engine hunting

[tc ozzie]

mine seems to be hunting alot when cold or hot and seems to have a bit of a flat sot when you boot it is there anything i can adjust
i have checked all plugs and coil and leads all ok what to do next

[NickT]

Try disconnecting the oxygen sensor electrical (blade) connector and see if it steadies the engine idle.
The connector is on the rear bulkhead drivers side (LHD).
You will see it if you remove the rear wheel and look for a single black electrical cable.

If it steadies out the idle then we can narrow it down to a fuel mixture problem.

Double check that all vacuum pipes are connected correctly, especially the ones on the distributor solenoid bullkhead side of the fuel distributor.

NickT.

[tc ozzie]

i checked all pipes they all seem ok it seems it just doesnt want to be floored it hesitates alot if ya boot it but when ya lift off it comes back slightly
it did used to hunt about when it is cold then settle out but now today i left it warming up for half anhour and it didnt settle it just keeeped hunttting all the time

[NickT]

I can't say for certain without actually testing it, but it sounds like the fuelling is not correct.

Does your car have a catalytic converter on or does it have a cat bypass pipe?

If it has a cat bypass pipe then disconnect oxygen sensor electrically as per previous post, then take it to a garage and set the fuel mixture to between 1 to 1.5% CO.

This is done using a long 3mm hex key (allen key) on the ventury near the fuel distributor. Only adjust in 1/16th of a turn at a time and only with the engine off. Replace the access hole plug after the change and before starting the engine.

Hope this helps,

NickT

[tc ozzie]

it recently has had the cat bypass pipe fitted so what you saying about disconnecting the o2 sensor is that the thing sticking out of the exhause near to were the cat was

[NickT]

That is the sensor. Follow the black cable and it will go to a blade connector. Disconnect this electrical connection.
You can see it if you remove the rear wheel as per first reply.

Good luck.

NickT

[tc ozzie]

ok i give this a try tommorow after work thankyou
will the motor run better or worse if i disconnect it
all im thinking is disconnecting it then a few days get the mixture changed

being on shift is a pain and i got to use the car

[Dan6457]

With the frequency valve an its control unit still there, won't disconnecting the sensor make it run far too rich all the time?

[NickT]

Dan1986 Wrote:With the frequency valve an its control unit still there, won't disconnecting the sensor make it run far too rich all the time?

Disconnecting the oxygen sensor will default the frequency valve to swith on and off at 50% duty cycle. The base fuelling is done by the allen key.

The car can have its base fuel set up too rich or too weak and can run poor when the engine is cold. When the car is warm and the oxygen sensor is hot enough, this will give feedback to the fuel computer that will makethe frequency valve operate to correct the fuelling. Even though the engine may idle correctly the base fuelling can cause poor acceleration etc.

I did a test in my car and set the base fuel to 4% co. Reconecting the oxygen sensor reduced it back to 1% but when accelerating it overfuelled and stuttered.
I did the same and set it to 0.5% and again it corrected to 1% but when accelerating it had no power.

Disconnecting the oxygen sensor electrically then setting the base fuel mixture will ensure that it will run correctly. (Assuming that the oxygen sensor is in working order)

Hope this helps,

Regards,

Nick.

[NickT]

NickT Wrote:

Dan1986 Wrote:With the frequency valve an its control unit still there, won't disconnecting the sensor make it run far too rich all the time?

Disconnecting the oxygen sensor will default the frequency valve to swith on and off at 50% duty cycle. The base fuelling is done by the allen key.

The car can have its base fuel set up too rich or too weak and can run poor when the engine is cold. When the car is warm and the oxygen sensor is hot enough, this will give feedback to the fuel computer that will makethe frequency valve operate to correct the fuelling. Even though the engine may idle correctly the base fuelling can cause poor acceleration etc.

I did a test in my car and set the base fuel to 4% co. Reconecting the oxygen sensor reduced it back to 1% but when accelerating it overfuelled and stuttered.
I did the same and set it to 0.5% and again it corrected to 1% but when accelerating it had no power.

Disconnecting the oxygen sensor electrically then setting the base fuel mixture will ensure that it will run correctly. (Assuming fuel pressures are correct and that the oxygen sensor is in working order)

Hope this helps,

Regards,

Nick.

[tc ozzie]

ok tonight have just checked all my plugs and found them all to be dry but black
i did however find two plug leads very loose i now have managed to make these fit the plugs better so there more secure and i also found a white wire off the resister on the back wall in the engine compatment this has now been fixed

but the car is accelerating better i can now get upto and past 70 with no hessitation but there is a slight stutter in places i will try again in the morning to see what its like when cold

p.s in the relay compartment you know were the two orange leads go in that relay housing that no longer has a relay in just these two fuses for that cooling fan thing myne fell out and i had to change the fuse and i forgot witch holes they go back in can some one put a photo up on here for me so i can see were the wires go

[bozzzydmc]

http://www.dmcnews.com/bulletins/index.html

These are always a good read.. specifically the one you want is :-
http://www.dmcnews.com/bulletins/ST-06-9.82.html

Personally i would replace the plugs / leads/ diz cap and rotor arm. If they are origional matey.

[tc ozzie]

do these deloreans normally hunt when there cold and stop hunting when there warmed up is this normal or should they stay at a certain idle speed all the time

myne is hunting really bad and i now not sure what to do cause i filled up on thursday and now my tank is empty i have no leaks

there is something really wrong i fill its been gradullay been geting worse this week

all my plugs were black

[Tourettes Tony]

as far as im aware they all hunt to certain degree, you may have an air leak somewhere, the lambda is correcting the mixture, try looking at the pipe to the dizzy and the one to the carbon cannister, its under the throttle assy, welcome to delorean ownership check them all to be sure including the one for the vaccuum flap thing thats on the rear of the inlet r/h/s TT

[tc ozzie]

this is hunting all the time though it cant be right
i will check for leaks i cant use it anymore its mad
its stuttering really bad at full throttle its chucking black smoke out the back when you try and boot it and its running very lumpy cold

im nearly at the stage of givin up