RRS 4.2SC Fluctuating RPM's at constant throttle
Discussion
Hi.
I bought 2month ago 2005 RRS 4.2SC. Near 100k miles. (155 000km)
It will work just fine. Until now..
Engine RPM's rapidly fluctuate up and down even when on a flat road under constant throttle, speed and load. For example, RPM's quickly move from ~1,250 to ~1350rpm to 37-38mph.
The condition only happens during the last minutes/miles/km of warm up. In other words, it doesn't do it with a cold engine and it doesn't happen with a fully warmed up engine, only in the last mile or so just before the temperature needle stabilizes. I have spoke with the dealer and they have no solution. While the RPM does indeed fluctuate, the vehicle speed will slightly fluctuate if use cruise control. I will notice it better? Problem start´s when engine temperature is +73C degree and stops approx when needle stops +93C. I let it cool say 30min, no problem at all. if i let it cool say 3hours, it will do it again.
I've never once noticed the condition at highway speeds (above 40mph)
It feels like the vehicle is searching for the optimal gear as it seems to be quickly shifting up and down (only 100rpm, e.g., between 4rd and 5th gear). Or some throttle hunt?
Condition does NOT exist when in sport shift mode. Condition exists even when cruise control is activated.
And went away if i raise speed say 3 to 5miles/h. (over 40mph) And lower speed with 4gear, no problem..
Throttle body was carefully cleaned and problem persists.
Mass air flow filter (MAF) was carefully cleaned and problem persists.
Air filter has been replaced.
Gearbox was flushed my garage approx 1500-2000miles ago. (2-2500km) Ravenol oil.
New PCV breather valve
New spark plugs, all other oils are also changed. inc supercharger.
Also i install DR Tranny shudder fix. Problem still persists.
All this start´s when i replaced the thermostat. Old one is leaking, dislodged rubber seal.
No fault codes.
I think. If the RPM fluctuation is the engine cycling between cold and warm. A cold engine has a closed thermostat and a warm engine has a fully open thermostat. Both are stable conditions. As the cold engine warms up to almost operating temperature, the thermostat cycles open and closed. The temp sensor could be positioned somewhere where it gets exposed to this alternating flow of warm and hot cooling water.
Computer/DTC reader will show stable temperature readings all the time, but temperature raising will slowing down after when engine hit +75C.
I just install old thermostat back, and tomorrow make and test drive when engine is fully cold again. And see if it happens.. It will slow temperature raising, and maybe get DTC code from bad thermostat, but is fault is gone, it must be some program issue etc?
Or bad torque converter? Whitch i dont believe right now..
I bought 2month ago 2005 RRS 4.2SC. Near 100k miles. (155 000km)
It will work just fine. Until now..
Engine RPM's rapidly fluctuate up and down even when on a flat road under constant throttle, speed and load. For example, RPM's quickly move from ~1,250 to ~1350rpm to 37-38mph.
The condition only happens during the last minutes/miles/km of warm up. In other words, it doesn't do it with a cold engine and it doesn't happen with a fully warmed up engine, only in the last mile or so just before the temperature needle stabilizes. I have spoke with the dealer and they have no solution. While the RPM does indeed fluctuate, the vehicle speed will slightly fluctuate if use cruise control. I will notice it better? Problem start´s when engine temperature is +73C degree and stops approx when needle stops +93C. I let it cool say 30min, no problem at all. if i let it cool say 3hours, it will do it again.
I've never once noticed the condition at highway speeds (above 40mph)
It feels like the vehicle is searching for the optimal gear as it seems to be quickly shifting up and down (only 100rpm, e.g., between 4rd and 5th gear). Or some throttle hunt?
Condition does NOT exist when in sport shift mode. Condition exists even when cruise control is activated.
And went away if i raise speed say 3 to 5miles/h. (over 40mph) And lower speed with 4gear, no problem..
Throttle body was carefully cleaned and problem persists.
Mass air flow filter (MAF) was carefully cleaned and problem persists.
Air filter has been replaced.
Gearbox was flushed my garage approx 1500-2000miles ago. (2-2500km) Ravenol oil.
New PCV breather valve
New spark plugs, all other oils are also changed. inc supercharger.
Also i install DR Tranny shudder fix. Problem still persists.
All this start´s when i replaced the thermostat. Old one is leaking, dislodged rubber seal.
No fault codes.
I think. If the RPM fluctuation is the engine cycling between cold and warm. A cold engine has a closed thermostat and a warm engine has a fully open thermostat. Both are stable conditions. As the cold engine warms up to almost operating temperature, the thermostat cycles open and closed. The temp sensor could be positioned somewhere where it gets exposed to this alternating flow of warm and hot cooling water.
Computer/DTC reader will show stable temperature readings all the time, but temperature raising will slowing down after when engine hit +75C.
I just install old thermostat back, and tomorrow make and test drive when engine is fully cold again. And see if it happens.. It will slow temperature raising, and maybe get DTC code from bad thermostat, but is fault is gone, it must be some program issue etc?
Or bad torque converter? Whitch i dont believe right now..
Like i say. I flush it approx 2500km ago. I replace new sump also. Steel one at the same time. And disconnect oil cooler hose and start the engine that i can fill new oil at same time. Approx + 10l of new oil. So it is clean now.
I understand that torque converter fault is very rare in petrol engine. And usually shudder fixx will hide the problem. Eaven if it is really bad.
I understand that torque converter fault is very rare in petrol engine. And usually shudder fixx will hide the problem. Eaven if it is really bad.
At gearbox in the way out would be my guess
I have a 545 bmw with the same symptoms
It is not necessarily the torque converter. My gearbox chap says it is the valve gasket that is not keeping the required pressure so the box is hunting and therefore affecting the revs.
On the bmw it can be realised without a box removal. But what is the torque converter like. Best to do bob and accept a £2200 bill.
I have a 545 bmw with the same symptoms
It is not necessarily the torque converter. My gearbox chap says it is the valve gasket that is not keeping the required pressure so the box is hunting and therefore affecting the revs.
On the bmw it can be realised without a box removal. But what is the torque converter like. Best to do bob and accept a £2200 bill.
At gearbox in the way out would be my guess
I have a 545 bmw with the same symptoms
It is not necessarily the torque converter. My gearbox chap says it is the valve gasket that is not keeping the required pressure so the box is hunting and therefore affecting the revs.
On the bmw it can be realised without a box removal. But what is the torque converter like. Best to do bob and accept a £2200 bill.
I have a 545 bmw with the same symptoms
It is not necessarily the torque converter. My gearbox chap says it is the valve gasket that is not keeping the required pressure so the box is hunting and therefore affecting the revs.
On the bmw it can be realised without a box removal. But what is the torque converter like. Best to do bob and accept a £2200 bill.
Do you mean that mechanical fault can go away after engine is warm. And start when engine is warming up. And go away if car speed change approx +-3mph. Eaven if press slightly gas pedal. Hunting will stop straight away. And speed goes up. Also it wont feel that it's slipping. Rev counter will moves nicely up without hunting.
Eaven if i drive up hills. No problem's.
Found this on some LR forum.
One way to identify a torque converter shudder is lightly touching the brake pedal, while carefully maintaining vehicle speed with the other foot. If the shudder immediately stops, with brake application, the problem is likely the torque converter clutch. When brake application is seen most torque converter clutches will be released. A trainedtransmission service technician can also test fortorque converter lockup using a vehicle scan tool, specific for the application.
How a torque converter lockup works.
My car still hunt's if press brake pedal.. i have been driving D3 tdv6 witch has got shudder/judder. This is not like that.. My car dosent shake at all.
Eaven if i drive up hills. No problem's.
Found this on some LR forum.
One way to identify a torque converter shudder is lightly touching the brake pedal, while carefully maintaining vehicle speed with the other foot. If the shudder immediately stops, with brake application, the problem is likely the torque converter clutch. When brake application is seen most torque converter clutches will be released. A trainedtransmission service technician can also test fortorque converter lockup using a vehicle scan tool, specific for the application.
How a torque converter lockup works.
My car still hunt's if press brake pedal.. i have been driving D3 tdv6 witch has got shudder/judder. This is not like that.. My car dosent shake at all.
Edited by Kokkolanpoika on Sunday 19th November 08:38
Edited by Kokkolanpoika on Sunday 19th November 08:39
Made couple of test drive. First time. Symbtoms last only 4second. Engine temp 53c. And max engine temp vas 60c.
Let it to outside. Temperature 0c. After 3h. It will make slightly longer than first time. But not as mutch as new thermostat.. Send e-mail to Bristol transmission. They wonder if it is torque converter fault. Why shudder fix dont fix it. Because it will usually fix it for period time.. i just wonder could it be throttle body electric fault. Worn "tps sensor"?
Let it to outside. Temperature 0c. After 3h. It will make slightly longer than first time. But not as mutch as new thermostat.. Send e-mail to Bristol transmission. They wonder if it is torque converter fault. Why shudder fix dont fix it. Because it will usually fix it for period time.. i just wonder could it be throttle body electric fault. Worn "tps sensor"?
Been a while..
Bought an iid tool BT version.
I found that engine rpm fluctutates approx 50-70rpm @ 60km/h speed when transmission oil temperature is +31c to 35c, After +35c fluctuating stop imedially. Transmission will go regulated mode in +31c temperature. And it will allloy turbine to slip 5% all the time. I found this on web, (it is regulated slip mode)
I found that when fluctutation is happening. Engine rpm will drop approx 50-70rpm, and then it will go up again, and then down.
Turbine and output shaft speed will stay stable.
Excample. Engine speed approx 1270rpm @ 60km/h turbine speed 1200rpm. This is constant readings when transmission temperature is above +35C. But when transmission is +31 to 35C engine rpm will drop near transmission/turbine speed 1200rpm, usually 1220rpm and then it will go back up to 1270rpm. And same again. If i raise/lower my speed up to 3-5km/h, it will stop. No other proplem, no shuddering/juddering etc- MORE GAS, BETTER RIDE!
All sensor readings look stable and no faull codes etc.
I´m thinking could the Ravenol transmission oil be guilty. If we look at the oil kineticviscocity at 40c temperature. ZF/Shell oil is 26.8 and ravenol has got 31.8. 40C temperature is quite close to 31-35C. Viscosity index ZF/shell 151 and ravenol has got 179.
Also found this.
https://www.usermanuals.tech/d/land-rover-lesson-2...
Read page 8 to turbine.
I understand that oil could flow inside the turbine opposite direction of the engine rotation and therefore the impeller. If the fluid is allowed to hit the impeller in this condition, it will have to effect of applying a brake to impeller.. If the transmisson allow 5% regulated slip all the time, like jaguar say. (it wont tell could be do that in bouth direction) Could this be an issue our ZF 6hp "hunting/surging" ? Similar effect like fluid pump cavitation..?
Porsche. page 246. Regulated torque converter lockup clutch. 50rpm difference between impeller and turbine is allowed. So near 5% like jaguar say.
https://books.google.fi/books?id=RaanuEGHWuwC&...
So could the issue be with turbine stator witch alloy impeller to turn slightly opposite direction, when fluid will hit the impeller opposite direction then hammering impeller/engine opposite direction witch cause rpm drop. Wrong oil viscocity/oil weight/dirty oil etc is not flow enought xxx temperature and it wiil help the issue..
Damn it is difficult to explain what i mean in different langue. Sorry, i´m Finnish
Bought an iid tool BT version.
I found that engine rpm fluctutates approx 50-70rpm @ 60km/h speed when transmission oil temperature is +31c to 35c, After +35c fluctuating stop imedially. Transmission will go regulated mode in +31c temperature. And it will allloy turbine to slip 5% all the time. I found this on web, (it is regulated slip mode)
I found that when fluctutation is happening. Engine rpm will drop approx 50-70rpm, and then it will go up again, and then down.
Turbine and output shaft speed will stay stable.
Excample. Engine speed approx 1270rpm @ 60km/h turbine speed 1200rpm. This is constant readings when transmission temperature is above +35C. But when transmission is +31 to 35C engine rpm will drop near transmission/turbine speed 1200rpm, usually 1220rpm and then it will go back up to 1270rpm. And same again. If i raise/lower my speed up to 3-5km/h, it will stop. No other proplem, no shuddering/juddering etc- MORE GAS, BETTER RIDE!
All sensor readings look stable and no faull codes etc.
I´m thinking could the Ravenol transmission oil be guilty. If we look at the oil kineticviscocity at 40c temperature. ZF/Shell oil is 26.8 and ravenol has got 31.8. 40C temperature is quite close to 31-35C. Viscosity index ZF/shell 151 and ravenol has got 179.
Also found this.
https://www.usermanuals.tech/d/land-rover-lesson-2...
Read page 8 to turbine.
I understand that oil could flow inside the turbine opposite direction of the engine rotation and therefore the impeller. If the fluid is allowed to hit the impeller in this condition, it will have to effect of applying a brake to impeller.. If the transmisson allow 5% regulated slip all the time, like jaguar say. (it wont tell could be do that in bouth direction) Could this be an issue our ZF 6hp "hunting/surging" ? Similar effect like fluid pump cavitation..?
Porsche. page 246. Regulated torque converter lockup clutch. 50rpm difference between impeller and turbine is allowed. So near 5% like jaguar say.
https://books.google.fi/books?id=RaanuEGHWuwC&...
So could the issue be with turbine stator witch alloy impeller to turn slightly opposite direction, when fluid will hit the impeller opposite direction then hammering impeller/engine opposite direction witch cause rpm drop. Wrong oil viscocity/oil weight/dirty oil etc is not flow enought xxx temperature and it wiil help the issue..
Damn it is difficult to explain what i mean in different langue. Sorry, i´m Finnish
It is ravenol 6hp fluid. Witch should fit zf6hp26 box.. Not 100% same stuff as original. But quite close.. i bought it from island 4x4. Also our local LR dealer use it without issue. Like they say. Petrol engine is rare in Finland. So they have no experience how it will work SC vechiles. It will rev smaller rpm than diesels.
Im thinking of buy zf own fluid after xmas. Approx 13£ inc vat/L. And hope for best.
Im thinking of buy zf own fluid after xmas. Approx 13£ inc vat/L. And hope for best.
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