15 replies to this topic

[Frazer stuart]

Hi minifans,

My 1993 cooper spi is idling strangely. It seems fine on startup, and drives absolutely fine but once warm the idle is strange.

Revs drop to about 1000 rpm, then climb to 1200 then drop from there slowly down to around 4 or 500. It sounds horrible but never quite stalls. If I then give it the tiniest blip of throttle (just enough to raise it around 100 rpm) then it will repeat the same - climb all by itself to 1200 then drop slowly.

The problems started when I fitted my maniflow stage 2 lcb. So the air box, throttle body and inlet manifold and all attached sensors have been removed from the car and reinstalled. I also flushed coolant.

Vacuum lines are new as of last year and have been checked visually for cracks. Elbows too. Stepper has been indexed and I can see and hear it doing its thing whilst indexing. Standard air box. I do have a vacuum gauge in the dash, reading the red vacuum line, but that has been there ages and never caused an issue.

It idled beautifully before the manifold install.

Anyone have any ideas? My GFs car just failed it's MOT so mine has to step up and be the reliable/only car now! I probably shouldn't have messed with it!!

[minisilverbullet]

Strange that it was all working before you swapped the parts off and on.- 

 

I think the advice by most is going to be -  plug it into code reader. 

[Frazer stuart]

Hey silver bullet. Yeah code reader is the logical next step you're right. On that note, anyone nearby Maidenhead with an spi code reader??

[FlyingScot]

Hey silver bullet. Yeah code reader is the logical next step you're right. On that note, anyone nearby Maidenhead with an spi code reader??

Check the pinned thread on this.....

Where is the lambda on the lcb? I’m hoping right at the bottom.....

FS

[Frazer stuart]

Hey FS. No I'm afraid the lambda is where the outer 2 pipes join up, so it's not reading all 4 cylinders, only 1 and 4. Not sure that would cause this issue though???

I'll check the pinned code scanner thread cheers

[cian]

Sounds like an o2 sensor/loom issue when the car is in closed loop its fine then goes to open loop and becomes erratic

[viz139]

My brothers MPi failed Irish NCT before we moved the lambda to the Y piece. There is definitely a mixture issue when only measuring two cylinders at idle, it was running lean.

[Frazer stuart]

Hmmmm. Well that's not great news. I've been really impressed with the quality and fit of the maniflow system. I wouldn't have thought they would design a system with such a fundamental flaw. And most injection LCBs that I've seen put the lambda in the same spot, just reading 2 cylinders.

I can't weld so I can't relocate the lambda myself annoyingly.

[minisilverbullet]

Hmmmm. Well that's not great news. I've been really impressed with the quality and fit of the maniflow system. I wouldn't have thought they would design a system with such a fundamental flaw. And most injection LCBs that I've seen put the lambda in the same spot, just reading 2 cylinders.

I can't weld so I can't relocate the lambda myself annoyingly.

 

Could very well be the issue. 

 

I not sure how the manifold system looks, but can you just replace the Y piece? 

[Frazer stuart]

Yes the y piece can be replaced relatively easily. I can get a y piece with a lambda boss already welded in for 45 squid on minispares - the fact that you can buy that kinda proves it is an issue!

After a bit of googling, I think you guys are right. In fact, here's a thread about the issue...

http://www.minifinit...t=70139&start=0

Apparently cylinders 1 and 4 run a bit lean so the ECU richens things up, causing issues with idle and emissions.

It's just really annoying that I've paid a load of money for something which essentially doesn't do its job properly! And my cat is presumably being poisoned nicely by the rich running. Brill.

So next step is to buy the y piece with lambda boss, blanking plug for the old lambda hole and extend the lambda wiring. This will take me a while but once it's done I'll post up whether it's worked.

Edited by Frazer stuart, 01 February 2018 - 06:55 PM.

[Sprocket]

Never had a problem with the maniflo manifolds.

Firstly, have you adjusted the throttle cable by the book?

I would be tempted though to say you have an air leak on the inlet manifold, but without actual data from the ECU it will be painful to resolve quickly or easilly

[xrocketengineer]

Never had a problem with the maniflo manifolds.

Firstly, have you adjusted the throttle cable by the book?

I would be tempted though to say you have an air leak on the inlet manifold, but without actual data from the ECU it will be painful to resolve quickly or easilly

It could also be on the exhaust manifold, before the O2 sensor. When cold, (open loop) runs ok, when warm (close loop) the sensor is detecting the extra oxygen from the leak and the ECU is overcompensating with fuel. I would think that if the leak is in the intake manifold then the idle speed would be fast. 

[Frazer stuart]

Hey sprocket - yeah I would have thought that maniflow know what they're on about!

Throttle cable adjusted as per Haynes - even gap at the lost motion link and stepper indexed.

Could I test for a leak by carefully spraying starter fluid around the inlet manifold???

Not sure how I could test for a leak in the exhaust to head seal other than visual inspection...

[MiniJosh92]

Definitely check that the flanges on both manifolds are of equal thickness so are pulling up onto the manifold gasket evenly without leaking. If in doubt check for an inlet leak by spraying a bit of brake cleaner around the manifold gasket while it it is idling to see if the revs pick up.

[xrocketengineer]

Here is an easy way to check for exhaust leaks. Make sure to check all joints before the O2 sensor.