replaced with a fuse.

I'm going to try replacing the resistor, but even if the coil is supposed to run at 9v rather than 12v, I don't see how reducing the spark intensity is going to help!

Seeing as the coil sits quie close the exhaust manifold I'm not sure how hot they normally get either.

If anyone has been here before and had a similar problem I'd love to know how you solved it!

Anthony

Anthony, my thoughts are in Red

I have a new problem now - what seems to be a missfire...

I think you still have problems related to your prior Thread

The original problem was noticed when the car was taken for its MOT on load the car missfired and emitted whiteish smoke. When the car is idling if you suddenly depress the accelerator. If you quickly stamp it to the floor the engine tries to stall. Less severe throttle applications causes the engine revs to dip and then it visibly shakes as it missfires.

I've seen this before when there are air leaks in the system - mixture randomly too weak causes unreliable combustion.

It would also hesitate and try to stall on you if pulling away at under 2000rpm.

Dissy cap, rotor arm and plugs are as new. HT leads are new. Plugs electrodes are a tan colour and correctly gapped at 0.8mm. Coil connections are clean it was good power.

Spark from king lead is good, spark from plug leads is visibly weaker but still reliable (will jump approx 5mm).

Sounds as tho' the ignition system is OK

This morning we checked the timing and found it to be out - close to 0* BTDC and adjusted it to read the appropriate 10* BTDC at 1000rpm. The vacuum advance was disconnected as per the manual, although this doesn't make any difference.

I use Unleaded on my Vitesse and have to retard the ignition to about 2 - 4 deg BTDC at idle

The mechanical advance works as the advance increases if you rev the engine. The vacuum advance works if you suck on the tube.

Thats OK

After this the car started a bit easier and revved better. It was then driven 5 miles to the MOT centre and was 100%. No missfiring, no smoke and good performance.

Probably because the car was not fully hot so the Coolant temp sensor was telling the ECU to richen the mixture offsetting the effect of an unwanted air leak as mentioned above.

After the MOT it was hard to start and driving it home it got progressively worse. It would not rev above 3000rpm- the power just faded away. It strugled to climb the hill up to the house, slowed right down and was smoking and backfiring (small flames from exhaust).

Now the car is fully warmed up and the temp sensor in not richening the mixture so the possible rogue airleak is causing improper combustion, and unburned gasses are entering the exhaust system and being randomly ignited depending up the fuel/air mix giving visible flames at the tailpipe.

All lead connections were checked and no problem found. The only thing seemingly amiss was that the coil was very hot. Aha! Makes sense - the longer the car ran for, the worse the missfire got. Problem solved?!

Replacing the coil with an identical cold ford one (stock of old ford spares!) didn't help. The car was hard to start despite a good spark at the plugs. It just wound over with no firing at all. Eventually it resumed the normal hard-to-start procedure and spluttered into life.

The same problems were still present when reving at idle. Removing the vac advance tube has no effect. The nipple that goes into the plenum is clear but is obcured by the edge of the throttle plate when the throttle is closed. We adjusted the throttle stop to open the throttle slightly and then reduced the revs back to 1000rpm by winding the idle screw right in. Plugging/unpluging the vac tube now had an effect on idle speed, but didn't cure any of the problems.

The vacuum orifice to the Dizzy must be completely occluded (shut) by the edge of the disc at idle. Thats how it is designed to work

When the leads were replaced a few days ago the car wouldn't start as only a couple of plugs were seeing a reliable spark. Replacing the leads with the old ones got the car started (just about). The new leads were tested and were ok, but the resistance was 2-3 times higher than the old ones, but not excessive (max. 60kohms). Seems like a marginal ignition system to me?

The new leads were caery carefully refitted the next day and we now have the same performance as on the old leads.

"Cleaning" the rotor arm and distributer doesn't help. Nor does hoseing it with WD40. The only thing obviously wrong with the distributer is that the anti-flash gaurd is cracked.

I'm not sure what voltage the coil is supposed to run at. Ours is getting 12v with ignition on.

I dont believe there is a ballast resistor in the system with electronic ignition.

The Haynes book-of-lies mentions a ballast resistor. The only ballast resistor I know of is the fuel pump one - which I have replaced with a fuse.I'm going to try replacing the resistor, but even if the coil is supposed to run at 9v rather than 12v, I don't see how reducing the spark intensity is going to help!

That resistor is NEEDED to limit the fuel pump pressure and reduce fuel pump noise. The Haynes book is mostly OK but was never fully updated for Efi systems, because the car went out of production before they could justify a full review of the book.

Seeing as the coil sits quie close the exhaust manifold I'm not sure how hot they normally get either.

They get hot- its an engine bay - its not a problem they made 300,000 + cars with the coil close to the exhaust. During normal operation the engine bay gets very hot and the coil can stand it.

If anyone has been here before and had a similar problem I'd love to know how you solved it!

I cant help thinking that you will have to go thro the whole Efi test process again in case you missed something.

Bear this in mind - the air fuel ratio must be correct at all times and the ECU can only respond the Changes in air flow via the AFM and changes in Conditions according to the inputs from the sensors.

It cannot cope with random changes caused by intermittant connection or wiring problems, unreliable engine earth connections and random/rogue air leaks

Even when you have checked all those conditions and inputs the ECU might be the culprit and can only really be diagnosed by substitution

I was lead to believe that the V8 was designed for unleaded use? Should I retard the timing? It's on normal 95RON unleaded at the moment.

I shall completely blank off the extra air valve and over-run valve and see how the engine runs. These are the only two devices which showed any problems in the previous tests.

When the car was driven to the MOT centre it was already fulled warmed up as it was taken immediately after doing the timing.

It did seem that the vac advance nipple was strategically placed. Thanks for confirming this.

My car doesn't have anything mounted to the coil that looks like an ignition amp. I believe it's on the dissy - black rectangular plastic unit with black/white wiring. There is a small condensor mounted to the coil and connected to one LT terminal. Is this just a noise supressor?

I removed the fuel pump ballast resistor because it was being a royal pain! At startup there wasn't enough current being supplied to the pump to turn it (I measured 4v on load at the resistor). The pump is an aftermarket part rated at 12v and I believe that all these roller-cell type pumps have an internal pressure relief valve. I will agree that the pump is a tad noisey from inside the car though!

The plan is to run a couple of tankfuls of fuel through the car and then replace the resistor. I couldn't determine whether the stalled pump problem was being caused by mank in the fuel tank or just BL's wiring.

Thanks for confirming that the coil does run hot. I wanted to ensure that the heat wasn't from the coil itself, which would obviously indicate a problem.

At idle all the system checks seem ok. I even double check the throttle pot output today seeing as it seem that rapid changes in throttle position was upsetting it. The reading was fine apart from the full scale deflection is only 3.3v - it's always been like this.

Are there any other engine earths besides the main one to the alternator bracket? I couldn't see any at the back of the engine.

At least the car has an MOT now anyway!

[quote="Chris P
One other thing I noticed looking in your EFi guides Ramon, was that
the fuel pump resistor is shown as a fuse.[/quote]

Well I'll go to the foot of our stairs, and it not even labelled either. This means that Rovers original error is perpetuated where ever that drawing was copied. tee hee.

Ramon

I've had another quick look at it.

Timing - I will retard this to 5 degree BTDC - thanks for the tip, I hadn't cottoned on that this car was from the days or 4 star

IIRC the throttle does open fully when you view the disc. I regard the low TPS voltage as a problem to be ironed out at some point.

I found the earth point on the back of the engine and cleaned everything thoroughly. There was only one ring terminal on the stud though and I didn't noticed any loose ones nearby?

The result was 0.00v drop to this wire (engine off) compared compared to battery voltage. It didn't change the TPS voltage readings though

I started the car (a little reluctantly) and let it warm up. The colder the engine is the more responsive it is to suddenly stamping down the throttle. As it gets warmer it starts hestiating/missing worse and worse.

While it was still cold I clamped the hose leading from the extra air valve to the plenum, this caused a drop in res.

When it was warm I clamped the hose leading to the extra air rail and it made no difference to the idle.

I did the same with the brake servo hose - no change

I did the same with the engine breather hose- this caused a small audiable drop in engine speed - so the breather system must be working.

I tried the "blip" test with each hose clamped and it made no difference.

The only thing that I found was that unplugging the small vac hose to the fuel pressure regulator (and blocking the pipe into the plenum) made no difference to the idle. Blowing moderately and sucking as hard as I could on this pipe had no effect on the idle. Also, reconnecting the hose, but clamping it made no difference to the outcome of the "blip" test. Is any of this normal? It seems odd to me

Anthony

I rigged up a pressure gauge T'ed off from the outlet of the fuel filter. The results were ~28psi rising to ~38psi on a full throttle blip. Which means the damn thing is working exactly as it should.

When blipping, if the throttle is held to the floor the engine can be kept in an almost permanent state of near-stall. Not shaking and obviously miss-firing, but just dying.

My next ideas: connect up the timing strobe and see that the mechanical advance is working on full throttle. I know it does work on gentle throttle openings.

Adjust the mixture screw in the airflow meter. When I first started trying to fault find the system I found the mixture screw was 4 3/8 turns out from fully in. I set this to the proper 2 1/2 turns. I'll try reverting it and see if anything happens.

Removing the vac pipe to the fuel pressure regulator and allowing air into the plenum did make a small change to the idle speed. I plugged up the tube when doing the tests.

The problem, whatever it is, is definitely temperature related. The car becomes more prone to it as the engine warms - this happens without exception. Also, because it once drove 5 miles without any hint of the problem makes me think that it isn't a dead component or bad setting, but something not operating as it should.

I agree that the TPS voltage needs resolving. Perhaps the ECU is outputting a lower than normal voltage because it's main feed is poor? As a pure guess I'd expect that it would cause unusual signals from many sensors.

I've made good the ECU earth on the block, but I have no idea where the ECU recieves it's power from? I'd much like to test this, plus do a resistance check on the earth. All I recall is a rat's nest of wires in the passenger footwell...

My dad wants to strip/clean/check the distributor to ensure the mechanical advance isn't sticking during sudden changes in engine speed. It can't hurt to try.

Anthony

I forgot to say, we don't have any means of swapping the ECU as a test. If it comes to that I'll buy another ECU (maybe an AFM too), on the basis that they can always be sold on.

I'm of the belief that ECU's get blamed for a lot of faults that aren't caused by them. As a piece of electronics it should really either work, or not at all. That's how I tend to think of them anyway

Anthony