hi every one i an a new member and just bought my first twin plenum rover sd1 vitesse on Monday,and i love it.but i have a problem,when the engine is worm it cuts out on idle,its done it to all day today,when stopping at junctions, also when i start it up in the morning when cold the the engine surges up and down on idle,be great full for some advice,thanks,richy

Rich, I think you have two issues there.

Hunting when cold is primarily due to a "slightly" rich mixture, comprehensively analysed here:

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Stalling when hot could have several causes, one of which is a rich mixture but there are several others including weak mixture, air leaks, ignition, fuel flow, ECU prob, etc.

Given the commonality above, check your spark plug condition and if a rich mixture is indicated, follow up on these probable causes of slight overfuelling.

# AFM Carbon Monoxide (CO) adjustment is maladjusted or the bypass gallery is cruddy reducing the available air at idle, inducing a degree of enrichment.

# Crankcase ventilatiion system partially blocked thereby reducing the fixed (not metered and not rogue) amount of foul air coming into the plenum from the crankcase, again inducing partial enrichment..

# The little hole (0.040" dia) in the left hand rocker cover breather blocked, having similar effect.

# An age-weakened flap spring in the Air Flow Meter (AFM) inducing unwanted enrichment at idle (and across the whole range).

# A stiff and aging Fuel Pressure Regulator (PFR) will raise the fuel pressure beyond 36 psi, enough to enrichen the mixture across the whole range, including idle, again when not needed.

# Its probably not air leaks into the plenum, but taken together with other things, who knows?

# Any combination of the above!

# Gross overfuelling seems very unlikely otherwise the engine would hardly run at all with its tell-tale fuel smell. So the usual suspects of gross overfuelling such as CTS, CSI, v.high fuel pressure, croaked ECU, TPS, etc. do not apply, at least to the symptoms you describe.

Because you have a Twin Plenum, anything to do with idle speed (including stalling) may be further complicated by mechanical faults in the throttle mechanism.

For the time being tho', the primary causes are identified and as follow up you may care to study further Efi system material available on my web pages.

Also there is a vast archive of Efi fault conditions and solutions on the Rover SD1 Club Forum with a user-friendly search facilty.

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hi thanks for your reply,that's a lot to take in,what i have done so far is cleaned all breather they were clear any way,i cleaned out the twin plenum pipe that goes to the air flow meter,and also cleaned air flow meter,then cleaned the little breather hole out on top of plenum,i have ordered ecu temp sender,and thermostat,that should be here to day or tomorrow, the thing is i am no good with electrics so i can't test any thing,i got a new vault meter but,but don't no how to use it.so in the end i will have to replace every thing,but we will get their in the end,and thanks again been very helpful,richy

Richy, Unfortunately Yes!, Lots to learn! My first recommendation included.

Quote:

check your spark plug condition and if a rich mixture is indicated, follow up on these probable causes of slight overfuelling.

How bad was the overfuelling, if any, according to the plug condition?

I mentioned fuel pressure but overlooked a second reason for marginally high fuel pressure. You mave have a rising rate FPR, incorrectly set too high. Pressure should never go higher than 36 psi, Its easy to measure - see page 5 of the pdf available here

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If you choose to randomly change components as you proceed, be aware, they cant all be faulty, so its an expensive route because in general, over 80% of all SD1 Efi system faults are due to air leaks, electrical connection problems and maladjustment.

You will find an article on using a multimeter here.

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along with descriptions, and test processe for all the SD1 Efi components here:

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including many technical articles related directly to the twin plenum
on the same download page.

Good luck

hi Ramon,thank you for your help,lots to get on with,and know i can learn how to use the malty meter,i will let you now how i get on with the car,thanks again.richy

hi,can a faulty thermo-time switch course the engine to run lumpy at times as if to much fuel is getting to the engine,and the engine seem to tick-over at 1500rpm,richy

Richy - read this for a full explanation

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This short answer is contained there-in

Yes! A faulty thermotime switch can cause uncontrolled over-fuelling during cranking if the internal contacts are permanently closed. Also the cold start injector can cause over-fuelling if its injection orifice is corroded or contaminated causing it to leak fuel continuously.

So the injector can be a possible culprit if its weeping slightly all the time

Disconnect the plug from the CSI and remove the injector from its hole, seal the hole with duct tape and try again.

What do the spark plugs tell you about the mixture.

hi,i have had the plugs out and they were black like sooty,does that mean its running rich.also found a plug of on the Auxiliary Air Valve,so i plunged it back in,it seem to run a bit smoother,but when up to normal temperature it just cuts out still on idle,can i fit a hotwire air flow meter on and will this work,i got suspicions on the flapper air flow meter as the black top has been of some time in it life, richy

R.

At last! Phew! Its tough getting you to follow advice. Black plugs! Proof that you system is running rich.


EAV connector off. Good discovery! Running smoother?? So has the hunting now gone? I Assume Yes! So the first problem is resolved because the extra air control was wrong creating the right conditions for hunting, I guess.

Assuming you cleaned the plugs thoroughly?

Moving on! Suggest you now go and check the other things that I already told you about - all of them - including the usual suspects for gross overfuelling.

Everything you need to know for testing is in my archive..

I think you also need to consider acquiring the Efi Manual.

I am not familiar with hot-wire other than it needs changes to the system and a different ECU. There are experts around. perhaps on other forums. V8, RR. LR. 4 X 4, etc.

hi ramon sorry mate about the plugs,i started it up this morning and still idles up and down,so today i played with the air flow meter after reading all about it from your archive,i weakened the mixture then taken the car for a run then tweaked some more,and got it running a lot better and more responsive,so i took the car to a garage to check the emissions,and the reading is.summary results co (4.50) & HC (1200).which the guy said it was a pass,& description is co 0.20%vol & HC 399 ppm. but know will have to wait till the morning to see if it idles right.but so far very happy with the running now,getting somewhere,i will let you know tomorrow to see how it starts.thanks ramon.and sorry i done your head in.

Well done Richy. What happens is: a person may fiddle with the CO screw to make it richer trying to overcome another problem such as a weakness inducing air leak. Then maybe the air leak gets fixed and the system in suddenly too rich.

As you will have read, the CO screw will be approx 2.5 turns out from fully closed if everything else is OK.

You will hopefully have sorted the rich running at idle now.

Moving on to idle speed, if still too high, it can be adjusted down but if it wont budge, study the Plenum essay for associated air leaks and how to test. It also explains the issues of cleanliness in and around the plenum chamber including breather and idle air galleries.

Another essay on Twin Plenum Idle Speed Hang-up addresses the mechanical adjustment issues that affect the TP assy and high idle speed.

its also about now you will begin to wish you better understood the whole Efi system as you are just scratching the surface, thus far.

Keep the faith, keep studying and stay sane!

hi ramon,this morning i started the car,and its sill the same idles up and down for about couple of minuets then the rpm rises over 1200 rpm until it reaches normal temp then idles as it should.so now what i have done is striped the manifold down completely of the car.i have ordered a new manifold gasket,i now got the manifold in my shed striped to bits,so far i can see it looks like its been sucking air in at the plenum,as someone had it before me and have had it of, then put it back on using bathroom sealant,in stead of hylomar sealant,i have now checked all seals,pipes and replaced all gaskets,new thermostat,new coolant senders,except the one that operates the cold start.can't get one anywhere.even rimmers is out of stock.i have washed the trumpets down with petrol as they were oiled up,so that's how far i got,my inlet gasket should arrive to morrow, any way,i will keep,you informed,richy

R. Its academic now but were you able to adjust the idle speed down with the adjust screw? With the plenum now off its an excellent opportunity to put crud contamination problems behind you for years. Just follow the Plenum and Idle Speed hang up essays.

Following cleanup, a suitable sealant for the trumpet housing to manifold and plenum chamber seals is a very light smear of silicon instant gasket. I understand, originally, there was no goo of any type from the factory.

There will be wear in the TP throttle quadrant, levers and mechanism generally but it can be dealt with using simple workshop skills. Twisted spindles are the only exception. Check you have all three spring correctly placed upon re-assembly.

Going back to the Cold Start Hunting, re-read the solutions and if it simply cannot be scared away, try adding the 10,000 ohm resistor workaround that Rover recommended. It solves the problem withoiut dealing with elusive causes.

Going forward, now is a good time to read about throttle pot and use an ohmmeter to test its function is smooth. From what you've described thus fa, it may not be faulty, but they are a sod when they go wrong, as a substitute replacement involves changing things quite a bit. There is a thread running on the SD1 club forum currently.

hi ramon,well i put all the inlet manifold back on the car and started the car up,and revved like mad,the only way i can get tick over was to adjust the idle screw right down as far as it can go,so any way i have taken the plenum back of,know i think i now what i done wrong,i had the Throttle Discs out yesterday to clean them.i put them back in and did a water test,put water down the inlet down the air intake.water just gushed out past the Throttle Discs,but fitted it back to the car anyway,as dont now much about this any way,so anyway got the plenum in my kitchen,i had a look on the forums,and i haven't lined up the Throttle Discs right,now i have done it,but what i need to know is, how how air tight or my water tight has the Throttle Discs got to,at the moment i poor water in and they just drip water out past the Throttle Discs,is that ok,thanks,richy

Richy, Water is a novel way of measuring disc fit, but not one that I have come across before. I used a torch. You can see exactly where there is a problem, water gets everywhere.

If the first time throttle plate fit in the tunnels was as bad as you describe, I'm wondering if the key passages in the following section of my Idle Speed Hang-up essay escaped your attention.

From yesterday

"With the plenum now off its an excellent opportunity to put crud contamination problems behind you for years. Just follow the Plenum and Idle Speed hang up essays."


Fit of the throttle discs to the air intake tunnels of the plenum chamber

• There is no throttle-stop adjustment screw on the Twin Plenum system and an airtight fit between both throttle discs and the intake tunnels is required. Set the quadrant as described using a torch to check the gap. Suspect discs can be changed if replacements are available, otherwise clean off all deposits and polish the edges and faces for significant improvement.

• Use needle pliers to close the split thread of the disc fixing screws before there are removed. Make an identity mark on one disc to ensure they can be refitted in their original tunnels. Inspect edges for dents or distortion and take extreme care with any renovation of the edges.

• Check the shafts for excessive wear or distortion and replace them if required. If new items are unavailable, again, the existing shafts might be significantly improved by cleaning and polishing. The shafts provide primary bearing surfaces so polishing in that area should be minimised. Dress the slots with fine abrasive paper and needle files to remove burrs or dents and ensure that each throttle disc slides smoothly in its respective slot to aid re-assembly.

• Upon re-assembly, smooth operation without friction in the intake tunnels is paramount. This depends upon axial location of the discs in their slots after the retaining screws are tightened. If a disc interferes with its tunnel, slacken the fixing screws with the throttle closed to allow the disc to centralise itself before retightening the screws. Incorrect axial or radial alignment will also result in unwanted air ingress around the discs. Use a thin blade screwdriver to lock the fixing screws by slightly opening their split threads.

• Central return springs are handed, so ensure correct location to avoid undue spring pressure.

The first and fourth bullets clearly stress how important it is and how to make the discs fit correctly.

here is the link.

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The twin plenum was only fitted to about 500 - 700 SD1's. Not an engineering masterpiece, so, by and large suffers from crud and poor maintenance, both inducing long term wear, so getting the things to fit all these years later requires care and perseverance.

As far as I know, my essay is unique in helping to achieve that. Follow it explicitly.

cheers, Ramon