Hesitant engine after LCB fit

[swindorski46]

I've just managed to put my car back together after fitting an LCB manifold to it.

It runs well at idle but is a bit hesitant/juddery when I rev it, once it's up to speed it's OK again.

What's that all about?

[chris.mapey]

Check that the manifold is all gas tight - no leaks, a small air leak around the inlet manifold will cause those symptoms. Also check there is oil in the carb dashpot.

Hope that helps,

Chris

[TVR SLag's BiL]

Agreed, there must be an air leak somewhere or a sensor loose

[Mr2Mike]

One thing to look out for is that the inlet and exhaust manifolds are very often different heights, which means the washers cannot clamp both manifolds correctly. Most often the cast alloy inlet manifolds are thicker than the flange on the LCB. If this is the case, either file/grind down the thicker flange, or construct some stepped washers.

If you have replaced the original cast manifold with an LCB and decent exhaust system, this always (IME) causes the engine to run very lean in the mid range and top end. This is only compounded by adding a K&N style filter. Unfortunately the only proper cure is to get the car on a rolling road with an operator with some decent SU experience.

As a stop-gap you could fit one of the needles that come with the "stage 1" kits, although don't know the needle codes of the top of my head.

[swindorski46]

Thanks, some good advice in there.

Just to clarify though I'm talking about an MPi car here, so no messing with needles.

Would a rolling road still be of benefit?

Cheers.

[Neil8p]

We had a new head fitted on our MPi and at first it idled like a bag of bolts in a washing machine.

Left the battery off for a couple of days while doing another job and found the idle was very smooth after we reconnected it.

Couldn't say for certain, but I'm guessing ours did some sort of ecu reset with the battery being off.

[jeffriesmullet]

on some cars you take of the battery charge it and put it bck on and itll be perfect on mpis isnt it pressin the throttle pedal 10times with igniton on then leave 4 2min then start up?

>> Edited by jeffriesmullet on Wednesday 16th June 18:16