friends 1.3 Mpi '98 felly (136 engine the car used to be ours) seems to have a terminal problem, will list the probles with it and see what y'all come up with!

- excessively lumpy / hunting idle will not idle with steady RPM when engine hot/cold

- quite a bit of mayo in oil cap (have done oil change will see if it recurrs)

- No registration of temperature at all on dashboard temp dial - at very least thermostat is flowing normally - when warm coolant is going into and out of expansion tank and radiator gets fully warm. No significant loss of coolant (see mayo above)

- alternator output is fine across rev range

- car runs fine at any engine RPM above Idle speed, so with foot on pedal just a little runs OK

- engine did not stall when unplugged MAP sensor (it always used to)

- no change in crap running when coolant temp sensor unplugged

- engine did not stall when unplugged Crank sensor!!!!! (wtf?)

- pulled battery for 12 hours, no difference

im thinking of five things that could be the issue,

1) cracked headgasket, but not around a major coolant line as no huge amount of coolant loss

2) intake manifold leak

3) Sensor goosed (MAP / Coolant Temp)

4) ECU goosed

5) Throttle position sensor + idle switch

anyone else possible able to shed some light on the issues? Much appreciated as always,

Gavin

1) Have you had a coolant exhaust test done? Only costs about a tenner, and eliminates all gasket issues except a water - oil way failure.

2) Have a listen, using a piece of tubing as a "stethoscope" If you hear a hiss from one cylinder that the others don't have, you have a winner.

(3) and (5) - Should throw fault codes?

(4) - Oh dear! I think you can get pre-owned ECUs, but make sure you get the immobiliser transponders with one if you have to go this route.

Engine didn't stop when you unplugged the crank sensor? Really?

Engine didn't stop when you unplugged the crank sensor? Really?

yeah, its didnt stall, just got slower and slower and slower and then just sorta stopped. before when it wall all working fine would immediately stall if crank/MAP sensors were unplugged!

at the moment the idle seems to be anywhere from around 300 up to about 2000rpm with harsh jumps each change, its not even remotely stable!

is it more than likely to be the HG? i have a sniffer and exhaust test booked for friday

If it keeps running without the crank sensor plugged in then there's something VERY odd happening - that should kill the engine stone dead for obvious reasons.

If it keeps running without the crank sensor plugged in then there's something VERY odd happening - that should kill the engine stone dead for obvious reasons.

yep, my thoughts exactly!

since its not mine and its not at my place its a bit diffucilt to diagnose any further. but tomorrow im going over armed with a haynes and a multimeter to do some serious probing!

give the inlet mani where it bolts to the head a spray with wd40 or similar while its attempting to idle. very common for the gasket there to fail and cause idle problems, also it would trigger a lean fuel condition so the ecu would over fuel trying to sort it which "may" be why it runs for a bit with no crank sensor..

DJ... we had an old fav spi that would happliy idle with the coil disconnected (was quite a party trick!!) due to the head being skimmed and the oh so efficient combustion chamber having lots of hot spots

Yeah, but a dieselling engine is one thing, this is something quite different! I remember the good old days when I had an escort van with a 1.3OHV engine in it, and it used to run on for quite a while if you let it. Thinking about it, old cars really were crap, weren't they? Spent so much time working on that old POS, whereas the Felicia just keeps on going, and it's basically a similar thing just with modernity added!

As Jim says, check everything, there have been many times when I've missed "the obvious" and spent hours/days chasing obscure stuff, and when I've realised what the problem is it's been simple...

Yeah, but a dieselling engine is one thing, this is something quite different! I remember the good old days when I had an escort van with a 1.3OHV engine in it, and it used to run on for quite a while if you let it. Thinking about it, old cars really were crap, weren't they? Spent so much time working on that old POS, whereas the Felicia just keeps on going, and it's basically a similar thing just with modernity added!

As Jim says, check everything, there have been many times when I've missed "the obvious" and spent hours/days chasing obscure stuff, and when I've realised what the problem is it's been simple...

yep, looking forward to giving it a good once over tomorrow. im thinking of checking things in the following order:

1) earthing points

2) ECU swap for a spare working one i found in my garage

3) Vacuum / inlet leaks and fuel pressure

4) Check all connectors for engine sensors and attempt continuity checking each sensor wire back to the ECU

5) take cover off throttle body and check inside and idle switch working

6) take to garage for HG and exhaust sniff test

hopefully, if im logical i should find the problem! would you agree this is a good plan?

cheerio, Gavin

EDIT: it a quick and dirty way of checking the coil to pull it off the plugs and rest it againt bulkhead and look for sparks from each point in the dark? i would normally use my timing gun to check HT leads but thats impossible on the Mpi ???

EDIT 2: thinking about it, they way its idling it kinds feels like the way my MR2 idled with 2 bad HT leads causing a misfire. possibly coil? plugs are brand new and i have since checked them they are all fine.

Edited 1 December, 201015 yr by poorly_felicia

Yeah, take the coil off, put 4 plugs into it and then turn it over, you should see sparks providing the bodies of the plugs are earthed. Someone else on here had a problem with a coil pack (MorrisPaul?), I had a brand new one I sold him, sorted the problem....

Not sure if you can do an ECU swap? Don't the SPIs have the immobiliser too, which would need setting to the new ECU (doable with VAG-COM, TeflonTom knows how).

In fact, if the SPI does VAG-COm you'd find it enlightening connecting that up, just a laptop, a cheap serial VAG-COM cable and teh free version of the software can work wonders, tells you a lot about it (if the SPI does do it, I don't know, not had one for any length of time beyond half a day!)

You don't need to take the throttle body cover off to check if the switch and pot are working, you can do that with a multimeter.

I'd do the ECU swap at the end, it's not often that they go wrong...

Yeah, take the coil off, put 4 plugs into it and then turn it over, you should see sparks providing the bodies of the plugs are earthed. Someone else on here had a problem with a coil pack (MorrisPaul?), I had a brand new one I sold him, sorted the problem....

Not sure if you can do an ECU swap? Don't the SPIs have the immobiliser too, which would need setting to the new ECU (doable with VAG-COM, TeflonTom knows how).

In fact, if the SPI does VAG-COm you'd find it enlightening connecting that up, just a laptop, a cheap serial VAG-COM cable and teh free version of the software can work wonders, tells you a lot about it (if the SPI does do it, I don't know, not had one for any length of time beyond half a day!)

You don't need to take the throttle body cover off to check if the switch and pot are working, you can do that with a multimeter.

I'd do the ECU swap at the end, it's not often that they go wrong...

i have the MPi mate and the spare ECU i got actually came off this very car a few years ago when we swapped it before for a similar issue, that turned out to not be the ECU so it should work just fine plug-and-play like. unless being without power for 3 years has made it go funny and forget codes and stuff. the car does not have an immobiliser though.

i would VAG COM but dont have lead and cant find anyone local other than main stealers who can do it. Im in Plymouth if anyone near me can offer use of VAG-COM ?

thanks for the other help though, will keep you updated!

Oh yeah, clearly says MPi! If the settings are still in the ECU (and it works that way) then it should be a straight swap...

VAG-COM leads are easy to get on eBay, maybe £10 or so? Best tenner you'll spend for diagnosing faults on them for sure - I think trying to work on modern ECU-ed cars without one is near impossible.

Oh yeah, clearly says MPi! If the settings are still in the ECU (and it works that way) then it should be a straight swap...

VAG-COM leads are easy to get on eBay, maybe £10 or so? Best tenner you'll spend for diagnosing faults on them for sure - I think trying to work on modern ECU-ed cars without one is near impossible.

You are not wrong there DJ , the software in the MPI ecu is a bit limited but it does store fault codes and will give some basic data from measuring blocks,