Menu toggle

idle problem..not again

M

muzz

New member
I can't throw any more money/time at this idle problem so I'm putting it out to you boys.

Starts fine when cold and will idle at 950rpm until you drive away then idle will nearly die then picks up. High revs are needed to drive due to hesitate and odd low revs until it's warmed up. Rarely when you put the clutch in from high revs the engine will almost die but then pick up.(warm)

New cap, rotor, leads and plugs.

What I have done

AFm checked as shown on Clarks garage
tps checked at dme plug and is correctly set at throttle body
no vacuum leaks
Engine temp sensor is within tolerance over temp range
icv is free of grim and rotates back and forth freely, it has a 12 volt supply

any help welcome
 
muzz,

There are two temp sensors, one for the dash temp gauge and one for the enrichment when the engines cold. Don't mean to be cheeky, but did you test the right one?

I agree with you changing the ignition components. Although I don't see your cars symptoms as being classic for a duff coil, its all that is left. Hopefully other members of the forum might give you a better consensus on that one.

Have you tried pushing the throttle cam back to make the TPS close. Sometimes they can be just on edge of closing at idle, but the throttle spring is just not quite stiff enough to close the switch.

A sticky injector, that works free when the engines been running a while?

Good luck mate
 

paul
i checked the blue connector the one nearest to the radiator ,that was within tolerance.
the car idles at 950rpm, the tps is set so that there is a click when the throttle cam is slightly turned as clarks garage.
the injector could be a issue, i will look into it.

thanks paul
 
Does being within tolerance when tested always mean that it will work properly. If theyre cheap then it may be as well replacing them anyway.

With regards to the ISV and the DME: I recall reading a long time ago, that a component can fail in the DME which is connected to the ISV. If the symptoms suggest an ISV issue but no amount of cleaning or fettling make a difference then this may be the cause.
 
http://forums.rennlist.com/rennforums/944-turbo-and-turbo-s-forum/753498-isv-problems-here-is-how-to-replace-the-driver-transistors-in-the-dme.html
 
There is also a temp sensor in the air flow meter which can be checked by multi-meter which could be causing the problem. I would also recommend fitting a new dme temp sensor to properly rule this out as from experience mine showed fine with a multi-meter but was giving trouble at operating temp......
 

thanks 944 man, if i can get double connectors for the isv plug so that it can be connected to the isv and to a volt meter and then run the engine what would the volt meter indicate from cold to hot engine.
this would surely indicate if the dme ok or not.

thanks alwigley, have you any ref for how to check the air flow temp sensor.
i shell buy the dme temp sensor tomorrow
 
Pleasure.

Sorry I cant help more, but Im not amazingly able technically - I simply have an extremely keen memory.
 
muzz when you pulled the temp sensor plug did your dash gauge read zero? if it did you pulled and tested the wrong sensor. I should have thought to mention this in my earlier post, hope i haven't sent you down a wrong track.

I forgot about the AFM temp sensor. It can be read via its multi plug. I expect this sensor only comes into play with the AFM itself, ie above idle and below 4000rpm and full throttle. Since your problem is with a warmed up car only, and this sensor measures air, not coolant temp, i think its not likely to be the cause.

The TPS click is caused by the spring in the switch. That's not to say the circuit continuity of the TPS is ok when you hear the click, best to test it with a resistance meter.
 

ORIGINAL: muzz


thanks alwigley, have you any ref for how to check the air flow temp sensor.
i shell buy the dme temp sensor tomorrow
Click to expand...
Sensible plan to ditch the DME temp sensor as they seem to fail in slightly random ways.

The AFM temp sensor guidance is in the Bosch Motronic troubleshooting section of the Porsche manual - gives instructions on how to check pretty near everything, most of which can be done with a multimeter, but is model dependant. A quick Google search should find you a downloadable version somewhere online if you don't already have !

Best of luck

Alan
 

cheers alwigley i shell look that up'

hi paul, i checked the one nearest to the rad and when check in the saucepan went through the range of temp to voltage.
also checked ohms at the dme connector for the tps and is set correctly.
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Back
Top