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Proton won't idle

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Very sad.

Not only has the Proton Aeroback been rear-ended by a boy racer, it now won't idle at all.

It revs clean and smoothly but when it slows to idle the revs just drop down until it cuts out.

It starts immediately again but when my foot is off the throttle it just dies off.

When driving at speed it's fine - no coughs or hiccups.

I've replaced all vacuum hoses and checked plugs which were new a few months ago. It had new rotor arm and distributor cap in the summer.

When I remove the little vacuum pipe that sits on top of throttle body it makes no real difference.

It's fuel-injected and doesn't use OBD11 - apparently it's an Mitsubishi diagnostic system.

Completely confuzzled...

The car is beyond economical (cosmetic repair) but was hoping to nurse it along until I found another old kipper..

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cable controlled throttle? Can you tighten it up to raise the idle speed? Dirty fix* but if its going to be nursed along for a few months and there is no MOT in the meantime it'll fix it I suspect. You'll just idle at 1200rpm rather than 700rpm?

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Does it have any sort of lambda system? Another dirty fix would be drill a hole in the throttle plate to keep the mixture right it would have to add more fuel to make up for the extra air. Extra air + extra fuel = higher idle speed.

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Does it have any sort of lambda system? Another dirty fix would be drill a hole in the throttle plate to keep the mixture right it would have to add more fuel to make up for the extra air. Extra air + extra fuel = higher idle speed.

Think it has oxygen sensors - It has a catalytic convertor and multi-point fuel injection. All from the Mitsubishi 4g15 engine.

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Air vacuum leak?

That's what I think. The car exhaust was given a shunt when the idiot kid rear-ended my car. The car has sounded different - before then the engine was as silent hum and you only heard the whirring of the autobox servos, etc. but not it sounds like a real engine. Wonder if there's leak around that at the front end somewhere.

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I can't remember if these have the IAC valve (idle air control valve). Probably carboned up.

Other possibility is a loose screw around the throttle body or a split pipe.

Sounds very much like you have a small air leak and I doubt that it is going to be expensive or difficult to repair.

 

I seem to recall some mention of a screw or a bolt on the bottom of the throttle body that can come loose causing an air leak but not sure if this is relevant in protons as well as Mitsubishi.

 

Good luck with sorting it out

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Guest Hooli

If it were a two litre 405 I'd check the MAP sensor. It's always the MAP sensor when this happens to a two litre 405.

 

That is logical as the MAP sensor is only used at low throttle/revs in most engines.

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Also any photos of the damage? Just because it's by all rights beyond economical repair doesn't mean that some folks on here wouldn't take it on as a repair if the car's in otherwise good nick.

 

Given the problems have started since the car has had a shunt I'd have a good dig around for anything that's been physically broken.

 

If the exhaust has taken a bit it's not impossible that there's a joint cracked (the front flexible joint was always pretty fragile on these as I remember) and a leak upstream of the O2 sensor can cause quite a few odd running issues.

 

Does this use a micro switch to detect closed throttle or just a standard potentiometer?

 

Don't assume that serving the throttle open a bit will necessarily work - some systems will get confused if it's reporting an open throttle that's totally static for more than a few seconds, assuming that there's a fault with the throttle position. I discovered that on the Lada when the throttle cable snapped...wedging it at 25% didn't work as the value wasn't changing, it kept throwing a throttle position sensor coherence error and dropping the engine to a (very rough) idle by messing with the fuelling. Good safety feature if the throttle ever stuck open though (as happened to us on a Fiat Panda once).

 

I'd reckon this is likely to be a wire/connector that's come off somewhere or been damaged rather than a component failure though.

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What would be the plan with the vehicle when you have finished with it too? If you are scrapping it I'd be willing to talk price for it for spares for mine.

Hi,

 

I'm in North Kent. Would be good to see it live on as a donor. I have new Pagid brake discs and Ferodo pads that are yet to be fitted. The engine's done 49k miles and is silky smooth.

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Also any photos of the damage? Just because it's by all rights beyond economical repair doesn't mean that some folks on here wouldn't take it on as a repair if the car's in otherwise good nick.

post-26409-0-67249500-1541611127_thumb.jpg

post-26409-0-98389900-1541611141_thumb.jpg

post-26409-0-19245200-1541611155_thumb.jpg

post-26409-0-24671700-1541611169_thumb.jpg

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I think under the bumper something has been pushed in. The rear quarter side panel looks fine -no obvious creasing, etc but rear door needs a slam now.

 

The interior is immaculate.

 

Here are pics of the Proton when I bought it in May. It will need some welding to the sills for the MOT in April.

 

It had new cambelt, water pump, tensioner, coolant/oil/filter change too.

 

I need something reliable now as I have to look after my housebound elderly parents.

 

 

post-26409-0-38133700-1541611949_thumb.jpg

post-26409-0-22226500-1541612029_thumb.jpg

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Check the earth point on the bulkhead, immediately behind the inlet manifold. The earth cable is too short at that point and it breaks inside the insulation, causing many issues that can include failure to start too.

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Any joy?

 

Fuel pressure should be min 64psi (unregulated)

Pressure at rail  should be 47.6psi (regulated)

 

Idle speed is controlled by ECU via stepper motor. There is a coolant operated fast idle valve next to it. 

 

Please do not adjust the base idle screw until basic check have been carried out. It's a bit of a faff to reset.

 

I have a picture somewhere if it helps.

 

 

Also you can check the reading on terminal 67 of ecu - should be 0-1v for idle switch on.

 

 

:-)

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Any joy?

 

Fuel pressure should be min 64psi (unregulated)

Pressure at rail  should be 47.6psi (regulated)

 

Idle speed is controlled by ECU via stepper motor. There is a coolant operated fast idle valve next to it. 

 

Please do not adjust the base idle screw until basic check have been carried out. It's a bit of a faff to reset.

 

I have a picture somewhere if it helps.

 

 

Also you can check the reading on terminal 67 of ecu - should be 0-1v for idle switch on.

 

 

:-)

Wow - sadly that's beyond my monkey-like spanner skills :-(

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Shame, looks to be a tidy one too.

Tis a shame. I really enjoyed this car throughout the summer. It started every time and I clocked up 6k miles since May without any issues at all. Even the original Blaupunkt cassette worked fine :-D With just two pedals it was like driving a dodgem.

 

Seriously dependable cars until boy-racers ram them from behind. Unfortunately I don't have time to fix and need a reliable car now to help look after my old folk. Otherwise I was going to get it welded underneath and see how many years I could get it through MOTs.

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Have to admit I really fancy one. A lot of the same charm as the Lada, but an easier car to actually live with in 2018.

 

They were better screwed together than a lot of budget motors too. The Malaysian people were (and still are) very proud of the old Saga (as it was known locally), and the "tried and tested" design use was very deliberately made decision. The earlier cars in particular were solid, they did thin the metal down it felt in the later cars.

 

Had one brief shot of an Impian a few years ago, didn't seem to be anything whatsoever wrong with it...comfy enough too. Felt a bit "soulless" but that's kinda true of most early 2000s cars I think.

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