Cold starting/fuel consumption issue

[Gene Simmons]

Hi all,
just wondering if anyone had any ideas.

It's a 90 Eunos, on a G with 90k miles.

Of late, when starting, it has had a rough idle, hunting between 1200 and 1600 revs, and sounds like it's not firing on all cylinders.
Once warmed all if this settles down, but the fuel consumtion is awful. I would put it mid teens to the gallon. It's going to go in the local Indy soon, but I was hoping one of you may be able to cast some light on it.....

Thanks in advance

Gene

[Defcon5]

When you start it and the engine is hot is it ok?

[Gene Simmons]

Yup.

Seemingly worse on damp morns also ?!?!?



ETA some speeeling n grimmer

Edited by Gene Simmons on Monday 21st February 23:41

[MX-5 Lazza]

Before you take it anywhere change the plug leads - that sounds the most likely cause.

[Jerwatt]

What should the revs start at normally? My 1.8 Mk2 starts at 1500 (in temperatures around 0C), dropping down the to 800 when warmed up. Not sure on fuel consumption.

[MX-5 Lazza]

Jerwatt said:

What should the revs start at normally? My 1.8 Mk2 starts at 1500 (in temperatures around 0C), dropping down the to 800 when warmed up. Not sure on fuel consumption.

That's not far from correct but possibly a little high when cold and a little low when hot. You should try setting the base idle to around 900rpm (I think it should be something like 880rpm).

[Gene Simmons]

Thanks lazza, will get them changed. Would that also explain the staggering fuel consumption?

[MX-5 Lazza]

Misfiring certainly wouldn't help. It could be a number of things though:
x Spark plugs
x Temp sensor
Coils
AFM
O2 sensor
Vacuum leak
Something else...

x These ones are fairly cheap and easy so probably worth doing anyway.

[Gene Simmons]

Okie cokes.

Spark plugs were done about 6000 miles ago, so will see what they look like, and replace the HT leads, see if it cures it. When warm it runs ok, other than being very thirsty.......

[MX-5 Lazza]

The plugs will probably be fine then.

[Defcon5]

I vote temp sensor - its telling the ECU its -100 so its pouring in fuel like its going out of fashion. When its cold its putting too much in for it to burn properly causing it to run like a bag of spanners

[Gene Simmons]

When starting from cold, a bag of spanners is about right. Sort of like a staccato noise rather than running smoothly. Normally resolves itself with a coupla mins running on the drive, but idles maybe s little higher than I would expect initially.