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MG Midget and Sprite Technical - Timing Advice - NMC!

Hi guys! Ive returned to the forum because i simply cant find the quality of advice on any other forums! All credit to MG owners, you do know cars!

I've just changed the head gasket on a 98 Fiat Punto 1.2. The head has been resurfaced. Ive put on a new timing belt and it seems to run well. I set the timing with the marks on the block and head.

The problem is the engine almost stalls when you lift off the throttle, when stationary. could this be a timing issue? Maybe a tooth out or something?

Heres a short video...the banging noise is the deteriorated catalytic converter thats being replaced tomorrow...

http://s185.photobucket.com/albums/x130/LMG5K/?action=view¤t=VID00054.flv
Rob McGeown

A clogged catalytic could certainly contribute to this. Otherwise, it is a classic symptom of a vacuum leak.
David "never touched a Punto" Lieb
David Lieb

Do you need to re-connect or reset the IACV (Idle Air Control Valve). Or maybe even recalibrate the throttle-pot once the battery has been disconnected & reconnected?

On EFI, the idle speed isn't controlled by a butterfly end-stop screw; it's controlled by a stepper-motor that bleeds air into the inlet under the control of the ECU. It provides for high idle speed when cold, and stable idle speed for normal operation.

If this valve is closed (and not being correctly contolled by the ECU) then the car won't idle.

Sometimes IACVs get gummed up with evaporated fuel and need cleaning. You can spot them between the engine-side of the air-filter and the inlet plenum.

A
Anthony Cutler

Thanks guys,

It idles OK, its only after you rev and let of quickly that i threatens to stall.

I'll check all the vacum hoses, but im sure they're all on securely. I've got a new cat coming tomorrow, so that will certainly make things easier to diagnose.

Its a very easiy engine bay to work on!


Rob McGeown

>>>>>>It idles OK, its only after you rev and let of quickly that it threatens to stall.<<<<<<<<

To me that would indicate a worn fuel filter, a fuel pressure regulator / fuel pump issue....This is just a guess, based on my own experiances, but a good starting place to look into

Are you sure a midget condenser didnt accidently fall into the engine and attach its self to the electrics.


Prop...We are Borg (midgets) condensors...you will be asimilated, escape is futile....Prop
Prop

Hi Rob,

Slightly off topic, but don't be afraid to mess about with the timing on this engine, it is a non interference engine, hence if you have timing wrong or even if the timing belt broke it will not do any damage to the engine as the pistons cannot hit the valves. Going from memory, i'm pretty sure you can adjust the idle speed (there is a stop screw) as this is only a single point injection engine.
Is there a rev counter fitted? if so is it reading erratically? this can be caused by a build up of iron filings around the crankshaft position sensor, and could be the cause of your problem.

Jim
Jim Redmond RWA Midget

This thread was discussed between 15/10/2009 and 20/10/2009

MG Midget and Sprite Technical index

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