[lsowden12]

Major development today, attempted to change the fuel filter, realised the nut was seized so the pipe bent, changed the coolant temp sensor, distributor cap and rotor, turned on the car, wouldn’t start,jumped the car with another car, started just fine but was still revving weirdly, looked in the mirror and saw this…

https://youtu.be/dN5NmCExpgc?si=9FDCva6oIe6TYUeP

Now this does look really bad, smells like burning, coolant level hasn’t dropped so I have absolutely no idea what could be causing it

[g259fsg]

Difficult to tell without smelling it. I think engine oil would be fairly obvious. Coolant leaking into the cylinders can cause this white smoke. A third possibility, I think mentioned earlier, is a problem with the brake servo where brake fluid is leaking and getting back into the inlet manifold. If there is a problem with the servo, it could also be the source of the air leak into the manifold and the unstable tick-over. You could disconnect the brake servo pipe from the inlet manifold and block off the hole to check if the servo is causing problems.

Earlier I suggested holding the HT lead to check for the discharge at the sparking plug, and Mr Teddy Bear advised against this as you could get a nasty shock. It's good advice to be a bit wary. If the leads are in good condition you shouldn't get any shocks, but I have done over the years with defective leads, so best to be careful. If you hold the lead and sparking plug by the big right-angle rubber plug connector you should be safe.

[lsowden12]

Difficult to tell without smelling it. I think engine oil would be fairly obvious. Coolant leaking into the cylinders can cause this white smoke. A third possibility, I think mentioned earlier, is a problem with the brake servo where brake fluid is leaking and getting back into the inlet manifold. If there is a problem with the servo, it could also be the source of the air leak into the manifold and the unstable tick-over. You could disconnect the brake servo pipe from the inlet manifold and block off the hole to check if the servo is causing problems.

Earlier I suggested holding the HT lead to check for the discharge at the sparking plug, and Mr Teddy Bear advised against this as you could get a nasty shock. It's good advice to be a bit wary. If the leads are in good condition you shouldn't get any shocks, but I have done over the years with defective leads, so best to be careful. If you hold the lead and sparking plug by the big right-angle rubber plug connector you should be safe.

Wouldn't a brake servo leak also mean the brake pedal would be affected? I haven't noticed any issues in regards to the braking force required for stopping
As for the HT leads one of them seems cracked anyway so I think the best bet is to just replace the leads and the spark plugs to just eliminate any of that from the equation but that suggestion was super helpful because I wasn't thinking about the possibility of the leads being a problem causer

[g259fsg]

On the brake servo, it's hard to generalise. Over the years, I've had brake servos where the braking was OK but when I serviced the servo, I found an accumulation of brake fluid in the vacuum reservoir. It depends on the design of the servo whether leaking seals would allow fluid to get into the vacuum compartment. The main symptom might be a drop in brake fluid level over time. I agree it's a bit of a long shot, but might be one explanation for the white smoke. If you suspect the servo, just disconnect it from the inlet manifold, and see what happens. You said it smelled like something burning. Was that an oily smell or a chemically smell? If the latter, it is most likely coolant.

I think you are doing the right thing to go over all the ignition system first. It's the easiest to do and often the most likely cause. There's a recent thread on here from another member who had mis-firing problems and loss of power on a 216 and it turned out to be a faulty coil. A friend nearby a few years ago had a 213 SD3 with the same problem, the engine died when he pressed the accelerator. There was a carb problem, but the main issue was a faulty coil with low HT output. I had a problem with a spark plug lead going high resistance a year or two ago, which resulted in a weak spark on one cylinder and rough idling and hesitancy. As Stan mentioned earlier, the spark plug leads shouldn't be more than 5-10k ohm resistance. Cracked leads could cause leakage and shocks!.

As your problem is unstable idling, there is maybe still something a bit dodgy about the air-fuel mixture, it's very sensitive at tick-over.

[lsowden12]

Yeah thats the thing, it could very well still be a vacuum leak thats really well hidden but it can't hurt replacing other things even if it doesnt solve the problem, just prevents them from showing up and annoying me at a later date

[lsowden12]

Right so this is likely going to be the last addition to this thread from me. I am 99.9999% convinced its the ECU convincing itself theres a problem that doesnt actually exist. For the second time I figured I'd disconnect the battery for a day and let the ECU reset itself, and for the second time the problem has magically gone away, started first time, no hunting, no high idle, no misfires, running absolutely perfect. Took it for a decent drive where under usual circumstances after about 5 minutes the car would be dying or revving at 3k rpm, this time none of that happened, straight back to 800rpm. But give it 2 days and the problem will start again

The thing is if the issue ACTUALLY existed I don't think the car would be running completely fine for a few days before deciding its unhappy again, and the lack of any evidence that a problem exists through multiple weeks now of me searching every milimeter of the engine bay and replacing pretty much every ignition component looking for something that could be throwing the car off would suggest it very well probably just is the ECU being stupid

I can't be bothered getting another ECU and resetting all the fobs etc to test said theory so I think the solution I am going to opt for here is installing a battery cutoff switch under the dashboard that I can switch after use every time the problem shows up again.

I really appreciate all your help, hopefully I won't have to post here again in a few weeks time

[Mr Teddy Bear]

That Sei in the Youtube vid should have a plastic manifold surely? being a M registered vehicle.

I have kept a known good quality ECU from the 414 that I scrapped two years ago, it was either new or refurbished and was sourced via the dealer in Wickwar who was working on the car. I also have the fob that is programmed to the ECU, plus the invoice for the work/part.

My experience of a failing ECU is that eventually the car doesn't start at all, hence it was low loaded to Wickwar for repair. Started as a flat spot at low revs and progressively got worse.

If you want to quote your ECU part number I can cross reference against the one I'm keeping in my spares box?
I know that it is a different part number to the one fitted to my L reg' 214 that has a alloy inlet manifold and is specced to the 94 build order [built Nov/Dec 93] It is unlikely to be suitable for my project car and I will sell it if it's the same part number if you want.

[lsowden12]

That Sei in the Youtube vid should have a plastic manifold surely? being a M registered vehicle.

I have kept a known good quality ECU from the 414 that I scrapped two years ago, it was either new or refurbished and was sourced via the dealer in Wickwar who was working on the car. I also have the fob that is programmed to the ECU, plus the invoice for the work/part.

My experience of a failing ECU is that eventually the car doesn't start at all, hence it was low loaded to Wickwar for repair. Started as a flat spot at low revs and progressively got worse.

If you want to quote your ECU part number I can cross reference against the one I'm keeping in my spares box?
I know that it is a different part number to the one fitted to my L reg' 214 that has a alloy inlet manifold and is specced to the 94 build order [built Nov/Dec 93] It is unlikely to be suitable for my project car and I will sell it if it's the same part number if you want.

Believe it or not it is indeed the alloy manifold, it could very well have potentially been replaced but the car was also registered on the 1st August 1994 which was the first day for the M reg so I bet it was built to the same L reg spec as yours.

ECU part number is MKC102570

[220 GSi turbo]

1994 was the changeover point from alloy to plastic manifold.

I have owned two August 1994 registered 214SEi 3-doors over the years. One had the alloy manifold, the other had plastic. Both cars were of known provenance and had not been modified.

Rumour has it that the plastic manifold coincided with the introduction of the less reliable damp liner engine.....

[lsowden12]

Huh, weird how they'd manufacture two cars for sale for the same time period and simultaneously have two different types of manifold. You'd think they would have just ran with the alloy until that specific variant had ceased production. Either way thats that problem solved, it probably is alloy from factory