Fuel economy going down sharply. *UPDATES*

[IcePickFreak]

Best bet would be to get it to a mechanic who can actually diagnose problems honestly. Someone needs to read fuel trims and see whats going on.

In the meantime cleaning the MAF wouldn't be a bad idea, and is cheap. Just be sure to get cleaner specifically labeled safe for MAF's (aka electronic cleaner). Also, the 4.3L is actually a good motor, but does have it's little quirks. The IAC valve get's gunked up and tends to stick. I'd pull this (2 bolts) and clean it as well. It's mounted on the back of the thottle body.

Below is a pic to show what it is, it's a pic for a z28 but the whole throttle body assembly is pretty close to the same on the 4.3L. I'd get some sensor safe throttle body cleaner for this. You can use the MAF cleaner here, but it's a bit weak, but DO NOT use throttle body cleaner on the MAF.

 

[shortylickens]

BUMP!!​

Alright, called up the dealership and they said cleaning the O2 & MAF sensors is impossible. They did say they would diagnose my complaint for 101 dollars.

Deal or no deal?

 

[exdeath]

Guys how you take all this shit off and make car run? It's ridicules all these gizmos they are putting on cars these days.

Anyone remember distributor, coils, starter, engine? I got 19 on a nowaday standards "big" nova forever.

Yeah I remember having to crank and stalling for 15 minutes to start up in winter because of a failing choke, same jets all year round, points failing in the distributor all the time, etc...

Underneath it's all the same as it ever was, just all the crap was replaced with solid state parts that last forever and never need messing with. When something like a sensor goes out, it's actually quite rare in the grand scheme...

 

[exdeath]

BUMP!!​

Alright, called up the dealership and they said cleaning the O2 & MAF sensors is impossible. They did say they would diagnose my complaint for 101 dollars.

Deal or no deal?

No deal.

MAF is very accessible to clean. O2 sensors not so much, they become contaminated and will pretty much be destroyed by any kind of cleaner capable of cleaning them.

MAF = just beyond the filter/inleft, remove inlet pipe and spray out with MAF cleaner/ electrical-plastic safe TB cleaner type stuff.

O2s you can test easy with a volt meter if you can find a test point (unplugging them and testing directly is fine, car will still run and just go open loop and maybe throw a code). They should cycle back and forth from .2v to .8 volt every second, slow enough to see on a volt meter. You only need be concerned with the front O2s, the rear O2s are only catalyst monitors and have zero input on fueling.

Other culprits:

-Coolant temp sensor, also easy to test, check voltage when cold, cross reference with service manual for voltage at the ambient temp, check again when hot, check voltage again at your engine's operating temperature (most cars run 180-190F). Will cause excess fueling because the engine is always "cold", may keep the EFI in open loop.

-Auto trans? Check fluid, torque converter lock up function, be aware of excess revs, delayed upshifting, etc.

-Vacuum leak causing excessive fuel trim. No noticeable problems because EFI is able to compensate for it and keep idle speed regulated (will show + fuel trims at idle, - fuel trims at 2k+ RPM, and will show very low idle control opening, despite having normal or higher than normal airflow at idle). EFI is extremely sensitive to unmetered air; something as retarded as a dipstick not seated right will allow unmetered air through the PCV system.

-excessive load on engine (trans problems, maladjusted parking brake, seized pulleys or accessories, etc)

Someone who knows how to use a scanner can log short and long term fuel trims, load, airflow mass, manifold vacuum, timing advance, idle motor duty cycle, etc, and should be able to zero in on the problem. That would be worth the $100 to you, but only if they definitively determine the cause. All the above manual tests can be observed real time on the scanner, eg coolant temp value from the sensor, eliminating a lot of manual labor.

 

[AMCRambler]

Check tire inflation too. I was about 8-10 pounds low on all my tires because my tire gauge was effed up. This killed about 2mpg on my GTO.

 

[shortylickens]

Check tire inflation too. I was about 8-10 pounds low on all my tires because my tire gauge was effed up. This killed about 2mpg on my GTO.

I keep all four at around 45 PSI, norm for tires of that size and a vehicle of that weight. And my economy has slowly gone from 18 mpg to 10 over the past couple years, so I dont think its the tires.

 

[shortylickens]

OK, my old mechanic definitely fucked me.

Got the front lower ball joints replaced two years ago so they would pass inspection. New mechanic today said they looked like hell and should probably be replaced. He didnt think they looked like they had been done a mere two years ago. They looked original to him.

He also said that 18mpg was extremely good and if I somehow managed to get that it was more luck or bad calculating than anything else, but 10mpg is still low. They are going to clean the fuel injectors and one or two other things. Should have it done this afternoon.

 

[LTC8K6]

Last couple months been using mostly premium.

Stop.

 

[shortylickens]

OK, got it back from the dealers mechanic, which I normally never use but I am pretty sure my local guy has been fucking me.

1st off: When I moved to virginia 2 years ago I was failing the safety inspection cuz my front lower ball joints were shit. My local guy claims to have replaced them both. When I recently complained of low acceleration and poor fuel mileage he charged me 340 to diagnose and couldnt find anything wrong. Claims he put in some sort of fuel cleaner that only mechanics can get ahold of. Also changed my fuel and air filters. Did my safety inspection last month and said everything was just great. No issues.

2nd:
Still having acceleration and mileage problems. Take it to Chevy dealer cuz I am suspicious.

He says the front lower ball joints look like shit and need to be replaced. Says they didnt look like could possibly be only 2 years old. Also noted I have some minor frame damage which was probably caused by a rock up in the mountains when I was bouncing around. Says my break pads are close to death. Those things confirm the old mechanic is incompetent and a darn fine thief. BUT..........
New guy also says its physically impossible to clean any oxygen or air flow sensors and they never ever have problems anyway.

3rd: The bill

A: Complaint $0.00
B: Diagnosis $0.00
C: Goodwrench Vehicle Inspection $0.00
D: GM Injector Service and diag for drivability $152.64
E: BG Air induction system service to remove harmful deposits in the intake $78.95
Fuel IND Cleaner $54.00
F: Replace Air Filter $16.95
Air Fltr $27.43
G: Fuel Filter $50.58
FILTER $28.96
H: FDCI REPAIR $0.00
I: Replace lower ball joints $326.39
Stud Kit $239.10
J: Sway link pins $80.92
LINK $44.66
K: Replace License Plate Light $12.88
Lamp $16.48
Bulb $1.40
L: Align Front End $69.95
Customer Pay Sha for repair order $1.75

$1223.73

So, did ol' shorty take it up the ass?
Should I have been in the garage with my father instead of playing video games all my life?

 

[shortylickens]

Oh, for reference the thing does not accelerate any better and it will probably take a couple tanks to see if the fuel economy improved. That 18 miles per gallon I got when I first bought it was just a fluke. It should never have been that high. So either I did the math wrong for two years and all of a sudden just got the math correct, or somebody was slipping magic go-go juice in my tank.

 

[fbrdphreak]

Yes, your old mechanic was raping you. Don't waste your money on special fluids or treatments. About the only thing is worth a damn is a transmission flush service. I would report your old mechanic to the BBB, what he was doing is outright theft IMO.

I hope this dealership actually removed your injectors and re-flowed them to ensure 100% performance. If they just ran some pressurized cleaner bullshit, I can't see that being worth the money.

You definitely paid dealer price on the rest of that stuff. A competent independent mechanic would have run you 2/3-3/4 of that cost. But you gotta do what you gotta do.

And it is NOT impossible to clean the mass airflow sensor. I'm assuming you have one - some newer cars measure air pressure in the manifold, but I'll bet your 4.3L beast has a MAF. If you buy a simple Hanes manual, it'll tell you how to pull the MAF. Then just pick up some MAF cleaner at the auto parts store and follow the direction on the can.

You can't clean O2 sensors, just replace them. I'd hope that dealership is competent enough to check any codes that might have been set by a failing O2 sensor.

As someone else mentioned, a clogged cat could result in severely reduced performance and fuel economy. However this too should be evident to a competent mechanic. If it is a clogged cat, it will get to the point that the engine will barely run or not even at all.

See how happy you are with the changes. If your fuel economy still sucks, I would do some research and find a place with experienced Chevy techs. The technology on your good ol' S10 is very common in Chevy's of that vintage and Chevy's of that vintage are very common, so you should be able to easily find an experienced place. Just make sure you get good references this time

P.S. I don't know that 10mpg is unreasonable for an 8 year old small pickup with the beastly 4.3L. That thing was NEVER easy on gas and if you're doing pure stop & go driving with more short trips than long trips, 10mpg is not unreasonable. Not great, but not out of the realm of possibility. If you really want to see how bad she's doing, fill the tank up at Station XYZ. Get immediately on the highway or a long 2 lane backroad. Drive gingerly at 55-65mph for maybe 10 miles. Turn around and drive back in the same manner. Fill up at Station XYZ again. Measure real world fuel economy, in a situation that is truly as ideal as possible for fuel efficiency. If it's still shit, you have a problem. If it's more in line with EPA estimates, you just have a gas guzzler

 

[LordMorpheus]

You CAN clean your mass air flow sensor, and a dirty MAF is a very common cause of a check engine light, poor mileage, and poor behavior under throttle.

That said, it sounds like your local guy was fucking you.

 

[Meghan54]

Oh, for reference the thing does not accelerate any better and it will probably take a couple tanks to see if the fuel economy improved. That 18 miles per gallon I got when I first bought it was just a fluke. It should never have been that high. So either I did the math wrong for two years and all of a sudden just got the math correct, or somebody was slipping magic go-go juice in my tank.

I think you still have a problem somewhere.

For reference, we have a 2002 Blazer with that same 4.3L V-6 engine.....a great motor, btw. The Blazer has, as of today, 225K miles on the clock. It still manages right at 20mpg on the highway and around 16mpg in city driving....depending on state of tune. I do know ours hates anything other than AC Delco products, esp. spark plugs, spark plug wires, cap, rotor. Have tried other brands of that stuff and in every case, performance dropped noticeably along with gas mileage.

But the nice part of the AC Delco plugs.....we do get right at 80K or so out of them before they begin to show they need replacing. As for the plug wires.....do NOT buy a set from Advance, AutoZone, etc. They'll rape you on the cost (Advance has a set of OEM AC Delco's for $155......). RockAuto, on the other hand, had a set of AC Delco wires, the exact same set in the exact same box as Advance's $155 set, for $25 + shipping.

 

[shortylickens]

Sorry I think I forgot to mention something. I never had a check engine light and none of the mechanics ever reported any error codes. All my complaints were just personal observation. So far as the onboard computer is concerned my vehicle is in excellent condition.

Thanks to everyone for the tips. I will try the other things mentioned probably after the new year when I have some new money.

 

[Vette73]

Sorry I think I forgot to mention something. I never had a check engine light and none of the mechanics ever reported any error codes. All my complaints were just personal observation. So far as the onboard computer is concerned my vehicle is in excellent condition.

Thanks to everyone for the tips. I will try the other things mentioned probably after the new year when I have some new money.

As said , many times, a dirty MAF will not throw a code. That and seeing as you said you had/have a K&N filter I be willing to bet your MAF is pretty dirty and is causing your air/fuel ratio to be off.

Throw the K&N filter away and clean MAF sensor and try that out.

 

[MegaVovaN]

Anybody think that mechanic who "fucked" him actually cleaned MAF sensor last time?

 

[halik]

CRC spray the MAF and replace o2 sensors.

And yes, you took it in the pooper with most of that stuff. Generally they will just pour 15 dollar injector cleaner in your tank and charge you $200 for diagnosis and cleaning.

 

[CraigRT]

Could be failed thermostat causing engine to run cold (with lower temps, this is a very distinct possibility) This in turn causes the engine to run very rich to try and warm itself up.

 

[thescreensavers]

Although a lot of people feel like fuel additives are BS (imo most are) I've had great luck with chevron w/ techron fuel cleaner

yes techeron has PEA so it works look into Redline SI-1 it has a higher PEA content then techron. So its better but they only sell the redline stuff at pepboys locally

 

[shortylickens]

Could be failed thermostat causing engine to run cold (with lower temps, this is a very distinct possibility) This in turn causes the engine to run very rich to try and warm itself up.

According to my thermostat the engine heat is just fine once it gets going, even in the winter.

 

[halik]

yes techeron has PEA so it works look into Redline SI-1 it has a higher PEA content then techron. So its better but they only sell the redline stuff at pepboys locally

There's also 3M one with PEA, but it's like 3x the price of techron. You can catch the latter for like 5-6 bucks on sale at advance auto.

It did kill my new fuel filter though after running a a bottle or two on couple galons of gas...

 

[thescreensavers]

There's also 3M one with PEA, but it's like 3x the price of techron. You can catch the latter for like 5-6 bucks on sale at advance auto.

It did kill my new fuel filter though after running a a bottle or two on couple galons of gas...

3M? lol since when do they make chemicals for cars, other then for paint and tape?


Hmm, it killed your fuel filter? How would it do that lol? The Return line?

 

[halik]

3M? lol since when do they make chemicals for cars, other then for paint and tape?


Hmm, it killed your fuel filter? How would it do that lol? The Return line?

Crap from the tank got lose and ended up in the filter. I guess it did its job

 

[kornphlake]

I had a 1999 blazer 2wd and it did in fact go through ball joints quickly, not two sets in less than 50k miles, but it went through ball joints more than most vehicles. I can't recall which brands are better now, but there are one or two brands of ball joints known to be less durable than others, it's a common enough problem that I'd expect a reputable mechanic to use the better parts.

The fuel filter should be replaced regularly unless you want to replace the fuel pump regularly, I found that out the hard way. IIRC the MPG on our blazer was mid to high teens on the highway and low teens around town, never 18 MPG around town.

I remember when the thermostat went out, I'd taken my scout troop out on a camp out in the desert, we'd had a cold, windy, uncomfortable night followed by a cold, less windy (thankfully,) uncomfortable 50 mile bike ride to finish the cycling merit badge. I was looking forward to getting into my blazer, cranking the heater and warming my chilled body at least half the day. When we finally got packed up and on the road the heater refused to blow hot air, even with 5 passengers and towing a trailer full of bikes, the heater never got above lukewarm. It wasn't an exceptionally cold day, the lows were in the mid 30s but with the thermostat stuck open the engine refused to warm up. I'm confident saying you'd know it if the thermostat wasn't working unless hell is actually the Hell in Grand Cayman and you never use your heater.