Drove it to see what MPG I could get 1st time I got 5 mpg.
2nd time drove like an old woman 9 mpg.
No leaking gas.
There's a one second pause max "when taking off" like if I give it gas then have to back off gas pedal a little it then goes. It mild though, but that's the only odd thing.
There's no smoke no gas smell...
113,000 miles
New Spark plugs, Wires, Idle Control Valve no warning lights. No Dirty Puddy Cat Smell?

Where would you start looking?



If I do give it gas it Roars like a Lion and takes Off NP.

 

Yeah, that's not good at all. Probably start with some data logging to see what the computer sees

 

Did you change your rear end and not your speedo gears causing your MPG calculations to be off?

 

No its stock no change...

 

As a point of comparison my 1989 Iroc (converted to SD), That is tuned and has highway mode enabled gets a legit 28 mpg highway.

 

I'd like to learn how exactly you achieved this? What is (converted to SD) and That is tuned and has highway mode enabled?
Teach me wise one .... I cant afford this Lamborghini gas MPG.

 

Our cars were advertised to get 15mpg city, 25 hwy. everyone knows what is advertised is never met in real practice. well, usually. T-Tops down, some downshifting, some pedal to the floor, gonna pull that 15 back some. I haven't calculated mine, but know its not all that great.

 

Yes but mines 10 mpg driving like Grandma!

 

converted it to the 90-92 speed density computer, then carefully tuned it and enabled highway mode, all else pretty much stock apart from exhaust system. These cars were very good aerodynamically and can get impressive highway mileage when your not beating on them.

 

Where kind of driving are we talking here? And for how long, for each episode?

 

Not trying to hijack this as I'm a novice myself, but here is what I did and I get 28 MPG on the highway as well.

Install ELB Dynamic EFI system. I'm running their Flash-II and have only been tuning for about a year - learning everyday still. My 89 GTA was a MAF car, with the ELB system, you simple re-pin a few wires going to the new ECM (Flash-II - replaces your old ECM) and connect a MAP sensor to a vacuum line close to the TPI plenum. You re-purpose the old MAF wires to now go to the new MAP sensor - bingo..you're now Speed Density (SD) and no longer MAF (Mass Air Flow). There are detailed instructions here: https://www.dynamicefi.com/

Once that's complete, you use the software to data log and TunerPro (free software) to adjust your tune. The ELB system has so many features, including HiWay Mode (lean cruise). You can tune out VATS, EGR etc. There are hundreds of pages here to read and learn, RBob (Dynamic EFI creator) is active on this board and always helps out with questions.
Having the ability to data log and see the Whats Up Display (WUD) is great for diagnostics and custom tuning. If your willing to do some reading/learning it's not overly complicated.

Good luck!

 

Thank You so much Reading up on it now only knew Mass Air Flow Sensors 1985 , 1986, 1988 TAs

 

You're The Best Hijacker ever! Glad you did! I appreciate Max Power TA Making This Known and I'm super grateful for your additional data dump Thanks 89 GTA 355 & Max Power TA.

 

Full Tank City only Driving 140 miles

 

I don't know how I totally missed your reply right above mine unless I started my reply and got sidetracked for a bit and came back to finish it and you had posted your reply in the meantime.

If you live in a big bustling city and it is constant stop and go driving in congested traffic I could see your gas mileage sucking.

I keep forgetting I live in a small town and driving through the city part of where I live is like 5 minutes max.

 

^That was my question^

Also, in town? Highway? What are the conditions. And how are you calc'ing your 9mpg?

 

City only driving will get you 8-10 MPG (or less) all day long, every day, and twice on Sundays. Many years ago, the solution to that was the "SV" upgrade option. A Schwinn Varsity tossed in the back would increase mileage drastically for in-town commuting. If the car has long legs, like 2.77 axle gearing, and there are lots of stoplights and merry-go-rounds, and your foot is on the brake more than once every 30 minutes, mileage will get to that point or lower. IIRC, there are NO roads in Florida where the posted speed is 80 MPH, such as in the other time zones, so there is little chance to make up for that dismal in-town driving mileage.

 

I missed that post. Good catch Vader. It's the "City driving" that's getting you the ~10 mpg, most likely.

 

If you live in a big congested city with constant stop and go traffic you really want to figure out what is causing this hesitation when taking off from a stop. That drivability problem could be eating up a lot of gas in constant stop and go city driving.

 

Hey There Vader,

Thanks Again for this Awesome mod I am going to look into this was well. There so much incredible knowledge in these forums.

I've had an 85 TBI TA and 88 GTA TPI 5.0
Before this 86 TPI never remember it this bad but that was 1989-1996 when I was age 16-23 years old.
I'm in the same city maybe its the gas prices are higher now.
Thanks again for the Feedback and Data!

Sincerely,
Jonathan

 

Ya it was all city I appreciate you Tom 400 CFI and Airwolfe inquiring and trying to help. I going to research those mods, but I know I have to see why its so bad I'll have to do a highway test. I'm thinking New Fuel Filter , New O2 sensors, and PCV Valves lastly Fuel Injectors. Fingers crossed * I love to get 28 hwy and A boost in the city too.

 

Look at the SPID label in the center console or rear storage compartment. The "G" codes should define the axle. A 2.77 Borg axle is not very conducive to achieving good stop-start driving mileage. My '86 is that way. If your other F-cars had a higher ratio, that could explain some of the difference.

 

Your more like Obi One Kenobi or Yoda with your Knowlege base you have. : )

 

Something is definitely wrong. The TPI 305/5spd/G92 3.45 geared 1990 I had would get 17-18 mpg in the city and close to the 30 on the highway not taking it easy. I was also getting about 13-14 in the city on E85 in a 5,300 lbs G20 conversion van with a fairly built up 350 TPI in it with a 3.08 gear. I have a 7,000 lbs Express van with a 500 hp 383 that still gets about 12 mpg around town on E85. Both saw 20+ mpg on the highway at 75-85 mph with lean cruise enabled. I would start by checking your wheel temperature. You could have a brake dragging. Next scan the ECM to get an idea of what is going on. It could have a bad coolant temp sensor, 02 sensor air, or faulty air select valve stuck on the manifold outlet that is causing the engine to run extremely rich. Next check your base timing. 9 mpg with a TPI engine in anything except maybe a loaded dump truck is way off.

 

I'm changing the Fuel Filter today. I was thinking about a o2 as well I have a Mechanic popping by, he sees if the ECM says anything about it. Well, I'm back not much on the ECM. He cleared OLD codes see if they come back. (Was no Check Engine Light) BUT WE can't get the Mass AIR FLOW Sensor to Line Up perfectly it's like warped always an edge cracked somewhat Open not truely open but.... I will get a new O2 sensor this one Look Original like everything is on this car.

Thanks Fast 355

to be continued ....

 

Is it stuck in open loop? Temp sensor maybe...

 

Truly....incredible. Is this a normal/regular thing?? Do all 3rd gens get close to 30 hwy?? I'm gonna have to get me a 3rd gen Econ-o-mizer!!

9 mpg is definitely low, but City driving can mean a lot of different things. I bet a caprice with an L05/700R4, 3.23....that's a city cop car, probably gets 2 mpg (but stellar GPH). So trying to use/gauge/diag using "city" mpg claims isn't that useful.

OP...if the car runs good, has no CEL, my advice would be to drill down a little deeper into the data. Fill the tank, go drive somewhere on an unimpeded highway, cruise at a consistent speed for at least 50 miles or more? Come back, top tank and do the math and share THAT with us. If it's over 20, it's about where a V8 3RD GEN SHOULD BE, and probably better than most are. If it's 12, then you have a problem that needs further attention. If it's "close to 30", you should enter a hypermiling competition.

 

There was a discussion about the system setting reset Closed loop & Open Loop. So I will See Thank you!

 

Well yes and no not going to be a dead horse but 140 full tank is not acceptable because I had 2 TAs 85 88 they were never that bad even with teenager me ... But anyway, we know my feelings.
The cool thing is it looks like I may have the original O2 sensor in the car and my exhaust is smelling pretty RICH $$$. Also have warp rotor that's why we believe the car chugs to a stop from the warping and the MAF is 90% seal not 100%
So, I'm Going to keep work on these fixes and see if I can get better mileage and I have to check the gears codes Vader advised. I am taking your advice as well, will do a highway Trip good idea! Just Dropped $600.00 dollars on Tires because my Eagle GT's with 33% tread left were cracking from dry rot now these have 65,000 Mile Warranty to go with my hypermiling :-) Take care & thanks Again

 

New Update I fill up the tank to take the car on a Hwy run and it's Puking out gas though the bottom of Evaporated canister when turned off.
This has now happened 2 times.
The 1st time this happen I thought that I over filled the Tank putting the max gas I could in. I had to get a replacement Evap canister.
Refill to full again but this time "the 1st stop click on the pump" I stopped the gas flow I did not add a drop more. Drove for 3 miles parked the car and now.
Its Started Puking up the gas again out the bottom of the Evaporator canister. "again".
This Car is wearing me down. Seem to do this when the car is at full tank only. If it's not gassed up to near or at full it does not Puke.
Is it's another Clue to the Bad Gas Mileage.
I thought this was a Fluke which is why I didn't mention it.

 

Alot of them do get high 20s and low 30s highway mileage. DynoDon put a TPI setup on a TBI engine and was getting 30ish mpg. Numerous stock TBI 305 cars have managed 30+ as well in fuel economy posts of the past. IIRC wasn't it you that used to claim similar mileage in a Crossfire car. I can find the post and jog your memory from bygone years if you need me to.

I think the 3.45 gear and manual transmission helped alot compared to a 700r4 and a highway gear. The manual does not have losses from a slipping torque converter and can be upshifted at any rpm desired and skipping any gear desired. Was not uncommon for me to skip a gear or two in town. The LB9 had plenty of torque with that gear to accelerate in 3rd from under 20 mph. In traffic I typically left it in 3rd at low speeds.

 

 

The lack of proper EVAP control is likely costing fuel mileage, especially when it purges raw fuel. The tank pressure control valve is suspect. Of course, the nearly 40 year old hoses should all be inspected.

The '86 still had a replaceable filter on the bottom of the EVAP canister, and that IS a routine maintenance item. My '86 will build tank pressure on the highway, just as you describe. The proximity of the exhaust system to the tank doesn't help, but a functioning EVAP should be able to handle the pressure. Over-filling the tank doesn't help, however, since there must be some head space in the tank for the system to work properly.

 

also achievable with a factory ECM.

383 here, TH7004R with a Gear Vendors OD behind it. 7730 ECM.

~2000 rpm at 80 mph with the double OD, with highway mode fueling kicked in... ~28 mpg highway.

And thats in an early 2nd gen Camaro... not known for aerodynamics....

 

Speaking of Highway mode does any one know what these setting do in the $8D SAUJP

Highway Mode Fuel, Exit if time >=, set to 60 sec so its turning off lean fuel after 60 seconds?

Switch19 Perform Highway mode SA TCC status check, none of the SAUJP bins have this checked off if the isn't checked is Highway mode spark not added?

Switch 19 In Which gear allow highway SA, confusing as the description states two meanings one being only in 4th or turn off the other being 3rd and 4th or 4th only, so does checked off mean only in 4th and unchecked 3rd and 4th

Also are there any ill effects lowering the timing for Highway mode fuel begin conditions factory is set at 10 sec it would seem you could squeak more mpg setting this even lower than 10sec

 

The SAUJP v7 has the following descriptions of what they do...

Highway Mode Fuel, Exit if time >=, : Highway Mode Maximum. It will be on no more than this time. Factory Default = 60 seconds.

I left this as the default in my bin. It'll wait 10 seconds to re-enter highway mode. It may not be a valid concern, but I figure I'm running a bit leaner (i.e. hotter in the cylinders) for a while, then let things cool back down for a bit, then re-enter highway mode. I run about 16-ish to 1 during highway mode. I'm not seeing the coolant temperature go up or anything like that, so I guess it's just being a bit conservative I guess.

Switch 19 (0x019) - Bit 4 - Perform HighWay Mode SA TCC Status Check (Y/N) : When set =0, and the TCC is LOCKED, subject to certain engine conditions being maintained for > 10 seconds, 3.87 degrees will be added to SA-TDC every pass through the Spark Minor Loop when SA-TDC is calculated.

I have this set to 1 in my bin. I already max out the spark timing to what I want. I don't want the ECM adding any more. I also have my highway mode spark advance table set to 0.

Switch 19 (0x019) - Bit 2 - In Which Gear Allow Highway SA (3 & 4 or 4 only ): 0 = Allow if in 3rd or 4th 1 = Allow only if in 4th. This setting of bit is ignored if 0x019 b4 =1 AND the TCC is UNLocked. Under these conditions, Highway SA will NOT be added to Total SA-TDC.

1 = Enable Highway Mode Spark Advance when in 4th Gear (Factory AUJP)
0 = DON'T Enable

Also left this as the default

 

So once in highway mode it will enable highway mode lean fuel for 60 sec then turn off for 10 sec and re enable?

 

You can set the enable time to whatever you want.

 

Yeah. I can actually see it on Tunerpro as it happens in real time (via the commanded AFR)

 

correct

 

For anybody that's interested, Here is a quick video showing how "Highway Mode" works on a TPI camaro.

 

Fred

 

Thanks Vader Again for this input. I'm going to have to start looking into a classic car repair man.
It's crazy MANY repair shops won't touch my car at all

 

Car "was" in Open loop you guessed it.

 

Round trip to Naples and Back to Gas Station 50.7 miles


Total Amount at Fill Up 2.77

Highway Mile are.... Drum Roll Hwy 18.30 Vs 10 City

 

Seems like you're close to where it "should" be. 18*15=270 range...that's way better than 140. If you ran through a longer drive, I'd expect that the number would go up more.

Did you find the problem with the EVAP system? That'd definitely hurt your numbers.

 

Yes PLEASE. I would LOVE for you to find that post and "jog my memory" of my CFI car that got "high 20's/low 30's"! Please show us this post.....

I've had 4, V8 3rd gens, 3 of which were stick. Of those, I've had 3.23, 3.45, 5 speeds, 6 speeds, 305's, 350's and a 400. Carb, CFI and TPI. Never saw high 20's/low 30's in any of them with any kind of driving. But please...show us where I "did".



How about the car that's being talked about in THIS thread?? How 'bout we help out the OP and do it w/realistic data, for his car and his driving? Hmmm? If you look at the link I posted earlier, he's comparable, based on his 50 mile run.

 

To be continued ... I'll will be working on that this week.

I'm going to Name My Car Regan since she's Possessed by a demon and likes to puke all the time


Here She is in her Blue Dress again causing more Problems.


I'll let you know what happens .. Say a Prayer for me and Our Country

Thanks Tom!

 

The TGO crew here has a really good history of successful exorcisms. We'll get her to repent, and you'll have to get your pea soup somewhere else.

 

Oh Love it ! Good ne