Idle goes bad when AC is ON

[MBC180K04]

Hi All,
Sorry if this was discussed before, already tried search and did not get my answer.
The issue is that when the AC is on, the engine goes into rough idle mode, the car starts shaking and you can see the wipers jumping on the windscreen, if I turn of the AC or move to N everything goes to normal, I get his issue only with AC on and gear in Drive
This issue was the reason I decided that my mechanic is an ***hole as he said this is normal (D and AC cause vibration)

Car is 2004 (pre-facelift) C180K with 75000 KM


Appreciate your feed back

TK

 

[BlackC55]

You probably have a missfire when under load which would suggest a ignition problem.

Where are you in the country?

 

[MBC180K04]

You probably have a missfire when under load which would suggest a ignition problem.

Where are you in the country?

I am not in Amman, Jordan.
How can I diagnose a misfire? if I had a misfire it should cause the check engine light to come on, right?

Thanks for the prompt response
TK

 

[television]

Hi All,
Sorry if this was discussed before, already tried search and did not get my answer.
The issue is that when the AC is on, the engine goes into rough idle mode, the car starts shaking and you can see the wipers jumping on the windscreen, if I turn of the AC or move to N everything goes to normal, I get his issue only with AC on and gear in Drive
This issue was the reason I decided that my mechanic is an ***hole as he said this is normal (D and AC cause vibration)

Car is 2004 (pre-facelift) C180K with 75000 KM


Appreciate your feed back

TK

I have not heard of this one on a late car, the main ECU speeds up the engine when selecting drive and AC, I think the only way to check would be to hook it up to a diagnosis machine

 

[BlackC55]

Seconded Malcom

 

[MBC180K04]

I hooked it up to the dealer scanner and came with no errors at all, could it be the engine mounts gong bad?

 

[recycled]

have you checked the belt tensioner?

 

[MBC180K04]

have you checked the belt tensioner?

Not yet, how do I know if it is bad? can it be causing a weird sound when I first stat the car? the sound is more like a belt going bad

 

[bolide]

If diagnostics show nothing it may be a bad a/c compressor causing some / all of the problem. Either that or you have more than one fault

If the problem only happens in D + A/C and not in P + A/C then logically it's not the compressor - unless there's something else going on when in D

Nick Froome
www.w124.co.uk

 

[Dieselman]

It sounds like the engine control isn't increasing the idle control to accomodate teh additional load of the AC and when in D.
try putting on all the electrical consumers such as RHW, lights, etc to see if it works then.

Do the revs rise when started from cold, then gradually fall back.

If not there is a problem with idle control, otherwise it may be an air leak problem causing lean mixture.

 

[MBC180K04]

It sounds like the engine control isn't increasing the idle control to accomodate teh additional load of the AC and when in D.
try putting on all the electrical consumers such as RHW, lights, etc to see if it works then.

Do the revs rise when started from cold, then gradually fall back.

If not there is a problem with idle control, otherwise it may be an air leak problem causing lean mixture.

I tried to shut down all the consumers and still get the same issue, the revs start at 1100 RPM when I first start in the morning and gradually drop to around 600 RPM

Is there a diagram for the air hoses around, I have bought the car 2 weeks ago and still working on finding my way around (so far found where to put my spring booster and bought the 07 key)

Thanks

 

[television]

600 is too low for idle, so maybe the the general idle needs to be increased, only be done on STAR

 

[MBC180K04]

600 is too low for idle, so maybe the the general idle needs to be increased, only be done on STAR

I thought the normal RPM at idle was 625 and mine is in that area, will add it to the list when I visit the dealer

 

[television]

I thought the normal RPM at idle was 625 and mine is in that area, will add it to the list when I visit the dealer

I have often found that 25 RPM can make a huge difference to the idle. I also believe that the K engines are a little more twitchy on the bottom end of the RPM. Have you looked at the rev counter when you turn the AC on

I have increased mine by 15 rpm to stop it rolling back on hills

 

[MBC180K04]

I have often found that 25 RPM can make a huge difference to the idle. I also believe that the K engines are a little more twitchy on the bottom end of the RPM. Have you looked at the rev counter when you turn the AC on

I have increased mine by 15 rpm to stop it rolling back on hills

I looked at the rpm when i start the AC and it does not change at all, i was expecting it to fall and cause the vibration but it did not.

I also have the one where the AC is always on unless you hit the AC off button, but it does not happen when the AC is on but the blower is off (Normal position) it happens when AC on and Blower on (either at Auto or one of the fan speeds selected)

 

[television]

There are some mods on your car, one is the partial load ventilation hose from crankcase to connecting pipe. this does what it says "Partial load"

 

[MBC180K04]

There are some mods on your car, one is the partial load ventilation hose from crankcase to connecting pipe. this does what it says "Partial load"

I tired to locate this pipe but found more than what I was expecting, tried to locate it in the Russian website with the diagrams but did not get through, is there a diagram or a picture showing that available?

Another finding, in Jordan we have only 1 grade of unleaded, 91 Octane, could this be the issue, I know that user manual recommends 95 octane gas, but looks like the only supplier is supplying only 91 unleaded, they 95 leaded, but I know this will cause more issues, although the manual says I can use leaded but will have to change the spark plugs more frequently

 

[television]

I tired to locate this pipe but found more than what I was expecting, tried to locate it in the Russian website with the diagrams but did not get through, is there a diagram or a picture showing that available?

Another finding, in Jordan we have only 1 grade of unleaded, 91 Octane, could this be the issue, I know that user manual recommends 95 octane gas, but looks like the only supplier is supplying only 91 unleaded, they 95 leaded, but I know this will cause more issues, although the manual says I can use leaded but will have to change the spark plugs more frequently

The kompressor has to be taken off to get to it. the pipe comes out of the block just above the alternator

 

[MBC180K04]

The kompressor has to be taken off to get to it. the pipe comes out of the block just above the alternator

does not sound like a DIY!!!! will get some one with better mechanical since to have a look at it, does it contribute to low fuel economy, I am getting average 14l/100 KM in town driving, but the town I live in have allot of hills and mountains?

Thanks for the help

 

[television]

does not sound like a DIY!!!! will get some one with better mechanical since to have a look at it, does it contribute to low fuel economy, I am getting average 14l/100 KM in town driving, but the town I live in have allot of hills and mountains?

Thanks for the help

I do not think that the 91 octane helps this issue,and this could be a combination of several things, all so small that on their own they would not show up. I would still speed up the idle a touch, just increase it to 640 and see what happens when the air is turned on