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High Revs / Vacuum


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S4 Vacuum pump was running on/off/on and after reading/posting other threads (see Lack of Performance) and checking the tubing and rubber elbows I realised they were perished/cracked/hard.

 

So first off I replaced the tubing from pump to solenoid #1 and then to solenoid #2 but kept the solenoid #1 to throttle jack tubing. Possibly a mistake (?) but the pump did stop after priming mostly with an occasional startup again especially if I moved the solenoids or wiggled the tubes.

 

Knowing that the EPBV valve is jammed open and the exhaust is going to be replaced soon anyway I disconnected the tubing from the valve and trimmed it at the solenoid end, inserting a 1" bolt tightly into the tubing after solenoid #2, as per the LEW technical guide to removing the EPBV.

 

The vacuum pump is much better - not perfect - as it occasionally re-primes but I figured that is normal ?

 

But now, on startup I get revs around 1800-2000 which seems normal and it drives OK but when I stop the revs will sit at 1800-2000 and then drop to 1200 when I come to complete standstill. So, as a test, if I select neutral and cruise to the lights from say 25 MPH down to 0 MPH the revs stay high until I brake and stop and then a few seconds later the revs go down to 1200.

 

Espritmon not showing any errors and I have reset the IAC using it to be sure. Also tried starting the car with half throttle. Also reset the BLM values.

 

I'm going to recheck the vacuum and cable tie the ends in case there is a slight leak at the solenoid ends. Would disconnecting the EPBV tube cause this if it's blocked off now?

 

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Understood but the EPBV was stuck open in the first place so in effect there was no restriction anyway. According to the LEW guide here http://www.lotusespritworld.com/EGuides/ETechnical/EBPV.html

the procedure is to block the vacuum tube completely with a bolt or similar.

However, they do say that it occasionally got high revs so perhaps I'll just put the tube back for now!

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Putting the bolt in the tube will simulate an EBPV anyway. There's no need to connect the hose back up if the EBPV is wired open.

The throttle jacking capsule will raise the revs if it is still activated, however.

For info, there is a single Changeover Relay which controls both the EBPV and Throttle Jacking Solenoids. When energised by the ECU, the relay activates the throttle jacking solenoid and allows vacuum to reach the Throttle Jacking Capsule which partially opens the throttle butterflies. See page 23 of EMH-2 for solenoid operation and vacuum routing.

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  • Gold FFM

Once you have done the reset iac and blm it will do slightly strange things as it settles in.

The key is reset both values. Run car up from cold to fans kicking in. Then take for a decent drive. That should then settle things down.

If it doesn't - something else is a wrong!!

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Only here once

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However, they do say that it occasionally got high revs so perhaps I'll just put the tube back for now!

As mentioned elsewhere, the ECM can still command a higher idle (independently of the Throttle Jacking System). There is still control via the IAC

Edited by Qavion
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Your braking to a standstill changing idle thing sounds odd to me. I can imagine a leaky brake servo affecting vacuum system pressure, but I would think less vacuum would cause the throttle jacking capsule not to move as much, reducing idle speed (at least until the engine had warmed up and the throttle jacking system had been disabled)

What else changes when a car is braked, besides road speed?

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Nothing else changes. It's a bit odd. A short while ago I started it up to come home and it sat at 2000 for a good while (2 mins) warning up. I turned it off and when I started it again it reved normally. Drove home fine but given the cool temp outside it still hit 100 on final approach.

I'm going to reconnect the vacuum tube and see what happens tmr morning. Will report back. Thanks for the advice.

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What else changes when a car is braked, besides road speed?

I meant from an engine management point of view.

To me, 2000rpm seems quite high. As previously mentioned, the throttle jacking system has to be disabled if the EBPV is stuck/wired open. If the throttle jacking system is not disabled, the idle rpms are being increased for no reason. Replugging your EBPV hose in is not going to make any difference to idle if your EBPV is truly stuck open.

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Nothing else changes. Everything is running fine. After I sorted the MAP sensor tube last week it was running ok. I only tackled the tubes because the vacuum pump was on/off/on

I still think there is a small leak though.

I'm going to reconnect the EPBV and see what happens. I was told it was stuck open but of course it could be not quite fully open? Also as mentioned having reset the Iac and blm it might still be settling in. Having said that it did Brands and back on Sunday OK.

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  • Gold FFM

You need to take a freescan log.

Check the iac will move you will hear it when you reset it and is fully clean.

Check the Tps readings as this does have a big impact.

Check the vacuum level on a manometer - it's in the service book what to expect.

Most importantly is you need to get pc onto it - otherwise it's just luck and guesswork

Only here once

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I was told it was stuck open but of course it could be not quite fully open?

If it is not fully open (by lockwiring or by vacuum), the flow will be restricted, and will slow down the engine due to exhaust back pressure (lower idle speed).

With the hose off, engine not running, it should be fully closed by spring pressure.

Looking at the picture of the EBPV in the manual, "open" pulls on the cable attached to the capsule, turning the cam clockwise (moving the cam away from the adjustable stop). Use this as a reference to see which way is open/closed.

Edited by Qavion
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  • Gold FFM

If the ebpv is a working module - it defaults to closed. To open you need a vacuum applied to it.

If it's stuck shut - it's gonna cause rough running - you need to do all the mod not half of it. And you need to be sure that you have done the mod properly !!

If it is not fully open - the ecu will try to adjust the revs by all sorts of means from sensor readings - and it could well be unpredictable. You need to take it off - and fix it in the fully open position. Or rip out the guts of it and block the pivot hole with a bolt. That way there will be no restriction

Only here once

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You need to take it off - and fix it in the fully open position.

 

 

If you need to go to the trouble of removing the EBPV, you may as well refit one of the readily available spacers instead ;)

 

See last photograph on this page:

 

http://www.lotusespritworld.com/EGuides/ETechnical/EBPV.html

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Apologies if I didnt make it clear that the valve actuator isnt connected to the mechanism on the exhaust pipe.

 

The valve/flap on the exhaust is stuck open, how far I dont know for sure. So even if the EBPV operates it wouldnt move anything other than it's own actuator in/out.

 

I've just reconnected a new vacuum tube back to the solenoid so it's as it was but with all new tubing to the pump. the only bit of tubing that hasnt been changed is the solenoid to throttle jack.

 

In a couple of months, the car will go to Rapid Mechnical Enginnering near Romford to have work done and top of the list is a new exhaust, no cat, probably from PNM unless anyone has any views on that?

 

So at that point there will be no EBPV and no throttle jack.

 

In the mean time, I'll run the car this morning and see what, if anything, has changed for the better or worse!

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  • Gold FFM

My 2 cents: on the turbo engines, vacuum is provided by a (mechanical or electrical) pump instead of engine plenum. So a vacuum leak should not affect engine idle. The only influence the vacuum system can have on the engine is via the throttle jack or EBPV. Make sure both are disconnected properly. And if they are not being used, you can take out all the vacuum tubes to and from the solenoids, leaving only the big pipe to the brakes (unless you have ABS, then the brake servo is hydraulically powered) and the small one to the HEVAC. The best way to avoid leaks is to simplify the system as much as possible. ;-)

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

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In a couple of months, the car will go to

 

 

I think what we're all trying to tell you that you will continue to have problems in the next few months if you have the EBPV disabled and the throttle jack not disabled. As an interim measure, you can disable the throttle jack the way you disabled the EBPV (although a ball bearing might be better than bolt for shutting off the vacuum (You might get air leaking past the bolt threads)).

When the car goes to your local garage, you can apply a final fix (removal of the throttle jacking mechanism).

 

By the way, the vacuum tube which runs to the throttle jacking capsule is susceptible to a lot of heat, sitting on top of the engine. It can go quite soft. Before I disabled the throttle jacking system, I think my tube was collapsing under the heat (every time vacuum was applied).

 

Hope this makes sense

Cheers

Ian.

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Thanks Ian. Now that I've put the EBPV tube back on, firstly it did seem to
fix the problem as I had not too high revs on startup and for the first
5-10 mins of running and stopping at lights/junctions the revs were fine.
However after warming up just before I parked up I gave it a quick burst
down the road and when I pulled up the revs went to 1800 and stayed there.
So it's not fixed yet.

I'll let it cool down and at lunch time connect up the laptop and see what
it's doing on Espritmon or Freescan.

I also have some spare tubing so I might as well replace the solenoid to
throttle jack. I just couldnt get to it easily and ran out of time on
Saturday,

Again, thanks for the advice and maybe see you later at the Ace Cafe ?

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I also have some spare tubing so I might as well replace the solenoid to

throttle jack.

 

 

I suppose if this vacuum tube was the source of a reasonable vacuum leak, then this might also prevent the EBPV from operating (assuming there is nothing else physically wrong with the EBPV or it has been wired open)

 

 

But if your final intention is to deactivate both throttle jack and EBPV, I really don't see the purpose of spending time on fixing the throttle jacking system tube. Ball bearings (or other blocking device) in the vacuum lines to the throttle jacking capsule and EBPV (at the solenoid ends) should remove any source of possible leaks in those lines and not give you unecessarily high revs when the car is warming up (and might even save you petrol money if you are doing lots of short runs on relatively warm days).

 

By the way, does your (underbonnet) cabin fresh air inlet open when the engine is running? (with your aircon controls not set to recirculate?) The plumbing for your cabin air control system is another common source of vacuum leaks (albeit minor ones due to the diameter of the vacuum lines).

 

Having said all this, your problems with high idle when the car is warm is rather unusual and may not be related to the EBPV or throttle jack. Anyway, I'm looking forward to seeing the results of your Freescan recordings, even though the results may not make sense with your car in its current EBPV/TJ configuration.

 

Cheers

Ian.

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Ok Ian. I'll give ball bearings a go.

And yes, the fresh air vents work. I want to re-test all of the vacuum again just be sure the pump isnt over-running.

 

Can you use Espritmon recordings? I'm not sure Freescan like my laptop - keeps saying it cant open the COM port even though it's configured correctly and Esprimon uses it find (obviously not at the same time!)

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  • Gold FFM

Please don't guess what is going on

Either the valve is open or shut or somewhere in between - it needs to be fully open! Make it so it is and then sack off the piping to the throttle jack etc

Then take note of my posts above - I've been through this - it may well be your tps .

Don't guess - methodically work through it stage by stage and assume nothing. An assumption could well throw you off course and lead to you spending more money than needed

Only here once

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Barry I appreciate your comments and the advice above. I'm not trying to be vague or guess.

To be clear, the EBPV valve on the exhaust pipe is jammed and doesnt move. I was told it is "open" but whether that's 90% or 100% I cant tell you. The actuator that's connected to the vacuum line is disconnected from the valve so if it actuates then the valve wont move. Ultimately that's not a good setup and it's all going to be binned very soon with a new exhaust system. Like wise I will have to lose the IAC setup as well. (It probably doesnt help fuel consumption overall anyway and removing all of that will be a good thing)

 

So back to the problem, the car has run OK with no "Check Engine" since I've had it apart from the "Lack of power" problem that turned out to be the tube to the MAP sensor coming adrift and in fixing that I replaced the rubber elbow to the MAP sensor. All was well after that.

 

So I have now run the vehicle today from cold and recorded a Freescan file which I've attached. I will analyse it too in the next couple of hours. If anyone with more expertise in this area can have a look and make any suggestions I would be grateful. Here is what I did in terms of driving to work (some back roads then some faster roads then industrial estate roads)

 

Run up Freescan, Ignition on, Clear ECU errors, Leave BLM "as is", Started CSV output

Throttle pedal to the floor, then off, then to the floor again, then off (to get a TPS reading)

Start car (no CEL)

Drive off with show/stop and start for a few speed bumps and one set of lights.

Pull away and attempt full throttle through gears 1,2 and 3.

Stop at lights.

Drive "normal" (ie no fast runs/full throttle) for the next 5-10 mins

Get to open road on industrial estate, go flat out in 2nd and 3rd

turn into nest road, go flat out 2nd, 3rd, 4th.

Turn round and do 2nd, 3rd, 4th again.

Turn into car park and park

After 10 seconds the CEL light comes on.

Sit for a further 30 seconds and then power off

 

File friday 210815.csv from Freescan attached.

 

 

If it helps in any way, on Wednesday I also created 3 files.

I started the car from cold, having cleared both the errors and BLM. Ran car for a short while and turned off. (see a.csv)

Started and drove down the road, not fast, and powered off (see b.csv)

Started car and drove back again (see c.csv)

 

 

Drove car

 

 

 

 

 

 

friday210815.csv

a.csv

b.csv

c.csv

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It's a pity you didn't take those photos when the CEL first appeared (i.e. engine running, ECM in closed loop mode).

From the Freescan manual: Code 35 is set when idle speed is 200rpm above/below desired idle speed for 20 seconds.

Sorry, I'm getting everyone mixed up again. I've forgotten if you've changed your IAC?

The event happened when your engine was warm, so the Throttle Jacking system should not have played a part, unless your throttle jack mechanism has stuck. Have you deactivated the vacuum tube yet with the ball bearing or similar device? If you have, have you also immobilised the mechanism quadrant temporarily with a zip tie or similar? (as per the Lotus Esprit World instructions). If the TJ mechanism is stuck open, air will still be getting to the engine via the throttle butterflies. If too much air is getting through, the IAC won't be able to control the idle effectively.

Note that the message logic also covers too low idle. This is probably why Freescan mentions a misfire. Was the engine idling roughly when the CEL appeared?

I haven't had the chance to look at your files yet (been having my own problems :) ), so have these read before going further.
 

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