dead spot when cold

[Oz2]

Hi All
The sx has developed a dead spot,starts ok levels out to idle ok but if I dab the throttle it dies let the throttle go and returns to idle......Once warm we are back in action, I thought it may be something simple as it is ok warm and that some of you have experienced.....We've had some awsome winter days here great morning runs, I hope you are all enjoying your early summer and that it lasts a while, looking forward to seeing plenty of BBWF pictures posted on here too for all us expat TVR'ers

[adam quantrill]

Engine Temperature Sensor? They can go open circuit at different temperatures then work again after. Check with an ohmmeter.

You are lucky, mine will not idle at all when cold for the first 2-3 minutes.

[Oz2]

Thanks Adam,

Ill have a look tomorrow, it's only just started doing it. when i start the sx i have to do it without touching the throttle if i do it stuffs up if i just turn the key and let it do its thing it levels out to idle within a few seconds. today when i went out it was switched off for about an hour when i started it to come home i dabed the throttle and it did it but not as bad, then it was fine again a good run home with a responsive throttle.

[Oz2]

ok,
Tested the thermotime sensor seems ok,
Tested the cold start injector again ok
fuel pump packed a sad, fitted a new one.
STILL has the dead spot, its like the old days with the manual choke, with the choke on if you gave it throttle it would die...well thats what it does, until it warm......Any ideas?

Adam

[Oz2]

adam quantrill said:

Engine Temperature Sensor? They can go open circuit at different temperatures then work again after. Check with an ohmmeter.

You are lucky, mine will not idle at all when cold for the first 2-3 minutes.

Hi Adam,
When you say engine temp sensor do you mean the one next to the thermotime sensor???

[adam quantrill]

Yes. You need to check it while it's in the funny idle mode too. Or else swap it out for a new one and keep the old one as a spare. Landrover dealers should stock them.

[combine]

stepper motor playing up , is it a hot wire , if not then you won't have one .They are prone to not working if dirt builds up inside spring .

[honestjohntoo]

Oz2 said:

its like the old days with the manual choke, with the choke on if you gave it throttle it would die...well thats what it does,

with that analogy it would be easy to assume that the mixture is too rich during the warm up phase? But the Efi system when running a tad too rich is not really prone to stalling and if it was running very rich you would smell it around the exhaust or in the engine bay.

To avoid guessing or just relying on good luck a few more signs/symptoms are needed.

It would be help you to inspect the plug condition at about that time to check for sooty or wet electrodes.

One plug from each bank is best, to see if both sides of the injection circuits are doing the same thing.

If it is running too rich then it does lead to a rather wide range of component possibilities, TPS, CTS, FPR, the CSI and TT - (both already checked?), blocked breather, AFM and ECU, so it would be really good to know which way to go. Ie, rich or weak or out of left field, perhaps even early stages of ignition amplifier failure which usually play up before croaking.

I actually think you may find the spark plugs are not affected as described - ie not running rich - then it could be running too weak during warm up, simply not enough torque when energising the throttle and the engine just dies.

Less components involved here, but it opens up the possibility of a minor rogue air leak - perhaps in the input tract or in some pipery around the plenum or even a rocker cover gasket breach.

Just describing all the possibilities, unfortunately leads to dark thoughts of a deep money pit so you don't wanna go there - I guess - specially if it turns out to be something simple?

Whatever, there are test processes for all the components and for air leaks all of which are covered in the 15 point health check to be found here

Gorra be worth doing, taking away any guesswork or potentially expensive scatter-gun component replacement, and it will also embed your familiarity of all the component locations, what they do and how they do it. Plenty of reading material too.

Just to put things into context, over 80% of all RV8 Efi problems in cars of the era, are due to local (Efi loom) electrical connection or air leak problems, usually involving zero cost to fix.

[Oz2]

"WOW", Thanks guy's that gives me a few things to look at and get the beast in PEEK condition.
After I bought it it was laid up stored at my parents for a year then on the ship and in ports for 2 months so the odd corroded joint should not be a surprise....I feel it may be an air leak at this stage so I replaced the large pipe from AFM to the throttle body as it was obviously NFG!!! so now I'll go through and check the others.
I will keep you posted and keep testing it so I can nail what it is..
Thanks again for answers to all my questions while I sleep...

Cheers
Adam

[Oz2]

So can you tell from this what AFM is fitted? ie. hotwire.....
And on the last pic what is the ally thing with the arrow on it as when i rev the engine the pipe that leaves it sucks almost flat....

[mrzigazaga]

That alli thing looks like it could be a breather?..The air intake pipe being metal is soaking up heat which can affect the running, It might look nice but is impractical..Although i could be wrong.

[Oz2]

mrzigazaga said:

That alli thing looks like it could be a breather?..The air intake pipe being metal is soaking up heat which can affect the running, It might look nice but is impractical..Although i could be wrong.

you may be right but it's all i could find to do the job for now, although it only gets warmish, the original one is cactus. Oh and the blue has to go,I couldn't find black...yet

[chedder]

The alloy thing is a thermo warm up regulator, if you look through it then it should be closed when the engine is warm and open when cold, there is a method for for testing it but cant remember what it is, Wedgie or Adam may be able to advise on how to test it.

Chedder

[honestjohntoo]

I am clearly out of my comfort zone looking at the component layout of your engine, so regarding the reading material recommended, you will have to sift thro' for the bits that look familiar to you,

The item you queried is an "extra air valve" which allows in more air when the engine is cold to boost idle speed during that phase, it then shuts off when the engine is above 35 deg C.

It is (normally) driven by two functions, a bimetal heating coil and inlet manifold temperature.

Read all about how it works from my web pages archive.

The fact that the plenum chamber suction is collapsing the pipe thereabouts - I never seen that happen - so I would venture that the pipe in the foreground has been refabricated from the wrong type of rubber tube (too soft), it does not look original.

Alternatively the valve might be stuck shut, but unlikely - and even when its supposed to be shut, in my experience, the pipe should still not collapse as described.

The AFM (foreground - second image) is a flapper but wierdly upside down and does not appear to be electrically connected. Perhaps it is just being used to connect the air filter to the air input pipe - with the old AFM innards stripped out????

The output of the body also feeds something else so I guess this is a modded Efi system and perhaps, not a flapper.

Like I said - not my comfort zone - there is stuff in those images I dont recognise.

[Oz2]

the afm is'nt stripped out and it is electrically connected, so not hotwire then? Then onto the throttle body and into the supercharger. I'll look at changing that pipe that is callapsing...
Just went round and tightened up all hoses none were real tight the worst being the servo vacume, i cut the end off it and refitted it. I'll test in the morning as the neigbours are and might not like me givin'n it large wiv me big v8

Edited by Oz2 on Friday 27th May 13:17

[Oz2]

adam quantrill said:

Yes. You need to check it while it's in the funny idle mode too. Or else swap it out for a new one and keep the old one as a spare. Landrover dealers should stock them.

I think I'll get one and swap it,they're only $60 so it will be worth a try.

[combine]

Looks like a flapper , not standard parts though so not sure whats inside box before air filter , if she pops and bangs on overrun then defo a flapper !

[adam quantrill]

Yes it's a flapper. I think I see the problem:

Oz2 said:

Your engine bay is far too shiney!!!

[Oz2]

chedder said:

The alloy thing is a thermo warm up regulator, if you look through it then it should be closed when the engine is warm and open when cold, there is a method for for testing it but cant remember what it is, Wedgie or Adam may be able to advise on how to test it.

Chedder

I took the pipe off and it was closed (engine cold) could this be my problem?

[adam quantrill]

That is the Extra Air Valve isn't it?

So the thermotime switch is supposed to open this electrically and also enable the "top" injector in the plenum to squirt in some extra fuel.

I think there's some good advice about it on Ramon's site here:

http://www.vintagemodelairplane.com/pages/Rover_Te...

However note that on the SX (if yours is like mine) the EAV air feed comes from upstream of the supercharger. This means that the air pressure inside the plenum could actually be higher than the feed to the EAV, so the EAV could actually leak air _out_ of the plenum - the opposite to that intended. So you may find that there's a one-way valve fitted between the EAV and the plenum on the SX. I think I can see yours under that black tie-wrap. So you ought to blow down the pipe in each direction and check it's operating correctly too.