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Mike, Technician
Category: Car
Satisfied Customers: 39198
Experience:  Tech Expert
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Volvo S40 Starts when cold or hot but difficult when in be

Customer Question

Volvo S40 Starts when cold or hot but difficult when in between
Submitted: 3 years ago.
Category: Car
Expert:  Mike replied 3 years ago.
Hello and Welcome -

My name is MIKE -Im happy to help / advise you with this..

Do you get any fault lights on at all?

Have you had any plug in tests / checks done - and do you have any results ?

Has anything else been changed other than the coil?

What mileage does the car have?

What is its service / recent repair history?

Rgds, MIKE........................................
Customer: replied 3 years ago.

1. Engine Mangement Light

2.Yes. Don't know

3.No. Coil changed to rectify fault

4. 115,000

5. Serviced annually. last one 11 months ago

6. No repairs



Expert:  Mike replied 3 years ago.
Hello again Simon -

Thank you for your reply and further info...

Just to clarify then now - you mention the EML is on... Is this on when you have the engine running ...??

As the EML is on, have you retrieved the fault codes? If so, what are they?

Is the car misfiring at all?

Rgds, MIKE.....................................
Customer: replied 3 years ago.





Also after starting from cold the engine over revs on its own accord after a couple of minutes. It then calms down and runs well.

After switching the engine off the cooling fan will continue to operate

Expert:  Mike replied 3 years ago.
Hello again Simon -

Thank you for your further info..

Ok - there are two things here that come to mind on this .

The first thing to so though is double check all your electrical wiring / connections - espeically earths.. and the piping around the engine - the air / vacuum piping - Any bad connections / leaks in these hoses causing un metered air ingress will cause what you have - so thats always the first thing to check - as a general check - before anything else...
If all is well carry on as follows -

Now a known fault is with the ECT sensor... thats the engine coolant temp sensor... this sends info to the Ecu - for it to then command the other engine management functions correctly. A faulty sensor here will cause what you have.. its a known fault too-

The other that will / can cause what you have is, a a dirty TB - thats the Throttle body unit..
We recommend cleaning of the TB unit internally- you need to remove the top cover to gain access and use a spray cleaner ( carb cleaner spray or suck like that you can get from any good car shop )--and thoroughly clean the inside barrel of the chamber - ensuring you clean the edges of the throttle plate -and , where the plate closes on the walls of the chamber when the throttle if off / closed...

Apart from the engine being in good condition service wise - ie, new or decent spark plugs -and of the correct rating / heat type, one or the other as above is the usual fault with what you have -

The other thing to mention though is - which is why I asked you about the EML ( engine management fault light )... if that is on as you say p then the ECU / management computer, will have logged fault codes re the fault you have... So - its advisable to have a local garage at least read the fault codes for you - ( this is done with suitable plug in diagnostic equipment ) -and then go from there with the results of the code test...

You mightfind the fault code test gives you another and / or different fault to the above - in any event, its normal practice to have the codes read if the EML is on -and go with that from there - Either way then as above, will see this issue cured / sorted out for you..

If there is anything more by all means get back to me and we can carry on...

>> Meantime >>>> Please do click on the "OK/ Excellent ratings" for me - Thank you in advance for that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Kind Rgds Simon - MIKE.


Expert:  Mike replied 3 years ago.
Hello again Simon -

Since my answer to you as above, I have notification that you have replied to me - but I see no actual message from you -

If it is that you sent me a reply / message , Im afraid its not showing - so please repeat it / resend it -- then we can progress..

Or, if its not that and we are actually done at least for now, please do click on the "OK / Excellent" ratings for me now at this point - Thank you Simon..

Best Rgds, MIKE.