hesitation (off boost)
Turbo Mini Forums

its time to ask the experts before it goes bang!
My turbo mini was running fine when I first put the engine in, but now it has developed a hesitation off boost on a light throttle, when at w.o.t, it smooths out but im 99% sure I can hear detonation. also I just thrashed fk out of it in frustration, and at the top of 2nd (about 4500rpm) I could hear what sounded like it flaming out the exhaust. now and again it will run on a touch too.


shortly after fitting the engine the coil packed up, I replaced the coil with a brand new lucas dlb 198, whilst I was at it I fitted a new set of ngk bpr7es plugs and a new dizzie cap, (the rotor arm is perfect) I have the part throttle lean off pipe blocked off, the ignition timing is set at 8 deg btdc (1100rpm vac disconnected) fuel pressure is at 4psi and the boost is set to 6psi, The car has the pink/white resistor type coil positive wire, so I intend to replace that with a full 12v feed, has anyone got any ideas? im reluctant to take it to a rolling road to see what's going on, I want to get it at least somewhere near first.
just to add im using the standard metro turbo fuel pressure reg and pump.

logic would say that this is a lack of fuel, and as it comes on boost the fuel pressure rises and the problem gets masked but the plugs look fine, slightly black if anything as is the exhaust.

is the dizzy clamp tight? the dizzzy do slip sometimes. They tend to retard so might just need a little advance and the clamp tightening back up!!! just a thought

can't remember for sure been a while since I have had a mini on the road but I think advance is clockwise

You're correct Mike, advance is clockwise

resistive spark plugs??

ngk bpr7es plugs

that did cross my mind maybe a set of standard champion plugs might be better, but surely the problem would get worse under boost/load if it were a plug or ignition issue?

Never read the post correctly. Comment of no use!

Edited by Star Mag on 22nd Sep, 2009.

It won't be anything to do with resistive plugs. You only way plugs can be wrons is if you have non-resistive where you need resistive. Having resistive when only non-resitsive are needed will have no detrimental effect.

I wonder if a service of the carb and maybe the 'T-piece trick' might be worth a try.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Assuming it has the electonic dizzy, if you have been running it with the pink/white ballast wire, the module may now be on its way out as it will not have been seeing a steady voltage (voltage at the end of the resistance wire is inversley proportional to the current being drawn by the module which goes up and down every coil charge/discharge cycle).

Just swapping it to the correct 12V feed might be too late.

Schrödinger's cat - so which one am I ???

ok I can understand that the module may now be goosed due to the incorrect supply voltage, I will have to keep my eyes on ebay to see if any crop up, there was a new one on there not long ago.

coild this also have caused the coil failure?

I think a carb rebuild would also be a good idea too, im off to search what the "t piece trick" involves

thanks for the replies chaps

Edited by Rod S on 23rd Sep, 2009.

Schrödinger's cat - so which one am I ???

Whats the dizzy part numberthey will run fine on other part numbers but are bet on 41392 or 42682 Correct the numbers if wrong.

Own the day

just rigged up the t piece trick, will have a shower then go thrash the nuts off it see what happens!!

FAILED!!

tried the trick, still the same, if you go from closed throttle to full throttle sharply, it hesitates and shudders, then the boost starts to build and it smothes out but im sure its detonating and if you hold second over 4000rpm it sounds like it explodes out of the exhaust, like a couple of loud bangs? getting a bit fucked off with it now, I think next step has to be give the coil 12v, pull the dizzie out and have a look inside make sure everything looks ok and re set the ingnition timing, and inspect the plugs

Have you had it on a rolling road at all?? If it's detonating then your timing and fuel/air micture could be way out.....