Misfire on idle and low revs but fine on boost
Turbo Mini Forums

Hi

I drove my metro turbo last nite and after about half an hour it started sounding like an Subaru at low revs but seems fine at higher revs and on boost.

It struggled to idle.

The engine has been freshly built to standard specs and there was no smoke while driving it.

Im thinking it feel like an ignition problem but has anyone got any other ideas?

I've had the opposite recently and it turned out to be fouled plugs - have you fitted new plugs? What are they?

Have you got an afr gauge fitted? Could be fueling

Plugs are NGK bpr7es and are only about 100 miles old.

The car has only just been rolling roaded so I would guess the fuelling should be fine.

I will check the plugs when I get to my garage. I think I have a spare set.
I don't have an afr gauge.

Rocker come loose?

In the 13's at last!.. Just

Sticky valve syndrome.

Own the day

ngk's dont like having fuel on them IMO.

deffo give them a change

Just done a compression test and number one is low.

Put some oil in and it didn't change.

Once everything is cool I will check the valve clearances.

Valve not seating correctly was the head rebuilt?

Just check the valve clearances and it made no difference.

I checked the compression again and now it raised with oil in the bore so I think it a piston or ring?

The head was not rebuilt, its the original 37k head.

How would I check for a sticky valve? Head off??

What has exactly been done to the engine on the build? It could still be a valve not seating correct regardless of the milage

Edited by scott the joiner on 17th Mar, 2012.

are we sure its not just dropping a plug?

Yes i moved to the darkside

Instagram @jdm_brett

When aster you doing the compression test. Hot or cold.

Own the day

The bottom end was honed with new rings and bottom end bearings.

The head was kept original as it all seemed ok.

The plugs are only about 100 miles old.

The engine was warm when the compression was tested.

Doesnt matter how old the plugs are, they can get fouled in a few minutes, I'd change them first before you look at anything else.

Edited by almichie on 18th Mar, 2012.

How much lower was cylinder1 compared to the other 3 results?

Number 1 has 6bar and 2,3,4 have 12bar.

I think it went upto about 8 with oil in.

I understand that plugs can go after a short time but that doesn't explain the lack of compression.

I'm going to ring the engine builder tomorrow as I've only done 1300 miles.

Dp

Edited by Tonywells on 18th Mar, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

The engine is all standard.

It was setup at track and road.

I was there when it was setup and it was setup to be safe and not for out and out power.

The operator was carefull and it was only taken upto 8psi.

I trust the rolling road operator 100%

I'm guessing I'm going to have to take the head off and have a look.

Also I've been very carefull with every part of the build and I've not even given it any real stick. Bloody a series!!

Back the hell up! Did I read right! Number 1 is only making 6 bar on compression!? Sorry but I just had to go into the workshop to check that on the gauge. Number 1 is in real trouble.

You have either forgotten to fit your rings or you have a bigger hole somewhere! If it were me I would be praying that it is sticky valve or poorly adjusted rocker. Either way off with its head.

Own the day

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Here is the rolling road print out.

Not sure about advance but it's a standard dizzy.

imo thats a low power for 8psi boost

Yes i moved to the darkside

Instagram @jdm_brett