I had a Rover 827 auto 1994. The ecu was thought to be faulty. I picked up a spare thro' ebay, fitted it, no programming required. Turned out the problem was elsewhere. I removed it and sold it back thro' ebay. My rover garage had told me it would probably need reprogramming but the spare worked fine.
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I've never known a dodgy ECU to cause high CO, it is more likely to be a sensor. I would start with the temperature sensor, but a diagnostics check might be in order rather than guessing.

 

thanks guys. the temp sensor was replaced a few months ago to cure an overheating problem.
why does an ECU need to be reprogrammed ? is it a specialist job ?

 

Was that the sensor for the radiator fans? there are several temp sensors, and the engine temp sensor (for the ecu, not the guage) often makes the CO's go high like that. A faulty one wouldn't make your car overheat, thats for sure.
Jim

 

What engine is in the car.

 

Its a 2 litre auto 1996.

New cat, lambda + temp sensor and engine red hot.

fast idle 1 - CO 4.17 HC 247 Lambda 0.88
fast idle 2 - CO 6.39 HC 402 Lambda 0.81
Argghh it's got even worse on the second fast idle. What's happened to my car ?

 

Throttle pot adjustment? Could be that it is not switching to the idle fuel map when the throttle is closed.

 

try changing plugs/dizzy cap/leads-its that far out it must be something like plug not firing or low compression on a cylinder

 

ECU is the most reliable thing on the car-doubt its that,cud be MAP sensor tho

 

thank for the suggestios. much appreciated. about to go and have a look now I've printed circuit diagrams and MEMs stuff.
The concensus seems its not the ECU.
Speed sensor, oxygen sensor, crank sensor, knock sensor, throttle sensor, temp sensor, air sensor, fuel sensor....
excuse my ignorance - what's the MAP sensor ?

 

A classic case of RTFM on my part. So MAP is the Manifold Absolute Pressure sensor to determine engine load. A seperate sensor on the KV6 but the load signal is "determined" within the ECM on a T-series. I learn something every day. I wish I could learn how to fix my car !

 

MAP sensor is inside ECU on T series-I have cut mine out of ECU and am running it externally-mine is a 620ti-below is a pic of the wire I'm running into the ECU for the MAP signal

 

Yep, the temp sensor I replaced was to kick the fans in.
It overheated regularly and then the header tank split. Every 800 in every scrappy hereabouts has no headertank.
I subsequently found that the previous owner hadn't put the wire retaining clip on the plug.

 

Then the first thing you should change is the ECU engine temp sensor. They are quite unreliable.

 

new temp sensor (for ECU) fitted this afternoon. £18. Will try and get it retested on Monday. Fingers crossed. Thanks for the help so far.
graham
when the car is sorted I'll ask AlexF about his MAP sensor setup - hmmm...

 

alexf2828 what type (symbol) of MAP have you used?

 

its just the same MAP sensor but run external in a box so I can play with it-can change resistance values etc & maybe try another sensor-also can measure sensor voltage etc

 

This may sound mad but the coolant temp sensor has an effect on emissions, and is a common problem with the T series, i don't think they cost a fortune either.

 

Put it on a neighbours analyzer this afternoon.
Still way too high on CO by a factor of 10. i.e. 3.27 %
I've replaced both coolant temp sensors (i.e. for the ECU, fans and temp guage) and the cat and the lambda.

 

Hi,
Was the car fully warmed up? TBH I don't trust those cheap analizers, I found they were only any use for setting up the mixture on carbs.

 

Haven't had a chance to reply to this thread earlier.

The car is running rich and fails MOT with incredibly high CO on fast idlel (3+ and 6+ %). Emissions fine until the engine gets hot.
I've replaced the coolant temp sensor (yep the right one), the cat and the lambda. A probe on the lambda doesn't fluctuate between 0.2 and 0.8 but is between 2.8 and 3 v !

I've had the ECU "read" (£45) and it only indicated a possible problem with the temp sensor or the MAP sensor. Understandable as the temp sensor has been replaced and I disconnected to vacuum to try and understand what was wrong.

So do I
(a) buy another coolant sensor thinking this one s duff (but it does kick the fans in - the original reason for replacing it)
(b) get the ECU diagnosed (new ECU + recoding =£195)
(c) fool the ECU by putting asbestos beads on the hot wire of the air temp sensor to make the engine thinks its running hot and thus reduce the fuel input (an idea from an semi-pro friend)
(d) scrap the bl**dy thing and stop throwing good money after bad.

 

It may seem a silly question, but is the airfilter clogged or the engine breathing badly ? One tip for lowering the emissions is to remove a vacuum pipe to let it pass the MOT. Find a vacuum pipe on the manifold that doesnt affect the idle too much ( or a spare nipple with a blank on it ) and try it on your neighboors analyzer again. 3+% is still high though. Is there a an air screw on the manifold near the throttle housing you can open up ?

 

I have just read your last post. It sounds like a sensor as the c.o. is getting higher as the engine gets warmer.. if you have changed the temperature sensor, is the harness damaged anywhere between the sensors and the ECU, making it set to an inaccurate setting.??

Also, as previously mentioned check the throttle potentiometer for correct fitment and throttle set up, cables, stop screws etc.

 

Did you get it sorted? I have had this problem on a few rovers cure stuff a rag up the tail pipe with the probe and fast idle the car. if it comes down you have a leak on the exhaust somewhere.