Leaks detected in the induction

[gavgavgav]

Got a new tool, a smoke tester. I was suspicious that the plenum spacer I have fitted was leaking as its quite fiddly to fit, and there is twice the gaskets. Turns out its sealed perfectly, what was a surprise was that I found. 3 separate leaks, the first being the stepper motor thought the motor and the electrical connectors. This was new from brit part a couple of years ago and done less than 1000 miles. The second looks to be from 2 places in around the throttle assembly, but its hard to tell, and the third a hole below the TPMS.

Stepper motor is an easy one, get one that's not s**t, and recommendations welcomed(!) I'm assuming that nothing should be leaking, What would be the culprit for the throttle assembly, and does anyone know if there is supposed to be a hole under the TPMS? (I've not removed anything). thanks.

[sixor8]

I expect the throttle spindle would not be airtight, especially with a bit of wear. If the leaks are very small, would the stepper motor not be able compensate? Especially since one is its OWN leak.

[scottliv]

I had the same issue. Smoke was pouring out the throttle shaft. It was solved with a new seal. AUD3577. It is an SU carb seal. I also had a slight one out the stepper,

[Belle427]

I wouldnt worry about it too much if the car runs ok, dont know what the one under the TPS is though.
Britpart=stpart so id maybe try to find an oem stepper if it concerns you.

[gavgavgav]

Thanks for the part number! I've installed a new bush and stepper motor from motorclan, having taken the plenum off the car, I am puzzled about the hole below the TPS. It looks purposefully drilled. Taking off the TPS sensor you can also see machining prepping for other holes to be drilled (see next top the TPS mounting hole). Does anyone have any idea what this would have been used for? I'm thinking of blocking the hole off. (both photos below is the plum turned upside down)

[eliot]

sixor8 said:

I expect the throttle spindle would not be airtight, especially with a bit of wear. If the leaks are very small, would the stepper motor not be able compensate? Especially since one is its OWN leak.

yeh agreed.

[Belle427]

The stepper housing usually has a small hose tail for the hose to the fuel pressure regulator, is this there on yours?

[eliot]

do you actually have a running problem - because the leaks dont seem significant.

[gavgavgav]

eliot said:

do you actually have a running problem - because the leaks dont seem significant.

I do, initially it was unstable idle at low revs when pulling off and reversing. If you started it and never touched the throttle it will idle fine, tough the throttle a little bit and sometimes results in kangarooing until stalling. This was improved with a new stepper as when using roverguage you can hear the old one lagging and slightly stuttering a bit, the replacement was much more responsive. Then failed a MOT for (very!) poor emissions, and roverguage showing excessive lambda trims short and long term, which is why I'm looking for problems. After performing a voltage test I've replaced the airflow meter for a new one, then gave a smoke tester a go for the first time to then see the 3 leaking areas. I don't know what is or is not significant, bearing in mind all these leaks are unmetered air I'm guessing it has an impact, not sure how much of an impact though.

[eliot]

gavgavgav said:

I don't know what is or is not significant, bearing in mind all these leaks are unmetered air I'm guessing it has an impact, not sure how much of an impact though.

Yes they are unmetered - but I dont think they are significant, but that's just an opinion. The only experience I have is leaving the bolt holes open when you remove the throttle heater plate - that causes a big enough leak (2 x 6mm holes) to throw the running noticeably out - but your smoke test would of shown that up like a beagle on 20 woodbine.

[Sardonicus]

If you do decide to remove said screws then you need 1/4 UNC bolts/screws or better still grub screws with thread lock applied you can then do away with the heater plate/housing

[eliot]

Sardonicus said:

If you do decide to remove said screws then you need 1/4 UNC bolts/screws or better still grub screws with thread lock applied you can then do away with the heater plate/housing

i thought it was 1/4 unc, but I thought saying it’s 6mm sized hole is easier to imagine

[gavgavgav]

Just to update - I'm leak free now, with the new seals s suggested by scottliv, new stepper motor from motor clan and tapping and blocking the vent hole there are no more seeps of smoke from the tester. Fired it up and it seems to idle fine, especially on light throttle. Next step is an emissions test.