expected gas mileage? - First Generation Forum

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expected gas mileage?
Tuesday, May 21, 2013 5:48 PM
With various and sundry replacement of parts, I've gone from 16mpg when I first got the car to 23mpg now. This is 95 percent in town stop and go type driving with a little highway when I need to get across town in a hurry. Can I expect much more than that? 23mpg seems really low for a little 4 cylinder but I realize there is a difference between this and say the honda motors of the late eighties and early 90s. Also, asking that wheezy little guy to haul around a small tank just seems unfair. The cimarron aint light lol.

what kind of mileage are you all getting?




Re: expected gas mileage?
Tuesday, May 21, 2013 5:59 PM
You can probably get a little more. Try running some cleaner like seafoam. Just remember it is only a 3speed so you will not be running low rpms on the highway and there is o overdrive.




On the inside my car looks like a fighter jet.
Re: expected gas mileage?
Tuesday, May 21, 2013 8:32 PM
I average 21-23 in my Z. It's all highway for me.



Re: expected gas mileage?
Tuesday, May 21, 2013 8:44 PM
I do use seafoam every other tank. Maybe try some in the oil or through the brake booster line?

I've replaced the injector, rebuilt the fuel pressure regulator, and replaced the alternator. The alternator seemed to give quite a jump in mileage. What else should I be looking at for a few more?



Re: expected gas mileage?
Tuesday, May 21, 2013 8:47 PM
Wish I could edit posts. I should say that it still seems like its spraying a lot of fuel at idle, and the car still vibrates at idle rpm unless i put it in neutral which raises the rpms up to about 1200 from 700 in drive. dont know if maybe its running rich?



Re: expected gas mileage?
Tuesday, May 21, 2013 11:30 PM
Idk being stupid tired but 23 in town is not bad really for the engines we have.As for the idle I will think a touch on the jump but could be the map sensor or idle air control or tps not adjusting correctly.



Re: expected gas mileage?
Wednesday, May 22, 2013 5:05 AM
On the older cars like yours you can check your injector spray pattern with a timing light. Just set it up like you normally would to check timing but aim the gun at the throttle body. You should see a nice v pattern. If you see a bunch of liquid droplets you have a leaking injector. Something else to check also is the fuel filter. It's recommended to be serviced once a year.



Re: expected gas mileage?
Wednesday, May 22, 2013 5:08 AM
Yeah the 3spd auto sucks for city fuel mileage, I used to average about 25-26 with mine with a very light right foot.
What year is that Cimarron? Could've swore Cadillac dropped the 4 cylinder when they redesigned the front with the euro headlights.








Re: expected gas mileage?
Wednesday, May 22, 2013 8:48 AM
With bad exhaust, I tend to average 25mpg summer/23mpg winter. Mine isn't in town, but rural roads into the city, then back. My average speed while going to/from work is about 35mph, but there are times I'm at 55mph.

So for being all in town, and I'm sure your caddy has some extra weight over my Hawk, I'd say that's not bad at all; but once you fix that idle problem, I would expect you to gain 1-2mpg.
Re: expected gas mileage?
Wednesday, May 22, 2013 9:47 AM
I will go ahead and do the fuel filter. I doubt it's been changed any time recently.

The map sensor, tps, and iac are all 50-70 dollar parts so I think I'll wait unless there is a way to narrow it down any. A rough idle is annoying more than anything.



Re: expected gas mileage?
Wednesday, May 22, 2013 6:12 PM
Yours sounds right down the middle John.

The wagon gets about 22 local. Maybe upwards of 30 on the highway. It has 2.0 OHV /Auto Title says it weighs 2358 LB.

Pontiac gets 1 or 2 MPG better it has the 1.8 N/A OHC / Auto Title says it weighs 2470 LB.

3rd Gen Cav gets about 22 local too. 2.2 OHV / Auto (4spd) Heavier - Title says it weighs 3000 LB.

'86 Ford Ranger Supercab gets around 24 local - 2.3 OHC / 5 Speed Title says it weigs 3100 LB.

Like Wayne mentioned , ours drops a wee bit in the winter too. Longer warm-up time/ Different fuel blends.

I have a little rough idle too, but then again I've got the idles cut back a wee bit. Trying to save a few revs for another day.

Also IMO there are a lot of times the TCC can actually hurt fuel mileage. If you drive a lot around 35 to 40 when the Clutch just kicks in it just lugs the engine a lot. A lugging engine turns slower and might last longer, but will consume more fuel in the process. 55 and better on the straight and flat is where a lockup Torque Converter really Shines!

My Prescription is drive your Caddy and have a blast!!



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Re: expected gas mileage?
Wednesday, May 22, 2013 6:49 PM
John-

I might be able to narrow your $50-70 list a bit. If your car has trouble at idle, it could indicate you have an IAC problem. Start the car and disconnect it and look for a change. I was having strange behavior on my MOPAR minivan and it turned out to be the IAC. I unplugged.plugged the TPS and things changed, not so with the IAC. As you mentioned you think you have a running rich at idle condition, I would take a look at the IAC as idle is when it becomes a key component.




Re: expected gas mileage?
Thursday, May 23, 2013 4:58 PM
so what if taking out the iac plug at idle in both park and drive does absolutely nothing? im guessing thats bad?



Re: expected gas mileage?
Thursday, May 23, 2013 6:42 PM
Yes, it would indicate there is a problem. I would have someone else with the same engine try it for comparison if possible to be sure.




Re: expected gas mileage?
Saturday, May 25, 2013 12:22 PM
replaced the IAC valve. now idling around 1200 in park and it seems smoother although I think it should be lower. goes down to 800 in drive but still vibrates the car at idle in drive.



Re: expected gas mileage?
Saturday, May 25, 2013 4:04 PM
Rough idle in drive, you could check for worn/cracked motor mounts or vacuum leak.












Re: expected gas mileage?
Thursday, May 30, 2013 9:09 PM
yeah, i need to replace the rubbers in the motor mounts. the one on the drivers side looks simple enough, but how much of a pain is it to get at the passenger side one under the power steering fluid container?



Re: expected gas mileage?
Sunday, June 02, 2013 7:08 PM
Replaced the drivers side and passenger front motor mount. Have the passenger rear mount to do tomorrow. The mounts very pretty cracked and squingy and needed changed, but it doesn't seem to have made any difference in the vibration in drive at idle. Maybe the final mount will be the key. On another note, the aftermarket mounts (Anchor brand) don't seem to be made very precisely. The slot for the bottom bolt on the drivers side mount was matched up incorrectly so I had to shave it back, and one of the holes for the top bolts on the passenger side front mount wouldn't like up no matter what I did, short of just jamming it in there cockeyed. It's held plenty secure by the one top bolt and the bottom bolt though so no worries.



Re: expected gas mileage?
Monday, June 03, 2013 9:27 AM
I would have expected more of a change with the iac swap. Vacuum is definately next on your list. Gonna try the dish soap method?




Re: expected gas mileage?
Monday, June 03, 2013 4:53 PM
created a new thread for the rough idle as it is off topic for this thread.





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