Efi "hunting"

[Guest Phil Slater]

Folks

 

I have got my engine running again - on all four cylinders this time - after having the injectors overhauled. (Don't believe the Haynes manual when it says there are no servicable parts, my local Lucas fuel injection place overhauled all four replacing some components and all for £47.)

 

The engine starts first turn of the key and ticks over nicely for the first few minutes but then the idle begins to get increasingly uneven and the engine starts hunting really badly. If I use the throttle to increase the engine speed a little it runs smoothly but starts hunting again as soon as I let the throttle off. I've replaced the idle control valve and that hasn't made a great deal of differance at all.

 

I squirterd WD40 around to try and find an air leak but there doesn't seem to be one. One thing I've noticed is that when I turn the engine off there is slight hissing sound coming from the servo for a second or two - I don't know if this is normal for a servo or not.

 

I've got my airflow meter connected to the throttle body with the original hose, but hanging down underneath, rather than being horizontal. I'm pretty sure I've read on this board of others who have mounted it vertically down so I don't think it should be causing a problem - but I'm no expert - unfortunately

 

So, folks any suggestions from those of you with a good knowledge of the injection system where I should be looking for the problem.

 

Any guidance, as always, much appreciated,

 

Phil Slater

[Guest rizla]

hissing servo a........that should not be hapening,could possibly be a bad gromet in the servo where the pipe pushes in........as a test(dont leave it like it)remove the pipe and around the plastic fitting wrap some ptfe tape,then lube it with some vasaline(no comments )and refit

 

has the hissing stopped if so you nead a grommit,if not it could be the pipe or servo unit

 

this may also be the cause of the hunting,another thing to try to cure hunting is,with some brake fluid on a rag open the throttle valve fully and clead the flap and the inside of the throttle body where the throttle valve will sit when closed,you wont believe how much scum will come of the ally

Edited March 20, 2004 by rizla

[Guest Battery Bill]

Or just remove the servo from the manifold and fit a bolt to plug the hole

[Guest bloke]

phil, got mine started this week (an drove it out of the garage yesterday -note to self, build the brakes!)

 

you have described mine also, will the eratic stuff be the eec trying to learn how to behave in a kit car after sitting for ages and not gettin a good chance to experience different driving conditions (might be the only time mine gets to sample 'slow' so it better get its head together quickly!), not sure about the hissing?

 

hth and watchin for any answers that come along

 

steve bloke

[Guest Robin Allison]

Try cleaning the by-pass air valve there not to good at the best of times. the spring in the air flow meter may need adjusting i've had to do that>

[Guest Phil Slater]

Well, today I've checked the outputs from the throttle position potentiometer, took the cover off the electrics of the airflow meter and checked the voltages and they were all OK

 

I also blocked off the servo to manifold inlet and that didn't make any differance either. I postioned the airflow meter horizontal to see if that made any differance - and it didn't

 

I'd already thoroughly cleaned the throttle body components so I'm sure that's not the problem.

 

The only thing I'm not sure about is the coolant temperature sensor - but could that have so much effect if it was defective????

 

So I'm stumped and still looking for suggestions

 

Any thoughts - please????

 

Robin I'd be greatful if you can please clarify what you mean by the "by-pass air valve"

 

 

Phil Slater

[Longboarder]

Been searching for info on hunting. Concensus of the sites I looked at is hunting means too rich. It's running OK when cold while the computer is enriching for cold start. As it heats up it is staying enriched leading to hunting. One site did mention that if a faulty coolant sensor isn't telling the EEC its getting hot but keeps telling it the engine is cold then it gets over rich and will hunt. It suggests measuring its resistance hot and cold to see if there is a major change, swapping it out or earthing it if it runs high resistance/cold, low/hot and see if this makes a difference. Haynes mentions 'an adjustable air bypass channel provides means of idle mixture adjustment' in the General information and precautions at the start of the injection chapter. Havent got a clue where this item is. Doesnt seem to be the idle speed control valve.

 

Nigel

[IanS]

Adjustable air bypass channel is the IACV is it not? The well known sticky valve on Ford engines.

[Guest Phil Slater]

Folks,

 

Thanks for the suggestions thus far.

 

Nigel: The temperature control sensor seems to be having little effect - even when disconnected so I've ordered a replacement from Kevin Coopers today. If this doesn't sort it, I don't know what I'm gonna do

 

IanS: thanks for your input. I've now discovered the Air Bypass Channel is actually on the airflow meter and is basically an allen screw set into the casting that I guess "does just what it says on the tin" . The channel allows air to bypass the meters main workings to give the initial idling mixture, the screw adjusting the amount of air allowed through. Although I gave the air flow meter a thorough cleaning I didn't adjust the setting of the screw so I can't see this being the problem but I will check the channel again for any foreign bodies etc.

 

Phil Slater

[Big Jim]

Phil,

 

I don't know anything about the EFI set up, but there is a very good article on our build tips about it, it mentions all the problems and cures that you seem to be plagued with, go have a look here. it's a zipped file, so you'll have to unzip it.

[Guest Phil Slater]

Thanks Jim,

 

but I'd already got 'em and I've been working through the recommendations but with no success as yet. I'm hoping it's the temp. sensor - I'll find out tommorrow when it arrives!!!???!!!

 

Phil Slater

[Guest Phil Slater]

Well I fitted the new engine management temperature sender tonight and I think it may have improved things. I say may have, 'cos of a bit of a cock up on my part.

 

As I said last night I had decided to check out the air bypass channel for foreign bodies and clean it out. I decided to do the sensible thing and count the number of turns on the adjusting allen screw when I removed it so I could get it back in pretty much the same position. What I should have done was count how many turns to screw it fully in, 'cos there was I counting the number of turns as I removed it only to realise it was turning and not moving out . Too late I discovered there was an "O" ring that was keeping it fairly firmly in position and I'd lost track of how may turns brought it out of the threaded section :boohoo:

 

Fortunately I had had a good look at how deep it was in the casting before removing the screw so I've got it back "somewhere close" . And, the car is running without hunting but I cant' get the idle speed below a thousand revs so I'm not sure if that is masking the hunting or not.

 

So a question, "does anyone know a just cause or impediment" why a Gunson Gastester Digital analyser - albeit stated for use with carb engines - could not be used to set the CO2 level at idle on my injection pinto?? If so, ye are to declare it, this is for the first time of asking

 

Please, any thoughts please?

 

 

Phil Slater

[Guest simonb]

Have you tried cleaning the inside of the AFM? This can help smooth things out. Also, it may be that the idle mixture is a bit too rich. I think this can be changed by turning the allen key on top of the AFM anti-clockwise to weaken it.

 

I wouldn't play around with the spring tension too much as this will have an effect on fueling throughout the rev range and not just idle.

 

If you have access to a CO meter, i'd set it to around 1.5% at idle (950 - 1000 rpm).

 

HTH

[Guest Julian B]

Have you changed the inlet manifold gasket and if so did you specifiy the injection gasket? Can you get it to run smooth on the throttle if you disconnect the idle valve?

If its hissing are you sure the cam timing is correct

 

HTH

 

Julian Brewer

Cumbria

[Guest Phil Slater]

Folks

 

with regards to the idle mixture. Gunsons themselves have now supplied the answer. Providing there is no catalytic converter their gas analyser can be used to set the CO2.

 

Phil Slater