Help required cold start/tickover issue....

[BrianTVR350]

Morning Boys,

I have a problem with my S2 350i

From a cold start, car starts up and runs at fast idle, so far so good...

Just seems to be taking longer and longer for the fast idle to drop to the standard 850 or so, currently the engine has to be fully warmed up 85-90 on gauge for revs to drop below 1000.

My current favourite culprits are...

engine temperature sensor

thermotime switch

extra air valve

ranked in order of cost!

Question 1... what does the jury think is the most likely faulty item.

Question 2... all above three parts are available from specialists. Does anyone know of a reliable source of quality temperature sensors and thermotime switches. (i.e not intermotor)

Discuss...

Regards,

Brian and a Red 350i

[Wedg1e]

Stuck thermostat? Enough coolant in the system?
Of your list I'd say the aux air valve was the likely culprit; could be full of gunk making it sticky.

[BrianTVR350]

Just to add...

car warms up properly, can see the stat open on the gauge and feel the swan neck get hot suddenly. And I've got rid of all the air locks.

Is it possible to clean the extra air valve? If so, how and with what?

Regards,

Brian and a Red 350i

[Wedg1e]

BrianTVR350 said:

Just to add...

car warms up properly, can see the stat open on the gauge and feel the swan neck get hot suddenly. And I've got rid of all the air locks.

Is it possible to clean the extra air valve? If so, how and with what?

Regards,

Brian and a Red 350i

Well, some sort of carb cleaner, WD40, diesel, paraffin... should all shift oily residue.
What you can do is take it off the car and connect 12v to it; you can then look through the device and watch the blade close (like a camera shutter, sort of...). There's only a small slit in the blade but you can clearly see it moving (slowly!). If the time it takes to close is similar to your warmup time, that may be the answer.

[400SE Dave]

Engine Temp sensor was a problem I had when I first got the Wedge and it gave many of the symptons you mention. Cost, less than a tenner! Available from many places, Rimmer Bros, Clevor Trevor, TVR parts etc etc. I got mine from a local motor factors, it was the same one as in a Range Rover 3.9, and it cost £7.

Give it a try as for sure it can't hurt and is only a few quid.

[chunder]

Seconded what Wedgie said, although with the vacuum pulling the disc it may stick a bit or close slower once installed.

I had problems with a couple where operation was intermittent and didn't seal well when closed, in the end removed it, made a bracket and fitted an on/off solenoid valve with a switch on the dash. Also linked it in to the fan relay at one point as was experiencing stalling and low idle with fans on, lights on and any parking steering lock, worked a treat until was no longer needed due to other changes.

[honestjohntoo]

BrianTVR350 said:

seems to be taking longer and longer for the fast idle to drop to the standard 850 or so, currently the engine has to be fully warmed up 85-90 on gauge for revs to drop below 1000.

The most likely cause is with the Extra Air Valve which is only responding to one of the two control factors required for it to close fully. For that to happen, BOTH heat from its internal coil AND manifold temperature must be present. A faulty connection to the Extra Air Valve is the most likely cause. This explains.

* The Extra Air Valve is a very robust component of the Rover SD1 Efi System and because of its simplicity should rarely fail mechanically unless there has been interference of the internal components with a screwdriver or similar intrusion. * It is however susceptible to electrical problems, as is any coil heating device but is much more likely to suffer from connection problems. * This is particularly so, because the electrical socket is inaccessible when mounted on the Rover SD1 manifold and the plug can become dislodged or the connections can become corroded whilst its inaccessibility prevents easy fault diagnosis. * The Extra Air Valve's robustness also means it rarely fails with regard to air leaks within the component itself but the same cannot be said of the rubber hoses connecting it to the air rail and plenum chamber respectively. * A fundamental feature of the Rover SD1 Efi System is that, providing the volume of air entering the engine is accurately measured by the Air Flow Meter, the Electronic Control Unit will always calculate the correct amount of fuel needed to maintain the required air/fuel (stoichiometric) ratio. * When the engine starts from cold the Electronic Control Unit also has to overcome a temporary increase in friction caused by the viscosity of cold oil. * There are no sensors measuring this but if ignored it will swamp normal idle speed and cause it to stall. * To prevent such happening, the idle speed of the engine is artificially raised by introducing more metered air to the engine via the Extra Air Valve.

Failing a faulty connection, the EAV and other components (except ECU) can all be tested with simple workshop instruments. For the EAV, go here. In the same archive are descriptions and tests for the other Efi components for your system.

The next most likely cause is a rogue air leak.

Edited by honestjohntoo on Tuesday 10th August 17:08

[chunder]

"BOTH heat from its internal coil AND manifold temperature must be present"

Not quite right, it's EITHER and OR rather than BOTH and AND.

The disc will spin to a closed position through either the heating effect of the electric element or engine heat soak, hence why it has no effect on revs when starting with a hot engine even though it has had no electrical supply for a while.

I'm not quite sure where the above was quoted from but never heard that the viscosity of the oil when cold would cause the engine to stall, I mean we are talking a large capacity v8 here, not something in a remote control car.

If it was a rogue air leak unless it's dissapearing as something is warming up it would affect idel full stop, not just the time it takes to return from fast to normal idle.

Edited by chunder on Thursday 12th August 03:30

[BrianTVR350]

Hi,

Progress of sorts...

Took the valve off last night.

Tried connecting it to 12v as suggested, it took 10 minutes or so to close completely, but I could still blow through it... So I cleaned it out by washing out with carb cleaner, 1st couple of washes came out black, eventually I was putting clear cleaner in and getting clear cleaner out...

Connected it to 12v again, still closed, maybe a bit quicker this time but could still blow through it.

Not 100% happy but put it back on the car (engine cold) Started up and tickover quite low, so took out on the road and warmed up properly. Arrived back home, car now hot, tickover really low @ 400rpm

Reset idle to 850rpm with the idle screw on the plenum.

Engine now drives properly and idles as intended, drops to 750 rpm when fan cuts in..

Will try a full cold start and warm-up this weekend (it's a chore, but it has to be done! ) and see how much effect cleaning has had.

Regards,

Brian (and a Red 350i)

[honestjohntoo]

chunder said:

"BOTH heat from its internal coil AND manifold temperature must be present"

Not quite right, it's EITHER and OR rather than BOTH and AND.

The disc will spin to a closed position through either the heating effect of the electric element or engine heat soak, hence why it has no effect on revs when starting with a hot engine even though it has had no electrical supply for a while.

Sorry Chunder, - unless TVR's use a different EAV to the earlier Rover SD1 system, regret to inform you, you are mistaken.

The following is a direct quote from page 8 of the the "Rover (Flapper) Efi Technician Training Manual" regarding the EAV unit.

The disc is turned by a bi-metal, which responds to both ambient (ie the coolant temperature) or to the heating wire coiled around it. This coil is connected to the fuel pump electrical circuit, therefore the coil starts to heat the bi-metal and begins to close the valve as soon as the engine cranks and runs. Once the engine is running, the combined effect of the heater coil and engine temperature closes the EAV fully between 60 - 70°C.

Clearly then, a combination of heating effects. Grab a copy of the manual and check it out. If you have Rover or TVR evidence to the contrary I would be very interessted to read it. I can scan a copy of the page for you if you wish.

chunder said:

I'm not quite sure where the above was quoted from but never heard that the viscosity of the oil when cold would cause the engine to stall, I mean we are talking a large capacity v8 here, not something in a remote control car.

If it was a rogue air leak unless it's dissapearing as something is warming up it would affect idle full stop, not just the time it takes to return from fast to normal idle.

That text came from my own web pages on the EAV with the facts sourced from original Rover Technician Training material and interpretted as required by ongoing experience. The passage regarding friction forces are my own words, because it is self-evident that in a very cold climate such as a UK winter, any engine, irrespective of capacity, will struggle to overcome initial friction/oil viscosity forces, hence the need to raise the idle speed when cold.

Worse, the Efi System, as used in the SD1/TVR runs quite weak at idel and therefor is torque deficient at low revs, making it susceptible to stalling on idle when under any load, as witnessed by Rover using two supplimentary air solenoids to overcome AirCon AND (Autobox) torque converter loads at idle.

The fact that "BrianTVR350" has now serviced his EAV and with a full 12 volts applied to the coil, could not close the airway even after 10 minutes, supports the "dual heating effect" design criteria.

Now, on-car, and hot, as reported it behaves perfectly.

My original contention was that he had a connectivity issue to the coil, which was a distinct probability, but also the same issue could have been caused by crud jamming with the combined forces of the two heating effects unable to close the valve.

The secondary suggestion regarding a rogue air leak was not misleading, simply a pointer to the possibility that such problems can raise the idle speed unneedingly and may be varied by heat affecting the flexibilty of the rubber connexion pipes as the engine heats up. Also with such an unmetered air flow condition affecting mixture control, any similar type symptom as reported makes it worthwhile looking for that type of fault.

Such are the beauties of analysis.

Hope this explains.

[chunder]

Hi Honestjohn,

Electrical connection alone is enough to spin the disc past the closed position, in time. Obviously it would be quicker if it was also picking up heat soak. I believe the reason you can blow through these slightly (normally one way only - maifold to throttle direction) when off the car is because manifold vacuum helps seal the disc againt the seat, which is why it then works ok on the car.

I understand the disc spins courtesy of a bi-metallic strip arrangement, it just needs heat, irrespective of whether that is from the electrical heater element or soak through the casing.

But then it wouldn't be the first time I've been completely wrong !

[BrianTVR350]

It's fixed...

and at a price a Yorkshireman approves of...

Think I had two issues in the end, the disk was sticking due to crap brought in from the plenum.. And from the behaviour of the tickover after cleaning it I suspect I had a slight air leak on the "straight" rather than "U" shaped pipe.

Now car behaves as the men from Rover intended...

Initial cold start... 1200 RPM...

after 1 minute... about 1000 RPM...

engine showing 70C... 850 RPM...

Now I only need to source a 6" piece of 16mm-5/8" ID silicone hose, anyone any ideas where to buy pieces this small? I can only find places which want to sell me a metre length, which is well over the top for what I want.

Thanks for all the replies guys.

Brian (and a Red 350i)

Now looking for another excuse to go on a test drive!

[TVRleigh_BBWR]

BrianTVR350 said:

Now I only need to source a 6" piece of 16mm-5/8" ID silicone hose, anyone any ideas where to buy pieces this small? I can only find places which want to sell me a metre length, which is well over the top for what I want.

Is this for vacuum i.e. single ply. if so I'll look in my hose collection and see what sizes I have, is so maybe able to put a bit in the post for a few beer tokens.
I think your find though people only sell 1M lengths. hence why I have lots of odds and ends.

[honestjohntoo]

BrianTVR350 said:

Think I had two issues in the end, the disk was sticking due to crap brought in from the plenum. And from the behaviour of the tickover after cleaning it I suspect I had a slight air leak on the "straight" rather than "U" shaped pipe.

Its good to be fixed, especially if there were two interacting faults, making analysis so much more difficult.

Just to clarify though, whatever crud you found in the EAV did probably not come from the plenum as you suggest, under normal conditions.

The air passing thro the EAV ALL originates from the AFM and then into the air rail adjacent to the idle air gallery, thro the air rail, part of which you are replacing, thro' the EAV and only then INTO the plenum.

That air is always from a normally clean source and does not flow in the opposite direction. EXCEPT, foul air from the crankcase breather gallery might cross the air intake tunnel past the open throttle plate and somehow get into the air rail.

UNLIKELY though, as any such foul air would normally be rapidly ingested into the combustion chambers by the in-rushing air stream from the AFM.

So in the very unlikely possibility is that IF there was abnormal positive pressure inside the plenum chamber, then air might flow the wrong way through the EAV taking plenum crud along with it.

Such a condition would be most unlikely unless there was consistent and unnatural backfiring thro the inlet manifold into the plenum chamber. Such events are not unknown, however, and if occurring, wrecks the AFM flap system.

Such crud as you found, then, is having to be deposited into the EAV innards for some more rational reason.

• badly perished air rail rubber pipes is a possibilty, eroded bits breaking off when air is flowing and getting stuck in the EAV orifice.

• The fact that you also discovered a possible air leak in the air-rail rubber pipe described, does suggest the perished rubber explanation might hold true.

• less likely, running the car without an air filter, or more likely, with an undetected breached air filter system might allow a small but continuous amount of airborne deposits to find their way into the EAV innards. However, one might also imagine a lot more long term damage to the engine if such a problem were to occur.

Normally though, for the reasons explained, the EAV does not suffer from ingested crud, so you have been somewhat unlucky to encounter that condition. Mind you, now that the EAV fault is fixed, none of the above Will be any more than of academic interest or consequence.

Mind you, a little enlightenment is no bad thing, if it is correct, and, because you have just experienced a duff EAV system and are familiar with the consequences, as a simple experiment you could try is to temporarily disconnect the electrical connector to the EAV and start the car from cold.

I believe you would find the resulting symptoms will confirm what I was advocating from the get-go, that the EAV will not fully close without BOTH the heat sources mentioned (manifold and electrical) being present to fully activate the bimetal mechanism.

Should you find the dissecting analysis of Rover Efi problems interesting, then there are lots of opportunities available to read through the available material and acquire a full and better understanding of how the whole kit'n'kaboodle works.