WORST running fbody ever, 11MPG please help!

[Reg Kmet]

Hey, well, as the topic states,my bird is seriously sick, for the past 4 months i have been averaging a sickly 11MPG city driving and this is killing me, im either going to have to put my baby down, or do my best to get it fixed. first of all, some history on the car

95 3.4L v6 M5. with approx 105k Miles on the clock. EGR valve blew off the cat at around 70k miles, and i blocked it off w/blockoff plate, except for the ses light all appeared good. rear end has 3.42's in it, i have delco rapidfire plugs and taylor wires (approx 15k miles on them) accell coilpacks and a new ICM (coilpacks all test good as does replaced icm) I do have asp underdrive pulleys, and a b+M ripper shifter. the exhaust is a different story. i have 1 broken bolt in the passengers side exhaust manifold, supposedley not causing any probs according to mechanic yet. had to replace cat, replaced with a catco, approx 20k miles on it, had some issues with the cat back, the pipe wasnt clamped too well and it was leaking after the cat. somewhat fixed this

Now onto the issues. #1, driving in the city, respectably i get 11mpg on average, im in canada i get around 280 k per tank of gas, almost around 11mpg. now the car hauls a$$ in 1st and 2nd gear, come 3rd and up, its like the car is stuttering i cant tell if the car is being starved or if it is backfiring, the car picks and chooses its fights, i can hammer on it and it may spit and stutter, or it may just honk and take off, easily chirping and pulling hard on the 1-2 shift, secondly, i have noticed alot of carbon on my tailpipes, if i park the car and rev it to 3-4 grand and hold it, i'll blow carbon all over the place. got a little bit of chatter in the valvetrain, nothing excessive con sidering the miles, and i have the tranny seal leakin, as well as an engine seal somewhere, on average, addin a liter of oil every 2 months, not a huge leak, but still there.

any help you can provide me with will be greatly appreciated!

Reg

[96RS Alex]

I was getting horrible gas mileage on my '91 Firebird until I realized the original O2 sensor was not replaced. I had the sensor replaced and decent gas mileage returned. With that in mind, you may want to try replacing the 02 sensors. Your vehicles computer had enrichened your fuel mixture due to a bad signal.
First clue was the excessive carbon you are spewing out.

If that seems to do the trick, Seafoam your 3.4L V6 for better results. Perform a Search for your personal review on the benefits of Seafoaming your engine.

[Reg Kmet]

Hmmm, i did 02's at around 65k miles, so thats a possibility, i am thikin of seafoamin, but its tough stuff to find up here, but i'll see what i can do,

[Turbo V6 Camaro]

fuel filter? that helps alot too

[FunkZ]

Is the SES only from the EGR? Is it possible there is another code hiding in there? Have you had it scanned?

Have you cleaned the throttle body out recently? Checked for air intake restrictions? What do the plugs look like? Are they all the same color/condition or is there a cylinder or two that are different?

How is the oil condition? Does it smell like gas? Pull the vacuum hose off the FPR and see if any gas leaks out.

[Reg Kmet]

Update, ok the egr's been unhooked for 2 years, and i have grown custom to the ses lights, and no i havent had it scanned, tried the paperclip deal, and no go. the intale appeared ok, and i will check into replacing the PCV and fuel filter, cheapo parts to fix. is there any merit to replacing the o2's at this point?

INTERESTING DEVELOPMENT

after work today i bought 2 cans of seafoam, i threw 1 can in to a little less than a quarter tank of gas, and honked on it on my way home. the stutter/mis/hiccups have been GREATLY reduced, i cant explain it but in park when i would rev it to about 4500 i used to get a very raspy ricey pop sound, that has dissapeared. thats with putting about 12 miles on the car. a bud is coming down in a few mun and we are gonna seafoam the engine. I'll update you guys tonight, but keep the suggestions coming!

I appreciate all your help!

[BLLDOGG]

either way, you need to have the code scanned. would you ignore an alarm when its trying to tell you something is wrong? no, so why ignore your cars way of telling you something is wrong?

[blacksport]

O2 Sensors? Spark plugs?

Is the smoke black? Taking the egr off is suppose to make cars run rich isnt it? Sounds like a symptom.

[Reg Kmet]

ok update, i am going to look into getting the codes scanned, im just short omn time and cash, but this was kind of interesting, back in spring, the car had a really bad stumble, felt like it was only runnin on like 5 cylinders, well over the past few months the probelem seemed to magically get better, lol. today the car ran champ when i added seafoam to just the lil bit of gas i had, then this happened, i added it to the crankcase, and then to the brake booster line (fumigating my entire parkade i may add, lol). now, it left 2 4 foot strips of black carbon behind each tailpipe, but even after a few good spirited runs, the car is back to running like original crap, something i noticed that was interesting tho was this, when i was removing the brake booster line from the master cylinder, the car seemd to all of a sudden perk up, as in run excellent when i hit a certian spot wich is now leading me to think , vacum leak possible? when i doused the seafoam in the first time i got white smoke in the engine compartment, is that normal? hopefully i am makin progress. Would appreciate if anyone has a pic of where the pcv valve is on our cars, i wanna try swappin that out tomorrow and see what happens. also i think i should be lookin into the EGR...

[Cat Toys]

Try Autozone.com repair info. it shows component location. Another cheap fix is to run an additional battery ground to engine. If you are getting carbon out the tail pipe then your plugs are carboned up. Check the coils. Pull them and look for cracks. Spark tests are very unreliable.

These cars were not made to be worked on without a computer. I bought a software package and a interface off ebay for under $ 100.00 now I just plug and log. No more guessing and testing. Having a baseline to compair it with kind of like before and after is neat . Now I just wash and wax.

[CamaroRob97]

Well if you get the smoke to come out the engine bay too, you obvisouly havea exhaust leak up there. If you had a vacuum leak you would suck in extra air and run lean not rich. You would have a higher idle also due to the extra air intake.

Does the 3.4 have the 16 pin gm obd1 hookup? If it does then thats why the paperclip wouldnt work.

You said your car has had a misfire or hesiation problem, that will deffentially kill your mileage, that stuff doenst really cure it self, things only get worse. Not burning all the mixture means lots of carbon buildup on the pipes.

CHECK your plugs they will tell you alot. LIke viper said if you never have changed the fuel filter then do it, either way it should be done.

Ya and not running a EGR will decrease gas mileage.

Once you check the basic stuff then people will be able to help you better.

[camaroman1181]

vaccuum issue? say that cuase you said the car ran better with the booster line off. could be a map sensor? also, a 95 3.4 will not work with the paper clip test. 94 usually wont test either. besides that, it sounds like you are running excessively rich. check the o2's if its not a vaccuum leak or map sensor. tps could be it too, or the idle control motor. keep us posted...

[Reg Kmet]

ok, here's what we can confirm, passengers side exhaus manifold has a broken bolt, and thus, prolly a small leak. the car seemed to run a little better when i played with the vacum hose, but the results were very short lived. I've got a new fuel filter here that im gonna throw in when i get a chance. I've got crap for tools here in the city so im gonna do my best to try and chek the plugs. i was under the impression that if my 02's were bad that after the car warmed up and went into open loop, then it would run like crap, buit it runs like crap from the get go when the comp is in closed loop.

[96RS Alex]

Hey Reg,
I hope by Christmas you get this beast running! If not, you may want to hint at someone for a decent handheld as a gift by then. Point is more help could be offered if we have codes to read and would expedite your resolution here.

Keep us posted on the fact finding, this will be good once we know what's causing your problems.

Oh yeah, good luck changing plugs in cold weather up there, you'll need certain tools and lots of patience.

[Reg Kmet]

lol, no kidding, i am used to "improvising" tools, my shop consists of an unheated, poorly lit parkade, lol. I may be on to somethng, next week im making the trek back to gimli (approx 75 miles away to my friend/girlfriends dad, who is in fact a mechanic who owns his own shop [img]smile.gif[/img] I shoud hopefully make some progress, thanks for all the support and help guys!

Reg