My name is Josh and I am lost; I have been keeping a record of everything including mpg since I've had this car, and after all this fixing and mending I am still getting an average of 10.7 mpg, i have been keeping track of my mpg since Jan 2013, Although i did get one random spike of 12.5 mpg.. My average stays around 10, which is contrary to the governments website ((http://www.fueleconomy.gov/feg/bymod...t_Camaro.shtml )) which states at a minimum i should get around 17 mpg...So after reading this any ideas would help, the only thing i haven't touched is the fuel rails, WHAT COULD I DO TO IMPROVE MPG???
BTW here is the general info and fixs I've done:

-1986 standard sport coupe
-2.8L V6 FI
-Timing is at factory recommended setting of 6 degrees (roughly but close)
-Have reset the idle screw to lowest possible idle, using factory recommended procedures
-Checked air flow system and cooling system all in good working order
-Have checked tps sensor and completely cleaned the throttle body and replaced the IAC valve and thermostat
-Set the TV cable to correct length (had a few shifting problems that this corrected)
-Have replaced fuel pump and fuel filter and verified lines are good and hold the correct pressure (although it doesnt retain pressure once you shut off the car but that brand of fuel pump i got apparently is meant to do that, but once you turn on the car with out turning it over the pump engages and pressurizes the lines..so no biggie i guess)
-Exhaust system has a brand new flow master and tail pipe, and if it matters can pass DEQ, we did have a leak at the manifold due to broken bolt and a bad flange gasket but have since fixed and mended everything and have no leaks..Also slapped on a brand new EGR valve
-New expensive tires
-Cruise control wires removed system still in place
- No visible vacuum or exhaust leaks
-New cap and rotor and spark plus/wires

 

Is your check engine light off? Does it ever come on? Thats terrible mileage, does it smell rich out of the tailpipe? TBI could be whacked out??

I have the 5.0 and get 25+ on the highway with 3.42 gears and the 700R4.

Possibly the V6 struggles to move the beast?

 

Well the idiot light used to come on a lot, when i got the car it needed a lot of t.l.c.....but it never comes on anymore, since I've fixed and replaced a lot of assorted parts and sensors on the car. Im pretty good about checking codes as soon as the light comes on and remedying the problem. As far as tbi, that's the fuel injectors correct? (this is my first project car...I'm in the learning phase) if so thats about the only thing i haven't replaced or screwed with because of cost, i don't want to replace it unless i get a pretty good "hunch" that there the reason my car sucks gas...and yes my car struggles on taking off and the trans isn't in superb shape but its pretty decent considering age, anyway once I'm on the highway and i hit highway speeds the car doesn't have any problems mainting that speed..its like cinder block on wheels lol..But getting to those speeds is slower than id like...slower than my moms v6 Camry

 

Ill go stick my face in the tailpipe tomorrow and tell you wether it smells rich or not never really noticed lol..thanks ill have someone else take a whiff too just to be sure

 

Verify that the ecm is going into closed loop.

Rolling resistance is also very important. Proper alignment and good tires. Check that none of the brakes are dragging. Failing brake hoses up front are notorious for not completely releasing the calipers, causing drag.

 

@Cudascious So i turned the car over today and took it for a spin, the computer threw no codes at me, so still no check engine light coming on....and no its not running rich and there is no smell of fuel..When you say "tbi could be out of whack", i have mpfi injection system with 6 fuel injectors..do you mean that? If so thats the only thing i havent messed with, is there anyway to test them without pulling the plenoum off?

@naf Tires are almost brand new and are good tires, inflation is correct and my alignment is good, Brakes do not appear to be dragging and when the car is on jacks the wheels freely rotate, How do I check to make sure my car is going to into closed loop mode?

Thanks for helping me out btw

 

"New expensive tires" - What size tires and wheels? Did you get the front end aligned when getting the new tires or is there anything at all loose in the font end? (alignment kills fuel economy)

Bump the timing up a bit from 6 to about 9-10*

What temp is the engine running at? If it's not got the stock 190-195* thermostat in it then replace it with the proper temp one.

Check ALL vacuum hoses and PCV hose, etc. for any signs of being loose, cracking, bad connections, etc. vacuum leaks can cause a big drop in economy too.

Clean the intake and throttle body and piston/valves of carbon/oil deposits - use your favorite method - seafoam, berryman's B12, cheap carb cleaner, water, etc. I've had the best luck with cheap old spray carb cleaner so that's what I go to normally (and I've usually got a can lying around when I get a new to me car).

 

@bwiencek
- I spent 500$ on the tires there michelin radial ta tires, and i went with the OEM size specs for the tires, i didnt have them aligned but i dont have any wear problems and i wouldnt think that alignment issues unless major would cause a drop of almost 10 mpg. So tires are not the issue
-I had the timing had 10 * and 8* with about 4 fillups per and no change in milelage..so i just back to factory setting which is 6*
-The temp never really goes past 220 but mostly 190ish is where its at once its warmed up and im driving around..and i do have the oem thermostat model on the car
-I have no vacuum leaks as i said earlier, Ive combed the car over and over and replaced anything that looked even slightly worn, all sensors are new and they are getting correct voltage
-Lastly I cleaned the throttle body pretty thoroughly with a new IAC installed and adjusted to spec...still no change

Thanks for the input, do you have any other suggestions?

 

Oh Multi port ok.

I was reading an article about fuel regulators being faulty and causing all kinds of problems.

I assume the idle comes down to normal when it goes into closed loop?

How about a possible obstructed catalytic converter? That will make it sluggish and kill mpg. But you should notice the car struggling to get to high rpm.

Im new to computer cars relatively, Ive been learning a lot since I got my Formula though.

Possible Tranny slippage? You said sluggish. I had an 89 Chev stepside that was running horrid. Did everything I could, in the end a junkyard ecu change solved all my problems

Have you reset your ecm since doing the egr and stuff?

Just trying to throw ideas out there.

Man I got some crazy stories about my neighbor and his love of seafoam, he doesnt use it even remotely like it should be used (directly injects it) and he uses it too much, now his truck smokes all the time (burns oil), I think he washed away important sludge and carbon that was helping to seal the old engine. Older engines can react negatively to intense internal cleaning....
lol

 

-FPR naw fuel pressure is steady, doubtful
-Closed loop does make my car return to a "normal" idle of 1,000 (factory is 4-500 but i think that might be unatainable)
-catalytic converter is good
-Tranny slippage no, but i do have high shift points, i think some doucher but a aftermarket part on the tranny that makes it "perform like a racing car" (mechanics thoughts on that)
-Yea i reset the ecm almost every time i do any-work on the car lol..i usually unplug the battery just to be safe

LMAO the seafoam huh? I used to use that stuff quite a bit, no oil leaks though....yet *knock on wood. I heard through the macgyver network that you can take a can of that stuff and feed into a certain vaccuam line and spot leaks because it somehow smokes...im wary of this shortcut sounds suspicious lol

anyway..my current thoughts
fuel inj issues? 275$
bad o2 sensor on exhaust pipe? $cheap
how would i check tthe fuel injectors without pulling the engine apart to get at them?

 

Fenderman@ Looks like you are putting that v6 back to factory condition. My camaro has the same problems...and I was going to throw an oxygen sensor on mine and hope for the best...cheapest fix for $20!

The next thing would be the fuel injectors. Look through the schematics, and pull/probe the connector, and read the ohms on the solenoid coils. They are suppose to be *exactly* greater than 12 ohms--otherwise replace, which is a breakdown of the coil wire. There could be other problems with injectors as indicated here:

https://www.thirdgen.org/forums/tpi/...e-testing.html

If the O2 sensor doesn't work, either aftermarket refirb injectors for me. I don't have the money to throw at this, or I would get a new ECM. Let us know the fix!!!

Mythbustors did an episode on tire pressure, and higher pressure tires get better mileage!!!

 

Verify closed loop before going any further. Best use a scan tool.

Most likely cause is stuck open loop causing a too rich condition and poor performance.

Scan tool will provide you with the data the ecm sees. Don't just throw parts at it.

 

Agree 100% - especially since you said it idles around 1000 RPM - that's way too high and to me says it's not going into closed loop operation - it's either not getting the engine coolant temp sensor signal (different sender from the gauge signal) or something else is causing it to run in "warm up" mode - I'd really check the resistance of the engine coolant temp sensor and see if it's within spec's

 

If it's idling at 1000, either his curb idle is set way to high, or I'd tend to lean toward massive vacuum leak.

 

@naf Throwing money* and parts at a vehicle is always a gamble. But in this case, an O2 sensor could very well cause a rich/lean condition...and I don't know the condition of that sensor...

Naf, If the engine is never in closed-loop mode, what would be the cause? o2 sensor! ecm???...But given the OP's statements, the o2 sensor was the cheapest on his list...

The ECM can be costly just to buy a new/used as with fuel injectors.

Lecture:
*Throwing parts at a vehicle absent of troubleshooting is "shotgunnning" it...But when you have a camaro that has been setting for a year, and you have multiple issues with symptoms pointing to the cheapest fix; its probably best place to start--and it generally removes that from the culpable list. The difference: a vehicle with mostly new parts to start, then "throwing parts at it" is just sloppy work, granted. But if you have more than several unknowns, swapping parts often works. I always keep my "old parts" for these situations. A quick fix keeps me out of a cold garage, and it can be the difference in a bona-fide hero fix!

**now carry on...(swap until you drop)--then get focused, and troubleshoot properly. It is merely technique. And don't get me started on technicians that never break things who do not fix things. Like the techs that order expensive parts and your vehicle sits in their bay for a week and it still doesnt fix the problem. I still have the $150 EGR invoice w/ $175 labor bill (old Saturn) from the dealership, because the code came back as EGR, instead of the actual $35 junk yard ignition! When you aren't paying $175 labor, you can buy a dozen O2 sensors and still come out ahead. We are all learning...swapping parts is part of that learning curve. Put it in perspective.

 

bwiencek,naf,Ozz1967: You guys might be right about the engine idle, if 1000 rpm is too high of an idle. I suppose with ethanol and corn fuel, engines tend to run sluggish these days...

What should the engine idle be at for the 2.8 L, V6? I had sifted through the 3rd gen forums and 1200 to 800 seems to be normal...

I will be putting in the oxygen sensor this weekend, so I will let ya'll know.

 

okay ill check the closed loop operation, ill do some research on that and how its supoose to work and how to test for it as well as look into getting a scan tool...here's one thing though when it warming up idle is at 1,500 rpms until operating temp is met then the idle drops to around 1000 rpms... so wouldn't that signify that closed loop mode is operational since the idle drops once operating tem pis met and that the actual problem lies within where the basline idle is?

 

bwiencek
okay ordered the part and installed tunerpro rt, did a diagnostic and it said closed loop is running although the idle increased as soon as i plugged the cable in and the whole time the idle was higher then what the ecm says it is....at least my rpm gauge is adifferent although i can tell y car is idling higher with that cable in

 

take a can of carb cleaner and spray around your intake gaskets and vac lines (carefully, in small doses) if you notice a change in engine speed and/or o2 readings you've just found a vacuum leak. as already stated coolant temp is important for CL operation as well as o2. what is your coolant temp sensor reading at operating temp? it should be around 200. also look at your blm's they can indicate a rich or lean condition. should be at or very close to 128. also, pull the vac line off your regulator and check for fuel in the line. these old cars rupture diaphragms all the time and i've seen new ones crap out too. check the MAF and see if its dirty too

 

Do a coolant temp sensor resistance test. It should be around 200 ohms at 195*.

 

ok will do, ill check all those things out and come back and post the results...may take a few days

 

rick90gta,ex-x-fire
Ok coolant temp sensor checked out good and blms are exactly 128 according to tunerpro and aldl when i plugged the cable and ran the car.
I pulled the vac line of the FPR and theres no fuel whatsoever barely even smell fuel and the pressure is at 39 psi. The maf sensor is clean and i pulled of the throttle body and cleaned it really well also..and still no vac leaks that i could find.
I also ohmd the fuel injectors and they all are good... so still have slightly high idle and poor fuel economy any other ideas?

 

and it is going into closed loop opertion mode, i checked with a scanner tool

 

have you done a base idle reset and tps adjustment? tps should be closed .5v open 4.5-4.8v. is your brake booster leaking vacuum? it's an often overlooked area. if you can, double check your timing with a light, with est disconnected. also take the vacuum line off your egr valve and check for vacuum at idle. the egr control solenoids fail sometimes, you should have no vacuum unless you are at cruising speeds. cleaning or replacing your iac may help your base idle speed, check commanded iac counts vs. actual counts with scanner.
i'm a professional and have drawers full of known good parts for these types of situations, obd1 cars unlike modern ones are limited in viewable data and the refresh rate is slow. i know this stuff can be frustrating, just keep with it and you'll find it!

 

Make sure the timing advances when you rev it.