Hunting on idle and poor running when warm/hot

[mister2mk1]

I currently have another thread running on here in relation to dashboard lights illuminating but I am sure this is completely separate -

I have in the past witnessed a lumpy idle with the revs hunting up and down which I cured by bleeding the coolant. However one restoration and full engine build later and I have a few (expected)issues which I am wondering if they are related to more air locks.

when I start the car from cold it ticks over fine (high revs but on auto choke) when warmed up (but not switched off) the car runs great no missing hunting or lumpy running. However if I switch her off for five / ten minutes and restart the car is lumpy as if running with a misfire after a while of driving if seems to resolve its self but is slightly embarassing when it people are having a nosey because its an older motor looking reasonable but sounding like a tractor!. Once its passed it back to it normal responsive quick self!???

After a 50 mile journey today and several experiences of lumpy running self curing itself on the final restart before arriving home I experienced the hunting on idle and even had other drivers sat at the lights next to me thinking I was up for a drag race as my engine decided to hunt up and down!! Fortunately the drivers next to me were responsible older drivers who just rolled there eyes and looked away whilst I raised my hands to suggest i was helpless!!!!!!!

Do you think these are two separate issues (intermmitent poor running and hunting) or do you think these are likely to be related to further air locks?

Your thoughts comments appreciated....

cheers

steve

[cartledge_uk]

The hunting sounds like air locks in the coolant. A serious and proper top up and bleed shoud sort that issue out.

I'd also check the timing is all in order

[vashy]

lumpy as if running with a misfire ...sounding like a tractor!

and this sounds like it's not running on all four..?

If it's not please describe it a little more, or record the sound if poss!

[Mike 'MR2' McHugh]

Just having a peek what the MK1 gang are upto . . . .Whats hunting ?

[cartledge_uk]

Just having a peek what the MK1 gang are upto . . . .Whats hunting ?

the revs 'bounce' up and down as if your blipping the throttle

[Mike 'MR2' McHugh]

Just having a peek what the MK1 gang are upto . . . .Whats hunting ?

the revs 'bounce' up and down as if your blipping the throttle

Ahhh ...cheers mate . .. what usually causes that then ? as above ?

[mister2mk1]

Just having a peek what the MK1 gang are upto . . . .Whats hunting ?

The revs go up and down on there own!! on idle....

and this sounds like it's not running on all four..?

If it's not please describe it a little more, or record the sound if poss!

It does sound like its running on three but then all of a sudden it will clear and be fine..... until the next time I stop and switch the ignition off...

At first I was thinking Dizzy Cap, Rotor arm, Leads plugs etc... but with it correcting itself I then began to think ECU???

[Lauren]

TPS may be something worth checking.

[monkeymax]

Did you replace the thermostat as a part of your engine rebuild? Does the car stay at correct temp once it's warmed up?

[mister2mk1]

TPS may be something worth checking.

I will check this but cant find my feeler gauges at the mo - would this be a possible contender for both lumpy running and hunting?

Did you replace the thermostat as a part of your engine rebuild?

no - but I did check the thermostat with boiling water prior to re-fitting...

Does the car stay at correct temp once it's warmed up?

The car had been running okay since rebuild - admittedly I have only ran it round the block etc since rebuild - but on Saturday took it for a proper run and incurred these issues - it did not overheat on saturday or on any of the previous runs out and did sit half way on the temp gauge.

It does appear to be running rich - very fumey???

Tonight I have checked plugs leads cap, rotor, and ignition timing and all appears okay. I have bled the coolant 3 times and can get no more air out of the system but the vehicle is still hunting.....

Is it worth swapping the ECU over with a spare i have??

Or is there some other simpler checks to do first?

cheers

[cabbydave1]

Steve theres loads of bits for the vac system at mine if you want them

[mister2mk1]

For info - tonight I have again bled the coolant and tried an alternate ECU - Car still hunting????????????????????????

[PW@Woodsport]

Remove the air intake pipe from the throttle body and with the engine running put your finger over a 5p sized whole inside the throttle body that is at the 5 o'clock position.... that should stop the bouncing idle or even stall the engine, if it does and bleeding hasn't cured it then you have a faulty waxstat.

[mister2mk1]

Great news - and a massive thanks to Cabbydave and Woodsport.

I have today replaced the throttle body which for those that dont know houses the waxstat....

This has cured the hunting and lumpy running.....

I have an exhaust leak so need to fix that next but can any one advise how to adjust the idle speed and mixture ???

thanks again

steve

[PW@Woodsport]

Idle speed is controlled by the air bleed screw on top of the throttle body (presuming the waxstat is fully closed and there are no other airleaks)

Idle mixture is adjustable on the screw right next to the MAP sensor.

[cabbydave1]

Glad to hear it Steve if you need a lift with the exhaust bob round one evening sorry there was a house full when you got here be even worse next saturday