99 1.4 - 'Check engine' light at higher speeds - Jimmy2134
Apologies if similar scenarios have arisen before & for the relatively long post. (Note: I have very little technical knowledge of engines and cars.)

Back in August, I took my Xsara for a drive, got on the dual carriageway and after about five minutes the temperature gauge had shot right up to max, so I pulled over and checked under the bonnet. A spring of clear fluid appeared to be coming from one of the pipes to the right of the engine, and there was a funny smell. All of the coolant in the coolant tank had gone. So I slowly drove it home. A few days later I took it to a local garage who had a look and said that the head gasket had blown and that it would cost £550 to put right (gasket refacing, pressure testing etc). I paid up and collected my car four days later. Driving it home and everything seems back to normal.

Two days later I take a trip to visit family (roughly two hundred miles away). Everything's fine. Five days later I take a trip back home, another two hundred miles. About twenty minutes into the drive, the 'Check engine' "K" light comes on. I seem to remember doing about fifty at the time. So, when I got back home, I took it to the garage and they hooked it up to a computer - apparently two codes, indicating two faults - one was the lambda sensor and the other the mixture control. They could only address the lambda sensor because the mixture control problem would need to be looked at by a Citroen specialist. So another £90 for the lambda sensor + fitting. At that point I was hoping that changing the lambda sensor would address the mixture control. But that was wishful thinking. The check engine light is back.

Prior to the trip back from the family visit, the check engine light hadn't come on in the four years I've owned the Xsara. I am loathe to keep shelling out money given the age/value of the car.

Some things I have noticed about the light:

* only seems to come on when doing relatively high speeds (above ~50mph).
* when it comes on it usually goes off within five or ten minutes, and on the whole stays off when I'm doing below ~50mph.
* the car drives fine, except that it is consuming slightly more petrol than normal.

Here are my questions:

* does anyone have any thoughts on specifically what the cause is, based on my description? (I have tried disconnecting/reconnecting the battery to reset the computer)
* am I correct in thinking that once the check engine light turns on, the computer will continue to operate in 'back-up mode' (i.e. less fuel economy), even after the light has gone out?
* the Haynes manual for the Xsara states that some newer models (within the R to W range) have an additional downstream lambda sensor, located after the catalytic converter. Is there a possibility that mine has two lambda sensors and that the garage needed to change the downstream sensor ? (they definitely changed the regular one)
* given that the car is only worth £500-£600, what would other folks do in this situation? I don't need the car for work or anything - more for convenience.

Thanks in advance.
99 1.4 - 'Check engine' light at higher speeds - Screwloose
Jimmy

Sounds like yet another sound oxygen sensor shot for telling the truth...

"Mixture control" is an ECU function - not a component. Why didn't your garage know that?

There are dozens of oxygen sensor codes - few require a new sensor, most refer to an incorrect mixture detected by that sensor.

You'll need to get the codes re-read and post the exact PSA numbers. There should be only one sensor on a '99 KFX engine. [Is that the code in the middle of the VIN number?]
99 1.4 - 'Check engine' light at higher speeds - Jimmy2134
Screwloose,

Thank you for your reply.
"Mixture control" is an ECU function - not a component. Why didn't your garage know
that?


Not sure, the garage specializes in engine reconditioning, not electronics so that could be why.
You'll need to get the codes re-read and post the exact PSA numbers.


With hindsight I should have asked the garage for the codes at the time, though I didn't envisage that I'd require them. I'll have go back to them and ask them to re-read the codes.
There should
be only one sensor on a '99 KFX engine. [Is that the code in the
middle of the VIN number?]


Yes, KFX is the code in the VIN number, so just one lambda sensor then.
 

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