Mileage, reliability, and improvement.

[CorsePerVita]

SO i'm new to the 911 world, but am familiar with my 914 and very familiar with the 944, although I understand there's a lot to learn with a 6 CIS system, no worries though.

Although it seems to me that I'm getting piss poor gas mileage. I read they'll get 20ish to 25 sometimes higher on the freeway. I put $15 in it, got about 4 gallons, and just on the way to work this morning burned half of a quarter tank on a 13 mile trip. Not a huge deal, but it'd be nice to a bit better economy and know he's running "as intended".

So a few things after browsing through the various pelican parts 911 forum...

I'm using premium but read I should really be using 87 or 89 octane? Perhaps this is one part of my bad mileage.. if indeed that's how the engine runs, okay cool. It's a 1982 911 SC Targa.. But i understand different engines run on different things. For instance one of my sportbikes has high compression, runs on regular, runs worse on premium with worse mileage.

Perhaps it's running too rich? Seems to respond just fine. Any sensors I should be testing to ensure mixture and accuracy?

I figured...

- try a different octane, see how it runs
- new air filter
- run injector cleaner through/fuel system (what do you guys recommend since you're familiar with CIS and know what works well with these cars)
- Vacuum hose replacement, they are old and brittle, time for new ones.
- I read my year has an O2 sensor (1982), may not be a bad idea to replace.
- Seems to have a moment on a cold start where the rpms drop and it'll sometimes die, then next startup is fine and it'll high idle till it warms up. Warm up regulator sticking maybe?
- Replacing all old connectors with new copper connector for wiring to make sure I don't have issues with resistance on sensors, etc.
- Tuneup, cap, rotor, wires, plugs
- God knows when the tranny was flushed, and probably do an oil change with brad penn while I'm at it.

Any basics I'm missing?

[johnsjmc]

There are very few sensors on a 1982 Sc . Piss poor gas mileage is common. The O2 sensor replacement is probably a good idea along with injector cleaning. Reg gas is all that is neede but use of premium shouldn,t change the MPG only the cost per mile. The base mixture is adjustable with a small allen key(3mm?) and leaning it a little will probably help. Be sure timing is set properly and brakes aren,t dragging.

[Laneco]

I have a bone-stock 82 that I use for work (way cooler than a rental car). The engine is bone stock 3.0 CIS. I very consistently get 25 to 28 on long trips, logged over about 15,000 miles of driving. I use 89 octane. All of your ideas for basic tuneup seem sound. But before you do any of that, I would suggest taking it for a couple hour drive. It's amazing what pushing clean fuel through the system will do for the car's well-being.

The fuel guage may be lying to you. Fill it up and run it down, then refill to get a more accurate analysis of your fuel economy.

angela

[CorsePerVita]

Alright so it sounds like i'm not totally crazy then, so I should be able to get better. I don't mind filling her up, it'd just be nice to spend more time driving and less time hopping at each station.

I'll try the things mentioned above and report back.

[T77911S]

first, always base mileage on a full tank of gas, not how far the needle moves.

not to insult you, but since i dont know you or your knowledge, i assume you dont know much about CIS, but that is OK.

you have several things going on, and it sounds like the car is new to you, so instead of trying to fix things individually ill give you an overall fix.

air leaks need to be fixed. you can relpace all the rubber on the CIS system and be done with it for a long time and not have to wonder if something is leakinng, or you could get a smoke test done and fix what leaks now, then later when something else leaks and it runs bad, try to find what is leaking.

your fuel pressures need to be checked. warm and cold control pressures. also check resisdual pressure

are you sure the O2 is even connected? i would replace and connect it up, but that is just my opinion, others may not.

tune up. plugs cap, rotor, wires, fuel filter, air filter.

verify power to the WUR and aux air regulator (AAR) and the operation of the AAR

set the mixture.

you do all that, your car will be back to normal and so will your mileage.

if it was me, i would just drop the engine, go ahead and do all this along with valve adjustment and tranny oil change and check the clutch for wear, wait, that is what i did when i bought my car.

[CorsePerVita]

Originally Posted by T77911S

first, always base mileage on a full tank of gas, not how far the needle moves.

not to insult you, but since i dont know you or your knowledge, i assume you dont know much about CIS, but that is OK.

No insult taken at all. Not only do I appreciate the helpful responses, but I appreciate people and their willingness to help me learn. I prefer to be a sponge and take it all in I am somewhat familiar with CIS as my 924 had it. I am converting to megasquirt on it, so it has been quite a while since I've taken the CIS adventure, and the 911 system seems similar with some differences, so I'm trying to learn. I understand I'm a "young'n" as some people would see it (i'm only 25) but I'm not afraid to dive in my car waist deep and go at it and learn. I do the maintenance on all my vehicles, so I am looking forward to working on my 911 I greatly appreciate your response as well as everyone and their responses as well. Thank you most kindly!

Valid point on the needle. I used my gps to compare my speedo today and also noticed that after my car sits for a while the needle returns up a bit and reads accurately. It seems to lie to me on the go, or after a drive. It appears not to be using nearly as much as I thought, you are correct.

Originally Posted by T77911S

you have several things going on, and it sounds like the car is new to you, so instead of trying to fix things individually ill give you an overall fix.

air leaks need to be fixed. you can relpace all the rubber on the CIS system and be done with it for a long time and not have to wonder if something is leakinng, or you could get a smoke test done and fix what leaks now, then later when something else leaks and it runs bad, try to find what is leaking.

I definitely am going to replace ALL the vacuum lines. Although seals and gaskets are an excellent suggestion as well, I will add these to my list. Thank you! Smoke test isn't a bad idea either.

Originally Posted by T77911S

your fuel pressures need to be checked. warm and cold control pressures. also check resisdual pressure

are you sure the O2 is even connected? i would replace and connect it up, but that is just my opinion, others may not.

I do not have the tools to do a pressure test, do you have a suggested tool to do so that I can hook up to the CIS system to ensure it's getting adequate pressure?
I am also NOT certain that the O2 is hooked up, I will check this. Everything on the car looks mostly stock, no major mods, so I assumed it would be, however, another valid point... not to assume, I will check it for certain.

Originally Posted by T77911S

tune up. plugs cap, rotor, wires, fuel filter, air filter.

verify power to the WUR and aux air regulator (AAR) and the operation of the AAR

Sounds like I get to pull out my multimeter! lol, no worries, should be fun to learn. Looking forward to getting to know the ins and outs of this car.

Originally Posted by T77911S

set the mixture.

Not entirely sure how to do this but I will look and do a search to see if I can find an article on here of how to do so. I do know that on my 924 touching the adjustment screw was a huge no no. However, if it is different on a 911 I will take your word for it. But before I do that, I will check the rest of these things and replace and tune up first to ensure all is "as intended" before messing with the mixture.

Originally Posted by T77911S

you do all that, your car will be back to normal and so will your mileage.

if it was me, i would just drop the engine, go ahead and do all this along with valve adjustment and tranny oil change and check the clutch for wear, wait, that is what i did when i bought my car.

Sounds like a plan to be honest. I saw the tool to check the gap for the valves. Seems about as simple as my 914 to do a valve adjustment, little more close quarters but straight forward. I planned on moving over to Brad Penn (if it isn't already using it) and also doing a tranny flush.

I saw pelicanparts has a huge tutorial on dropping the engine, so it shouldn't be a big deal. If I can do a 944 clutch in my garage under my car, pulling the engine out on my 911 should be cheese.

[T77911S]

i took it out to do all this to make it easier and i was doing so much it made it worth while.
valves adjustments are much easier on a stand, along with removing the CIS.
dont forget there are injector sleeves that need to be replaced too.

you dont need a MM to do simple voltage/power checks. a $10 test light will verify voltage.

i would do all the work, get it running and take it to a shop and have the mixture set, once everything is all done. then you should be good to go for quite a while.