1993 960 Really poor fuel economy

[93Regina]

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Maybe need to test coils and test oxygen sensor as to why poor fuel economy.

A coil-assembly can and do fail with time; here is all I could find: 960 Specs: 1994, and Ignition (coil) problem

Does yours have individual coils for each spark plug?

[Kappy5003]

Yes separate coils for each plug.

I'm running iridium plugs, I read somewhere they may be a problem, I ran them in my Motorcycle for around 30,000km until I had some carby issue, swapped out to normal and better idle.

I noticed recently that that idle seems a little higher than normal, after running for a whileI read that they can't be adjusted.

Would a faulty idle speed motor
(a) affect running rich/lean
(b) Impact on oxygen sensor.
Can an O2 sensor cause rich running, which I believe is happening, and not through a code, even though a code popped up some time ago, but hasn't returned since.

I just started car and noticed when I rev slightly and on back off i notice missing.????

[lummert]

If you have some copper plugs that are left over from before the iridium plugs try putting them back in.

[93Regina]

separate coils for each plug

They say there are wiring issues...etc...with that setup.
.

plugs

Always, use OEM's designated plugs....believe it or not, they work!

I noticed recently that that idle seems a little higher than normal

Vacuum Leak(s) can over-ride idle-motor. Use propane around intake manifold[

By chance, does your engine have an EGR valve? If so, it may be time to remove/clean it...also, the pipe work that goes with it needs to be examined, inside.

coil

With engine running, one might unclip each one, one at a time, and see if engine rpm drops more/less. It would be nice to have a digital tachometer.

Coil - Recently, I replaced a coil/wires on a 35 year old truck (GMC 7000), and it made a big difference.

Coils do fail with time...with engine running at night, one might look for sparks going off a coil.

I wonder if anyone has converted to a different ignition system setup...like maybe using GM's coil setup?

[FlorenceTravis]

Yes...with two O2 sensors, there will be a code on more up to date vehicles.

At the point when parts like flash fittings, wires, O2 sensor, and so on, have not been supplanted in quite a while, supplant them.

Fuel Injectors - Around here, it cost from $10.00 to $15.00 (US) (each) to have injectors assessed/clean; with more established vehicles, they ought to be pulled and tried.

Pressure Test - If all chambers are comparative, then, at that point your issues are identified with above, no doubt. You should also check what is an engine immobilizer