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stator

Diagnostic / ECU specialist in Plymouth area

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Anyone know a specialist in the Plymouth area who can help me sort out my annoying 17 year old Lupo?

Map sensor error comes on every few minutes. Garage say there's nothing wrong with anything. Sensor replaced a couple times.

So I need it fixed before the next MOT next year.

Need someone reliable, worried I'll find someone who will waste hundreds of pounds not fixing the problem.

 

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There's a fault in that department, doesn't mean the sensor is at fault.

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Probably a manifold/air leak downstream of the throttle. You usually get this fault if at idle on a warm engine, the vacuum is too weak. ie, air is getting in somewhere. Sensor reporting a plenum vacuum that should be stronger, but isn't. So looks like the sensor is messing about. Try blocking off any sources of external air temporarily. Like brake servo feed.... those vacuum pipes do have a tendancy to crack/split at the joins.

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Brake cleaner is your friend.

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Never thought of using that... i always use a tank of propane with a hose. 

@stator the extra air mixed with extra fuel (gas/solvent whatever) makes the engine rev up when it has more mix to burn :)

when it revs up, you've found the leak.

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Brake cleaner is cheaper😂

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Saying that I’ve got a decent vac tester and diag machine at home that I’d probably use first if it’s raining.

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Thanks for the tips, but they're beyond me to be honest.

The manifold leaks were all repaired by the garage previously, the error has not gone away.

That's why I'm looking for someone who can diagnose the fault or replace the ECU etc

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What engine is it and what codes?

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Just had an idea... it is possible, that the ECU internal fault diagnosis thing is getting mixed up.

It's probably backing off the idle air circuit (which controls the idle RPM) if there is a leak (still), and it's picking up the O2 sensor readings as the mixture being too lean. As in, too much air compared to the amount of fuel that the ECU has decided it needs for a steady idle. It knows what sort of injection timing is normal at idle, and is probably running at "end stop".

But. It is possible that poor fuel flow is also resulting in a lean mix. Fuel filter? Pump? Hose leak? Fuel pressure regulator? Vacuum connection? At full throttle, is there a lack of power after a few seconds? = fuel problem.

I doubt there's an ECU fault. The vac test concept shows how well the engine is sucking in air. The higher or stronger the vacuum at idle with hot engine, the better the thing is running. Engines that can run with really strong vacuum at idle are usually very efficient and generate loads of torque. So the vacuum level is a good indicator of engine condition.

The MAP (inlet manifold absolute pressure) sensor measures the vacuum level to work out how much air is available. Then the ECU works out the right amount of fuel to inject, based on RPM, coolant temp, air temp, ambient air pressure, load demand and previous cycle exhaust result (O2 sensor). If the previous result is out, it tries changing injection amounts to get back to the result it's looking for. 

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I'd even contemplate testing the wires with a continuity tester in case it is rubbing somewhere.

Sometimes under the battery.

If the timing was off they do throw up codes in odd places.

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It's the 1.4 16V AUA engine

Error code is this one

http://wiki.ross-tech.com/wiki/index.php/17566/P1158

 

It's been happening for 5 years, to varying degrees. There were some leaks in the manifold which caused problems and were repaired. The error went away for 3 months.

But most of the time it causes no problem at all. Engine always seems to have full power.

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Maybe the repair didn’t last? But I’d definitely be checking the wiring to the sensor from the ecu. As has been suggested. 

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I couldn't even identify the wiring from the ECU to the sensor to check it

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Fortunately for you it is all colour coded.

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Yeah, pull the shroud back from the sensor and the cables with have colour codes, then look for the same colours at the ecu end and check for continuity. Saying that though if it’s intermittent you can’t guarantee a faulty reading, could do with a proper test point kit and then wiggle the loom about.

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Take the battery out and look under the tray.

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Sausage is a sausage.

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My bet is that there still is a leak from what's been said. Probably used the latest formulation hylomar blue sealant on the gasket face which is new, different, and environmentally firendly. It's been ruined. Get some high temp silicone.

yeah, if MAP was completely wrong, it'd probably be gutless and run in some sort of limp mode. If it's ok at full throttle, that tells me that it only happens at high vacuum. Idle. =Leak.

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It hardly ever goes into limp mode. It's done it once or twice in 5 years. Restarting the engine immediately always fixed it.

When it had a real leak, it started thumping on gear changes, as it's an automatic transmission.

 

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