Hi there

A few weeks back I changed my plugs, inlet gaskets, gave the throttle body a good cleaning and all new filters etc.

At first when I re-connected everything up revs did not fall when changing gear, but I discovered the small hose which goes into the air intake pipe just before the throttlebody was not fully pushed in, once this was done the car drove much better. However I think I may still have a small vacuum leak.

The symptons are:-
If I am changing up at sub 3000rpm, it takes the revs 1-2s to drop back down too 1000-1500rpm so unless I do a slow gear change its a tad jerky. So if I say accelerate in 2nd upto 2500rpm, put clutch in the revs will take 1-2s to drop back to 1000rpm otherwise they hold at 2000-2500rpm for a second or so. The way around this is either change gears slowly when changing sub 3000rpm or rev the car past 3500rpm and there is no issue because the revs fall instantly too 2000ish rpm it just takes another 1-2s to get too 1000rpm, so high rpm changes are smooth.

The other thing I've noticed is if I am cruising along and just dip the clutch the revs will hold at 1500-2000rpm, sometimes even a little higher.

Lastly if I take my foot of the accelerator in gear I don't gear any real engine braking effect and the instant MPG counter slowly gets towards 60-75mpg, but surely it should read 99mpg the moment you lift off, or do you need high speed and top gear to get 99mpg with no throttle input?


1. Should I be trying to reset the throttle body? If so I've read the procedure but am confused it says connect battery negative cable, well its already connected, should the first step of the reset be to actually disconnent the negative cable and if so how long for before reconnecting and then following the guide? (I've tried this now, did not seem to change anything)

2. If the above don't work is there any way to test any of the vacuum lines for a leak like maybe disconnecting and blocking a pipe etc?

 

Hi there

Just disconnected the battery negative for a couple of minutes. Re-connected, started car, allowed to warm up, turned off and restarted immediately, allowed to idle for couple of minutes and then went for a drive.

Though things have marginally improved, revs fall marginally faster and if you dip the clutch whilst cruising along at say 50mph, the revs fall quicker but still hover around 1500rpm before falling that bit more.

So I still think I may have a very slight vacuum leak somewhere.

 

Can I disconnect this pipe from the intake and block them up as a test to see if that solves issue? Am I right in thinking its just a camshaft/oil/vapours that go up through that pipe and back through the intake to be re-burnt to lower emissions? If so will it do any harm to just disconnect and block both as a test?









What I have noticed is this pipe at the back of the engine on passenger (PCV Eblow/Hose I think) side where it looks like someone has bodged a pipe with some duct/insulation tape, cable tie and custom hose, take a look:-








Is this suspect pipe part of the vacuum pipe system as you can see in picture it connects to plastic piping that runs under the inlet manifold towards front of car.

 

Oh the car is a 2000 S-Type 3.0 V6.

In short when changing up through gears at sub 3000rpm the revs increase by 300-500rpm when depressing the clutch and then take 1-2s to return to idle.

Or if you put the car into neutral whilst cruising along the revs will eventually/slowly drop too circa 1500-1700rpm and only drop to idle when the car comes to a stop.

 

Hi Gibbo205, yes, you have a vaccume leak. Re-check your work. both vaccume and electrical connections. The V6 is problematic with the gaskets for the intake manifold runner control solenoid and vaccume line under the engine cover going to the brake booster. The pipe you pictured aren't vaccume routes. You may plug the blow-by tube running from air intake tube to cam cover to see if this is leaking. Joyce's Jag (Rick) has the same engine and is our expert regarding this concern. He'll attend to your thread, as he's also a forum moderator. Be well chap.

 

Read fuel trims at idle & 2500rpm in P (or N). An elm327 can do it, less than £10 on ebay. But with that engine & year, yes you likely have a leak.

 

Ive just removed my PVC elbow:-



[img]http://img838.imageshack.us/img838/4821/pvc2s.jpg[/img]

That does not look standard to me, that connects into plastic pipe which plugs into the throttle body. Is this the PVC vacuum line, could it cause me issues?

 

That's not a stock pipe. Fill it with water and plug both ends-look for a leak, or just replace it with stock pipe.

 

Hi there

OK I've changed the PVC elbow in the V of the engine, this had a hole in it and I've also changed the other elbow at the back of the engine which connects to the vacuum line which plugs into the throttle body and is part of the same vacuum line as the elbow in the engine V.

Although my problem is not as bad the car is still not right.

I've tried spraying carb clean all around but the engine revs held steady so nothing was revealed.


Does my car need to go through some re-leaning process now it no longer has a hole in the PVC elbow or does my problem still persist.

Should I have changed the PVC valve whilst I was doing the PVC elbow, could the valve cause my issue?

My problem which is I get a minor rpm surge where I depress the clutch, so for example I am accelerating gently in 3rd upto 2250rpm, I depress clutch to select 4th and the moment I depress clutch the revs will surge/rise too 2500rpm and then drop down too 1500rpm. Or if I am cruising along at say 40-50mph and let the car coast by putting into neutral the revs will only drop too 1500rpm and the car will only idle when one comes to a stop.

This is obviously annoying and does not help MPG.

Is there any test I can do to try to rule stuff out, people have mentioned disconnecting vacuum lines, blocking them up to test, but I am really unsure of what I should be disconnecting and blocking up etc, pictures would help.

At a standstill the car idles smoothly and fine plus the car has no loss of power, no CEL/error lights and drives fine, just this issue is a rather annoying niggle that is starting to do my head in.

 

Good. Did you check the intake manifold runner control gaskets? They're very prone to leak on the V6.

 

If you mean the larger row of three gaskets that come in pairs then yes I did, both the top set and bottom set. Seem fine and sealed well, no oil leaks, all very dry down there.

I am now wondering if I even have a problem and if this is just normal behavior for these cars?

My car idles perfectly fine at about 700ish RPM and is silky smooth. No CEL/Error lights and the car seems to have full power and revs freely all the way round too 6500rpm.

My problem is that when I depress the clutch pedal I get a very slight surge/increase in revs by approx 200-250rpm if changing up gears below 3000rpm and the revs fall a little slower than one would expect. So if you change gear really fast for example 3rd-4th with rpms sub 3000rpm when you place into 4th gear the revs could be higher than actual road speed which cause a bit of lurch and not so smooth gear change. If I change gear slowish then not an issue or if I rev the car beyond 3000rpm then not an issue. Is this normal for these cars or do I still have a gremlin in my car somewhere?

 

You may still have a vaccume leak, sticking throttle body, or throttle position sensor. The engine RPM's should drop quickly following depression of the clutch. Check the throttle body for sticking, etc. Be sure the airbox is clamped down securely and hose from airbox to cam cover is snug and not leaking. The intake manifold runner control gaskets are located at top of manifold runners. They seal off the solenoid actuated by wide open throttle, causing the upper intake runners to come into operation. Use the "Search Forum" feature: Type "Intake manifold runner control gaskets leaking", or send a private message to Joycesjag (Rick). He's our V6 expert and adroit with localizing faults, especially vaccume leaks.

 

 

This thread is nearly eight years old now. "bfsgross" has not posted since 2013; "Gibbo205" appears to be still active and appears to be driving an F-type now. You might want to try a PM to Gibbo205 and see if he remembers the solution to his problem.

Good luck