xrsxj

Hey guys i was hoping for a lil bit of help with my mileage and passing my california emissions. I have been looking around for a while on the boards and i seem to see alot of posts about poor gas mileage. I can't seem to find a correct answer in my case though. my car is almost all bone stock 305 TBI except for an open element. And from what i have heard and what i believe at elast that the open elemnt should have actually improved gas mileage not decreased it. Heres my problem

13 - 15 babying the car in cities only and 16 - 18 babying highways mostly at 70 mph. i was able to pull off a 20 once but i htink it was a fluke. I replaced my plugs with plat. plugs about 1 month ago and it stayed almst exactly the same the wires about a year and ahlf old as well as my EGR valve. Ontop of all this the only way i can pass smog is to retard teh timing at least 2 degrees but far better when its retarded all the way down to 6 degress,.... those are without the EST. the power seems dead on for about 150HP at the wheels. I seem to have problems passing SMOG on all things but mostly HC and hence the reason for the plugs.... but still its no better gas mileage. I recently decided since im all the way out here in california and ambient temp is rarely under 75 to switch to a 160* thermostat to see if that would help gas mileage... it did slightly but in the pprocess of changing that i borke off a bolt in the intake manifold and instead of taking it to place right away i decded to try to extract it myself.... needless to say ...bad idea.. ended up paying about $50 to get it retapped. after that i replaced te intake manifold gasket and now i have an oil leak... a bad one... I am pretty sure the iol leak is at the rear of the engine... but i think i can get that any help on ANY of this would be awesome and thanks in advance.

Dewey316

get a new GM o2 sensor, as o2 sensor go out, the engine will run richer than it should. i also wouldn't suggest a 160* stat, you engine won't run warm enough to get into closed loop mode (this could also be part of your rich condition, as the open loop setup tends to run a little rich) if you are worried about over heating, go with 180* other than that, general tune up stuff like, cap and rotor, plug wires, PCV valve, oil change, ect.

MrDude_1

try this.


take the air cleaner assembly off... remove the spacer ring

start the car.. you may get a SES light since the air temp sensor is disconnected.. thats ok, the light will go out as soon as its reconnected.

watch the injectors spraying...they should have a nice even cone...

if they drip or splatter, its time to either have thoes cleaned or replaced.


the injectors alone got me back alot of my miliage... the EGR got me back the rest.. this may be your emmissions problem too.....

r90camarors

A clogged cat could be huting you as well.

xrsxj

thanks guys.... most of your ideas i have tried but forgot to mention.... one i have replaced my cat about the asme time as the wires.. as well as my o2 sensor and mileage has still been the same.althouh cap and rotor i was planning on replacing as well as the coil right in the next month or so as soon as i get my next pay check. I was going to do a PROM upgrade with the therm. but in the meantime my gas mileage actually went up a lil bit with the addition of it.... i checked my injectors they aren't running prefect but on a scale of 1 to 10 i would say about a 8.5 maybe 9.. they could use a cleaning but other than that they don't seem to bad... i rebolted all my manifold bolts.. it turns out that i had the torque spec off by 15 ft/lbs ... i couldnt' test the leak but i am pretty sure that that got it. if not ... back to work... now they are all properly in at 30 ft/lbs... so after cap and rotor im going to see if the gas mileage will get any better....if not i'll see about a PROM any other ideas... id be glad to hear em' thanks alot guys for all the help you can offer...

Slade1

Have you replaced your distributor cap and rotor?
How strong is your ignition coil?
O2 sensor's age/condition?
Is your tranny's torque converter locking up?
Is your engine getting warm enough for closed loop operation?
Do your injectors fire cleanly?
Condition of the EGR system? SES light with code 32?

You need to have a strong ignition system to burn fuel effciently.
Your coil must produce a strong spark in the first place from the ignition coil. Then the spark must have a good conducting path.
This means from the coil to the distributor cap, to the rotor to the wires to the plugs the spark path must be good to produce optimum spark. The gap must be set to at least 0.035 inches to get by emissions well. timing must be dead on.

Stock TBI engines run better with more timing, but too much and it becomes a hinderance due to the characteristics of our setup. between 2-6 degrees is usually optimum for a generally stock TBI. I'm speaking from dyno tuning here. After that there's some pinging.

Once ignition system is clean, go with your O2 sensor. I'd replace it if it was stock, over 2-3 years of age and running rich (ie high HC levels).

I'd run an injector cleaner/fuel system cleaner in the gas tank and then change fuel filter. Observe the spray cone of the fuel injectors. If its a fine cone, its ok. If it drips down like a leaky faucet, clean it up or replace them if necessary.

Temperature plays a big part in these fuel injected engines. too cold, no closed loop = enrichment mode. A 170 or 180 stat is a nice touch b/w temp and power. Emissions and mileage may find a stock 195 more accomodating.

Your EGR system is a vital piece to highway mileage. Basically if you manually open it all the way, your engine should stall, choke and die. Back in sept I learned about that. My hi flow cat and y-pipe setup reduced back pressure to a point that getting the damn thing to open was a fluke. Even if it was open though it wasn't doing much. Replaced it, cleaned up the egr passages and it passed cleanly. now it also stalls if opened completely. On highway it works by recirculating exhaust gasses back into the combustion chambers. This has the benefit of cooling the chambers down as much as 1000 degrees. The ecm then advances timing and reduces the amount of fuel used. the result is better mileage.

If it still doesn't liven up your engine, you may want to look at other aspects. Burning oil via valve stem seals or piston ring seals, the latter which is grounds for a new engine ie 350.

A slipping tranny, or one that doesn't lock up also would waste fuel. You'll notice that your rpms will fluctuate quite a bit if it is slipping or not locking up properly with varying load.

xrsxj

thanks for all the advice man im gonna be lookin over everything that u suggested some random stuff... EGR, O2 and wires are about 1 and half to two years old bought them in december of 2001 right after i bought the car. baout 6 months ago i ran a fuel system cleaner althoguh i don't think i've changed my fuel filter in a while or at least not since i've owned it. the injectors spray decent, it looks like they are clean and clear but the cone is kinda bogged down like u know when u turn a sprikler on and right at the beginning it does that lil thing where it looks like a lemon shape thats about how the injectors look... im geussing not enough fuel pressure which would prime for a fuel fiter change, correct me if im wrong but that seems to make sense so thats on the agenda speaking of changing the fuel fliter any tips on how to pull that off wiht no problems. anyways as for the ignition system, im gonna take my coil to autozone as well as my TPS to see if they are working properly adn up to spec after that prolly i'll replace the rotor and cap because i took a look at them and the spark terminals were a lil corroded althouhg im not the most experienced person when it comes to judging it so let me tell u how they looked and u tell me if they are good to go or not.... they llooked like they had about .5 or 1 mm of white residue on the spark tips and the rotor looked a lil worn like maybe a burn mark but they looked decent enough other things i could tell u abotu the car is that cold start takes about 2 to 4 seconds, warm start is damn near half a second maybe 1 at the most, if htat helps you guys to tell me if the ignition system has a problem then awesome if not just random information. i don't get any ses lights although rarely when i push the clutch in to slow down or stop about maybe 1 or 2 times a month it drops from about 2000 and dies on me, first time it happend the power steering had went out and i had just been freaking out and when i saw the RPM was at 0 laughed and started her back up no problem, so i don't know wy that happens its not the driving cuz its happend at about 15 miles per our to 35 miles per hour before. and fromt hat u can tell a lock up would not be the problem cuz i do beleive that the t-5 or any manual transmission for that matter doesn't contain one but i could be wrong, so please correct me i hate having incorrect information. as far as i can tell eerythign else is fine. the only MOD's to it are an open element althoguh i did change my thermo and for some reason after changing the thermo the mileage wasn't effected at all... in fact i beleive it may have gone up so thats really confusing. f theres anything else i could tell you guys that will help you guys to help me i'd be more than glad to share.

oh yeah and by the way you guys have been awesome so far thanks for all the help, you saved me from having to buy a honda(im shivering at the thoguht of it) when i couldn't get the car to start again.

Oh yeah and by the way even after i replaced the o2 sensor abck in december of 2001 the mileage and emissions still barely passed.

ShiftyCapone

iTrader: (7)

Dewey, where do you get a GM O2. Autozone and other give you a bosche one don't they. Atleat that is what they gave me. I have a bosche one and I to run rich and as a result have poor mileage. I got rid of the platinum plugs but I am still a bit rich. I blame O2. I need to data log to be certian but the car is 2 hours away.

Ronny

iTrader: (1)

gmpartsdirect.com

sqzbox

What part of the emisions test are you failing? That should tell you something. They like you to freak out in cal. so you will pay them to fixit for you by not telling you anything about what is wrong. (been there). I payed the money for my GTX once and I barely made it home! but I had the sticker!!!! so I fixed it back!

joshwilson3

.

90RS305

Is it actually right? I had a hanes manual and it was the biggest piece of $%!& on the planet. NOTHING in it was correct about my car except for the fact it said I have 4 wheels.

13-15 huh? Wow, I don't know where my car gets it?! I have the EXACT same setup (stock LO3 with open element) and I get 20 in the city and a mind-boggling 30MPG on the highway! Car has almost 117,000 miles on it, too. Does it normally run rather hard, or is it still a strong car? Check out your tranny too, if it's working too hard that could be a big factor...

Bruce (90RS305)

MrDude_1

theres 2 books for our cars.

one is mostly 82-83 and other early car stuff.... its red.

theres a blue one thats later model stuff.... thats the one you want.

nick harmon

not trying 2 step on your toes mr.dude, but the blue haynes manual is **** too! but as far as changing the filter screens on the injectors the book does tell u how to do it. but even without it, its pretty straight foward and self explainitory. it really is quite simple, you should have no probs, just dont mangle the gasket if you dont have a new one. ive done it twice now and havent screwed anything up yet, and when it comes to working on anything after 1979, im a total tool.

MrDude_1

lol...i agree that the book doesnt tell you nearly enough...


i mainly use it for the wiring diagrams in the back....




installation is reverse of removal. for further direction, please take the car to a professional. your miliage may vary. offer void in alaska and hawaii. no purchase required. see dealer for details.

nick harmon

xrsxj

well im failing jsut abou every part of emissions but especially hydro carbs... and i was tlaking baout the fuel filter not the injector filters im prettys ure those are fine i could be wrong, wither way i'lll check those too... thanks... is there anythign else that could be screwin the car up ... i got it to pass emissions by retarding the timing 6 degrees and it passed on everythign easily is that any help

90RS305

hehehehahehahahe.....*snicker*.....HAhahAHahAHHAHAaha!!!


.......I think I just dropped a lung......

xrsxj

ok guys i changed out my distrib. cap and rotor and my fuel filter it already feels better now to see if the mileage goes up, oh by the way i advanced the timing by 4 degrees and got almost 16 MPG at maybe 3 gallons WOT most of the time, so im optimistic thanks for the help, any more ideas would be awesome you guys are life savers.

xrsxj

ok guys my mileage went up but its still not where id like it. ROughly estimating i'm gettin about 16 to 17 MPG city/highway... 10 times better than it was, io got about 225 to about 13.750 gallons, which i like better than 190 to 14.5, thats at about 65 miles of highway the rest city driving, is that the best mileage i can expect or can it get better from there ???

Dewey316

thats doing pretty good, due to gearing, and design these cars don't do well city wise, on a hi-way trip you should be getting mid 20's around town the best people get is 18-19 range, but alot of city milage comes from driver habbit.

MrDude_1

that sounds about right if theres any city traffic..... you really dont get into the 20s until you get around 90% hwy driving....... but if you have hwy gearing and are light footed, you can get some amazing road trip numbers....

90RS305

You have the EXACT same setup I do (305TBI T-5) and I get 20mpg city/29-30mpg highway. Keep in mind this is RACING EVERYONE AND THIER MOTHER... I have done nothing to my car, and it has 117,000 miles on it. You do have room for improvement. It may come from an engine rebuild, but it can get better...

Bruce (90RS305)

xrsxj

nah man that exaust in your sig is a major upgrade. It makes it an extremely large difference but in fact i do beleive that i could make it to about 18 MPG stock but not racing like mad, i need to clean the injectors still. compression was checked about 15000 miles ago and was dead on perfect. Im using 87 pump gas and its workin fine with me im not complaining about my 17 MPG thats a **** load better than 13 to 15 at best what i was getting before. Thanks for all the help you guys i can't stress that enough you guys have helped me save hundreds in mechanic fees. i owe u guys and every member on thsi board that at least tries to help there fellow F-Body owner ... thanks again

90RS305

Actually to be honest with you it didn't really do jack or squat (still a little annoyed about that) but yeah it was getting that gas milege from the get-go. Ohh, lol, I didn't know you were pumping 87 in it. My car hasn't gotten a drop less than 91 since I bought her. Bet ya if you used it for a month or so you'd see it jump up to where I'm at. MAJOR difference...

Hey man your welcome. I think I speak for everyone on the boards here that we're here for just that purpose. Glad we could help and happy driving!

Bruce (90RS305)