Guest Recian Posted January 8, 2012 Share Posted January 8, 2012 Well after doing my rebuild i've put the first 1000 miles on the car and in the process i've noticed the highest MPG ive ever got in the car is 22. I can fill the car up and process based on my trip and it came to about 21.8mpg. The CRT displays 21.5-22.5 depending on the driving i do whether it's mostly city or highway but it wont go over 23.0. If i go through my IPC and monitor it at 70mph the "Instantaneous" mpg is never higher than 24/25. I assume since most of my driving has been about 40 miles hwy one way so i should be getting average of about 25-27 especially with new everything ontop of having a more open intake/exhaust. The previous owner said he could get over 30mpg hwy driving here from raleigh (about 2 hours away 55-70mph all the way) and that was with the engine on it's last leg before I rebuilt it. And he had the same intake and exhaust system that i do now (i havent changed anything aside from rebuilding the engine and replacing the trans) Anyone have any ideas? Also it seems to get better mpg on 93 than 87. I got 20.5 with 87 and i'll get 22mpg with 93 Link to comment Share on other sites More sharing options...
2seater Posted January 8, 2012 Share Posted January 8, 2012 Does the transaxle have the same final drive ratio to the original? My stock 2.97 1990 shows 2000 rpm @ 72 mph in lockup. A good active O2 sensor has a substantial affect on mileage. Link to comment Share on other sites More sharing options...
Guest Richard D Posted January 8, 2012 Share Posted January 8, 2012 Could new engine still be tight? Link to comment Share on other sites More sharing options...
Guest Recian Posted January 8, 2012 Share Posted January 8, 2012 the O2 is new and at 71mph (checked with a radar check and im 1mph low so that's 72) i am at 2000RPM so the final drive is right. I dont know if it's normal for these being 2 tons worth of car but it is a bit sluggish at takeoff but does great once youre moving to kick down and pass and whatnot. Im not sure if the .040 bore (which was required to make the engine seal up like it should) is requiring more fuel to fill the combustion chamber or the 170k mile, 23 year old injectors are just getting weak demanding longer fuel trim duration Link to comment Share on other sites More sharing options...
Guest 89 Maui Posted January 8, 2012 Share Posted January 8, 2012 2seater has very valid points with the ouput ratio and also the O2 sensor.But are you sure that you didn't leave a shop rag in the air cleaner box?HahaGoodluck Link to comment Share on other sites More sharing options...
Barney Eaton Posted January 8, 2012 Share Posted January 8, 2012 Bad cam sensor can ruin gas mileage. Link to comment Share on other sites More sharing options...
Guest Recian Posted January 8, 2012 Share Posted January 8, 2012 it's possible i've got a defective sensor of some kind. I've tried to use ACDelco parts as much as possible but alot of my engine sensors and modules arent ACDelco because they dont make them anymore. Im really curious if an intake leak could cause this because the car does seem to have a rough idle when cold and it feels like it wants to die when you put it in gear when it's cold. Warm it's not so bad but if you turn it all the way to the left or right in gear it will die out. say if you were to back into a parking spot and pull up and turn the wheel to the opposite side if youre in D or R it'll stall. It just seems like the engine is for lack of a better term "weak" like if im not careful it could die in gear. Idle RPM is about 650-700 range Link to comment Share on other sites More sharing options...
Guest Mc_Reatta Posted January 8, 2012 Share Posted January 8, 2012 There is a pressure sensing switch on the steering rack that is supposed to raise the idle when the wheel is turned hard or near full lock.Go into diagnostics and select ECM Inputs. Scroll to EI 78 for this switch.With engine idling and in park display should read HI. When wheel is turned hard to the left or right is should switch to LOW.If it doesn't change, check the electrical connector is attached. The switch is on the upper side of the rack on the drivers side. You can see the switch easier from the top, but I found it easier to work on from underneath. They can also leak fluid. Link to comment Share on other sites More sharing options...
Guest Mc_Reatta Posted January 8, 2012 Share Posted January 8, 2012 Have you replaced, or checked and cleaned the MAF? Link to comment Share on other sites More sharing options...
Guest Recian Posted January 8, 2012 Share Posted January 8, 2012 I thought it should have some kind of switch in the rack. I'll check that. I replaced the MAF prior to the rebuild along with the cam sensor and pickup, crank sensor, coil and mode and O2 sensor Link to comment Share on other sites More sharing options...
padgett Posted January 8, 2012 Share Posted January 8, 2012 Might also check the air in the tires - going from 28 to 32 is worth 3 mpg in my coupe on the highway. Link to comment Share on other sites More sharing options...
Guest Recian Posted January 8, 2012 Share Posted January 8, 2012 i put a brand new set of michelins on friday night and set all the tires to 35. I found the rough idle conscern today. Turns out the larger hose that hooks to the cruise actuator had cracked in half and fell off. Replaced that and the idle smoothed out. Im getting somewhere Link to comment Share on other sites More sharing options...
2seater Posted January 10, 2012 Share Posted January 10, 2012 The overbore shouldn't change the fuel requirements dramatically. It did add a few cubic inches but only a small percentage of the engine size. Have you checked the fuel trim values and O2 sensor cross counts in diagnostics? If you had one vacuum leak, there may be others? The other possibility would be a leak in the exhaust in any of the piping ahead of, or close to, the O2 sensor. Raw air entering the system may fool the O2 sensor. The note about the engine still being in the process of running in probably has a bit of merit also. Lastly, having the injectors cleaned, or traded for rebuilts, can be done for a reasonable cost from several online vendors. A more expensive alternative is the new style Bosch injectors with a better spray pattern which seem to have a positive effect on mileage. There has been at least one thread about them. You can do a simple test of basic injector operation by cycling them on and off from diagnostic overrides. The engine should idle with the IAC unplugged and cycling the injectors individually will give a crude idea of the balance by watching the rpm drop. Link to comment Share on other sites More sharing options...
padgett Posted January 10, 2012 Share Posted January 10, 2012 Could also be winter formulations of gasoline. Link to comment Share on other sites More sharing options...
NCReatta Posted January 11, 2012 Share Posted January 11, 2012 My MPG has dropped signifigantly since about late November.. I wasn't sure if it was something going on my car (no codes) or what.. Maybe it's the winter gas like Padgett said?Of course, it doesn't help much that NC DMV made me put a cat back on my car (and it sounded so good too :mad:). Late October: 22 mpgLate November: 19 mpgEarly January: 18.3 mpgI'm not too happy. :mad: Link to comment Share on other sites More sharing options...
farnelle Posted January 11, 2012 Share Posted January 11, 2012 You guys need to keep your foot out of it. Unless you are doing mostly city driving, your Reatta should get in the high 20's. I have three 90's and one 91. I have not checked the 91, but all three 90's get between 27 and 29 mph highway. I normally drive about five mph over the limit weather, traffic and roads permitting. Climate control is set to automatic and I use cruise when possible. That mileage is with a passenger and luggage. On the other hand, I recall my 89 did not get quite as good mileage. I think in the mid twenties. Link to comment Share on other sites More sharing options...
Guest Richard D Posted January 11, 2012 Share Posted January 11, 2012 (edited) it's possible i've got a defective sensor of some kind. I've tried to use ACDelco parts as much as possible but alot of my engine sensors and modules arent ACDelco because they dont make them anymore. Im really curious if an intake leak could cause this because the car does seem to have a rough idle when cold and it feels like it wants to die when you put it in gear when it's cold. Warm it's not so bad but if you turn it all the way to the left or right in gear it will die out. say if you were to back into a parking spot and pull up and turn the wheel to the opposite side if youre in D or R it'll stall. It just seems like the engine is for lack of a better term "weak" like if im not careful it could die in gear. Idle RPM is about 650-700 rangeIt was very cold here last week, down to a little less than 40 F. and If anything mine was idleing slightly faster than normal, showed no sign of stalling or even being loaded from steering hard, left or right. When put in gear it slows down about 100 RPM to 750, normal warm RPM is 650. Could you ISC be bad or slow?ps. With 145,000 miles I get22-24 city 29-30 at 65 with cruise on. A/C on. Edited January 11, 2012 by Richard D (see edit history) Link to comment Share on other sites More sharing options...
Guest Recian Posted January 12, 2012 Share Posted January 12, 2012 i dont have a/c atm. Need a high side line to fix it. (If anyone's got one lying around let me know) nor do i have cruise. It is ON on the dash switch but it wont set. I drive it like a grandma drives a buick. Since NCreatta seems to be getting the same results i am with mpg and I know how crappy of a state i live in so I think NC is going past their 10% ethanol limit seeing as 93 octane seems to make it run better and get better mpg. That happend in my sentra a few years ago. It turned out I was buying from a s**ty gas station and when i started going to a station i knew was good that had less than 5% ethanol and it ran much better. Also my wife's hyundai used to get 27 even in city which is around 200-220 per 1/2 tank and now she's getting 200 from 3/4 a tank. I think it's NC's winter fuel Link to comment Share on other sites More sharing options...
Guest Richard D Posted January 12, 2012 Share Posted January 12, 2012 Does anyone make a single use kit that will tell you the % of ethanol vs. % gasoline? Down here most marina pumps sell pure gasoline as does most Marathon brand stations. Link to comment Share on other sites More sharing options...
Guest Recian Posted January 12, 2012 Share Posted January 12, 2012 doubt it. If ppl knew how much ethenol was really in their gas there'd be serious issues. The govt would shoot anything like that down before it got into production Link to comment Share on other sites More sharing options...
Rawja Posted January 12, 2012 Share Posted January 12, 2012 doubt it. If ppl knew how much ethenol was really in their gas there'd be serious issues. The govt would shoot anything like that down before it got into productionFive bucks.Ethanol Fuel TesterFire up the black helicopters. Link to comment Share on other sites More sharing options...
Guest Recian Posted January 12, 2012 Share Posted January 12, 2012 lol also you can test it using a clear soda bottle. fill it about 1/3 with the gas. then add some water to it. the gas will float on the water. use a sharpie and mark the water line on the bottle. seal the bottle and shake it. not too much because it can expand and possibly pop the top off. once you shake it good sit it down and let it all settle. if theres any water or alcahol in the gas itll stick to the water you added and the water level will rise. if it goes signifigantly over the line then odds are the gas is loaded with alcahol or even small amounts of water. its a trick i have to use alot in the shop because nissans will run like crap if their ethanol to gas ratio gets too high. Link to comment Share on other sites More sharing options...
padgett Posted January 12, 2012 Share Posted January 12, 2012 So, all you need is a bottle ? Is that how the Michigan thing works ? Thought it would be more balls like for anti-freeze.Lessee, premium costs about 25 cents/gal more than regular. That is about 8% more than regular. How much better mpg do you get ? Link to comment Share on other sites More sharing options...
NCReatta Posted January 12, 2012 Share Posted January 12, 2012 So, all you need is a bottle ? Is that how the Michigan thing works ? Thought it would be more balls like for anti-freeze.Lessee, premium costs about 25 cents/gal more than regular. That is about 8% more than regular. How much better mpg do you get ?My thoughts exactly.. Not sure how much $$ I want to fork out to find out though. Maybe I'll get a half a tank of premium and see how I do. Link to comment Share on other sites More sharing options...
padgett Posted January 12, 2012 Share Posted January 12, 2012 have to gain about 1 1/2 mpg just to break even. Link to comment Share on other sites More sharing options...
Guest Recian Posted January 13, 2012 Share Posted January 13, 2012 with regular the reatta is sluggish at best and gets about 20-21 on a good day. With 93 it has more pep and gets 22-23. Which still sucks seeing as i do alot of hwy driving since i've got a 40 mile trek one way to work. Link to comment Share on other sites More sharing options...
padgett Posted January 13, 2012 Share Posted January 13, 2012 I was driving 20 miles to work, about 5 mi surface and 15 mi freeway & getting 23-24 in my 88 on 87 PON. Link to comment Share on other sites More sharing options...
KDirk Posted January 13, 2012 Share Posted January 13, 2012 Mileage on both my Reattae is not what is should be. Granted, I have a lot of short trips but even so, on the highway it does not get to where I think it should be (using the fuel economy monitor on the 88). We are stuck with blended gas here, "contains up to 10% ethanol" stickers on the gas pumps no matter where you go. Not aware of any station in the STL area that sells "pure" gas. Does premium actually contain less ethanol as a rule? I have to run 93 octane in my Deville, but have not tried it in either Reatta. Kind of doubt I would pick up enough extra MPG's to justify the extra cost. It is just frustrating to get mileage so much lower than what it really should be. KDirk Link to comment Share on other sites More sharing options...
2seater Posted January 13, 2012 Share Posted January 13, 2012 You have to look at the pump to see about the ethanol content. In my area, and probably nationally, the fuel must be labeled that it contains ethanol. Some stations do offer non-ethanol premium in my area, but I was told the best pure gas octane available here is 91 and the ethanol blended premium would be 93. My experience has been a 3% mileage reduction with the 10% ethanol blend. In the past, before the widespread usage of ethanol blends, my cars experienced the best mileage with 87 octane. Excess octane usually slows down the ignition process somewhat to allow for higher compression and/or greater ignition lead, which usually makes the engine feel smoother, but it wasn't the best for fuel mileage. Now that ethanol blends are almost unavoidable, the experience has changed. Link to comment Share on other sites More sharing options...
padgett Posted January 13, 2012 Share Posted January 13, 2012 Higher octane gasolines burn slower than lower. Ethanol is an "octane improver". A computer car designed for regular gas is going to be set for less advance than one for premium and will probably be slightly retarded for 93 if designed for 87.Back in the day, if you ran a regular gas car on premium, it was best to adance the distributer 2-4 degrees to compensate. It is a little more difficult with a Reatta.However if retarded, the O2 can be perfect but MPG will still suffer since it would need more gas produce the same power.All of this is a kludge to hit peak chamber pressure at about 10 degrees after TDC (and that is a function of crank/rod/piston geometry) but is your real goal.Meanwhile modern thinking is to use direct injection to permit high compression without detonation as slowly gas engines become more diesel-like. Link to comment Share on other sites More sharing options...
Bushwack Posted January 13, 2012 Share Posted January 13, 2012 I don't know if this helps Recian's problem, but for others, how about some Seafoam?Never tried it but I expect to within the next couple weeks. My silver car is getting terrible city mileage (11..12mpg). From what I've read, giving your engine a Seafoam enema can do some good. Link to comment Share on other sites More sharing options...
zoltanb Posted January 14, 2012 Share Posted January 14, 2012 I found BG44 to be a lot more effective cleaner. Link to comment Share on other sites More sharing options...
KDirk Posted January 14, 2012 Share Posted January 14, 2012 Zoltan- That BG is some good stuff, have used it before. Be advised though, running it through the throttle intake (the recommended procedure) will make the car smoke out the exhaust like you've never seen.Did Seafoam on my 88 last spring, didn't seem to make much difference. I have used it with better results on other cars. KDirk Link to comment Share on other sites More sharing options...
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