Peugeot 306 (1993 - 2001) - 1998 1.4S - intermittant ECU light | Technical matters | Back Room Forum

What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks

Tue 29 Jan 2008 21:55

1998 1.4S - intermittant ECU light - tonylds

Hi
Can anyone help with my problem please (Peugeot 306 Meridian 1.4 S reg petrol)

The ECU light on my my peugeot 306 intermittantly comes on and the engine jutters, but only after travelling on a motorway for about half an hour. The light goes off again but the engine continues to "jutter". The problem then suddenly clears and may not occur again at all on the rest of (or the return) motorway journey.

I took the car to a diagnostic test station who told me the lamda oxygen sensor and the idel valve had both logged codes

Does anyone know if Lamda sensors fail intermittantly like this or is the fault likely to be the idle valve. I'm wondering if it is the idle valve because when this problem first started (on a motorway journey) I kept stalling after I came off the motorway (traffic lights etc) and found this was because the idle valve was completely closed. I took the idle valve off the car and slowly pushed the plunger open a bit and this cured the stalling at junctions. The car also seemed to idle around the correct speed.

If it could be the idle valve, could someone explain why because I don't understand why a problem with this should affect the running of the car at speed -

Thanks for any help

Tony

{yet another subject header requiring attention because the sticky posts, etc were ignored!}

Edited by Dynamic Dave on 30/01/2008 at 00:35

Reply | Report as offensive | Link

Tue 29 Jan 2008 22:10

Peugeot 306 1.4 S reg intermittant ECU light/ - Screwloose

Tony

You seem to have the idle code covered.

Don't fall for the common mistake of shooting the messenger - what was the exact code [or wording] of the oxygen sensor code?

An engine that is on 3 cylinders is pumping a huge amount of cat-destroying unburned oxygen through into the exhaust - of course the oxygen sensor will flag a code; too lean; lack of activity; sweep rate; fuel trim.... etc. etc.

None of those mean that the sensor itself is faulty - it's warning of something amiss with it's signal that needs investigating.

Remove the coilpack and look hard for the word Sagem on it. Once you find it, throw it as far as you possibly can and get a Bougicord-Electrofil one from the dealers, complete with four new extensions and a set of genuine Peugeot plugs. [Throw the existing NGK ones after the coilpack....]

Don't wait until it backspkes the ECU and you need one of those as well.

Reply | Report as offensive | Link

Wed 30 Jan 2008 19:51

Peugeot 306 1.4 S reg intermittant ECU light/ - tonylds

Thanks for the info - I'll look into that but do you (or anyone) know why a faulty idle valve shoudl cause intermittant "juddering" problems when cruising. I thought a problem with this component would only cause idling problmes because, once the throttle is open, it doesn't do anything ??

Reply | Report as offensive | Link

Wed 30 Jan 2008 21:49

Peugeot 306 1.4 S reg intermittant ECU light/ - Screwloose

Tony

You're assuming that the idle valve is causing the problem - it isn't.

What is causing the problem doesn't leave codes.

Reply | Report as offensive | Link

Thu 31 Jan 2008 20:21

Peugeot 306 1.4 S reg intermittant ECU light/ - tonylds

Sorry about that - was getting a bit confused there. When you say the cause of my problem doesn't leave codes do you mean it could be the coil pack that you mentioned, or that it's intermittantly running rich/lean hence the oxygen sensor code. If the latter how do I find out what's causing my problme to occur after about half an hour only on motorway journeys

Thanks

Tony

Reply | Report as offensive | Link

Thu 31 Jan 2008 21:00

Peugeot 306 1.4 S reg intermittant ECU light/ - Screwloose

Tony

Only the later-level ECUs on these will flag a proper code for a coilpack fault. On your year they will flag-up false codes for everything but that; injector fault, ECU fault, idle fault - all sorts.

If it's misfiring, then you should expect the oxygen sensor to see something wrong with the gases and flag it up. Doesn't mean that there's necessarily anything wrong with the oxy sensor. Hence my question about the exact code.

As coilpacks are the prime cause of "juddering" on these, particularly when overheated; have a look at it's make and at the plug brand. Peugeot plugs ONLY on these.

Edited by Screwloose on 31/01/2008 at 21:01

Reply | Report as offensive | Link

Sun 3 Feb 2008 21:32

Peugeot 306 1.4 S reg intermittant ECU light/ - tonylds

Thanks again for the info

My coil pack is a Sagem so guess I'd better bin that. Why is it important to change plugs as well

Also, thinking over all my problems I think my ECU may already be damaged in the Idle valve drive circuitry section because of the following:

1) After I had lots of misfiring on a motorway journey, my idle valve was fully closed so I stalled at junctions - if a spike has damaged the output drive circuit I can see how this could happen

2) When I replaced it, and it wasn't at the correct position for the normal idle speed, the ECU didn't auto-set it.

Does this seem logical because I'm sure I haven't suddenly got 2 independant faults (idle valve AND misfiring at speed)

There was no specific code logged for the oxygen sensor - the tester just said - "oxygen sensor circuit" (or words ot that effect). As you said, this code could have been caused by the misfiring (which is likley to be caused by the coil pack)

Thanks again for your help with this

Reply | Report as offensive | Link

Sun 3 Feb 2008 21:48

Peugeot 306 1.4 S reg intermittant ECU light/ - Screwloose

These have a totally unique [nobody else wanted to know after this fiasco] "phase detection" system, that takes the place of a simple cam position sensor that everyone else uses.

It analyses the shape of the "feedback ringing" in the low-tension of the coilpack to determine which cylinder of the last pair of sparks actually fired and which was wasted. This means that the coilpack [a very high-voltage risk area] has to be connected to some very sensitive parts of the ECU. [Ignition areas are normally well firewalled.]

If anything other than genuine Peugeot plugs are used, it upsets the coilpack and can lead to backspiking. NGKs seem particularly bad for this. When it says use only OE parts in the handbook - on this one it means it. [Good policy anyway.]

Fit that Bougicord coilpack; four new extensions and genuine plugs; if it's fried the idle circuit, get your own ECU repaired by BBA etc. to avoid coding hassle.

Reply | Report as offensive | Link

Ask Honest John

Sell Your Car

Real MPG

Fuel Calculator