Megane idle problem

Haakon

1000+ Posts
Ok brains trust, this one has me stumped. I've looked at everything and this thing still idles like this. Throttle body calibrated, no vacuum leaks (in fact its wandering around 200-350 KPa, should sit around 400 so not a leak), o2 readings look ok.

The engine did come from an automatic car and is now in a manual - could it have different inlet cam timing that the manual ECU is not dealing with causing more vacuum...?


Idling

Exhaust sound on idle
 
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JoBo

1000+ Posts
No video:( Idles fast? By how many RPMs; regular or irregular/hunting. Consistently hot and cold?
 

Haakon

1000+ Posts
Hot and cold. Has a bad Rev hang when changing gears too.

I’ve been swapping parts over from the Scenic to rule stuff out, including the manifold. I’ve swapped fuel pumps, injector seals, coils, plugs, throttle bodies, new o ring seals on upper manifold, new map sensor, new PCV valve, ruled out leaking booster or fuel vapour line. Hours and hours chasing my tail.

One last thing is replace lower manifold gasket, which I’ll do when I get a new engine mount (tried a cheap mount and it died instantly…) as the lower manifold is structural.
 

JoBo

1000+ Posts
Sorry, i'm only guessing - injectors clean? Any feedback from the alternator? O2 sensor? No exhaust blockage? I know, a shotgun guess:(
 

Haakon

1000+ Posts
And this is an engine that was running perfectly before being plucked complete from the hail munched car, sat in the shed for 6 months and fitted to the body donor.
 

Fordman

1000+ Posts
I would call that "hunting". You can even see the "gases" inside of the exhaust tip changing as it hunts in rpm.
And is the vacuum gauge fluctuating slowly in time with the hunting, or is it fluctuating rapidly?
In some ways the slow fluctuation points to the air filter being partially blocked, or some other vacuum leak. Maybe try without air filter, or with one if it isn't fitted at the moment.

Aside, is it really in the range 200 - 400 Kpa? That is tyre pressure numbers. Like most people still work in tyre pressure PSI, most vacuum readings are still in Inches Hg, and all the old (and new) charts are in "Hg. No matter, it's all just relative.
But I don't understand your first post - "no vacuum leaks (in fact its wandering around 200-350 KPa, should sit around 400 so not a leak)", so if it should be around 400, doesn't lower 200-350 indicate leaking?

And that exhaust outlet - I was trying to work out the video angle, it looks like the exhaust outlet is pointing downwards somewhat inboard from the edge of the car, strange, interesting?
 

Haakon

1000+ Posts
I would call that "hunting". You can even see the "gases" inside of the exhaust tip changing as it hunts in rpm.
And is the vacuum gauge fluctuating slowly in time with the hunting, or is it fluctuating rapidly?
In some ways the slow fluctuation points to the air filter being partially blocked, or some other vacuum leak. Maybe try without air filter, or with one if it isn't fitted at the moment.

Aside, is it really in the range 200 - 400 Kpa? That is tyre pressure numbers. Like most people still work in tyre pressure PSI, most vacuum readings are still in Inches Hg, and all the old (and new) charts are in "Hg. No matter, it's all just relative.
But I don't understand your first post - "no vacuum leaks (in fact its wandering around 200-350 KPa, should sit around 400 so not a leak)", so if it should be around 400, doesn't lower 200-350 indicate leaking?

And that exhaust outlet - I was trying to work out the video angle, it looks like the exhaust outlet is pointing downwards somewhat inboard from the edge of the car, strange, interesting?
 

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COL

Alpine A110
Not sure what the problem is, but the only suggestion I can come up with is everything plugged in correctly? I would double check all the plugs and pipes to make sure they are in the correct place and properly connected.

After that make sure you have correct fuel pressure and ignition timing is correct.

Good luck with it.
 

AlexB

New member
200-350 KPa is indeed tyre pressure numbers, MAP reading at ign on and 0 rpm, or at Wide Open Throttle at sea level is usually 101Kpa (1013mbar) and the diagnostic screenshot above shows it ranging from 239.3-422.7mbar which rounds out to 24-42KPa.

Is the engine harness also from the auto? The manual ECU may not know it's in idle mode if the harness has unterminated connector for the auto Park/Neutral sensor, or is missing the wire from the clutch pedal to ECU (if such an input is used for this vehicle).
 
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AlexB

New member
looking at the 14 deg swings in the diag tool screenshot for PR126 ign advance after anti-pinking correction, is there a graphable value for knock on it's own or ign adv before knock correction?
 

Haakon

1000+ Posts
looking at the 14 deg swings in the diag tool screenshot for PR126 ign advance after anti-pinking correction, is there a graphable value for knock on it's own or ign adv before knock correction?
Advance and advance after pinking correction are the same, so that jsut says there no correction going on. I think the ecu is chasing timing as it stumbles at low rpm
 

AlexB

New member
A problem with diagnostic tools on a pc is update rates are not sync'd to the frequency domain and confuse what is chasing what.
How do you know Advance and advance after pinking correction are the same?
e.g. In the screen shot PR448 lags PR126 by at least 1/10 of a second, in reality they would be synchronous.
e.g PR055 RPM doesn't correlate to the PR448 ign adv, in general, when an ECU can't control idle via the IAC (or DBW throttle blade) it will retard the ign advance to drop the revs, graph shows the opposite.
e.g. PR055 shows rpm decreasing when ign is at 12deg for 2seconds and increasing with ign at -2.2 for 2 seconds, the opposite to what I'd consider normal.

Which brings me to my diagnostics mantra, garbage in = garbage out and check that all required inputs for a manual ECU are present.
 
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AlexB

New member
Is the teeth for the Crank Angle Sensor part of the flywheel? If flywheel was changed and not located by a dowel on the crankshaft, could it be offset by one bolt making it over advanced?
 

Alain

New member
Ok brains trust, this one has me stumped. I've looked at everything and this thing still idles like this. Throttle body calibrated, no vacuum leaks (in fact its wandering around 200-350 KPa, should sit around 400 so not a leak), o2 readings look ok.

The engine did come from an automatic car and is now in a manual - could it have different inlet cam timing that the manual ECU is not dealing with causing more vacuum...?


Idling

Exhaust sound on idle

I am fairly certain that there are two different TDC sensors for the 770 and 771 engines. For the 2006 F4R770 manual with ND0015 man. box it should have a sensor without the cable part no. 8200513668 or Vemo V46-72-0079.
Alain
 

Haakon

1000+ Posts
I am fairly certain that there are two different TDC sensors for the 770 and 771 engines. For the 2006 F4R770 manual with ND0015 man. box it should have a sensor without the cable part no. 8200513668 or Vemo V46-72-0079.
Alain

Nope, same sensor and part number. Have swapped those anyway...
 

Haakon

1000+ Posts
Is the teeth for the Crank Angle Sensor part of the flywheel? If flywheel was changed and not located by a dowel on the crankshaft, could it be offset by one bolt making it over advanced?

It is a new (eye watering expensive...) Valeo dual mass flywheel (there is well over a grand in just the clutch and flywheel!!!). But they dont use dowels, one bolt is offset and they can only go on one way. If it was out by a whole bolt hole, it wouldnt even start.
 
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