16 replies to this topic

[adster]

My spi is running very rich, and very hot..! the gasses from the tailpipe are really hot?

 

I've removed the air filter housing and i can see that there is a constant flow of fuel from the injector, is this right?

 

The spark plugs are getting coated in black soot very quickly, probably from 10 mins of running.

 

It managed to use about 6 litres of fuel from just running for about an hour off and on.

 

 

[Phil-R]

Just thinking about  your other post where your heater matrix isn't getting wam... Does the coolant temperature on the dashboard get up to half way (and stay there) It's screwed into the bottom of the manifold and shares some of the piping close to where you suspect a blockage.

 

SPI goes into limp home mode very easily if it spots a problem with one of the sensors. This causes it to use a rich fuel mixture to be on the safe side. Usual suspects are:

 

MAP sensor piping from the manifold to the ecu. thoroughly check all the plastic joints as they are known weak points.

Lambda sensor failed or disconnected

Coolant sensor failed or disconnected

Air temp sensor failed or disconnected

 

Lots of posts on here about rich running injection, so have browse and see if any one else has reported additional symptoms that you can also check for.

[adster]

should the injector be constantly injecting fuel?

[minimat]

Yes otherwise the engine would stop.

[Phil-R]

It fires directly onto the back of the butterfly in a series of pulses that trickles into the manifold. You won't be able to notice whether the amount of fuel is wrong just from looking, as it just won't idle if it's noticeably wrong.

 

What you may be able to spot is this... Listen and try to gauge the rate at which the injector pulses occur within a few seconds after starting. If the ECU goes into limp home mode because it detects a sensor fault, the pulses will suddenly double in frequency (and reduce in pulse width), maybe after 15 to 60 seconds of idling. It's very subtle but quite obvious once you see it happen.

 

Before you do anything else though, clean up your spark plugs and look out for the original symptoms you originally posted. Since you've cleared the coolant blockage in you're other post, this could also have been the cause of this problem if the coolant sensor was reporting the wrong temperature

[spiguy]

As Phil-R says, it is essential to know here if your coolant sensor is now registering the engine temperature. If not, then the car will do exactly as you describe as it thinks that the engine is stone dead cold. I have this problem on one of my minis which is off the road, where some radweld type stuff solidified and the flow out of the thermostat housing to the heated inlet (where the temperature sensor is) got blocked. The temp guage does not move at all when the car is running, and the exact same thing happens - car runs rich, plugs soot up, stinks of petrol etc.

[adster]

The gauge is registering now, sits at the halfway mark once warmed up.
Heres the problems that im getting;
Low RPM
Blip the throttle and it cuts out
Plugs fouling up very quickly
Seems like its not giving full power
Getting very hot exhaust gasses from the tail pipe, and it sounds like a lot of compression.
And finally the cat is getting very hot and staying hot after the car has been switched off.

Edited by adster, 06 December 2014 - 09:37 AM.

[firstforward]

You could have a lambda sensor that is now coated in soot as a result of your previous problem. If this is so it will not work as it needs the oxygen to penetrate the platinum layer to reach the zirconium oxide, so basically it is buggered. The  sensor really needs to be tested with a multimeter etc.

 

2 years ago I had a similar problem, I checked the vacuum hoses but I missed a small hairline crack in an elbow. Because I missed this and ran the car for a few thou miles it buggered the lambda sensor, they should be changed every 60K miles anyhow.

[adster]

I was thinking it could be the lambda sensor, are the spi and mpi lambdas the same? As i have a spare one from a mpi.

[Steve220]

I was thinking it could be the lambda sensor, are the spi and mpi lambdas the same? As i have a spare one from a mpi.

Yes they are.

[Ethel]

Hot usually means a lean running engine, perhaps the cat is blocked or it's burning some of the excess fuel in the exhaust.

[adster]

I removed the cat and it seemed to running a bit better, i then found a split vacuum connector, changed that and its running a lot better..can i see if the cat is knackered? It doesnt rattle when shaken.

[FlyingScot]

You can't tell by looking at it. I would be tempted to put it back in with new gaskets and give it a damn good run.
As Phil-R quoted above the vacuum pipes are the first thing to check as until you are sure the MAP is controlling properly everything else is a guess (unless you have a code reader).
Sounds like the combo of the solving coolant issue and the vacuum pipes have you back in a good place.

I would make sure all the service items are in good order (oil, air filter, plugs and tappets) and then give it a nice run to get everything properly hot and see if she runs better.

FS

[Alpenflitzer]

If the the exhaust is sooty then lthe cat is easily plugged. I cleaned a plugged cat by blowing the soot out with air pressure. If the cat is cold you can also in addition fill it with gasoline and shake it hard, let it stay for an hour and shake again. Gasoline only kills the cat if the cat is hot and can react.

 

 If you have a strong light you can see Honeycomb structures. If you do not see the structures then it seems heavily plugged. What happens is: The soot is still burning after you stop the engine.

In essence then you can throw away the cat because the platinum-rhodium catalytic layer is dead. This layer is the catalyzing element.

 

The worst thing is, if ignition causes little explosions into the exhaust. Then, the cat is definitely destroyed in its catalyzing function.

 

If your cooling system is free of blocking elements then I would change the coolant temp sensor, the oxygen sensor and the cat (--> next MOT !). Before you build in the lambda sensor you have you should measure it.

 

As far as I know from my 93 SPI, the SPI has NO MAP SENSOR. This one is only for the MPI.

Edited by Alpenflitzer, 07 December 2014 - 11:17 AM.

[FlyingScot]

SPI certainly do have a MAP sensor how do you think they control the fuelling parameters....
SPi MAP sensor is inside the ECU soldered onto the MEMS circuit board. It's the thing you are connecting the vacuum pipes to......with a black plastic spigot on the outside next to the electrical connector/s.

Catalyst is a coated ceramic honeycomb surrounded by ceramic fibre to cushion it in the metal can. If you can see light through it it's worth putting it back in as I wrote above. They can survive a certain amount of abuse and given the cost its worth trying.

FS