dCi Revs slow to drop between gear changes, starting problem - Renault Forums :: Independent Renault forum

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dCi Revs slow to drop between gear changes, starting problem

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Old 9th May 2011   #1
lags04
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dCi Revs slow to drop between gear changes, starting problem

Q1.

I have an 04 Lag II dCi, when changing gear the revs aren't instantly dropping, and in fact give a slight kick before they do.

Also, when coming to a stop, the revs are dropping low, and has stalled on occasion, but as soon as stationary they rise to normal again.

It has been suggested the latter is the turbo pressure sensor on the plastic intake pipe going from the intercooler to the inlet manifold?

I tried one from another car but the orange light on the dash came on, the glow plug (curly line)one and what looks like an engine block (usually ECU symbol), as soon as the original was put back this went off, they where a different shape (plug at 45deg on the other one, original is totally flat) but I don't think that matters?

Q2.

Also, I noticed that the reverse lights weren't working, so removed the plug from the switch and fed power through it to see if the lights would work, in order to check for continuity, which they did, so this would suggest a faulty switch.

Thing is, after I did this, the car wouldn't start without the clutch pedal being depressed, suggesting the car is in gear, which it wasn't, after a while this recified itself but has now returned.

I have noticed that the switch that the clutch pedal is meant to depress when fully up isn't actually touching the pedal, it's about 1mm away, though pressing this in by hand doesn't make the car start without the pedal being depressed.

Could this be down to the faulty reverse switch?

The car recently had a new turbo and EGR (not second hand).

Q3.

When you start the engine the fan fires up straight away, and stays on until you turn the engine off and the shut off valve activates, as soon as the shut off valve activates the fan goes off, so it's not been wired directly to the ignition as some do if there is a faulty TS.

Temp is just below half way which is normal, but I'm sure my last Lag II dCi didn't do this?

Any help greatly appreciated.

Last edited by lags04; 9th May 2011 at 05:01 AM.
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Old 9th May 2011   #2
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Re: dCi Revs slow to drop between gear changes, starting problem

Ref Q1:

Just noticed an error and I can't edit, it's not a picture of an engine block, it's a square with a zigzag line, but when that sensor (TPS/MAP) is disconnected there is no power.

Disconnected the MAF and that made no difference, as I had cleaned it with engine cleaner spray, and I read that this can damage them?

It didn't actually start with the problem with the revs until after I cleaned the intake system with Nitrox rocket boost spray, but can't think how that could have caused a problem, coincidence?
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Old 9th May 2011   #3
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Re: dCi Revs slow to drop between gear changes, starting problem

Anyone?
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Old 9th May 2011   #4
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Re: dCi Revs slow to drop between gear changes, starting problem

The so-called wonder spray may have damaged the sensor elements in the MAF sensor. It;s not recommended on engines fitted with a MAF.

Also applying voltage via the wiring loom to the reverse lights may not have been a good idea.
The lighting and starting systems are comtrolled via UCH's and they don't like voltage up the wrong way if you get my drift. Most work at around 2.5 volts.

It may be worth checking if the clutch switch is actually working correctly - you'll need to remove it in order to test.
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Old 9th May 2011   #5
lags04
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Re: dCi Revs slow to drop between gear changes, starting problem

Like I said, disconnecting the MAF made no difference, so I dobt that is at fault?

The Nitrox wasn't applied through the MAF but after it, and I've used it in the same way on my old Lag dCi without issue.

Regards starting, you have to depress the clutch in order to start the engine, meaning it thinks it's in gear, so a switch somewhere is working, but the pedal isn't touching the switch when it's fully released, how many switches are there on the clutch pedal? Pressing the pedal switch at the top doesn't do anything regards starting.

Any ideas on the revs and the fan?
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