Last spring I picked up a 1987 924S with 52K miles. Since then I've put about 2,000 miles on the car, and I've been getting about 21-22 MPG over that time. Previously, I had a 1986 944 for ten years, and I consistently got 27-28 MPG during normal driving, and 30+ on road trips. So, the 21-22 in my 924S seems off.

Here are relevant things I have replaced since buying the car:
timing belts
spark plugs
ignition cap, rotor, and wires

Tire pressures are good.
I have passed the Maryland emissions test.
I smell no gas while driving or parked, and I have observed no fuel leaks.

I have NOT replaced the following items:
fuel cap (although I believe the emissions folks checked it)
O2 sensor
fuel filter


A search turned up some comments about replacing O2 sensors and gas caps to improve mileage.

Thoughts?

Mark

 

I had a 924S, my odometer didn't work, but I do remember it getting about the same amount of usage as my old neon. So around 24 MPG. They have a higher 5th gear so the RPM's are turning more at highway speeds. I seem to remember that it would be about 3 grand at 60-65 MPH?

When I first got my 924 it was a little rough well lets be honest it was a junkyard bound car that I brought back to life. I replaced all the same stuff as you as well as the o2 sensor. There was some improvement, but still didn't run 100%. Well one day I noticed some black soot from the tailpipe. This was after a short drive. I help up a towel to the tailpipe while running and it was black in no time. I found out that my FPR was bad. That could be your issue as well. Does it seem to run rough at idle? Shake a lot?

If you want I have a spare FPR 2.5 bar. I'm not sure if it would fix your problem or if mine is even still good. Hasn't been used in 2 years. Let me know.

 

A HIGHER 5th gear means you RPM will be LOWER........

 

924s runs at a higher rpm at the same speed compared to the 944.

 

It is my understanding that the 924S has a lower 5th gear than the 944, thus the higher RPM and greater fuel consumption. Although I'd be surprised if that would account for all of the discrepancy I see between my 924S MPG and what I had with my 944.

When I bought the car it was awfully rough at idle. I guessed motor mounts and replaced them, and that solved the roughness. The motor on my 924S now seems to be running smoother than my 944 ever did. No more shaking.

The muffler on my car is aftermarket. After I first bought the car I once started it in my garage with the door closed, and it sprayed black soot all over the door. That problem seems to have gone away, and I wrote it off to the fact that the car had been sitting for many years without being driven much.

If the engine is running smooth, is FPR still a suspect???

 

I would try and get a Fuel Pressure gauge and check that first. Also you can get a univeral O2 sensor for these cars for pretty cheap. You can pick them up at Auto Zone and what not as well.

 

I have a 1988 944 wich has the lower fifth gear. I would say I average about 24 MPG. I get about 28 MPG on the highway and around 20 or 21 around town.

If the 1987 924S has the same greaing then your MPG sounds about right to me for City + Highway driving.

 

You will get slightly lower mileage on the S due to the gearing. Change the O2 it's probably due. One other thing that causes high fuel consumption is the throttle position switch. If it doesn't click with the throttle at idle you can adjust it using the throttle stop screw. The TPS acts as a fuel cut of at idle and if it's not set right you will have higher fuel consumption. Some details about it here: http://www.the944.com/shudderm.htm

 

My 924s averaged 18mpg in the city and about 23-24 on the highway. My 944s is 19/27ish (i have a heavy foot)

 

The '87 924S should get about 21 to 27mpg per the salesmans brochure when it came out.



I get about 22 to 29mpg if I drive normally. If you read about 34mpg and higher it may happen if you are going down hill from Flagstaff to Phoenix but not normal.

If your car has the smaller throttle cam, not the original with a leg on it, you will get less mpg. The smaller throttle cam is good for dead accelleration starts but uses more gas.

The O2 sensor. Get a universal Bosch interchange and splice the O2 sensor in with the "posi loc" or crimps and heat shrink. DO NOT SOLDER

Do not use a cheap aftermarket O2 sensor. Bosch only!

The DME temp sensor can be bad. The temp sensor sends a signal to the DME for cold starts=more fuel. If bad it may be sending the wrong signal.

Your injectors. If they are original, get them tested, cleaned and balanced. www.witchhunter.com or others. They wear out.
There is aBosch interchange for $40 each if you want new. The OEM are expensive. New injectors will cure a lot of problems.

Pull the vac hoses from the FPR & FPD and check for leaks--put your face up to the part.

Spark plugs--Use only cheap copper Bosch or NGK--toss the platinums!

Just a couple of ideas--many more.

GL
John

 

do the o2 sensor and fill the tank a few times see if it changes at all.

 

i seem to be in the 23-26 range with my 924s. ive seen better and ive seen worse. fuel mileage really suffers when you have to run 3200rpm to keep up with traffic on the highway. either it is better than my bronco

 

I ordered a BOSCH universal 3-wire (15735) earlier today. I plan on doing brake work this weekend, so I'll tackle the O2 sensor while I have the car off the ground. It cost me something like $60 with shipping, so I figure that's not a bad investment in a 25-year-old car. The engine sure does seem to be running smoothly; if the new O2 sensor doesn't produce any improvement in mileage, then I'll look into some of the other suggestions.

Thanks for all of the advice, and I'll update this thread as I get more info.

Mark

 

20-23 around town, 27-30 on the road for my 87 924S. For the record(I could be wrong) the early 83/84 944 had the same 5th gear as the 924S.

 

I just put an 87 924s block in my 85.5 944, and otw from the SF bay to LA, I was getting 29-32 mpg (before the grapevine, anyway)

I was FLABBERGASTED. On the streets I get much less noteworthy mileage, and is hard to figure as my odometer gear is toasted, but those are my two cents.