6 replies to this topic

[Russ_IW]

Hi. I've got some running issues developed on my 93 SPI, which I have initially put down to an air leak or similar (got a few things to check through later on today).

But after a quick run last night the cat was glowing cherry red, which I understand is a result of burning excess fuel in it (due to the poor running).

 

I've been doing a few miles in the last couple of weeks after it sitting idle over winter, so it may have been glowing for the last 2 weeks - i've just never noticed until last night. How hard-wearing are the cats on minis, is it likely that the cat is now knackered too? 

 

Not sure if the cat has ever been changed and it looks pretty manky. Obviously I'll get the engine running properly first before replacing.

[Fast Ivan]

an air leak anywhere before the Lambda can cause over fueling, this could cause the cat to over heat, but it could also be blocked

I think you have the right approach -  sort the running issue then look at the cat, with a view at replacing it

[Midas Mk1]

Reckon its a shout its blocked imo. 

[Russ_IW]

Cheers for the replies.

So, had a look last night with the aid of the Haynes manual.

First port of call was the MAP sensor fuel trap. Previous owner has removed it and crudely bypassed it with a bit of copper tube    Purchased a new one with correct pipes.

Second, the inlet manifold PTC heater is disconnected. Unfortunately my arms don't have 15 elbows to be able to reconnect it, so will have to do a bit of stripping down to reattach.

Wiring and connections to the Lambda sensor looked okay, so won't touch that for now.

Had an air leak from the brake servo banjo, so nipped that up (not related to the other problem). It was actually close to dropping out!

All other vacuum pipes are in good condition and pressure checked for leaks, so they're crossed off the list.

 

You got to love fault finding!

[jamesquintin]

You should replace the vacum hoses even if they look fine...

Q
 

[Pops_Guild]

If you’re doing a bit of strip down to get the PTC heater reconnected you should check that it’s still ok. They tend to fail with age, basically if you remove it and it rattles it’s dead. A working PTC helps things. Also would recommend you replace all vac pipes, they’re a service item on injection minis

[Mikey205]

It may well be running very lean. I’ve seen down pipes glowing cherry red due to running lean.

The main way that the ecu alters fuelling is via the lambda sensor, especially in closed loop (ie when running at normal speeds at normal operating temperature). This could well be stuck especially if the car has been sat for extended periods of time. If you’ve a multimeter you can back probe the wiring connector and see if the lambda switch’s while the engine is running. 2 wires will be the heater element, the other two will be the switching wires. Your aiming to see around 0.2 to 0.8 of a volt, switching. Stuck at a high voltage means it’ll go weak and visa Versa.
Next port of call will be the coolant temp sensor or looking for an air leak.

Oh, and a word of caution. Don’t fit any aftermarket engine management sensors. Stick to genuine or the equivalent from Bosch NGK etc.

Mike

Edited by Mikey205, 25 March 2019 - 09:56 PM.