Espace v6 24valve oxygen sensor

[Blackadder]

Well here it is..


Proud owners of our new 2001 Grand Espace Initiale 3ltr V6 auto. The car is great but....

We had previously given the car a test drive and fully inspected it, couldn't find any faults. The garage arranged for the car to be serviced and we picked it up last Saturday. The garage was a 200 journey and the problems started on the home journey..

After stopping half way for lunch, the SERVICE warning illuminated when we re-started the engine. Turning off then on again appeared to clear the fault.

The next day the SERVICE light came on again and the engine would misfire at low revs when trying to pull away. Reading back through previous posts on this forum there was a comment regards over-filling with oil causing a misfire. I checked the oil level and had to drain off 1.5ltrs in order to bring the level down to the correct level.  At first there appeared to be an improvement as the SERVICE light did not come on but the engine still had a misfire at low revs.

The following day both SERVICE and the misfire were back.

The car was taken down the Renault dealer on Thurs for diagnostics - apparently the oxygen sensor was at fault. This was replaced but when taken for the road test the SERVICE light came on. Repeat diagnostics still showed a fault with the oxygen sensor. They have had the car all of today and they have been checking cabling between the sensor and the ECU but without success.

They will continue with their "repair" next week but I was wondering if anybody else had experienced this particular fault. Also could the over filling with oil have anything to do with this fault.

Thanks all

[Anders Dinsen]

Hi there and congratulations on your car.

The oil level being too high is certainly not good and is known to kill the ignition coil module. It is one module consisting of three seperate coils and it sits under the cover on the front cylinder bank between the cam shaft covers.

What usually happens is that one of the coils goes bad. You misfire is most likely due to that, I'd say.

Obviously the oxygen sensor was not the problem, and if the computer has detected it to have failed, it should revert to a default setting which will actually be quite close to optimal: I.e. a defective oxygen sensor should generally not cause any misfiring.

But on the other hand, the oxygen sensor can fail if the coils fail, since you will be sending unburnt fuel into the exhaust from at least two of the six cylinders. The same goes for the catalytic converter, which also doesn't like a lot of unburnt fuel.

I really think you should have them check the coils carefully and replace them. Unfortunately they are pretty expensive, but you may want to try the Citroen/Peugeot equivalent - I think it's priced more reasonably than the Renault part (but is the same).

- Anders

[Blackadder]

Thanks Anders for the suggestions.

I will pass on to the garage what you said reference the coil pack.

I'll update you with any progress???

Dave

[Will Falconer]

It's very easy to overfill with oil - don't take too much notice of the 'oil level ' gauge on the dash.
The dipstick is also very hard to read accurately when you've got nice clean gold coloured modern oil in it!

When I overfilled mine the effect was for oil to drip on to one of  the coils and cause a misfire at low revs, but no damage was done.

[Blackadder]

Just thought I'd give you all an update.

Renault had the car for four days trying to locate the fault. In the end they replaced the oxygen sensor and the sensor lead. My wife went down to pick the car up on Friday - jumped in, started the engine and guess what - the same fault is still there.

So the car went back in Tuesday of this week and is currently still there.

Since we had the car back over the weekend I performed a few more road tests on it:

Starting the car first thing mornings was fine - no warning light and no sign of a misfire. The car was driven for around 30mins taking in slow town traffic and motorway sections. There was never any sign of any problem.

All further journeys that day had the warning light come on as soon as the engine started and was followed by the engine stalling while ticking over or I would try and pull away with the result of the engine spluttering and misfiring.

The next day was the same - first journey of the day, no problem. Second journey approx 30mins later and warning light + misfire again.

I let the car completely cool down - six hours - and strted it again. It started/drove without fault. I then turned the engine off but restarted after 1 minute. Again no problems. I continued with this leaving the engine slightly longer each time. When it got to turning the engine off and leaving it for 5minutes the fault returned. All other attempts after that also resulted in the warning light coming on straight away.

The fault is either present straight away after starting the engine or the car starts and drives fine. The fault never happens part way through a journey.

I am thinking the problem is not wiring/connector related but to do with engine temp. Trying to drive the car with the fault is like trying to drive with a cold engine and no choke. (remember manual chokes ??)

I've suggested to renault to change the engine temp sensor. They had plans of replacing the entire engine wiring harness next.

I'll let you know when (if) it's fixed.
Dave

[Anders Dinsen]

I've suggested to renault to change the engine temp sensor. They had plans of replacing the entire engine wiring harness next.

I'll let you know when (if) it's fixed.
Dave

Don't they have the Clip? Will it not tell what the problem is? If the service light comes on, then there's a fault code stored in the computer. If that fails, then they need to reproduce the problem in the garage (and since you can, they can too!), and with Clip connected, sensor readouts sholuld tell them something about what's failing.

Replace the engine wire harness?? Don't let them do that. And besides, that isn't even possible without removing the engine altogether.

Your note about the choke suggests that it is sensor related (mixture is too lean).

Sorry, but I think your garage is not giving your car the attention it deserves.

- Anders

[Blackadder]

Hi there

They have done "clip tests" and as far as I can gather it only reports back oxygen sensor fault.

They have replaced the temp sensor and HT leads but still the same fault.

I don't want to suggest that main dealers offer poor service but replacing two sensors and a set of HT leads in 8 days. that's going some.......

Dave

[Blackadder]

Here is the latest.......

Renault have had the car for 3 weeks. Having changed oxygen sensor, temp sensor and HT leads the fuel injection ECU was giving the same "oxygen sensor" fault everytime. They eventually came across what appears to be the underlying fault - the connector between the engine wiring harness and the ECU was corroded.

They attempted to get it working by cleaning up the pins as best they could but without success.

I then heard from the garage that to get the car working would require a new ECU and wiring harness, the parts would take two weeks to get hold of and that the job would cost the best part of £2000.

I replied by saying that I would live with the fault for now.

We collected the car thismorning and to our surprise, it's working perfectly - no sign of any misfire and no warning lights coming on. I can only presume that when they fitted everything back together for the final time the pins must have made good contact.

This leads me on to my next quest for info. I don't really want to leave the connector as it is as I'm sure it's only a matter of time until the fault returns.

Firstly I want to have a look at cleaning the contacts myself - I don't mind spending all day cleaning them if it saves me £2000... Apart from disconnecting the battery first, is there any precautions I should take when removing / disconnecting the ECU?

Secondly I was going to look into replacing the actual connector on the loom. Do you know if it's a 35 of 55 pin connector? I've a quick bit of looking on the web and have come up with this as a possible candidate for the socket (if it's a 55-way connector)
http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&M=BYPN&PID=169674&PN=963534-1#features

Finally if the ECU pins look bad, is there any chance of changing the connector or is the ECU totally sealed.? I was thinking of getting an ECU off eBay (Bosch Motronics for about £10) and attempting to swap out the PCB mounted connector. I know it would be a difficult job and that you would have to take ESD precautions but I'm bit of a dab hand with the old soldering iron.

Any input from you guys would be very much appreciated..

I must admit it was great getting back in and driving her today - that V6 is sooo sweet.

Oh yeah..is there a special king of grease for putting on contacts to stop this happening again??

Dave

[Anders Dinsen]

Hi Dave

I'm sorry to hear that the garage did not manage to fix the problem in all that time, I can't say I'm surprised, but they really should!

It sounds likely that bad connections is the real problem, and the ECU connector is certainly one possibility. Regarding procedures for disconnecting, the only thing you should do is to disconnect the negative battery terminal before removing the connector. You can then inspect it carefully.

It will probably be a good idea to remove the ECU from the car to check the connector on that under proper conditions and clean the tabs in the connector.

I don't know about the 24v ECU, but the one on the four cylinder engines (8v and 16v) is molded in epoxy, and you can't do any kind of repairs on that - it's likely that this ECU is the same. But then again, it should be possible to clean the connectors to get proper contact.

Regarding grease, I think any kind of non acid grease can be used, but the particular connector should be sealed already, so it may not make any big difference.

I would carefully scrape the connectors clean with a screw driver, I think that should work.

I can get you a pin out if you need.

- Anders

[Blackadder]

Cheers Anders

If you are able to get the pinouts that would be of great help - even if it was a case of confirming that there was corrosion on the pins relating to the oxygen sensor.

I had a quick look today and it would appear the ECU for the 24v has a removable casing. I think cleaning whats there initially before I go changing stuff is a good plan.

I'll see if I can get some photos together when I inspect it closer.

Regards
Dave

[Anders Dinsen]

Unfortunately the pinout is only in the diagram, I don't have a list at hand, so this is self compiled (and incomplete obviously, but should give you the most important ones):

48+49: pick up coil
1, 20, 21: ignition coils
10+21: oxygen sensor (four wire type)
12+53: throttle potentiometer
44: air temperature sensor
45: water temperature sensor
11+30: knock sensor 1

I can't figure out where the second knock sensor is connected because there's an undocumented connector going to the rear cylinder bank...

But this should give you something to start with

- Anders

[Will Falconer]

Just an added thought on this. After my timing belt was changed last Summer the car developed a misfire at low speeds.

I traced it to the ECU not being clamped back on to the mounting plate correctly, presumably causing an inconsistent earth.