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Hello.

 

So I have an ABD with GT fueling/ignition I've put back together and it just won't idle. Happens whether the engines hot or cold. I can hold the throttle down and have it at 1500-2000 rpm but any lower and it'll just bog down and die with throttle still open, unless I blip the throttle and hold it at 2000 again to save it. This has allowed me to set the base timing atleast.

 

When I go to set the idle I can't lower the rpm close enough as it'll bog down and cut out so I've held it at 1500 rpm to try that way but the idle screw doesn't seem to be doing anything no matter how far it's adjusted.

 

When I unplug the blue coolant sensor it bogs down and dies unless I hold the revs up high at the same time, I can lower back down to 1500-2000 once unplugged.

 

I had it timed and idling with no exhaust on the other month but forgot to save the settings. Only change has been putting the exhaust on post lambda.

 

Crank and cam cover breathers vent to air right now.

Vacuum for fuel pressure reg to side of throttle body is fine, others are disconnected and blocked off.

New gaskets on intake, throttle body, exhaust and head.

 

Timing marks line up.

Tried two dizzys - 030 905 205 AB and the other AE.

Two different AFMs

I'll be trying a new blue sensor when the shops open on Monday but I'm not confident this is the issue.

 

Slightly worried about cylinder no.1 valve + piston though it could be the MAF flap from back fire or something else knocking. Only happens sometimes and I assume valve contact would be a constant noise?

 

There is more to this story but it's already a long read so any questions please fire away and any suggestions would be appreciated.

 

 

 

Edited by JoeUK
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  • JoeUK

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steveo3002

its the AB dizzy you want 

 

yes piston contact would be always not random 

 

kinda sounds like an air leak not letting the idle drop down , if you do buy a new blue temp sender only buy genuine , alot of non genuine ones are rubbish...regardless a warm engine should run and rev up with it disconected , i doubt its that  , can check its resistance with a multimeter easily 

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Thank you for the reply. Would a air leak cause an artificial high idle? It's just the revs can drop down but they keep dropping and the engine cuts out so I have to hold the throttle down to keep it idling but if I try to hold it any lower than 1500+ then it'll still bog down and die anyway.

 

I was going to test the blue sensor but I did some checks before and found some worrying signs. Cylinders 1, 3 and 4 have oil or fuel in the piston dishes, I think oil tbh. Cylinder 1 is the worst as it seems to be around the edge of the piston and walls of the cylinder too.

 

Spark plugs 2, 3 and 4 were really black so maybe oil being burnt rather than just over fueling? Weirdly cylinder 1 sparkplug was clean like it hadn't been firing. I suspect it's coming from the head gasket or the valves.

 

bottom end was lightly honed and new rings put in a few thousand miles back.

 

The head gaskets new and tightened correctly but I know people here have had to over tighten them before to seal, is there any angle of tightening I should aim for to help the gasket seal without snapping head bolts?

 

the valve guides were replaced (reason for second rebuild) though I didn't feel they had done a very good job as some felt loose when I checked it over and the oil on the valve and dropping it test didn't seem too great either. I feel I should tighten the head bolts to try eliminate the gasket first and if it's the valves then I'm giving up on this car for a while as it was just meant to be a run around and can't keep spending money on the engine.

 

Any suggestions welcome please.

Cheers.

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steveo3002

next step would be a compression test

 

when its driving...does it make good power like it should ?  does it use excess oil? 

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