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MG MGF Technical - Fuel/Ignition timing/Sensor Issue??

For some of you that dont already know I have a MGF with a

Fully ported head
Piper 633 Cams (BP330M)
Vernier Pulleys
Vader Induction
VVC inlet manifold (My mpi head was ported and matched to it)
52mm Throttle Body
Lightened flywheel
Daytona Back box
Completion Ignition Leads

Ever since I've installed my new head and cams last June, I have had issue with stalling from high revs to low revs.

I have replaced the IVAC and played with the idle screw on the throttle body but to no effect. The sparks are new, along with the rotor arm and dizzy cap. The head has been correctly timed to the cams (44/66)

At this moment in time I do not have a 4-2-1 manifold but it is my 30th on Friday!

The stalling issue was starting to get on my nerves a bit! I believe if I went down the route of having a new ECU (Emerald) and getting it rolling road setup this would have alleviated the problem but as I am getting married this year I cant really justify that kind of spend!!

After researching this kind of problem on various cars and magazines, a possible issue with stalling could have been with the Fuel Pressure Regulator. Apparently when you let go of the accelerator the pressure drops. There can be a large tolerance on this. So I thought for the sake of 80 I would give the FSE power boost valve a shot. I did not order the gauge for this (but may still!)

Well the car no longer stalls! I had to turn the valve slightly anti-clockwise but jobs a good un!


The car runs like a dog now under load (driving) it is especially bad from cold. It jumps around like a mad thing! Under heavy acceleration from 3500revs -> everything is ok, in fact Ive really noticed an even smoother acceleration. From a slow rev e.g. cruising at 40mph soft acceleration the engine splutters. Once warmed up things do get easier but its not right.

The Idle is smooth now as well. Before fitting the FSE, the car idled very erratically. The car pops and crackles now (I would imagine miss-firing) it used to before but from cold it sounds like an Uzi! Lol

What can the problem be then? It must be something else?? Has anyone had any issues with the IAT valve on the manifold? Could the crank sensor be faulty? I thought it could be the fuel pump or injectors but under heavy use everything is fine.

The problem has just changed from one thing to another. Am I getting closer to the cause?? I dont really want to spend 50 on sensors if I dont have to, but I will!

Please help me!!! Any ideas??? I really want to start track days this year but with my car in this condition I just wouldnt feel confident.



Chris Glen

The problem is caused by the poor manifold vacuum at idle, the solution is to back the cam timing off to 45/40 and/or adjust the balance of air between the TB and the IACV, judicious adjustment of the TB *will* cure the problem. I have seen it on dozens of engines.

Dave Andrews

Hi Dave!

Sterling work though on the head. The lightweight flywheel i fitted after the work that you and I did has made the car even more fun!

Before popping over to you again to asjust the cam a little, Is it just a case of adjusting the Idle screw with the cap on? Should I buy a guage to acuatley set the Fuel Pressure?
Chris Glen

Quick Update.

Backed the idle screw back a whole turn this morning and reset the throttle body (accelerator six times)

The car still feels jumpy but not half as bad.

I think I will continue "tweaking" I shall order a FSE guage so I can set that acurately.

You may still hear from me again Dave!

I dont like calling you up as you seems to spend most of your life on the phone!!

I was thinking about 3.2 bar??? Can you change the FSE presure on the fly or do u have to switch the engine off during re-adjustment?
Chris Glen

This thread was discussed between 17/01/2007 and 18/01/2007

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