Engine revving flat out, won't idle properly

[daisy123]

Hi everyone,

M42 engine, revving flat out when turned on, any ideas what could get the idle back to normal?

Many thanks

[DaniTD]

Stuck throttle flap on throttle body or its linkage. Check that the linkage is not maintaining throttle open.

[Brianmoooore]

Engine can't rev. without air, so check the throttles are closing onto their stops, and check for air leaks into the inlet after the throttle body.
If these are all OK, then the only other way the engine can get air is via the idle control valve being open more than it should. Block off the supply hose to it if necessary, to check. Engine should barely run in this condition, unless the throttle is held slightly open.

[daisy123]

Thanks for the advice,

Have done the above and have attached a few vac hoses that weren't yet connected.

Now when turned on the first time in a day she's choking a lot but not revving flat out then I switch off and then when I turn it back on again almost immediately, she revs flat out again.

Could it be possible this could be linked to fuel starvation then too much fuel?

[cypriot_boy_2k7]

How's your throttle cable? Is the throttle body butterfly open or closed

[daisy123]

FIXED! Thanks everyone for your comments and suggestions. It ended up being that tiny pipe that goes from behind the throttle body onto just below the manifold, it had split open, only saw it today when taking the inlet manifold off. amazing that such a tiny thing can cause so much of a problem!

[Brianmoooore]

Is that everything engine wise fixed now then? Working exactly as it should?

[daisy123]

Yes I believe so! - If only I'd found that pipe before the whole engine swap malarky... Engines running great, I haven't took her for a drive yet as need to connect clutch up and attach seats etc. Have pretty much finished all interior wiring and put the dash etc back in, a few minor things to finish off then MOT! I'll bring her up to see you when she's back on the road! Shouldn't be long! Thankyou so much for all your advice Brian, really really appreciate it!!

[Brianmoooore]

Are you missing the plastic bulkhead piece that the engine relays and wiring cover mount on? I've found one in my workshop that I don't think is mine, right where your engine was stored.

[daisy123]

Yes!! I was going to buy one this week as thought it was just lost! Thats great news thank you Also quick Question for the last leg of the putting back together: Where does heater resistor go? The last piece of the dash puzzle is being put together this evening! Thankyou!

[daisy123]

Found where the heater resistor goes, managed to climb into the passengers footwell and get my head under the dash and a couple of wire homes became apparent too