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Old 02-26-2011, 11:07 PM   #1
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Default MAF X bad gaz mileage.

Bonnie 1992 SSEi (*/C) with 50600 ml on it.

My car itī* running flawless as should be; fast and strong engine but I had a big drop in my gaz mileage since a two months ago . It was around 18ml/gl in a city drive and a 21ml/gl at a freeway even with our bad brasilian gaz (low octane) plus 25% of etanol and drop to half of this numbers.
It has a new NGK 55 cooper plug set. new wires,filters.O2 sensor, EGR cleaned. intake manifold gaskets okay, no vacum leaks and fuel pressure regulator with no leaaks too.
I disconnect the MAF sensor and for my surprise the car dindīnt change this behavior, still
fast and strong.
Asks: Am I in a Limp mode?
Does I have a bad MAF?
If yes for #2 does a bad MAF hurts a gaz mileage as is hurting my pocket?
I have had check the MAF plugs and itī* okay.
If someone here can give me some tips I will appreciate.
Regards.
Malachias99
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Old 02-26-2011, 11:18 PM   #2
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Things that will effect mileage is a bad O2 sensor, a dirty MAF, a plugged air filter, low tire pressure, ethanol in the gas, bad spark plugs, old plug wires, weak coils, a bad fuel pressure regulator, and a evil right foot. Also, make sure the transmission is shifting in to 4th gear.
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Old 02-27-2011, 01:15 AM   #3
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Default MAF x Bad gaz mileage

Quote:
Originally Posted by Danthurs View Post
Things that will effect mileage is a bad O2 sensor, a dirty MAF, a plugged air filter, low tire pressure, ethanol in the gas, bad spark plugs, old plug wires, weak coils, a bad fuel pressure regulator, and a evil right foot. Also, make sure the transmission is shifting in to 4th gear.
Dear Danthurs:
Thanks a lot for your quick replay. As I said I have a brand new O2 sensor (Delco)/plug and wires/new air filter (get at RockAuto by the mail) and a correct tire pressure.
I donīt belive that the etanol (25%) it`* a culprit because I have run this car here in Brazil since 1992 with the same bad gaz and gettin a 18/22 ml/gl. (city/freeway).Fuel pressure regulator itī* okay with no leaks and steady 44psi running.
I clean up the MAF with etileglycol but it wasnīt dirt.
About the a evil right foot I didnīt change my behavior drive stile.
I belive that my car itī* shifting okay till the 4th gear (Lockup?) because I can fell and see the tachometer change the RPM.
Is there a way to make sure it? Iīm surprise because my mileage drop to 9ml/gal.
What about the pluggeg and unplugged MAF with no behavior changes.
I belive that my MAF isnīt send a signal to the ECM and this ECM put the car at Limp mode. What do you thing about?
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Old 02-27-2011, 02:24 AM   #4
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Oi, I don't have much experience with your exact model, but I do have plenty of experience with the effects of the distinct realities of US vehicles imported to Brazil. I'll include some background info that you already know for sure about the "patria amada" so folks here can get a better idea of these differences.

#1 item I'd check would be the Fuel Pressure Regulator as recommended in the previous post. The alcohol content in gasoline can get much higher than what'* on the pump, it will eat away and degrade anything rubber at a much higher rate than the 10% allowed in the US.

How many tanks have you been through since you started getting this horrible mileage? The gas may have been "enhanced" with diesel too, as often happens.

Have you checked the fuel pressure yet? More importantly the leak down? A stuck (the gas down there kills the useful life of the injectors in half many times) injector will kill you mileage. I had this problem with the 4.3 Vortec in my Astro Van, the gas kept eating the injection "spider", GM finally started making theses components resistant to high alcohol content in fuel around 1998, so if your components are original...it'* going to be fun for a while, BTDT and got the T-shirt.

Sorry I couldn't offer more insights, but as I said, I don't have any direct experience with your model. If you're near the Campinas area and decide to give a mechanic a shot at it, there'* a tech I know who'* very good with these early GM imports, let me know if you'd like his contact info.

Boa Sorte mano.
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Old 02-27-2011, 10:35 AM   #5
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No change when unplugging the MAF makes me think there is a issue with it, but that'* a expensive swap unless you have access to another one to try. Pull the vacuum hose off the FPR and smell the hose, if you smell gas, the FPR is shot. When you drive somewhere and park the car. Is it hard to start when you come back? If so, could be a leaking injector, or a sign the FPR is leaking.
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Old 02-27-2011, 07:52 PM   #6
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Default MAF x bad mileage

Quote:
Originally Posted by cobram View Post
Oi, I don't have much experience with your exact model, but I do have plenty of experience with the effects of the distinct realities of US vehicles imported to Brazil. I'll include some background info that you already know for sure about the "patria amada" so folks here can get a better idea of these differences.

#1 item I'd check would be the Fuel Pressure Regulator as recommended in the previous post. The alcohol content in gasoline can get much higher than what'* on the pump, it will eat away and degrade anything rubber at a much higher rate than the 10% allowed in the US.

How many tanks have you been through since you started getting this horrible mileage? The gas may have been "enhanced" with diesel too, as often happens.

Have you checked the fuel pressure yet? More importantly the leak down? A stuck (the gas down there kills the useful life of the injectors in half many times) injector will kill you mileage. I had this problem with the 4.3 Vortec in my Astro Van, the gas kept eating the injection "spider", GM finally started making theses components resistant to high alcohol content in fuel around 1998, so if your components are original...it'* going to be fun for a while, BTDT and got the T-shirt.

Sorry I couldn't offer more insights, but as I said, I don't have any direct experience with your model. If you're near the Campinas area and decide to give a mechanic a shot at it, there'* a tech I know who'* very good with these early GM imports, let me know if you'd like his contact info.

Boa Sorte mano.
Thanks a lot "mano" been so far and trying help someone at "patria amada".
I had running out two gaz tank with this horrible average ever filling up at the same gaz station that I know the owner. (Itī* very confidente) The gaz is so bad as you know but itī* the same that I have been filling up since 1999. My FPR itī* okay with no leaks or gaz smell. I had my injectors clean up and checked for the correct spray and time. Itī* like a brand new injector with the amount spray and time okay too. Please rush me up the adress or phone of the gay at Campinas. Iīm at Uberlandia/Mg (not so far).
Once again thanks for the tips. Keep in touch.
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Old 02-27-2011, 08:05 PM   #7
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Default MAF x bad mileage

Quote:
Originally Posted by Danthurs View Post
No change when unplugging the MAF makes me think there is a issue with it, but that'* a expensive swap unless you have access to another one to try. Pull the vacuum hose off the FPR and smell the hose, if you smell gas, the FPR is shot. When you drive somewhere and park the car. Is it hard to start when you come back? If so, could be a leaking injector, or a sign the FPR is leaking.
Dear Danthurs:
As I said, my FPR itī* okay; no leakeage or smell gaz and the car behave flawless.
Start like a flash cold or hot.
Itī* drive me crazy about the MAF plugged or not this still a bullet at the city and road.
Does my ECM has a LIMP MODE?
I still believing that the culprit will be this MAF sensor.
Regards.
Malachias99
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Old 02-27-2011, 09:07 PM   #8
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If you were in limp mode, you would know. Personally I would change the MAF. Unplugging it should cause the engine to stumble.
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Old 02-28-2011, 09:31 PM   #9
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Default MAF x bad mileage

Quote:
Originally Posted by Danthurs View Post
If you were in limp mode, you would know. Personally I would change the MAF. Unplugging it should cause the engine to stumble.
Dear Danthurs:
I agree with you. Unplugging it should cause the engine to stumble, but nothing hapens whem I do it. Plugged or unplugged itī* the same behavior. (Fast and strong with no hesitation at any speed or gear). Iīm going to follow your advise and order a new MAF
at RockAuto.I will let all the member here that is traying to help me to know what will be the gaz average after a new MAF installed.
For now I thanks a lot to all. Keep in touch.
Regards.
Malachias99 (Brazil)
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Old 02-28-2011, 09:32 PM   #10
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Ya, no change tells me it'* not working.
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