Rover 25 1.4 Impression, 03 plate, 77K - Fuelling issue
Discussion
Hello all
Hoping to tap into some K series knowledge
Sorry for the long post. I'm not good at describing issues with very few words!
The car in the title I took over from my Dad recently to use as a daily. I eventually traced a coolant loss to a worn water pump, so I've replaced that and changed all 3 belts / tensioners, a full service etc etc (all genuine stuff from Rimmer Bros).
I'm now happy with it except one thing: the fuelling!
It's both way too rich from cold (tonnes of unburned fuel after cranking) and way too lean when hot (bogs down pulling away and spark plugs read as too lean). I don't know where to begin with ECU troubleshooting. I did some research and discovered it's a Motorola MEMS system, but it appears to be a right faff connecting to it.
The mpg is a rather good 46 at the moment and it's really, really, really slow. A slight incline with just me and no luggage onboard will drop the speed from 70 to 60 in 5th way too easily, even for 84hp. I have to almost floor it to maintain the speed.
The cam timing is c0ck on. Checked it several times, but it was like this before doing the cambelt.
Using the lower tech 'process of elimination' approach, where do I start folks?
I've noticed 2 sensors on a water elbow on the engine, a 4 pin sensor in the intake (presumably load (MAP) and air temp), the throttle sensor and a lambda sensor. It's a very basic engine (which I like), so it can't be too difficult to trace, hopefully!
It's always been a good starter and idler.
I'm leaning toward a water temp sender. ECU thinks it's colder than it is, but wouldn't run super rich at all temps though? If I pull the black one (upper) sender with the motor running, the rpms rise and the rad fans come on, so I guess the ECU was happy with that one. What does the lower sender do?
Any help would be much appreciated as it's a great little car apart from that!
Hoping to tap into some K series knowledge
Sorry for the long post. I'm not good at describing issues with very few words!The car in the title I took over from my Dad recently to use as a daily. I eventually traced a coolant loss to a worn water pump, so I've replaced that and changed all 3 belts / tensioners, a full service etc etc (all genuine stuff from Rimmer Bros).
I'm now happy with it except one thing: the fuelling!
It's both way too rich from cold (tonnes of unburned fuel after cranking) and way too lean when hot (bogs down pulling away and spark plugs read as too lean). I don't know where to begin with ECU troubleshooting. I did some research and discovered it's a Motorola MEMS system, but it appears to be a right faff connecting to it.
The mpg is a rather good 46 at the moment and it's really, really, really slow. A slight incline with just me and no luggage onboard will drop the speed from 70 to 60 in 5th way too easily, even for 84hp. I have to almost floor it to maintain the speed.
The cam timing is c0ck on. Checked it several times, but it was like this before doing the cambelt.
Using the lower tech 'process of elimination' approach, where do I start folks?
I've noticed 2 sensors on a water elbow on the engine, a 4 pin sensor in the intake (presumably load (MAP) and air temp), the throttle sensor and a lambda sensor. It's a very basic engine (which I like), so it can't be too difficult to trace, hopefully!
It's always been a good starter and idler.
I'm leaning toward a water temp sender. ECU thinks it's colder than it is, but wouldn't run super rich at all temps though? If I pull the black one (upper) sender with the motor running, the rpms rise and the rad fans come on, so I guess the ECU was happy with that one. What does the lower sender do?
Any help would be much appreciated as it's a great little car apart from that!
You may already know this, but the 82bhp 1.4 16v engine is exactly the same lump as the 101bhp version used in other models. The power was reduced to 82bhp simply with a modified throttle body that does not permit the throttle to open fully. Replace the throttle body with the "full fat" version and you get the cheapest and easiest 19bhp ever.
If you fit the alternate Throttle Body [ TB ] without the restriction, you will also need to fit the different length Throttle Cable to suit.
The restriction is arranged by the simple process of fitting a longer Throttle Valve Crank along with the longer throttle cable and throttle stop. Thus, in its restricted form, the valve can only open 45 degrees and not the full 90 degrees in the unrestricted TB.
The actual bodies of these TBs are identical. The longer crank and the throttle stop restricts the valve opening fully. Someone I know fitted the shorter valve crank in place of the restricted one but, it was a fiddly and time consuming job. That was a few years ago. Better now to visit your local "remove it yourself" car breaker yard and get an unrestricted one and do not forget the matching throttle cable too. 10-15 quid remove it yourself last time I got one.
Well worth doing and it really allows the little K-Series to fill its lungs and fly. You will notice a big improvement in performance particularly when using the gearbox's lower ratios to get a move on. A healthy K-Series is still capable of punching above its weight even by more modern design standards. .
The restriction is arranged by the simple process of fitting a longer Throttle Valve Crank along with the longer throttle cable and throttle stop. Thus, in its restricted form, the valve can only open 45 degrees and not the full 90 degrees in the unrestricted TB.
The actual bodies of these TBs are identical. The longer crank and the throttle stop restricts the valve opening fully. Someone I know fitted the shorter valve crank in place of the restricted one but, it was a fiddly and time consuming job. That was a few years ago. Better now to visit your local "remove it yourself" car breaker yard and get an unrestricted one and do not forget the matching throttle cable too. 10-15 quid remove it yourself last time I got one.
Well worth doing and it really allows the little K-Series to fill its lungs and fly. You will notice a big improvement in performance particularly when using the gearbox's lower ratios to get a move on. A healthy K-Series is still capable of punching above its weight even by more modern design standards. .
SuperchargedVR6 said:
I've noticed 2 sensors on a water elbow on the engine, a 4 pin sensor in the intake (presumably load (MAP) and air temp), the throttle sensor and a lambda sensor. It's a very basic engine (which I like), so it can't be too difficult to trace, hopefully!
It's always been a good starter and idler.
I'm leaning toward a water temp sender. ECU thinks it's colder than it is, but wouldn't run super rich at all temps though? If I pull the black one (upper) sender with the motor running, the rpms rise and the rad fans come on, so I guess the ECU was happy with that one.
What does the lower sender do?
Any help would be much appreciated as it's a great little car apart from that!
The Blue Lower sender's sole purpose is for the temperature gauge reading. On the car the blue one is difficult to see as it's hidden under the Coolant Elbow. Here's an Elbow removed from the car and inverted to show both sensors. It's always been a good starter and idler.
I'm leaning toward a water temp sender. ECU thinks it's colder than it is, but wouldn't run super rich at all temps though? If I pull the black one (upper) sender with the motor running, the rpms rise and the rad fans come on, so I guess the ECU was happy with that one.
What does the lower sender do?
Any help would be much appreciated as it's a great little car apart from that!
The Black, sometime brown sensor is the one that supplies Coolant data to the engine management ECU. They do not last forever and possibly the one on your car has seen better days. Disconnecting it with Ignition on will run the Radiator fan as you've already observed. A new one may prove money well spent. Aftermarket ones sometimes do not shape up and although more expensive. OEM sensors are a safer bet.
As a matter of interest, this picture shows the Restricted Throttle Body fully open :~
This is the unrestricted one fully open :~
We have two of these Rover 25s ( 2002 and 2003 cars ) in the family and both are little fliers giving economical and reliable service. Cost buttons to run and maintain. Both currently showing 80,000 miles odd. A family friend has an older one still going strong showing 140,000 miles.
This is the unrestricted one fully open :~
We have two of these Rover 25s ( 2002 and 2003 cars ) in the family and both are little fliers giving economical and reliable service. Cost buttons to run and maintain. Both currently showing 80,000 miles odd. A family friend has an older one still going strong showing 140,000 miles.
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