LagondaNet

[ksumrall]

Hello,

I finally took my lagonda (13441) to get smogged in California. I was pretty sure it wouldn't pass, and I was right. As a matter of fact, they never even sniffed the exhaust. The car idles too high (about 1800 rpm) and thus they can't start the automated sniffer.

So, i took a quick look, and I see the throttle cable comes in from the front of the car, and is attached to a linkage assembly that rotates the throttle of all 4 carbs together. However, the cable is already fully loose when the gas pedal is not touched, so I'm not sure what else I can adjust. I haven't taken the airbox off to get a better view, but I thought I'd ask here first.

Also, what is the other cable attached to the linkage assembly that goes off towards the firewall and the passenger compartment? I haven't had a chance to trace it yet.

As always, thanks for your help in advance!

[david]

Unfortunately there is unlikely to be a simple solution to this.

First, if the idle is truly at 1800 RPM, it is a surprise that the gearbox is still functioning OK, it must go into drive or reverse with quite a bump.

If held in drive or reverse against the foot brake, there is risk of damaging the torque converter if the engine speed is still somewhere around 1500 - 1800 rpm.

So, the first thing to do is determine what the true engine speed is by use of a separate tachometer and most higher end (such as Snap On) timing guns will have an engine speed display as well.

It may well be that the idle speed has been raised to try and improve the idle quality so just reducing the idle speed may create as many (if not more) problems than it resolves.

The high idle speed may be due to either the throttle setting and/or a fault with the ignition vacuum advance system (or even the basic setting) - there has been quite a lot of discussion about this between Arnaud, I think and Jonc, so look at this as well.

If the prime objective right now is the smog test then there are a couple of things you can try BUT if you want to use the car and run it reliably with no risk of (expensive) engine damage you will, as is always the case when setting up an engine, need to ensure the ignition system is set up correctly and works as it should throughout the engine speed range.

If you want to reduce the engine speed just to try the smog test, look into the following:

Make sure there is no vacuum supply to the ignition advance capsule at idle, if there is, this will increase the engine speed at idle and also reduce the idle quality. - I think, but am working from memory here so will gladly be corrected - that the vacuum retard capsule should be supplied at idle, so reducing the idle speed and smoothing out idle quality.

The switching of the vacuum states to the vacuum advance/retard capsule at idle and off idle is controlled by a microswitch that is operated by a small lever hanging down from the throttle linkage bar between carbs three and four - ensure it is set correctly and the switch is depressed with the throttles closed.

In theory, all four carbs are balanced to each other and also side to side, the linkage set and the idle speed governed by the throttle stop setting on the front carb, so, if you are very lucky, unscrewing the throttle stop on number one carb may reduce the idle speed.

The best way to get to the idle speed set screw is to use a small socket and knuckle joint - 1/4" drive sockets are the best (only?) ones to use as access is difficult. I think the size is 5/16" or 8mm.

The added problem you have with a US spec car is the access (or lack of) due to the large aluminium air intake assembly, as opposed to the Euro/GB spec cars.

The extra cable may be a choke lever cable (in which case check to make sure the chokes are not still on even with the knob pushed fully in) - but this goes to the other side of the carbs.

If the cable is on the same side, it is maybe the cruise control cable that loops under the manifold and round to the cruise bellows on the side of the engine bay.

Hope this gives you some ideas for a start

David