the flyin' scotsman

Steve...........do you recall how many vac. ports the throttle body has?

3 or 4...........just curious.

Also, when the throttle body was off did you clean the vac. ports?

Your description of your cars idle could be my car.........exactly the same............how is the idle when stone cold?

stevedavies

Just thinking about the fuel pressure question, not sure how to check pressure quickly, but each time I have opened the fuel system prior to taking intake off there has not been evidence of great pressure in the fuel ? Should pressure be evident/obvious?

stevedavies

Malcolm, there are 3 ports on the throttle body, 1 on intake ( flappy valve). 3 on throttle body are , 2 near MAF and 1 further back on body. Port nearest maf connects to carbon cannistor diapragm(?), next one is main connection to 5 way spider connector. Connection further back on body connects to fuel vent diapragm. No didnt try to clean vac ports, although can feel vacuum when disconnecting them serially ( will recheck a.m.). Idle when stone cold is 800-900rpm and solid. Only afer approx 5 mins will it rise to 1100rpm.

the flyin' scotsman

There's a check valve at the output of the fuel pump that should keep the pressure up.

Theres a time vs pressure spec in the WSM that I dont recall............let me look it up.

Here is the WSM data:

the flyin' scotsman

ok you have 3 vac ports.

there should be 2 on top and one below the throttle body.

Of the 2 on top the farthest to the MAF is the main vac source for all the 'petrol' related items (2 diaphrams, reg., and auto trans). The other top port should face the opposite direction and is for the fuel vapour sytem.

The port below should go to the air pump diverter.

Pic from Dwaynes intake epic:

stevedavies

Malcolm, yes thats exactly it.i was trying to find the same photo, but ran out of ability trying to load it!
The throttle body connections are identical to mine. I renewed all connections while doing the refresh. Good to verify they are correct. My current thinking is that the problem is unrelated to the work I have done as it has had no noticeable effect on the idle speed. I dont think it has changed at all since I did the work. The cold / hot idle speeds have not changed at all.

Mrmerlin

did you get any info on a fitting a rebuilt MAF

the flyin' scotsman

BTW Steve.............I watched the Spurs/ Inter game mid week.............can't say I've been so excited about the play of 'Brit' player for quite some time.........Gareth Bale is superb

On topic........let us know how the car idles, cold and warm, with all vac ports plugged in parallel.

stevedavies

Malcolm, yes watched it too...its even better than that for me, Gareth Bale is Welsh!! I am Welsh living in South Wales. If only we had more than one good player in Wales then the International team would be in good shape!! Will try plugging all 3 this morning and let you know.

Mr Merlin...I had MAF rebuilt by JDS this week. It was 4% low. Car runs better with rebuilt MAF. No hesistation and responds quicker to blipping throttle. Exactly same idle characteristics ( John predicted this, but wanted to eliminate as possible cause).

stevedavies

Malcolm, tried plugging all three ports. Idle seems to be independant of vacuum connections either open, plugged or connected. Idle starts at 800 cold and is 1100rpm when warm.
I tried starting the car ( car always starts real easy) and letting it warm up without touching throttle. Car started and run at 800rpm as the car warms the rpm gradually increases and over space of 10mins reaches 1100rpm, where it sits solidly, gently idling around it. I tried fitting air box and filter, no difference. Disconnected 02 sensor no difference. Air con isnt working so that isnt relevant for this.
I can feel vacuum at all ports when disconnecting them

John Speake

Apparently this high idle was a pre-existing problem that was present on the car when Steve bought it a few months ago. So what originally might have caused it is not known.

I don't think the idle control loop is doing any controlling. This may be because there's an overwhelming airleak (seems unlikely) or there something external to the LH that is stopping the loop do its job.

With the ISV loop working correctly, you should get a high idle speed when the engine is cold, gradually dropping to the 675rpm that is correct for your S4. You car behaves exactly the reverse of this !

I could loan you a "Spanner" diagnostic tester, so you can trigger the ISV from the LH for fault finding.
You could also try the "idle adaptation " sequence, although I doubt this would be able to complete correctly.

Hilton

The variation in cold to warm idle speed indicates to me that its something to do with coolant temperature.

Have you tested both pins of the temp II sensor to ground? Its the Blue Bosch 2-pin connector on the right side of the coolant bridge (from driver's seat).

Each pin is a separate sensor - both should measure same resistance when compared to ground. They feed the coolant temp. data to the fuel and ignition ecu's.

stevedavies

Hilton, just checked it. Engine is warmish. Each pin measures 1.04k to ground.

stevedavies

John, I am not familiar with spanner? I agree with you in that it seems to be external to what I have done to date. The fact that before and after the idle is unchanged both with cold and hot engine. The idle also seems to be independant of vacuum lines ( ie connected, plugged or open circuit ) and 02 sensor. It sounds closed loop to me, but I may be wrong. I can hear the speed dropping, but then correcting itself back to 1100rpm. Note the ISV was changed as part of the refresh and as I said earlier behaviour is same

stevedavies

John, I just looked at your website, I understand what you mean by hammer!! I would appreciate a loan of one to help diagnose this problem. I am literally out of ideas now!! Introducing some technology would certainly assist my fumbling in the dark!