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Idle problems

P

pruyter

Donation Time
A few days ago the idea was to collect my Tiger from the shop where it has been nearly 11 months. All the work I had ordered was done and I was satisfied with the result. However after a test drive I noticed that the idle r.p.m. was far to high. When the mecanic tried to adjust the carburettor the idle mix scew adjusting had no result i.e. there was no effect on changing the position of the screw. Besides that the idle was not smooth as I was used to.
This all is very strange because all the jobs I had told them to do had nothing to do with the engine, in fact the engine has never given me any troulbe before.
It amazed me however that the cold start now did not need my special treatment to get the car to start: this procedure was waiting until the pump did not making any noise and then switch of the contact and wait of a minute and after 3 or 4 pumps of the accellerator pedal it started immediately. I have done this for more than 28 years and it always worked. But now no procedure is needed it starts right away, very ver strange.
So how is it possible that this idle problem occured while there was no work done to the engine?
All I know is that the shop removed enigen plus gearbox from the top (now from below after removing the fron suspension). So I guessed that while removing the engine the engine is tilted backover and perhaps some dirt in the carburettor has moved and disturbed the float needle in the carburettor. But after inspection of the carburettor is showed that the carburettor was very clean, no dirt what so ever.
The brake servo was removed and sent to a specialist for inspection and in order to remover the engine the waterpump was removed. Other than that the shop did not touch the engine no other than placing new spark plugs (which I had not ordered) to my disappointment they had placed Bosch spark plugs which I don't like but anyhow this can't be the cause of the strange idling i.e. to high when warm and not smooth and not responding on the idle screw.
So I am very curious if somebody has an idea what could be the cause of this.
Thanks in advance!

Regards,

Peter
 
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Peter you don't mention what type of carb you have.. you just say the idle has now increased...
The carbs with the electric cold start could cause that kind of problem... If they moved it, knocked it.. that would increase the idle speed separate and not be impacted by the idle mixture.
 
Hi Michael,

I have the standard Autolite Tiger carburettor. Could an air leak be the cause? I was thinking on the brake servo which was removed in order to inspect it on faults and maybe the rubber hose from the servo to the intake manifold has some minor cracks?
The irritating thing is that this engine has always had a very smooth idle and now suddely after having been in the workshop I have this problem while nothing has been done to the engine or the carburettor. They have changed the timing from 2 degrees befor TDC to 6 degrees before TDC but that should not have any influence on the idling isn't?

 
If you have vaccun leak the car will run roigh and be ok when you open the throttle.

A stock carb has a power valve.. they can get stuck and would make the idle bad
 
High idle that you cannot bring down by unscrewing the idle speed (not mixture) screw says vacuum leak.
Most likely it is the carb to spacer or spacer to manifold gasket.
 
Easy check for the vac leak.. spray some carb clean around the base of the carb and manifold and see if the idle changes ...of ifle picks up . Vac leak
 
Reading this comments I start to doubt with which screw the mechanic was trying to get the idle speed down.
I understand that when it regards the screw that changes the throtle position then an air leak causes that there is no change in the idle speed.
But if it regards the mixture screw which does not change the idle speed what is in this case the probable cause?
 
Based on memory, ford carb has two mixture needles under front of carb base, pointing to rear of car. They should be under the fuel inlet pipe. Beginning setting for those would be screw them in gently seating them and then screw them out counting turns.....say one and three quarter turns out. Now for vacuum leaks, I like to listen for the hiss of a hose that has fallen off or broken. Use one of these without the probe, just an open hose: https://www.harborfreight.com/mechanics-stethoscope-63691.html?_br_psugg_q=stethoscope Or, three feet of hose with a funnel held against your ear. You can hear most vacuum leaks, confirm by spraying ether, brakleen, propane or such fuel; engine RPM will respond when you find a leak.
1720457419503.jpeg
 
Oh, and the secondary throttle valve can stick open, giving similar symptoms. . Spray inside and out with lubricant, actuate linkage (with engine off). Reach down secondary bores with long skinny screwdriver and tap on throttle blades, using a pool cue action, to ensure the throttles are closed.
 
Peter, I see you have several threads/posts regarding the idle and cooling issues

since having a "shop" have a go at making your car Better.

What have you concluded/ fixed to get back to square one.

DW
 
Hi DW,

Well the situation is now that I received last Friday an email from the workshop where the Tiger was fixed and they informed me that the car is ready to go. I have not had the time to fetch the Tiger, so I don't know what the situation is right now. What I do know is that when I fetched the car the first time from the shop ( the 26th of July 2024) that the throttle cable was sticking with the result that I nearly collided with another car when I was using my hand to get the gas pedal back when I was driving. Of course I was bloody mad at the shop, after an investigation I discovered that the workshop had installed the cable to high at a clamp near the carburettor. It was installed in a way that the outer cable pressed on the inner cable with the result that the throttle was sticking. Well that is fixed now. I had to bring the Tiger back after 500 km in order to check the differential in which a new axle and new gears were installed. I know now that the inspection revealed that all is well in the differential. At the same time they installed a new high efficiency radiator and a 6 blade Ford fan. I myself had already installed a new expansion tank plus a new radiator cap of 13 lbs. Earlier a 15 lbs cap was installed. I have also instructed the workshop to bring the timing back to where it was i.e. 2 degrees advance instead of the 6 degrees advance as instructed in the workshop manual.
So as soon as I have the Tiger back again I will test if everything is allright now and then I will come back to you and inform you about the results.

Regards,

Peter
 
Hi Dw,

In the meantime I have my Tiger back from the repair shop and now I have had the time to find out what the results are.
Well for the first time in nearly 30 years there is no leaking of coolant any more.
Secondly the engine temparature is now as I like it. With an outside temperature of 26 Celsius (nearly 79 Fahrenheit) the enigne temperature is about 85 Celsius (185 Fahrenheit) and while waiting for a traffic light it will rise to 90 Celsius (194 Fahrenheit).
The idle is about 800 rpm.
When I bought the car in 1995 it came with louvres in the bonnet, the horn holes blocked and with an electrical Kenlowe fan.
I have added to this a 6 blade Ford fan and a high efficiency radiator, this happened during the last repairs a few months ago.
I have waiting here in my garage a brandnew FlowKooler thermostat (160 Fahrenheit) which I don't expect to use.
In the meantime the ignition timing is set back again from the 6 degrees advance as mentioned in the workshop manual to the 2 degrees advance where the car came with when I bougt it. I have done some investigation and I learned that with the modern fuel the engine temperature rises more than normal and this is not caused by ethanol but by the additons to the fuel that are nowadays much different from the fuel that was for instance used in the sixtees. I use Ultimate from BP as fuel and this is in my country 100% free from ethanol which is not the case in every country.
By the way: ethanol is not causing higher engine temperatures but at the contrary lower engine temperatures.
As I have mentioned before: the rising of the engine temperature started after the timing was set back to the WSM-specifications. A friend of mine who accepted my advice to set the timing to WSM-specifications experienced exactly the same only much worse than my experience. So he has set the timing back to about 3 degrees and all is well again.
The only thing I can do more without breaking the bank is to make an airdam between the underside of the radiator and the front cross member.
I have some foam laying around and that foam can be squeezed between radiator and cross member.
I hope I have informed you enough if not just say so and I will try to help you out where I can.

Regards,

Peter
 
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