High fuel consumption

[ametisto]

Hey everybody,

I hope this is the right forum and the question hasn't been discussed before (I checked but found no satisfactory answer).

I am in Mexico and have recently bought a GMC Jimmy (1999). The problem is the fuel consumption. A full tank gets me just under 200 miles in the city and 300 miles on the highway. I am aware that those kind of trucks use more fuel than your average compact car, but that seems a bit excessive. Since I don't know much about cars and am not a native speaker of Spanish I run the risk of being ripped off by the mechanic. I would therefore like to get some recommendations as to what to tell the mechanic. I figure that it's probably better to tell him exactly what to do and what to replace instead of leaving the truck with him and asking him to fix it. Any help would be greatly appreciated.

Thanks,

Dan

 

[Z15]

They have small fuel tanks, maybe 16 gal or so. Also the fuel where you are may be ethanol or something worse. You will always get worse mileage with ethanol, up to several mpg less.

Some things you can check yourself.

Air filter? Often overlooked, if you have not replaced maybe it needs to be.

Tires? Are they properly inflated and in good condition?

Those are 2 major items that can affect fuel mileage.

If its 4 wheel drive, make sure its not in 4 wheel drive. I know a lady who bought a vehicle and was driving for nearly 6 months in 4 wheel drive. She never realized it.

 

[ametisto]

Thanks. The tyres are almost new and properly inflated, but I haven't checked the air filter yet. The previous owner had the car serviced a few months ago but I don't know if they checked it. How can I tell if it needs replaced?

 

[ametisto]

If its 4 wheel drive, make sure its not in 4 wheel drive. I know a lady who bought a vehicle and was driving for nearly 6 months in 4 wheel drive. She never realized it.

Good point. That occurred to me, too, but I forgot to mention it. The 4WD indicator light seems a bit erratic and doesn't work properly. How can I tell whether I'm driving in 4 or 2WD?

 

[Z15]

Remove the air filter and look at it, hold it up to a light and see if you can see light thru it.

If you are in 4wd you should feel resistance in the steering especially when making tight turns. If you feel binding, its int 4wd in all likelihood.

 

[Molson02536]

Hey everybody,

I hope this is the right forum and the question hasn't been discussed before (I checked but found no satisfactory answer).

I am in Mexico and have recently bought a GMC Jimmy (1999). The problem is the fuel consumption. A full tank gets me just under 200 miles in the city and 300 miles on the highway. I am aware that those kind of trucks use more fuel than your average compact car, but that seems a bit excessive. Since I don't know much about cars and am not a native speaker of Spanish I run the risk of being ripped off by the mechanic. I would therefore like to get some recommendations as to what to tell the mechanic. I figure that it's probably better to tell him exactly what to do and what to replace instead of leaving the truck with him and asking him to fix it. Any help would be greatly appreciated.

Thanks,

Dan

Start with the simple Dan and clean your MAF sensor. You can pick up the MAF sensor cleaner at Auto Zone or Napa and do it your self. Also replacing the air filter will help also and check all your vacuum lines. Common for the vacuum line on the driver's side of the engine on top of the intake manifold to crack and go bad.

Good luck and keep us posted, oh the other question also, is the RPM at 2,100-2,200 at 70 MPH??? that's where you should be with the torque converter locked up.

 

[ametisto]

Thanks for your answers so far. I'll check the things you've told me so far and then I'll let you know how it's going.

Again, thanks a lot. Really appreciate your help.

Dan

 

[River_Tam]

Good luck and keep us posted, oh the other question also, is the RPM at 2,100-2,200 at 70 MPH??? that's where you should be with the torque converter locked up.

Just asking the question, but wouldn't that very depending on tire size and gear ratio. I see from the Vin decoder that my 97 had 3 different tire size options and 2 different gear ratio options. I ended up with 235/75/15s and a 3.42 dif ratio

 

[ametisto]

Ok, so I went to AutoZone and had them scan the car for faults and that's what came up (I'll try to translate as best as I can but my Spanish isn't all that great):

1. P0304
failure in cylinder no.4
possible causes:
- ignition failure - spark plug(s), spark plug cables, bobina (ignition coil? not sure)
- vacuum leak
- failure of the injector
- fuel pressure too high or too low

2. P1870
Sliding of the transmission components

Explication:
The transmission in the 4th (gear?) engages with the clutch of the connected turbine and the electronic modul ECM has detected an extreme slippage when comparing the velocity (speed) of the output shaft with the one of the input shaft.
possible causes:
- check level of transmission fluid
- internal transmission failure

 

[Molson02536]

Ok, so I went to AutoZone and had them scan the car for faults and that's what came up (I'll try to translate as best as I can but my Spanish isn't all that great):

1. P0304
failure in cylinder no.4
possible causes:
- ignition failure - spark plug(s), spark plug cables, bobina (ignition coil? not sure)
- vacuum leak
- failure of the injector
- fuel pressure too high or too low

2. P1870
Sliding of the transmission components

Explication:
The transmission in the 4th (gear?) engages with the clutch of the connected turbine and the electronic modul ECM has detected an extreme slippage when comparing the velocity (speed) of the output shaft with the one of the input shaft.
possible causes:
- check level of transmission fluid
- internal transmission failure

The P1870 is common to happen on the 4L80E transmission that is in our Jimmy's. The boost valve will eventually go weak witch causes the transmission line to be low.

Visit a transmission shop and have your transmission service. Replace the transmission oil and filter and while the transmission pan is down, have your Boost valve replaced with a 0.049" boost valve and sleeve. This will bring your transmission line pressure back up and firm up your shift and eliminate the slipping unless the clutches are worm.

The other thing also you may want to do if you would like a firmer shift is to replace your servo with Corvette servo. With replacing the boost valve and servo with the transmission service should run you just under $200.00 and if your just going to do the Boost valve should just be right around the $150.00.

The cause of the boost valve is about $35.00 and the servo is about $45.00 and in most places the cause is less, depending on your local area and which brand they have to offer.

As for the P0304 is a misfire on #4 spark plug, might as well give your Jimmy a tune up and replace all your spark plugs and your distributor rotor and cap and run some http://www.seafoamsales.com/ through your engine.

Good luck and keep us posted.

 

[ametisto]

T
Visit a transmission shop and have your transmission service. Replace the transmission oil and filter and while the transmission pan is down, have your Boost valve replaced with a 0.049" boost valve and sleeve.

I'm down in Mexico. Do you know if I can ask the mechanic to do the transmission service?

As for the P0304 is a misfire on #4 spark plug, might as well give your Jimmy a tune up and replace all your spark plugs and your distributor rotor and cap.

Plugs, wires, cap rotor, air filter, fuel filter and oil change. Anything else I am missing? Somebody recommended Lucas transmission fix, which is available here in Mexico. Not sure about the product you recommended.

Thanks a lot for your help.

 

[ametisto]

Can any regular mechanic do the transmission service, or do I have to go to a special transmission place?

Re the tune up: plugs, wires, cap rotor, air filter, fuel filter and oil change. Anything else I am missing? And can you recommend a certain type of plugs?

Which of the Sea Foam products do you recommend?

 

[Molson02536]

Can any regular mechanic do the transmission service, or do I have to go to a special transmission place?

Re the tune up: plugs, wires, cap rotor, air filter, fuel filter and oil change. Anything else I am missing? And can you recommend a certain type of plugs?

Which of the Sea Foam products do you recommend?

Go to a transmission place, they have the most experience in the issue your having with the transmission. As for the tune up i use http://accel-ignition.com/ProductDe...jID=595&minID=5951&selection=9&minselection=0 on my jimmy.

Good luck and hope this link helps on how to use the Seafoam, http://gmcowners.com/gmc-forum/showthread.php?t=13770.

 

[Leprikon_84]

Здравствуйте, подскажите пожалуйста, есть тут кто - нибудь русско-говорящий???

Очень срочно надо((

 

[Molson02536]

Здравствуйте, подскажите пожалуйста, есть тут кто - нибудь русско-говорящий???

Очень срочно надо((

Как мы можем Вам помочь??

Molson02536

 

[Leprikon_84]

Как мы можем Вам помочь??

Molson02536

У меня шумит задний подшипник генератора, я хотел узнать его размеры что бы поменять. и хочу узнать как правильно пользоваться полным приводом. на какой скорости его можно включать и выключать или обязательно надо останавливаться? И хочу узнать, сколько у него расход топлива литров на 100 километров? Мне кажется что он сильно много расходует бензин(((

 

[Josh110]

Start with the simple Dan and clean your MAF sensor. You can pick up the MAF sensor cleaner at Auto Zone or Napa and do it your self. Also replacing the air filter will help also and check all your vacuum lines. Common for the vacuum line on the driver's side of the engine on top of the intake manifold to crack and go bad.

Good luck and keep us posted, oh the other question also, is the RPM at 2,100-2,200 at 70 MPH??? that's where you should be with the torque converter locked up.

Molson, why is it common for the vaccum line on the drivers side to crack like that? I have a similiar problem on a 1987 GMC Jimmy. And do you know of a good place to buy new vaccum lines?

 

[Molson02536]

Molson, why is it common for the vaccum line on the drivers side to crack like that? I have a similiar problem on a 1987 GMC Jimmy. And do you know of a good place to buy new vaccum lines?

Just from the heat of the engine and time. The rubber vacuum line gets dry rot and cracks. I replace mine every 5 years as part of maintenance, there not that expansive at most auto parts store.

Good luck and keep us posted.
Molson02536

 

[Molson02536]

У меня шумит задний подшипник генератора, я хотел узнать его размеры что бы поменять. и хочу узнать как правильно пользоваться полным приводом. на какой скорости его можно включать и выключать или обязательно надо останавливаться? И хочу узнать, сколько у него расход топлива литров на 100 километров? Мне кажется что он сильно много расходует бензин(((

Для вас заднего подшипника, было несколько разных размеров, которые были использованы на нашем Джимми. Вам придется ехать к дилеру и дать им свой VIN номер вашего Джимми, чтобы получить право размера подшипника.

Для бензина, убедитесь, что MAF датчик чист и ваши дроссельной заслонки чистый и с новыми воздушными фильтрами каждые 6 месяцев. Замена топливного фильтра также легко сделать, и вы можете подобрать все, что нужно в большинстве автозапчастей хранить таким образом вам не придется бегать вокруг.

Удачи и держать нас в курсе.

Molson02536