Two engines down - Time for an engine swap!

[stagnetti]

it was the same feeling as though someone were kicking your chair from behind just enough for you to notice and grow irratble but not enough to constantly snap your neck to and fro.

Filters were all in good nic although they could probably have been changed more often than they were. But every other week or so i would hoover out the box to ensure no gravel / dust, etc. was getting sucked in.

Care wise i've invested a lot into this little car and I really don't want to part with it but i am nervous about getting a(nother) rebuild complete only for this to happen again (the blowing up part not the juddering) hence the question about a conversion to a more reliable lump

[pinger]

The TIK pipe - it runs from the filter box to the turbo (compressor) inlet - all firmly attached and no splits or detached pipes?

Trying to remember more from the ethanol thread. At circa 3500-4000rpm (IRCC) ECU goes closed loop meaning that rather than read from Lambda sensor (open loop) and be able to vary mixture accordingly, it goes to preset settings for which there are no compensations if there is eg, an air leak or plain wrong settings (bad remap?) or at a guess, any data corruption from the sensors that are being read (boost?).

I think your problem is peripheral ie, not in the engine but one of the control systems. It shouldn't judder at 70mph (or any speed!) and that implies weak mixture to me - an exhaust valve killer. Solving this (whatever it is) problem will be easier (by a margin too huge to contemplate) to sort than transplanting an engine.

[stagnetti]

Nope, no leaks anywhere along the air flow route. TIK was replaced with the silicone jobbie and leak tested with no issues.

If it is the ECU going from open to closed and something can be done to fix the data set it uses which is fouling up the mixture, I would feel a lot more comfortable rebuilding!

Out of interest why would an engine switch to a predetermined config. above a certain speed? Surely when under power your sensor readings are your bible? Seems like a crazy design flaw to me - perhaps an emissions hack?

I wonder if piggybacking an aftermarket ECU onto the original loom would help to solve this. Use it to control the engine and the original for accessories.

[pinger]

If it is the ECU going from open to closed and something can be done to fix the data set it uses which is fouling up the mixture, I would feel a lot more comfortable rebuilding!

Out of interest why would an engine switch to a predetermined config. above a certain speed? Surely when under power your sensor readings are your bible? Seems like a crazy design flaw to me - perhaps an emissions hack?

.

I think, it allows the fuelling to be richened (standard practice) for high load conditions to suppress detonation(without the Lambda sensor trying to correct back to leaner). I think it is the part of the ECU the remappers map - but trying to get info from them is like getting blood from a stone.
If it is the problem then a better map applied to your ECU might be the cure. I'd be looking to monitor the air/fuel ratio (Lambda) while driving (esp during the judders) via a device connected to the OBD port. It might be worth checking you have the correct ECU - and not one from a fortwo (assuming they are interchangeable).

[137699]

It did have an issue where at 70mph it would judder slightly. Above and below this perfectly smooth. It was like that from purchase.
Took it into a garage for a check over and coudlnt see any reasons as to why this was happening. They concluded that the ECU may be having some issues reading the sensors and over/undercompensating with the air/fuel mix. So replaced the 02 sensors and fuel sensors and had the OEM map reflashed to the ECU to be on the safe side... no effect at all. There was never a loss power though and the idle was smooth as butter. Just meant if i wanted a comfy ride i had to sit above 70

I can tell you exactly what your problem is - your rear reluctor rings are split, rusty &/or missing teeth. Replace them and it will fix this issue. And replacement rings cost £6 on ebay. Or £30 or so for some decent ones from Smartmods. Just a bit cheaper than an engine rebuild or replacement.

The stutter you feel is the ESP system momentarily cutting power to compensate for what it thinks is a slide.

[pinger]

I can tell you exactly what your problem is - your rear reluctor rings are split, rusty &/or missing teeth. Replace them and it will fix this issue. And replacement rings cost £6 on ebay. Or £30 or so for some decent ones from Smartmods. Just a bit cheaper than an engine rebuild or replacement.

The stutter you feel is the ESP system momentarily cutting power to compensate for what it thinks is a slide.

Would the ABS not be shaking like a dog ****ting as well?

[137699]

No - it simply registered what you would consider to be a misfire at certain speeds. I have had it on 2 smarts and know plenty of others who have had the same.

[mikerj]

Out of interest why would an engine switch to a predetermined config. above a certain speed? Surely when under power your sensor readings are your bible? Seems like a crazy design flaw to me - perhaps an emissions hack?

Pretty much all petrol engined cars that use narrowband sensors do this, especially turbocharged ones. At high RPM and load a richer mixture is needed to keep the temperature of pistons, valves etc. within reasonable limits, but a narrowband sensor is only useful for determining the stoichiometric point (about 14.7:1 for petrol). Therefore closed loop control is disabled and the ECU adds fuel based on an internal fuel map. There are some corrections used even when in open loop; the long term fuel adaption which is determined whilst in closed loop is applied, as well as compensations for altitude and air/engine temperature etc.

[ossy]

Only 2 engine!
I done 4 engine ,in 8 years .