Had my Jag back a couple of days after they stripped down to replace the valley hoses, SC off, intake stuff removed etc. Tech said he cleaned the throttle body because the idle was rough - I don't think it was that rough at all.

Just took it for a drive, start up idle was relatively smooth at around 1500 rpm. I drove for about 10 mins to the store, put it in park and let it idle - tach is smooth. What I feel through seat is a very slight rumble which lasts for about half a second smooths out and repeats. I don't remember it doing this before the service work. Once I put the Jag in drive with foot brake applied I no longer feel the "disturbance in the force".

I had my dashcommand/obd2 connected, stored code said left and right bank lean. Now I'm not sure if that was the condition before the repair work. The codes don't clear with the dashcommand, so maybe the SDD is needed.

Any ideas on this? - the car runs great otherwise.

 

You've got a vacuum leak of course. There are several places at and around the throttle body to check. A smoke check would be the quick solution to finding out where.

 

Are you basing this on the idle or the lean banks codes (I think that code was there before)

 

He’s basing this on the fact that you had the car worked on and that when you depress the brake it smooths out since the brake booster works off vacuum, Plus a lean mix means theres more air than fuel.

 

What I could do to check that the brake booster is somehow affecting the idle or not is to go to drive and apply electric park brake and see the effect. Definitely something to think about.

I'm not sure that that lean code(s) is new, I think that was a stored code before the car was worked on. I'm pretty sure my OBD2 does not clear that - the lean mixture does not show when reading the codes earlier. Although I do get an occasional O2 sensor code that clears than comes back on occasion.

 

Ok - this mornings test:

1) Cleared stored lean left/right bank codes (I needed to clear on the stored codes page)

2) Started engine, let it come to warm idle speed - blew a good shot of propane at the throttle body area with propane torch - no change in engine sound.

3) used duct seal to attach glass tumbler par filled with brake fluid - see video:


4) Put car in gear brake fluid smooths out (rpm drops slightly) foot on brake

5) Applied electric park brake, foot off brake - no change i.e. vacuum booster not affecting engine.

 

Buy a cheap smoke tester on amazon and you should be able to determine where the problem is coming from if its a vac leak

 

Don't see how a smoker detector is going to help - smoke is going to get past the throttle body and through the open valves - unless I have misunderstood how they are used. The propane torch never revealed any leak around the throttle body, if the leak was there the propane would have been sucked and ignited and the change in the engine would have been noticed. I'll look further into the situation.

 

Fer cripes sake...use a smoke tester. The propane thing is inaccurate and mostly a waste of time.

You are misunderstanding how they work. Engine is off. TB is covered with a solid block (not a rubber glove). Pressurize the vacuum envelope with smoke, usually via the line that goes to the brake booster, and you will see smoke being pushed out of various places. The pressure should be solid, like what you get from a shop pump (I used a 4" plumbing cap on the TB with a hose clamp).

Your orings are old, so your oil fill gasket will leak, and various plug-in hoses will also leak. Possible your TB gasket and EGR gaskets will leak. If you have a 4.2, very possible some injector orings might leak. I smoked mine and replaced a half dozen orings, a couple of injector orings, and the PCV gasket before I got my Long Term Trim close to 0% left and right bank. Rather than look at the code, look at the LTFT actual values at idle. ON the NA 4.2, they trigger a code at + or - 20%, when they should be at 0%. So if you posted a lean mixture code, your LTFT should be pretty far off. A low-light environment and a small flashlight helps you pinpoint the smoke egress.

Good luck

 

Not getting lean codes - that was an very old reading. I don't have something to measue LTFT values via the obd2/dashcommand app on my Ipad. I guess I could fire up the SDD.

Quite a bit of work there when this vehicle was just in the dealership. I'll be in contact with Monday. Car was fine before the work.





Just started the car up to recorded engine noise when I noticed this bolt on the thermostat housing was hanging out nearly unscrewed - makes me wonder about the quality of work.

 

Maybe a leak somewhere else...

Look at the trims at idle (hot engine). All should be near zero.

 

A loose bolt, makes me wonder what else was missed

 

Me too - found something else weird - when I tried the car again today - holding the engine at around 2000 rpm then letting the pedal release
the rpm drops to 1250 and holds there till I tap the gas peddle again - there is some thing weird going off here - when the idle sits at 1250
and I tap the gas there is a squeak noise as the car settles back to 750 rpm

 

McJag222,
From the first response you have received excellent responses/adWeiss all.
However, there seems to be a gap in understanding.

Try this: The vehicle discussed is a Toyota Tacoma, but the principle is the same.

You might also look at an inexpensive tool such as TorquePro.

Observing and understanding the combustion process is fun and easy.

At some point in the learning process, you will slap you forehead and say: " I HAVE a V8 ! "

OK, poor joke, but you will have that Eureka! monent.

Good luck. Keep us posted.

PS: have a tête-à-tête with the shop owner and/or consider a a different shop.

 

You shouldnt be doing this much work to rectify someone else’s incompetence. Send it back!

 

It better be a V8 Bill - thanks for the link. The dealership is 3 hours away. I went through this process to glean as much info as possible for the service manager and depending on how this turns out the complaint dept.. I've emailed them all the info on here.

See response to Bill re-work. The car is going back tomorrow on a flat bed tow truck hopefully. I'm doing the "work" to establish this is their incompetence.This is part of my ammo.

 

I have Dash/Command - which shows the fuel trims maxxed out at idle which indicates a vacuum leak - when I took the car for a drive at around 80 km/ph the fuel trims fell down significantly which indicate there is a vacuum leak - I sent this pic to the service manager - also posted it in the fuel trim thread.

 

The car is at the dealership, tow guy arrived at 11:00 AM. What gets me is they could have easily have connected the IDS/SDD software to check for vacuum leaks/fuel trims after the strip down that was done. Would have taken less than 30 mins to do the check. This a main JLR dealer in a major city...grrrr

 

So I got my car back thursday. Service report:

Smoke tested intake system. Found vacuum leak from throttle body. Found throttle body gasket had slipped out of place during installation. Replace throttle body gasket
and smoke tested again. Found vacuum leak from the oil filler neck lower seal and a very small leak from the MAP sensor O-ring seal. Replaced oil filler neck O-ring seal
and smoke tested again to verify no other large vacuum leaks.

Cleared faults codes and PCM adaptations.

When I picked up the car the idle was rough again at cold - settles down after 40-60 seconds. Service manager said the system will take time to adapt - not overly optimistic that there are no small vacuum leaks on the inlet manifold/intake system/gaskets/correct torque down.

 

Congratulations, sounds like you are on the right track.

Let us know how it goes after PCM re-adapts in fifty or 100 miles.