idle adjustment?

[longbow]

Laptop time.... Throttle pots, link bar and idle screw - combination of either or all.

[marcus1970]

InverCerb said:

Morning all.

Car had a 12k service last week, everything was good, but it wasn't until i stopped for gas up the M1 on my way home to Aberdeen that i noticed it was idling high and steady at 1400rpm.

So after a few days of this i adjusted the throttle cable as advised by the garage, but this had no effect as it just made the cable slack, so i backed off the throttle stop, which has worked to an extent, but now i have to sit until the engine has warmed up a bit as she won't idle when cold!

Any ideas please?

Cheers

Rob

I'm doing mine at the moment and it's a b*stard of a job and really getting on my t*ts.

One top tip, the idle screw may look like jurassic nuts and bolts, but even quarter turn adjustmenets up or down make a big difference.

MB

[julian64]

I fear the garage has created a air leak in the inlet manfold some how.

My guess would be air is getting past the butterflies. Check all the clips especially the ones that form the cross at the front.

Check all the butterflies are closed and sealing properly.

[marcus1970]

julian64 said:

I fear the garage has created a air leak in the inlet manfold some how.

My guess would be air is getting past the butterflies. Check all the clips especially the ones that form the cross at the front.

Check all the butterflies are closed and sealing properly.

Any chance you could elaborate a little bit please.

Cheers

MB

[TVRleigh]

Easy way to check for air leak, is to spray some easy start around the engine,
If your rev's go up you have a leek.

if not it maybe you have a faulty temp sensor, if the car will not idle when cold.

They must have set the idle at cold, hence the fast idle when warm.

[julian64]

marcus1970 said:

julian64 said:

I fear the garage has created a air leak in the inlet manfold some how.

My guess would be air is getting past the butterflies. Check all the clips especially the ones that form the cross at the front.

Check all the butterflies are closed and sealing properly.

Any chance you could elaborate a little bit please.

Cheers

MB

Well. The engine is idling high because its getting a weak mixture at idle. The only reason an engine can increase in speed is if you get more air and fuel into the cylinder with each bang.
The air is the only part of the equation your right foot controls as the rest is controlled from the lambda and the engine fuel input. Too much fuel and too little air and the car engine would just stop/run rough/slow. Too much air and normal fuel and the engine runs at high revs with little power. (This is a fair old generalisation)

So, air is getting into the cylinder of your engine. More air than the throttle butterflies themselves should be letting in.

From the cylinder to the airbox.

Inlet manifold cracked or not sealed.
Butterflies remaining open despite throttle cable slack.
Vacuum tube off or not sealed. on each inlet bank and the cross at the front.

Next step. Take the inlet pipes off because they have little effect on idle.
Start the engine, and let it warm up on idle.

If you have a syncro pop it in each inlet and read airflow at idle. Likely your culprit will be there.

If no syncro then push finger on each butterfly in tern to see if they all have the same effect on idle running. Men, at this point would cover the whole of one inlet with the plam of their hand and monitor the change in idle running when the engine tried to suck their hand in.

Of course you could just use the diagnostic software and look for the lambda which never moves , or possibly throttle pot set too high.

If you are near me, I'd be happy to lend a hand.

[thegreengoblet]

julian64 said:

I fear the garage has created a air leak in the inlet manfold some how.

My guess would be air is getting past the butterflies. Check all the clips especially the ones that form the cross at the front.

Check all the butterflies are closed and sealing properly.

I had similar symptoms and it was due to these valves not closing. The reason for mine was that the small internal throttle return spring had snapped - this spring connects to the end of the rod that connects to the throttle pots.