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[Tick Tock]

Hi Guys, I'm looking for suggestions as to where to look next regarding sluggish take-up on my 2.5V6 engine (manual transmission).

Today I've taken the plenum off, checked all the vacuum hoses and connections and I've still got the same problem. It's purring like a kitten on tickover, but pulling away it's sluggish and the engine vibrates. Over 3000 revs and it runs sweetly and accelerates well, but anything under that it isn't happy.

I've ruled out plug leads, spark plugs, dis pack, oil leaks or water in the plug wells and breather system. I've tried to understand more about the multirams and have an identical car for which I can compare with. I've read that blipping the revs to over 4000 should actuate the rear multiram, but neither of the engines do that.

So I'm now stumped.... hoping someone may have a suggestion or know the root cause.

[TheBoy]

After you turn car off, if you disconnect vac hose from multiram actuator, can you here the vacuum?

If not, check one way valve in reservoir

[Tick Tock]

Both front and rear multirams operate when a vacuum pipe is connected. When you say 'actuator', do you mean the electrically operated valve?

Vacuum present at front T piece after vacuum tank, but rear looks to be fed from the nearside air intake which doesn't seem to have vacuum.

[TheBoy]

Pretty certain both multirams fed from tank near alternator.  Check Marks DTM's diagrams in the Guides section for how they should be routed.

[Tick Tock]

There's been no recent work on the car so it's piped up correctly (was running fine until yesterday).

So for clarity, should I be looking at front or rear multiram for this low RPM problem?

[Tick Tock]

In the Omega maintenance guide - vac pipes setup, it shows both multirams piped from the vacuum tank (near the altenator), whereas on both my cars the rear multiram is piped from the nearside air intake  - according to other sources this should connect to the fuel pressure regulator which isn't shown for clarity on the maintenance guide.

They've both been working fine with this arrangement.

Should that nearside air intake pipe go to the fuel rail? It doesn't appear to produce vacuum when engine is running.
 

[sjc]

If both vac reservoirs are working then it won't really matter which one the rear multi-ram is connected to, but it sounds like the one beside the cabin filter is not holding vacuum.

Would be worth temporarily plumbing it to the front vac reservoir to see if things improve.

As mentioned in the guide... The fuel regulator has a pipe that goes to the throttle body and doesn't connect to the other vacuum pipes.

[sjc]

Also, the rear vac reservoir supplies the infamous heater bypass valve... if the diaphragm in that has ruptured then it will create an air intake leak... easy to test by removing the vac hose from the HBV and plugging the end.

[Tick Tock]

I'm beginning to think that some re-plumbing might be in order, although both cars have been piped this way and working well for over 10 years (as acquired). I've also seen other images on this forum of cars piped this way. Even if it is incorrect, this problem only started yesterday.

So what we're saying is, this pipe should go to the fuel regulator?

[sjc]

I'm beginning to think that some re-plumbing might be in order, although both cars have been piped this way and working well for over 10 years (as acquired). I've also seen other images on this forum of cars piped this way. Even if it is incorrect, this problem only started yesterday.

So what we're saying is, this pipe should go to the fuel regulator?

Correct - the hose from the IAC pipe should go to the FPR.

The one for the rear multi-ram will be the typical thin rigid plastic hose with a 180deg rubber elbow on the end

[Tick Tock]

Thanks so far for the assistance.

IAC pipe now on FPR -  rear multiram now connected to front multiram pipe - problem remains.

Disconnected and sealed all cabin & HBV vacuum pipes to eliminate - problem remains.

No vacuum being held after switching off engine.

Could it be the vacuum tank?

[sjc]

You could try switching a tank from your other car.

Presume there's no fault codes showing?

[Nick W]

Thanks so far for the assistance.

IAC pipe now on FPR -  rear multiram now connected to front multiram pipe - problem remains.

Disconnected and sealed all cabin & HBV vacuum pipes to eliminate - problem remains.

No vacuum being held after switching off engine.

Could it be the vacuum tank?

Of course it could.


But it's much more likely to be one of the vacuum pipes or connections that litter the engine bay.


I would suggest a cheap handheld vacuum pump and careful inspection to track down the leak.

[Tick Tock]

Every day's a school day!!

No fault codes showing (apart from 21 earlier [paperclip] when I forgot to plug the ICV plug back in) doh.

I'll make a start on swapping the tanks - handy having more than 1 car.

I've been through all the pipes in the engine bay with a fine tooth comb, nothing chaffing or likely to cause a leak.

[Tick Tock]

Tanks swapped and no change  :'(  I've had enough for today.