E60 M5 - Idle RPM Rises When Warm
Discussion
Hi there, long time reader first time poster, hoping I could get some help regarding a high idle rpm on my M5.
The issue is that when coming to a stop or sitting at the lights the revs will rise from 750 rpm to 950-1000 rpm. This only happens when the oil is up to temp circa 100 degrees.
The car runs great so not a huge issue but it has a Hayward & Scott back-box so the rise in noise is certainly noticeable and it does become quite boomy at 950-1k rpm to the point where its a bit annoying/embarrassing when sitting in traffic.
It recently had a big service where I replaced a load of things including spark plugs, oil filter, air filters, micro filters, rocker cover gaskets, oil cooler.
I have read conflicting things over on M5Board; some say its normal and its the cat being kept at normal operating temperature however some say their cars do not do this and its a sign of something going wrong. Some think its an air leak somewhere.
I have cleaned the MAF's which had no effect. I have INPA/DIS and have no faults on INPA.
I have measured my battery at 12.2v after the car had sat for a night so I'm thinking that it could be the battery or alternator. The battery measures 13.8-14v at both 750rpm and 950rpm idle-ing.
I am thinking of replacing the battery, then mafs, then o2 sensors to see if that fixes it but thought I'd post on here before I go down that slippery slope.
Any ideas or possible tests I could run in DIS? Thanks.
The issue is that when coming to a stop or sitting at the lights the revs will rise from 750 rpm to 950-1000 rpm. This only happens when the oil is up to temp circa 100 degrees.
The car runs great so not a huge issue but it has a Hayward & Scott back-box so the rise in noise is certainly noticeable and it does become quite boomy at 950-1k rpm to the point where its a bit annoying/embarrassing when sitting in traffic.
It recently had a big service where I replaced a load of things including spark plugs, oil filter, air filters, micro filters, rocker cover gaskets, oil cooler.
I have read conflicting things over on M5Board; some say its normal and its the cat being kept at normal operating temperature however some say their cars do not do this and its a sign of something going wrong. Some think its an air leak somewhere.
I have cleaned the MAF's which had no effect. I have INPA/DIS and have no faults on INPA.
I have measured my battery at 12.2v after the car had sat for a night so I'm thinking that it could be the battery or alternator. The battery measures 13.8-14v at both 750rpm and 950rpm idle-ing.
I am thinking of replacing the battery, then mafs, then o2 sensors to see if that fixes it but thought I'd post on here before I go down that slippery slope.
Any ideas or possible tests I could run in DIS? Thanks.
If you have DIS, keep an eye on the coolant temps (I guess it can be done with INPA too)
If a thermostat is stuck open, it could overcool and that will raise the indle speed.
The other things that sometimes do that are air leaks, but the ECU is smart enough to spot that before you'd even notice and store a fault code.
If a thermostat is stuck open, it could overcool and that will raise the indle speed.
The other things that sometimes do that are air leaks, but the ECU is smart enough to spot that before you'd even notice and store a fault code.
Thanks for the replies, much appreciated.
I will monitor the thermostat and update the thread but it sounds like this is normal for the s85.
I may just buy a standard back box and stick that back on. As great as the H&S exhaust sounds on the go, the drone at 950rpm idle can become tiring. Bit of a shame as idle at 750rpm has no such problem.
I will monitor the thermostat and update the thread but it sounds like this is normal for the s85.
I may just buy a standard back box and stick that back on. As great as the H&S exhaust sounds on the go, the drone at 950rpm idle can become tiring. Bit of a shame as idle at 750rpm has no such problem.
If there are no errors in the DME in INPA, it's not likely you have a thermostat problem. There are two tank venting valves down in the valley of the engine which feed a secondary intake on the idle actuators. These are problematic at times and a lot of strange idle problems can be fixed by this.
Also, there is a tank vent carbon canister in the right rear wheel well. This gets clogged over time and prevents proper tank vacuum relief. Some have even noted the tank collapsing in a bit. It's cheap, probably under 100 or so in parts and a 30 minute job to change it out.
Finally, is there any difference between the AC compressor being on or off?
The mss65 DME uses a torque calculation model that is extremely complex. The alternator and AC compressor are two of the variables it takes into account, especially at idle. If there is a difference between AC on and off, it may just be related to that.
Also, there is a tank vent carbon canister in the right rear wheel well. This gets clogged over time and prevents proper tank vacuum relief. Some have even noted the tank collapsing in a bit. It's cheap, probably under 100 or so in parts and a 30 minute job to change it out.
Finally, is there any difference between the AC compressor being on or off?
The mss65 DME uses a torque calculation model that is extremely complex. The alternator and AC compressor are two of the variables it takes into account, especially at idle. If there is a difference between AC on and off, it may just be related to that.
jcolley said:
If there are no errors in the DME in INPA, it's not likely you have a thermostat problem. There are two tank venting valves down in the valley of the engine which feed a secondary intake on the idle actuators. These are problematic at times and a lot of strange idle problems can be fixed by this.
Also, there is a tank vent carbon canister in the right rear wheel well. This gets clogged over time and prevents proper tank vacuum relief. Some have even noted the tank collapsing in a bit. It's cheap, probably under 100 or so in parts and a 30 minute job to change it out.
Finally, is there any difference between the AC compressor being on or off?
The mss65 DME uses a torque calculation model that is extremely complex. The alternator and AC compressor are two of the variables it takes into account, especially at idle. If there is a difference between AC on and off, it may just be related to that.
I've read the fuel tank vent valve DIY and carbon canister threads over on M5Board and it looks relatively straight forward. I'll price up the parts and have a go at it soon and report back. Also, there is a tank vent carbon canister in the right rear wheel well. This gets clogged over time and prevents proper tank vacuum relief. Some have even noted the tank collapsing in a bit. It's cheap, probably under 100 or so in parts and a 30 minute job to change it out.
Finally, is there any difference between the AC compressor being on or off?
The mss65 DME uses a torque calculation model that is extremely complex. The alternator and AC compressor are two of the variables it takes into account, especially at idle. If there is a difference between AC on and off, it may just be related to that.
There is no difference between the AC being on or off, it will always rise to 950rpm. I tested it today and perhaps it took a little longer (few seconds) before rising from 750 to 950 but nothing noticeably different.
Also, just wanted to say thanks. I've read a lot of your posts over on M5Board and they saved me a lot of headaches and cash when diagnosing the cause of a misfire and 'reduced engine power' - it was a faulty ionic control sensor as per your posts.
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