Cruise control

[littlepippin]

Can anybody help with this one - my 2 litre twin su version, soft top, is driving very well, and is responsive and fast and doesn't drink too much of its supermarket petrol. Idles lovely and smooth at 850 rpm.
It's a very slight niggle BUT, on a long drive of, say, 1 hour plus, it seems to take an increasingly long time between gear changes for the revs to drop (which they always eventually do) down to idle speed, making for a frustrating drive. Also, there is the effect of the car sort of driving along by itself quite happily, foot off gas pedal, like cruise control, although it is slowly slowing down.

It means you don't have any engine braking/retardation and are on the brakes quite a bit more than one would like....

Dash pots have 3 in 1 in, as I thought that was better in the cold'ish UK winter as I take it out all year round.

Thanks for your help in advance,

Sean.

[saabfast]

Have you stripped and cleaned the pistons in the carbs to make sure they are not dirty and sticking. Also the linkages get dirty and can get sticky, not returning fully. Try 'washing' with some engine cleaner and a light oiling. I find the idle can be a little variable at times but not to the extent of 'self driving'. The other possibility is a sticky advance/retard on the distributor, check the vac unit is OK and the plate and springs free.

Where in TW are you? I live off Forest Road, happy to meet up sometime for a look and compare notes.

[littlepippin]

Hi Saabfast,

I have cleaned the throttle spindle etc with carb cleaner, and lightly lubed like you say. Pretty sure they are returning ok. I am gonna go and look at the dizzy, and the pistons in the carb.

I am in Rusthall, and the lock up is right near the White Hart. Be good to meet if you are so near. Need your mobile number, and I will text you.

Cheers for the pointers.

[saabfast]

PM sent Sean

[gr8]

Have you checked the carbs to see if they have a poppet valve fitted?

If they do replace them with a solid disc - I had this very problem!

[littlepippin]

Hi gr8, just google imaged poppet valves, so I know what to look for. Gonna head up to the car and take a look. Did some more exploring yesterday, and the more I look, the more I am convinced it is the throttle shaft sticking/binding slightly at about the 2000 rpm position, at one or both carbs. Thinking about this, that probably is the point that gets more wear at a normal cruising speed possibly ? Anyhow, I have sprayed a liberal amount of carb cleaner followed by 3 in 1 spray to see if it loosens it up a bit. It is not an issue if you quickly "blip" the throttle, only if you slowly release the accelerator pedal, or hold it steady which is exactly what you do when normal driving.
I read on another forum (MG I think) about somebody fitting a stronger throttle cable return spring, but not going to go down that route - it doesn't seem like the correct solution to me.
Cheers for the tip.

[FI Spyder]

If the throttle shaft bushings are worn, the shaft can/will bind. The bushing can be replaced. Best left to some one that can do this (what I think is delicate work). The bushings are drilled out and new ones pressed in. In our club we have a member that does that often (for a modest fee) usually as part of a carb rebuild when needed. There are few jobs I won't tackle as they are mostly simple when broken down to their component parts but this might be the one job that I would leave to some one that has done this before.

[Hasbeen]

I once made up a plate to bolt down where the factory fitted that silly EGR valve. This plate had a post on it to mount a slightly stronger throttle return spring.

I'm not sure if this spring did much to improve the car's idle, but I'm sure being unable to refit that ERG valve did heaps. It is my considered opinion that they do much more for the car's performance when sitting on the bottom of the garbage bin, than when attached to the car.

Just one idea on improving your idle.

Hasbeen

[sonscar]

Another place to look is the bent wire connecting the throttle actuating cams.The holes wear oval and the wire forms grooves causing a sticky action.Replace it with some ball jointed purpose made throttle for a silky smooth action.Steve.

[saabfast]

I once made up a plate to bolt down where the factory fitted that silly EGR valve. This plate had a post on it to mount a slightly stronger throttle return spring.

Hasbeen

Thankfully in the UK we did not get EGR valves. Had a very quick look at Sean's car today and there is slight play in the front carb spindle but it sounds and idles OK. Also the spring plate is on upside down so the spring is binding on the inlet manifold which might not be helping. Didn't have time for anymore. Great Union Jack colour scheme in vinyl wrap, makes the car stand out, even some of my neighbours have commented on it.

Also interesting that it is X reg ('82) but has round door lock buttons and a twist lock boot (didn't make a note of the VIN). Must have sat in the dealers for a long time before registration!

[busheytrader]

Wedges also stuck around at the wholesalers. I had a short spell at Henlys wholesale department in NW London back in 1981. There were lots of TR7's going nowhere in a multi storey, mostly FHC's, awaiting orders from dealers. They were kept company by some MGB's.