406oc.co.uk

Hi

I have 1997 beast, that goes like a train, but it idles like a badly idling thing idling badly!

It is fine when it is stone cold but when it heats up it goes from virtually cutting out to 2000 rpm and back again until it eventually cuts out.

Also when warm it will cut out unless I heal toe it when coming up to a junction. Very annoying. If this happens it wont start again by engaging the clutch. It has to be re-stared on the key after a complete switch off. Again not always easy.

The car is pretty much worthless so I need to fix it a minimal cost or nothing.

Cheers

sounds like a duff pump

I forgot to mention if I disconnect the throttle potentiometer. it runs as smooth as you like at idle. This makes me think it is not the pump. Also it has just had a replacement pump and was working fine. The replacement pump is displaying the same traits, but has only done about 500 miles or less so I would be surprised if it was that.

I am thinking it must be electronic especially with the pot. disconnected making it run smooth.

Cheers

Biggles wrote:I forgot to mention if I disconnect the throttle potentiometer. it runs as smooth as you like at idle. This makes me think it is not the pump. Also it has just had a replacement pump and was working fine. The replacement pump is displaying the same traits, but has only done about 500 miles or less so I would be surprised if it was that.

I am thinking it must be electronic especially with the pot. disconnected making it run smooth.

Cheers

Had exactly the same problem not so long ago. Was told on this forum that it was the pump.
I took it to a good Pug engineer who read the codes and discovered a faulty engine temp sensor.
Though he didn't have one in stock, one was ordered and in the meantime he reset the error codes and that fixed the rotten idle.
I was told that the reset of the ECM may have fixed the issue for some time or it could re-appear while the temp sensor was giving the wrong info to the computer. In fact, the car behaved perfectly until and after the sensor replacement three weeks later.
If you search through this forum, you'll probably find other posts confirming the same diagnosis.

Sorry James, but every problem with 2.1TD's is not necessarily the pump.

Where is this sensor? Can it be disconnected for test purposes?

Cheers

Biggles wrote:Where is this sensor? Can it be disconnected for test purposes?

Cheers

Sorry Biggles, I can't tell you that, but I was told that you shouldn't disconnect it and in any case, disconnecting it doesn't fix the problem.
The only way is to actually clear the codes and reset the ECU.

Mine was a different car after the ECU reset.
Perhaps someone else can comment, but I couldn't do the reset myself by disconnecting the battery for a couple of hours so I suspect that the ECU has some form of non-volatile memory or backup battery in place.

The temp sensor is easy to replace (took five minutes by the engineer) and isn't terribly expensive (cost A$38 which would equate to about 15 pounds I guess).

Cheers Z

==========================================================
1998 406STDT 2.1 TD
205 Renault Scenic 2.0L petrol

i'd second what zeebee says. It's almost certainly the fuel temp sensor. The good news is that it's really cheap to fix - cost me £40 to get it diagnosed via the fault codes (although I was telling the garage that I was sure it was the sensor!) and have it replaced. My 2.1 has been brilliant ever since.

Hi

Where is this sensor? is it on if those on the fuel filter housing?

The problem has taken a new twist though. To get around to problem I pulled the throttle cable up tight which gives me around 2500rpm, BUT if I put my foot on the brake it drops to 1100 RPM but only after a second or 2. As soon as I take it off it jumps back to 2500. RPM. I have tried this with the vacumme connected & disconnected.

So what the heck is going on there then?

Biggles

Hi

Where is this sensor? is it on the fuel filter housing?

The problem has taken a new twist though. To get around to problem I pulled the throttle cable up tight which gives me around 2500rpm, BUT if I put my foot on the brake it drops to 1100 RPM but only after a second or 2. As soon as I take it off it jumps back to 2500. RPM. I have tried this with the vacumme connected & disconnected.

So what the heck is going on there then?

Biggles

As I said, I don't know its exact whereabouts, but I'll try to find out.
The behaviour you see when you touch the brakes is normal and is telling you that the ECU is still controlling OK.
Because the thing is a "fly by wire" throttle...that is, there is no physical connection between the fuel command and your right foot, there has to be some mechanism whereby the command to stop..ie putting your hoof on the brake, results in the fuel supply being cut back to a residual value. It's a safety requirement otherwise you could find yourself embedded in the back of someone.
You still NEED to have the codes reset. You only risk damaging something by mucking around with things you don't understand.
For instance, disconnecting sensors while the ECU is powered up runs a serious risk of damaging both the ECU AND the sensor! (Not to mention the possible damage of over revving the engine)
These are really too good an engine to risk mistreating in this way and resetting the codes will almost certainly return your car to its former self.
Hope you can resolve it soon. Algy and Bertie would agree with me.