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Wild idle on Zetec Blacktop


Chris Broster - Bristol & Bath AO

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jonjh1964

Chris,

 

If you can get to Yeovil I’ll show you how to balance Jenvey ITBs and lend you a synchrometer. Happy to show you on mine if you don’t fancy bringing the Westfield.

alternatively there’s a Terryathome video on YouTube that helps. What ECU  have you got fitted.

 

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On ‎07‎/‎07‎/‎2019 at 18:29, Chris Broster - Bristol & Bath AO said:

I did however find that one bolt from the throttle linkage mounting was missing on the ITB and this was causing the linkage to swing when accelerator pushed. Great service from Jenvey - replacement free and next day delivery.

 

Yes said you had a bolt missing on the linkage which you have replaced, are you sure that bolt isn't your issue, depending on which bolt it is you may have tightened it and it's changed the rest position or isn't allowing the full release or return of the linkage? On an unloaded engine it doesn't take much of a throttle opening to allow the engine to run away up to those sort of revs.

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Chris King - Webmaster

You say you replaced the fuel pressure regulator - is it set to the exact same pressure as before?

 

Have you connected the MBE to a PC and checked the TPS settings are correct?

 

A note of caution on an MBE ECU though - do not mess with TPS itself or the settings without an understanding of what is involved in setting it first. 

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Dave Eastwood (Gadgetman) - Club Secretary

Just to double up on what Chris said, under no circumstances alter the physical position of the TPS on an MBE ecu without knowing the exact position it should be!

 

They are unlike practically every other aftermarket ECU, in that there is no easy programming mechanism for the uninitiated to reset the TPS maximum and minimum figures.

 

With an MBE system, the TPS position is typically set with a multimeter so that with the throttles in the "closed" position, the signal output of the TPS reads a specific Voltage. Don't move it without knowing either the Voltage, or how to find it out from your engines maps.

 

Bare in mind that different start maps for different engines sometimes use different TPS closed Voltages, too. Somdont just assume it will match someone else's.

 

While the actual settings and engine sensors may differ, there are, or were, some really, really good set up guides for installing Jenvey's with MBE ecu's on the SBD web site. It's worth digging them out and having a read just to familiarise yourself with the process.

 

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Chris King - Webmaster
11 minutes ago, Dave Eastwood (Gadgetman) - Club Secretary said:

under no circumstances alter the physical position of the TPS on an MBE ecu

Yep. As has been discussed before, been there. 

 

I “played” with the TPS location on my first engine when the car wouldn’t idle properly - and I also adjusted the throttle stop - along with the fuel pressure. This three way mess (not helped by a faulty FPR gauge) resulted in a complete re-map!

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Chris Broster - Bristol & Bath AO
On 12/07/2019 at 17:01, the stoat said:

To test for leaks in the inlet spray the outside with something flammable like carb cleaner, if the revs rise you have a leak and if they don't there is no leak.

 

Just tried all the above and no joy so think it must be butterflies open or leaking manifold or TB seals? 

 

Cheers @Stoat, again for the help, I,ll try that one out.

 

Trev, never a stupid question, yes wound it all the way out.

 

b*******ed if this warm weather isn’t tormenting me too!

 

 

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Kit Car Electronics

Stick some photos up looking into throttles and above them? Wouldn't take long to unbolt manifold and bodies to check gasket/ O-rings, also check injector seals as those O-rings can also split. This really shouldn't be so hard to find- you'll kick yourself when you do...

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Chris Broster - Bristol & Bath AO

Thanks again for all the help. JJ we are in Yeovil next Sunday (hoping to go to Sherborne Classic Car Show) so if you are free that would be fantastic.

 

To answer:

  • TPS have not touched this as understand the delicacy of this.
  • Sadly don’t have PC and Lead to connect ECU up - all Apple house, have old PC being updated and leads are on order! 
  • Throttle linkage bolt- you may have a point as even with throttle cable disconnected still racing. 
  • I cleaned all the trumpets, before and around the butterflies last night, no obstructions.
  • will try the external leak test today
  • failing that it will be unbolt TBs and check gaskets and also the Injector seals

i also have a call booked Monday with Dave at InterPro who mapped it before the fateful Castle Coombe Track Day and he is going to talk me through trouble shooting. 

 

Cheers 

 

chris 

 

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Have you adjusted the throttle stop on the Jenvey bodies? I had a ridiculously low idle (less than 500rpm) and I found an adjuster between the two banks - wound it in a bit (a tiny bit!) and got a steady 800ish

 

Could it be that even though you've backed off the throttle cable adjustment, you've still got the stop on the butterflies partly open

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Chris Broster - Bristol & Bath AO

And the winner is.......

 

 

 

 

 

 

 

 

@Snappy!!!! 

 

Last night I removed the bolt, Circled in BLUE, I had fitted into the throttle cable to throttle linkage mechanism (that holds it to the TBs).  This 'allowed' the linkage to move with accelerator depression and in effect rotate the linkage from horizontal to approx 10-15o  below horizontal (Blue Line) - this had the effect of pushing the actual TB throttle linkage/backing off and shutting the butterflies. 

ITB_Throttle_Linkage_(2)_LI.thumb.jpg.a250c6e66a713d720a59cca40d1000aa.jpg

When started it was at 500 rpm!!!!

 

So wound in the idle screw until at 900 rpm and then shut down.

 

Then disconnected the 90o transfer arm from the cable bell crank to the butterfly actuator and refitted the bolt, hence securing the cable linkage in the horizontal.  Then with some trial and error and adjusting both the 90o arm and the locating screw/ball joint until it was smooth in operation.  Each time starting to check still on idle....several attempts here (including me winding in when should have been out and 180o out etc etc)

 

Then finally at right idle and smooth unimpeded movement I adjusted the throttle cable to be tighter, with 2-3 mm play before take up.

 

So, as mentioned before, the engine was behaving correctly with correct fuel, air, spark to go broooom....just that the 'correct' fitment of the throttle cable linkage had caused the mechanism to advance to approx 3000rpm position.

 

Now that is all done, time to refill Main and Diff gearboxes, fit seats, seat belts, roll bar and get out for a test blat!  Hopefully before Summer disappears...

 

I cannot thank you all enough for your advice and buckets of patience whilst I eliminated so many 'possibles' and got back to the start...and yes @Kit Car Electronics, Mike I have kicked myself several times over for such a simple fault that I added by correcting a different error.

 

Chris

 

 

 

 

 

 

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Thats what the club is all about, so many people who are happy to help.

Every time I have needed help I have found it via wscc..😘

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Chris Broster - Bristol & Bath AO

Finally got the car all back together today and managed a quick trip round the block. 

 

Now back to check all levels are spot on and connections, fasteners and clips etc are fast and leak free.

 

Happy days 

 

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Chris King - Webmaster

Excellent news Chris. Just in time for some rather glorious weather!

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