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Discussion Starter #1
Hi,

have been having on-going probs with my 164, initially following an oil change which resulted in a cam cover gasket and spark plug oil well seal change, along with new plugs and air-filter (air-filter being an aside as was simply advised the K&N fitted did not filter well).

Anyway, it used about 35 litres/5 gallons to go 80 miles; idles worse and worse as engine warms, but never stalls, and gets some strange loud noise above 4,500rpm at high load - which is needing less and less of a high load to induce. Engine itself revs fine to 7000 rpm.

Today, on advice of Steve (Alfista), unplugged the engine management temperature sensor on the thermostat housing, while it was idling from a dead cold start, and instead of the enging cutting it momentarily idled faster and then carried on idling almost normally. Plugging it back in and unplugging it again, engine still running less than a minute from cold, made no change what so ever.

Unplugging it from hot makes no change but understand that this is normal.

My conclusion is the enging is running excessively rich and this thermostat housing sensor is probably running correctly and simply making things worse by adding extra fuel when cold.
Question is, what could possibly be making the engine run rich if it is not the temerature based part linked to the thermostat housing temp sensor?

All suggestions very welcomed, thanks.

Richard
:confused:
 

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Discussion Starter #3
The O2 sensor caused this on my 12v. Not sure how different the engine management systems are between the 12v and 24v though.
Hi Ryan,

Is the O2 sensor the one on the air filter assembly? Am guessing the 12v and 24v will be similar in this respect.

Thanks,

Richard
 

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Look for loose or dangling grounds.

Paul
 

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Discussion Starter #7
Look for loose or dangling grounds.

Paul

Have a dangling ground that should run between the cam cover on the rear bank and the underside of the throttle module. It's dangling because it is a total pig to re-connect and have already had to do it twice (due to doing the cam covers twice as was supplied with wrong gaskets) and when holding it against the parts in question makes no discernable difference - at least at idle.

Will look out for other earths that may have come off and see about kicking myself to bolt this one back up. Thanks.

Richard
 

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Have a dangling ground that should run between the cam cover on the rear bank and the underside of the throttle module. It's dangling because it is a total pig to re-connect and have already had to do it twice (due to doing the cam covers twice as was supplied with wrong gaskets) and when holding it against the parts in question makes no discernable difference - at least at idle.

Will look out for other earths that may have come off and see about kicking myself to bolt this one back up. Thanks.

Richard

If you can't get to dangling ground for intake throttle body just add a new one from intake or throttle body to engine or head anywhere it is easy to access bolts.

As for O2 sensor connector on 24v it is a 4-pin connector and should be somewhere above tranny underneath Air Flow Meter (AFM) black inlet hose area.
 

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Have you simply put a voltmeter and read the signal from the O2 sensor? Also there is a test for the coolant temp sensor. Your 24V should get better than that. My S was getting 13 mph on the track track in Detroit this summer. I would expect around 16-20 MPG depending on driving style and condition of the motor.
 

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On a recent trip, my 94LS averaged 25-28 mpg at cruise speeds averaging 75-80 mph on the freeways, and full of luggage.
 

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Ls Mpg

Richard I took my LS on a trip last fall traveling at 75 to 85 and I was getting 24 tp 26 mpg with a faulty module for one bank of cylinders. It is much worse around town, but I never calculate it. It does run very smooth hot or cold.
 

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The different gearing in a LS must really improve gas mileage. My last trip to Fort Worth, I averaged 21-22 mpg, but of course I was running behind schedule so I was averaging 95 mph with bursts up to 105. Long trips running the same 80-85 I get about 23-24 mpg.
 

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On a recent trip, my 94LS averaged 25-28 mpg at cruise speeds averaging 75-80 mph on the freeways, and full of luggage.
...and with a 100% style quotient.
 

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Discussion Starter #14
Have you simply put a voltmeter and read the signal from the O2 sensor? Also there is a test for the coolant temp sensor. Your 24V should get better than that. My S was getting 13 mph on the track track in Detroit this summer. I would expect around 16-20 MPG depending on driving style and condition of the motor.
Hi,

No, I haven't. Where should I put the voltmeter to check it. Have to work on my car in the street so a pain to get underneath it. Any connectors under the bonnet I could check it on?

Thanks.

Richard
 

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Discussion Starter #15
Have now had the O2 sensor replaced and it makes a stunning difference. The car is faster than ever and fuel economy is miles better. If I had known it could make such a difference I'd have done it when I first bought the car, 2 years ago with 87,000 on the clock.

Still have a dodgy idle but performance wise it is better than ever.

Thanks to everyone who chipped in!
 
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