Whats plugged into the Plenum ?


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New member
Jul 18, 2021
Hi Guys
In the process of stripping down my 1.7 for next season , just taken off the plenum & inlet manifold and appart from the odvious ( brake servo vac pipe & throttle body pos ) what are the other pipes and sensors , especially the little box bolted to it which when taken off reveals two round chambers and a bellows looking piston , sits adjacent to the throttle body ?

Can any be discarded ? or by-passed , am looking to fit a different plenum and need to know what I must keep .

Thanks in advance


Not really. As the name suggests, it controls the engine idle speed by controlling the amount of air that bypasses the throttle butterfly. I mean you could, and blank off the two holes but it won't idle. Just out of curiosity why would you want to?
Bloody icv… so innocent and insignificant looking but a real slag when she gets iffy.
Unlike the girlfriend it’s easy to change though…!
The Air Intake Control valve (AIC) mentioned can be cleaned out with Air Intake & Carburettor spray to provide a smoother idle, acceleration and compensation for accessory load on the engine speed (power steering, brake booster, aircon, etc.). If you take it off (NOT remove it permanently!), it's probably best to re-fit it with a new sealing gasket, to prevent any unwanted air leaks into the inlet manifold. A little bit expensive from a Ford dealer for a small piece of waxed paper, but it does have what looks like silicone sealant around both sides of both port holes, presumably to give a good air-tight seal.
I cleaned the original AIC valve on my Puma 1.7 years ago, as it was getting very jerky and balked when slowing down and the revs dropped through about the 1,500 rev mark! The spray got loads and loads of black crud out of it and I did follow online advice to replace the gasket. It definitely made a good improvement to smooth running for quite a few years.
If anybody uses this spray USE GLOVES AS IT IS A VERY AGRESSIVE DEGREASING SOLVENT AND WILL REMOVE THE OILS OUT OF THE SKIN ON YOUR HANDS, ETC. (from a lifelong lilywhite handed office worker!)!
The AIC valve is quite surprising, as although it is quite small, it can actually provide enough bypass of air passed the throttle body butterfly plate, to boost the engine IDLE speed to over 4,500 revs - YES, over 4,500 revs at IDLE!!! I found that out when I eventually decided to replace the original a few years ago, with a new aftermarket one bought from THE popular online auction site. There is supposed to be an engine management computer (PCM) routine for recognising and setting up a new AIC valve for most cars, including the Puma (Goggle it to find out), but which didn't appear to work in my case. The replacement got taken off and the original put back on - no harm done!
The AIC valve also results in (not causes) the infamous over-revving problem, apparently previously referred to on Puma forums something like the "Cruise Control Effect". That happened to my Puma, but that was down to two pairs of worn, broken, frayed wires for the power steering (PAS) high pressure sensor and the aircon magnetic clutch, which gave wildly incorrect signals the the Power Control Module (PCM), causing it to tell the AIC valve to "really boost those revs to stop the engine stalling!".
These two pairs of wires were the only wires to exit the end of a semi-rigid plastic tube (harness) protecting them in the engine bay up to the location of the PAS HP sensor & aircon magnetic clutch. However, the end of this plastic tube unfortunately wore through the insulation of all four wires, breaking one of the aircon clutch wires (making that inoperative) and the shorting between them all caused the confusing signals to the PCM and the resulting over-revving!
Just a thought to point out - has anybody else seen reports on this and other Puma forums of engines over-revving when the aircon is turned on? Just saying......
Anyway, thanks to Ian at Pumabits, a few years ago, for splicing a new piece of harness with replacement connector plugs for the PAS HP sensor and aircon clutch, to replace those four failed wires. That completely cured the over-revving and even got my aircon running again for a while (along with a re-gas).

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