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MG MGB GT V8 Factory Originals Technical - Intake manifold heater on EFi

I was just reading some archives... Came across something about an "intake manifold heater" and the vacuum leak from the 4 holes not being plugged if this device is removed.

I don't know if this device is on my engine or not. Can someone tell me what this thing looks like and where it is located?

The archive stated that this is sometimes overlooked. And I know for me and my conversion, it wouldn't be the first thing that I've overlooked!!

I have been dealing with a crazy engine idol and a long start up (cranking to long) for the past few years on and off.

I am now trying more than ever to narrow out vacuum leaks. Since we all know.. Vacuum leaks suck! No pun intended!

Thanks for any help,
Wally
Wally Jonker

Bolting to the underside of the trumpet cover, directly under the throttle mecanism, just prior to where the rubber/plastic air conduite from the air flow meter attaches. Above the rocker cover.
At least thats where it is on unaltered manifolds/plenums. It is/was a thing about as thick as your fingers that has two water pipes sticking out of it on the LHS. Water circulates through these to keep the throttle manifold warm. When you machine an inch or so off the plenum/manifold there is not room for it, so people take it off and block up the bolt holes that held it on. I screwed the orrigional bolts back in with some epoxi and ground off the excess and heads. You will have to take off the trumpet cover and turn it upside down to see if your holes have been blocked off.

Your base idle may not be set right. This gave me some difficulty for a while, the engine would not idle, sometimes. Instead, smoothly shutting itself off. I would have to switch off the ignition and then restart to get it to idle. The base idle problem was disguised by the computer compensating, something it would not always do.
Orientation-Standing on the portside of the car, front to your left, back to your right.
After the engine warms up, block off both ends of the rubber tube on your right that goes to the idle control valve at the back of the trumpet cover. The computer uses this valve to control the idle and you want it out of the picture when you're setting the base idle.
You can fine adjust the idle by using the idle adjust screw just on the right of and above the air intake, butterfly valve. It is an alan keyed screw under a blanking cover (approx 1 cm diameter)that you need to prize out. You can only go so far with this before the air intake starts to make an irritating whistling noise. This means you should do a coarse/big adjust by taking a large pair of plyers and bending the throttle stop plate back/down a little. Sometimes there is an idle adjust screw in this stop plate, in my case not. In my case I believe that at some stage this had got a knock and allowed the throttle spring to close the air flow valve off entirely. About 1 to 2 mm was enough. After that fine adjust with the alan screw etc. You do need to do all the usual blipping to "clear" the engine between adjustments.
Peter

Just struck me, Temperature sensor may be faulty/not connected. One guy I know of had his fuel temperature sensor wire plugged into his water temperature sensor and VV.
Peter

Peter,
Thanks for the reply. I can eliminate the manifold heater as an option for vacuum leaks. It is still on the engine. My Plenum is un-modified.

On the subject of the temperature sensor, is there an aftermarket one that I can purchase? I've read that many of the Lucas sensors can be replaced with other (way cheaper) sensors and get the same results. I've been told to change it out by others, but Im trying to fix anything cheap (like vacuum leaks) first!

Thanks again,
Wally

Wally

This thread was discussed on 09/04/2006

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