An engine running issue with my R500 K-Series - any ideas?
Discussion
I have a running issue with my K-Series R500 that I would like to share with you. I would welcome any suggestions on diagnosing the problem. After a long blat on open non-restricted mountain roads without any issues at all (oil pressure, fluid temps, engine, gearbox, suspension, electrics all spot on), I have an approximate 14 mile drive back home in 30 to 50 mph restricted roads in moving traffic, but no traffic jams. After a while I get a few wafts of fuel, a little popping in exhaust from the over run. A couple of miles from home coming into town the engine starts to run lumpy and I start stalling as I decelerate and down shift from 3rd to 2nd gear. I have a brand new Bosch starter & battery so starting the engine again is no problem.
The throttle bodies have been balanced, & the car idles perfectly, a part from the situation described above. The throttle potentiometer has been set correctly as well. Recently I took out the crank sensor which was covered in muck, cleaned & then I re assembled it. That has reduced the amount of stalling on down shifts at low speed but not cured the engine running rough after a long blat resulting in it stalling. Back in the garage I have noticed a more than normal amount of soot in the exhaust end & reduced mile per gallon at the gas station. Nothing has been changed on the standard MBE ECU which was originally set up by Ministers & was perfect. This issue is new this year & has not occurred in this way for similar blat trips for the last 4 years. Any ideas? Running rich at low speeds, yes, but why occurring now and not before? Engine heat soak aggravating a faulty crank sensor (even though I have cleaned it), or faulty lambda oxygen sensor or faulty injector?? Fuel pump pressure to high, maybe, I just don't know? Naturally as I near home and meet more traffic I slow down & the engine fluids temps increase, however the fan comes on & the temps are controlled and the car never over heats. Also I would like to add that the alternator and all earths & fuses have been checked & are all ok. The car has done 8,000 miles, 98% on the road. Recent engine compression & leak test results showed it to be in good health.
I have limited mechanical knowledge beyond what has been explained here so any advice is much appreciated.
The throttle bodies have been balanced, & the car idles perfectly, a part from the situation described above. The throttle potentiometer has been set correctly as well. Recently I took out the crank sensor which was covered in muck, cleaned & then I re assembled it. That has reduced the amount of stalling on down shifts at low speed but not cured the engine running rough after a long blat resulting in it stalling. Back in the garage I have noticed a more than normal amount of soot in the exhaust end & reduced mile per gallon at the gas station. Nothing has been changed on the standard MBE ECU which was originally set up by Ministers & was perfect. This issue is new this year & has not occurred in this way for similar blat trips for the last 4 years. Any ideas? Running rich at low speeds, yes, but why occurring now and not before? Engine heat soak aggravating a faulty crank sensor (even though I have cleaned it), or faulty lambda oxygen sensor or faulty injector?? Fuel pump pressure to high, maybe, I just don't know? Naturally as I near home and meet more traffic I slow down & the engine fluids temps increase, however the fan comes on & the temps are controlled and the car never over heats. Also I would like to add that the alternator and all earths & fuses have been checked & are all ok. The car has done 8,000 miles, 98% on the road. Recent engine compression & leak test results showed it to be in good health.
I have limited mechanical knowledge beyond what has been explained here so any advice is much appreciated.
DVandrews said:
Altitude may be an issue, if the ECU doesn't have barometric pressure compensation then it will run rich at altitude, this can cause rough running and a little plug fouling...
Dave
Quick off the mark! Yes my local blat starts at sea level and goes to over 1500 metres and I also thought it was the air pressure sensor, somehow giving a stuck reading at 1500 metres to the ECU which became noticable when back in slowing moving traffic at sea level. However this item has been replaced recently, unfortunately the problem remains.Dave
Ult-Jim said:
Thanks all for the ideas. I was holding off on a new throttle pot thingy, but that does look the way forward. Will report back if that is the culprit part. Cheers Ult-Jim.
Just borrow one off another K series car to check your system. They are the same items from roadsport to R500!
freerange7 said:
What is a throttle pot please and where is it located on the engine?
Phil
Hi Freerange7. It is a throttle potentiameter (throttle pot)I guess you can describe it as an electrical component measuring throttle response for the ecu, but I am no expert. Picture here:Phil
and x marks the spot here (forward end of roller barrel):
Use a cable tie to make sure nothing is touching or rubbing against the throttle pot as in my photo. I have been informed in the past that vibration may disturb the device, whether that is true or not I don't have a clue, but sounds plausible!
Easy to replace if required. Unplug old one, two screws and slides off. New one slide on, plug it in. Then use a multi meter to get the correct voltage at idle which should be 0.43v. Just rotate the device to get the correct voltage. The adjustment is literally a mm or less so be patient if you don't get it quite right the first time. Best to semi tighten bracket and adjust slowly. Measure voltage with multimeter positive terminal on middle terminal of throttle potentiometer plug terminal (peel back outer rubber portective seal to expose) and negative on engine block. Have friend to assist with holding negative terminal on block to prevent multi meter terminal leads getting caught in any moving parts of engine
I hope that helps. Ult-jim
Ult-Jim said:
It is a throttle potentiometer (throttle pot)I guess you can describe it as an electrical component measuring throttle response for the ECU
Gives a signal to the ECU to show how far open the throttle is, which combined with the revs allows the ECU to work out the load and go to the correct load sites on the fuel and ignition maps (sometimes referred to as "alpha-N", where alpha is throttle angle (assuming a butterfly TB) and N = revs, versus MAP sensor, hotwire, etc which are all different ways of giving load information to the ECU). Hence if this (in effect) variable resistor is up the spot, your ECU doesn't really know exactly where to look on the fuel and ignition maps, therefore you get poor running and poor throttle response.
fergus said:
Ult-Jim said:
It is a throttle potentiometer (throttle pot)I guess you can describe it as an electrical component measuring throttle response for the ECU
Gives a signal to the ECU to show how far open the throttle is, which combined with the revs allows the ECU to work out the load and go to the correct load sites on the fuel and ignition maps (sometimes referred to as "alpha-N", where alpha is throttle angle (assuming a butterfly TB) and N = revs, versus MAP sensor, hotwire, etc which are all different ways of giving load information to the ECU). Hence if this (in effect) variable resistor is up the spot, your ECU doesn't really know exactly where to look on the fuel and ignition maps, therefore you get poor running and poor throttle response.
It has cured the poor running and throttle response. Still interested to know whether a rolling road session could get the last 5/100ths of the engine running even smoother.
Hi all,
I've not (until now) got round to posting about a running issue I've been having but on reading this thread, wonder if it's the same issue.
I've got a 1600K Supersport, just over 5k miles. For a few weeks now it has been hesitating/stuttering (best way I can describe it) under hard acceleration, mostly but not always, but mainly when the engine is up to temp i.e. doesn't do it when it's cold (not that I push it at all when it's not up to temp). Otherwise running fine and while it still pulls strongly, the hesitation is clearly not right and disconcerting when I pull out to overtake and I find I don't have all the beans.
My mechanical knowledge is next to zero when it comes to the intricacies of engines so I was assuming I'd have to take it somewhere to be looked at. Is there any chance, do you think, that it's the throttle pot as described here, or any other ideas ? All suggestions gratefully received but simpleton language is best, please !!
thanks,
Andy
I've not (until now) got round to posting about a running issue I've been having but on reading this thread, wonder if it's the same issue.
I've got a 1600K Supersport, just over 5k miles. For a few weeks now it has been hesitating/stuttering (best way I can describe it) under hard acceleration, mostly but not always, but mainly when the engine is up to temp i.e. doesn't do it when it's cold (not that I push it at all when it's not up to temp). Otherwise running fine and while it still pulls strongly, the hesitation is clearly not right and disconcerting when I pull out to overtake and I find I don't have all the beans.
My mechanical knowledge is next to zero when it comes to the intricacies of engines so I was assuming I'd have to take it somewhere to be looked at. Is there any chance, do you think, that it's the throttle pot as described here, or any other ideas ? All suggestions gratefully received but simpleton language is best, please !!
thanks,
Andy
Ult-Jim said:
fergus said:
Ult-Jim said:
It is a throttle potentiometer (throttle pot)I guess you can describe it as an electrical component measuring throttle response for the ECU
Gives a signal to the ECU to show how far open the throttle is, which combined with the revs allows the ECU to work out the load and go to the correct load sites on the fuel and ignition maps (sometimes referred to as "alpha-N", where alpha is throttle angle (assuming a butterfly TB) and N = revs, versus MAP sensor, hotwire, etc which are all different ways of giving load information to the ECU). Hence if this (in effect) variable resistor is up the spot, your ECU doesn't really know exactly where to look on the fuel and ignition maps, therefore you get poor running and poor throttle response.
It has cured the poor running and throttle response. Still interested to know whether a rolling road session could get the last 5/100ths of the engine running even smoother.
a rolling road session, with a fast acting wide band lambda sensor fitted, with an experienced operator will allow you to really fine tune the maps and crisp up transient throttle response (via potential tweeks to accelerator clamp settings and so on). You will also know that the maps have been setup for YOUR engine fuel/airflow/exhaust characteristics, rather than a generic map, which may have dips in the torque curve when applied to YOUR setup. The driveability factor (ignore peak power) is worth having the car (well) mapped for. What ECU are you running?
Hi, 8,238 miles. Going well, just does not like 3,500 revs and dribbling the accelerator in 40mph of traffic! Added 150 miles today, Antibes, Gourdon, Route Napolean to Castillone, D2 through mountains, tunnel section trumble in to Nice and a Blitz on a fast clear motorway (during rush hour - very rare) and back to Antibes. All sorted, but I do have a new strange clicking noise when changing gear / accelerating / braking on the right side of the engine. Will investigate after summer solstice festival which goes off in my local town, Antibes. Ult-Jim.
Ult-Jim said:
Hi, 8,238 miles. Going well, just does not like 3,500 revs and dribbling the accelerator in 40mph of traffic! Added 150 miles today, Antibes, Gourdon, Route Napolean to Castillone, D2 through mountains, tunnel section trumble in to Nice and a Blitz on a fast clear motorway (during rush hour - very rare) and back to Antibes. All sorted, but I do have a new strange clicking noise when changing gear / accelerating / braking on the right side of the engine. Will investigate after summer solstice festival which goes off in my local town, Antibes. Ult-Jim.
Pleased she's going well Jim, one of the few cars I regret selling.What is critical with throttle pots is that load site 0 is set to the corresponding value in the throttle index map. Its not always 0.43v as can be seen is this example (off my R300)
The load site 0 however is the datum which controls the fueling. Look at the fuel map and you will see how a very small voltage inaccuracy can make a big difference to the fueling, especially at the initial throttle openings.
It is absolutely critical to get this right. A small deviation in voltage (less than 0.1v) will make the car run very badly.
Its worth noting that often all that is required to fix a rough running Cateham Rx00 is a recalibration of the throttle pot. This is particularly true of the Titan bodies Caterham use on the Rx00 cars, as the mounting for the throttle pot is not that secure and it can vibrate and move, or if the attached wiring gets moved this can also move the pot a very small amount. The amount of movement whichy will throw the throttle pot out is minute. You cannot physically see it.
I personally strongly recommend a dribble of Araldite Rapid along the top of the throttle pot - effectively bonding it to the throttle body so it cannot move.
The load site 0 however is the datum which controls the fueling. Look at the fuel map and you will see how a very small voltage inaccuracy can make a big difference to the fueling, especially at the initial throttle openings.
It is absolutely critical to get this right. A small deviation in voltage (less than 0.1v) will make the car run very badly.
Its worth noting that often all that is required to fix a rough running Cateham Rx00 is a recalibration of the throttle pot. This is particularly true of the Titan bodies Caterham use on the Rx00 cars, as the mounting for the throttle pot is not that secure and it can vibrate and move, or if the attached wiring gets moved this can also move the pot a very small amount. The amount of movement whichy will throw the throttle pot out is minute. You cannot physically see it.
I personally strongly recommend a dribble of Araldite Rapid along the top of the throttle pot - effectively bonding it to the throttle body so it cannot move.
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