2006 xc90 v8 - Rough idle in drive while on brake..

humberto103 · Post by **humberto103** » 10 Aug 2016, 13:43

Coming to a stop in drive I get a low idle. Driving the vehicle and coming to a stop in neutral, idle is good-does not fluctuate. The car has turned off coming from reverse to drive trying to parallel park

I haven't been able to find any vacuum leaks in the system.

A little history-car just purchased and from day one idle issues
Had the valve body replaced / shifting flares - good as new
plugs - after market
fuel filter -after market
air filter - aftermarket
fuel pressure switch - oem
Vacuum switch - oem
cleaned maf sensor

Swapped blower motor, resistor and cabin filter

Throttle body pulled - was clean / disassembled and cleaned. per vida dice less than 2% error

Manually check fuel rail pressure 60psi / per ECM 69psi

pulled some codes / attachment - not much that I can tell

Bought it for the wife and kids but cant have it stall on them.. we switched

humberto103 · Post by **humberto103** » 11 Aug 2016, 11:47

I did a hard reset and she drives better. Might be a placebo affect Idle is still low in drive. About the lower end of 500rpm in drive. In neutral rpm's about 680 The car doesn't shake as much in drive. Vacuum I get about 8.9 hg in drive while on the brake. I get normal values other wise. 20's

humberto103 · Post by **humberto103** » 16 Aug 2016, 21:08

Question for you guys

Are my vacuum hoses supposed to have clamps

Vacuum switch
Vacuum ejector
Electric vacuum pump

On my intake manifold and my throttlebody I have clamps

I guess if anyone has a picture that would be awesome

Tks

humberto103 · Post by **humberto103** » 17 Aug 2016, 16:59

Per vida, the above do not have clamps.

I can't upload a pic

Post by **Roger_850T** » 18 Aug 2016, 21:22

I looked pretty closely at the trouble code readouts you uploaded, and they all look pretty normal. Specifically on the low idle speed code, I see
Intake air pressure at 670 hPA (= ~9" Hg vacuum)
Engine speed 581rpm
Short term fuel trim at 3.13%, long term fuel trim at 0%
81 seconds after engine start, engine temp at 55°C
EGR at zero, purge valve at zero (so should not be affecting anything)
Throttle angle at 7.06%, desired throttle angle 13.33%

I am of two thoughts. First, it seems that perhaps the throttle is not opening quite like it should - it's commanded to be wider and it isn't opening. However you had it removed and cleaned, so if it was sticking that would hopefully have been fixed.

Also, the car is drive-by-wire, and the same control for the idle air also controls the air at the rest of the time, so if it was failed, the car would not drive at all.

Second, I keep coming back to a vacuum leak somewhere, and unmetered air getting in to the engine. Especially as you report that it runs this way all the time. I ran into this on an 850, and eventually I found a small rubber vacuum elbow that had disintegrated from the heat. That one had similar symptoms. Maybe look again for something like a small vacuum elbow failed, or some other vacuum leak, maybe pull the plastic covers off the heads (especially the back one, as well as the one by the PS pump) to look more closely.

Hope this helps!

Roger

Post by **Roger_850T** » 18 Aug 2016, 21:31

Regarding vacuum hose clamps, I found this in the Starter Motor replacement procedure, where you have to pull the hoses all out for access:

Installing vacuum hoses
Install:
- the vacuum hose to the vacuum pump; secure with the quick-action lock
- the vacuum hose on the brake vacuum valve
- the vacuum hose on the intake manifold; secure with the clamp
- the brake vacuum valve in the retainer
- the connector to the brake vacuum valve.

Hopefully this helps.

Roger

humberto103 · Post by **humberto103** » 19 Aug 2016, 11:51

Back to the drawing board.. thank you for the reply Roger

On a separate note.. part number 8687937(Solenoid valve) is there a way to verify its functionality. Resistance value maybe.
Function Group 251 : Inlet manifold - in VIDA

I took a picture but cant upload..

humberto103 · Post by **humberto103** » 19 Aug 2016, 17:13

That doesn't look good

humberto103 · Post by **humberto103** » 19 Aug 2016, 20:54

Cleaned the upper intake-just where the gaskets sit. Replaced the short pvc hose and upper intake gaskets.

I turned the key to the 2nd position and off to set the throttle body.

Turned her over and rpms went up passed 1200 and Didnt seem to want to come down.

Pulled the battery terminals to do a hard reset on the ecm

Back to the square one-idle low in drive

I'm going to keep driving it

humberto103 · Post by **humberto103** » 24 Aug 2016, 13:21

Quick up date,, I wanted to verify the Neutral check in the adaptives were set ok. For some reason I was not able to complete it. The wife took the car this morning to run some errands and stated that when she got back it died out on her-parallel parking. I connected VIDA to pull the codes.

TCM-P074400 Torque Converter Clutch Solenoid Circuit Intermittent

In VIDA
diagnostics/vehicle communication/tcm/activations - lock up solenoid slu activation

what exactly should I be looking at to verify my SLU solenoid is not causing this error