Hello, My name is Mike. I am here to help you with my 25 years of being a certified mechanic. I work for fixya around my own auto repair stores I have in the north west. Here is some tips for you to check out that can cause poor fuel economy. Please read complete information below.
Clean MAF
Clean Throttle body
PCV Valve
Spark Plugs
Tires
K&N Filter
Sea foam
Lighten out car load
Also if you have not messed with the TB check your vacuum lines for cracks.
if you cleaned your TB a relearn procedure may help. Past customers of mine were having a
mileage and other problems and I removed the cable from the positive
terminal for about thirty seconds. This causes the computer to reset.
It helped the gas mileage a lot and also cleared up other problems.
my vacuum lines some were dry rotted and cracked.
Other area, is if replacing the ECM, could help fuel mileage. Some times the code won't come up on that being poor, because it is operating enough to not trip a code, even though your mileage is poor.
Another thing to consider if the fuel filter should be replace and injectors cleaned to make sure there is no restrictions.
Here is my conclution sense there was a lot of information I just wrote to save mileage, and even tire air pressure set at about 33 on your car.
Now here is what I would first do to not play this part and replace game:
To make life easy, drop into a local Auto Zone ( its free), and have them put on there hand held computer and have them see what codes come up on there machine. Then if a code comes up, then that narrows it down on what needs to be fixed or replaced. Next if no codes come up, I would first do this.
Replace fuel filter
Replace Spark Plugs and Gaped according to manufacturer specks. DO NOT just gap them to what some things is right, gap them to manufacturer specks, as if not, this can cause other damage to things like your 02 sensor etc.
From Auto Zone, they sell little portable can kits, that you tap right in and to clean injection system.
Next thing is even though you replaced 02 sensor, there is another one that
that can partially clog first which is the precats in the exhaust manifolds, that is something that can check with a engine pressure test. Engine pressure test with give you and idea of flow. I hope some of this helps. Please let me know if you need me to pinpoint closer as your symptoms get more detailed or any new codes you discover via Auto Zone or some other place.
I am here to help you from start to finish. Keep Me Posted, Mike
Thanks for all the info.. The 89 Maxima doesn't have a computer diagnostic only a manual.. That's why i'm stuck in this situation but i'll go through your list of fine facts and hopefully will go back to the great mileage i had once upon a time :) Thanks Mike!!
Well, I assure you if your patient and keep me posted with every detail you can as you go through my list, I assure you WITH your details to me and inspections I will help you get to the root and get you some better fuel mileage. Thanks Mike.
Well i just finished a compression test and the spark plugs were pitch black and the results were...
(Plug 1 = 142)(Plug 2 = 150)(Plug 3 = 150)(Plug 4 = 150)
(Plug 5 = 155)(Plug 6 = 140)
Hello, thank you for getting back to me with your compression readings. Ok let me make this real simple for you. Do not waste your time testing plugs and wires and all that. This is mechanic 101. Almost any mechanic knows, that with symptoms of a car that is a 1989 that is running rich, eating fuel like crazy, black exhaust, after checking 02 that is good, EGR that is good and new muffler and cad cut out, that this is for sure a plug and plug wire issue along with fuel intake cleaning. Now let me explain something. Never ever, replace just one wire or plug. Anytime with these type of symptoms and compression checking out ok, but plugs black, then skip the testing, waste of time. Put new plugs on and new plug wires. If not, then it will happen again. Sometimes small hairline cracks will cause a ark and miss fire and foul your plugs again. Even the best experts can miss that. HERE is your solution, replace all plugs, replace all plug wires. SHUCKS, you can get pretty good kit to do this. Price break if you buy them all with them. Just ask for there 10%discount. A lot of people do not know they will do that if you just ask. CONTINUED NEXT POST
ALSO while your there you need to clean your fuel lines, additive in with fuel as well as cleaner for intake. Trust me with that much black and running that rich needs a good fuel intake cleaning out
Don’t worry about gap, auto zone also when you buy the plugs, they will even tell you gap setting or they will even gap it them self. DO NOT gap to someone’s opinion. Factory gap setting are for a reason. You don’t want to burn something up cause of guess work or some guy’s back yard opinion. 99% of your problem will be solved with new plugs, wires and carb/fuel system cleaned out. Just tell Shucks when you buy your parts, that You want to clean out carbon from carb build up etc… They will show you and give you right product. My 3 service centers have been using them for years. Good People. Have a good Night. MIke
If you would like anymore help or more PROFESSIONAL advice, feel free to get back to me.
Hello, as you read in start of my ad>>Clean MAF
Clean Throttle body , And Like I said PLEASE replace plugs and wires, you might save now getting cheap,but later you will have other issues. And the MAF to save, rather then replacing to make up for the cost of PRIORITY of changing plugs and wires,. So to save some money, CLEAN your MAF and replace plug wires and plugs. I can not stat that enough. If you go in forum and talk to the manufacturer and parts places we deal with this is a major problem, if people try to fix this issue you are having with out replacing plug wires and plugs with this issues that has happened the age of your car. AGAIN simple mechanic school 101. rule we live is don't go cheap now to cause expensive later. Mike
Its been a pleasure helping you with your problem, And of you can anytime call on me to help you. As you can see you have a a lot of information here to solve your problem. Once you REPLACE your plugs and REPLACE your plug wires, and clean or replace your MAF, you will be fine. My lead mechanic at one of my stores as we speak have the same issue going on with one of his cars he working on, and same car is yours, but one year newer. He did exactly what I instructed to you, and car is running strong and clean. So, as you can see this will solve your problem. Again, thank you so much. Glad to help. If you were in my local area, I would have you come into one of my 3 service centers and check it out for you, but i believe you have enough information is you follow my steps, that problem will be solved. Again, thank you, Mike.
Well all the gaskets were shot.... The intake manifold one was the worst
Hello ... Mr. avatartg1rpm'
I am glad got to the bottom of it. Of course replacing those gaskets you will be back in shape. I was hoping that was going to be something little cheaper and simple fix. All us experts i think did a real good job getting the old brain a turning. I am thrilled that the problem is known, now just have to fix it of course. Thanks for the follow up. Mike
Well it's not exactly over i have a 96 Blazer S10 LT.. I bought a charger from walmart and it arked back to fuse number 2 and welded it together and needless to say it caught the whole dash on fire.. So i bought the harness the dash and the new transfer case control module.. Here is the problem.. I have everything installed and the only thing im having issues with is the TCCM because i had to hard wire it and there are a lot of the same color wires.. I know i have a problem because the shifting is off the ABS comes on when i accelerate and when i push the 4x4 button it clicks in the box before it blows the fuse... I hope i can win against this one Lol.. Thanks for all your help!!
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With that kind of gas mileage your spark plugs are/should be black, first I would remove the spark plugs ans perform a compression test to determine the condition of the engine, you should be getting readings around 130/170 but the cylinders can only be 20% differance, replace spark plugs with a set of autolite's with gap @.044
a good set of 8mm spark plug wires.
Do you have a check engine light? At 6 mpg your not running very good, is the car a slug? let me know the compression and we will go from there.
I'll give it a whirl. Thank you.. And yea its definetly not moving it's fastest but the check engine light hasn't turned on. I also forgot to mention that the exhaust is pitch black and it runs super rich
yep, to much fuel or not enough spark, the compression test will help determine the problem.
Well i did the compression test and the results seem fair to me and... Yes the Plugs are pitch black and smell like gasoline.
(Plug 1 = 142)(Plug 2 = 150)(Plug 3 = 150)(Plug 4 = 150)(Plug 5 = 155)(Plug 6 = 140)
Good, that tells me the piston compression rings and the valves are good, now check the spark, your looking for a blue spark, not yellow,
Not to sound stupid but how exactly do i go about that? I'm kinda new to this.. Thanks
ok, thats cool, remove a spark plug (I would use a spare plug) and connect the spark plug wire to the plug, (this will shock you if your no careful) have someone try to start the car and hold the spark plug 1/2 from a ground (engine ground is good) now, don't touch the car when holding the spark plug wire and hold the plug wire with a good pair of insulated pliers, when the engine turns over a spark will happin, doing it at night helps, then I want you to replace the spark plug and the wire , start the car and spray the spark plug wires with water, at night works great, remember your looking for a blue spark and checking the wires for cracks and deteriation, let me know the results
The factor gap is .044 on the spark plugs, Please don't just throw parts in the car, remember it's your pocket book, I am heading towards the MAF, this controls the air/fuel mixure, if this is defective it will pour fuel into the engine, but the electrical has to be tested first or you will be chasing your tail.
Mechanic 101 is to check fuel, air and spark, not throw parts at the car, and hope for the thing to fix itself, been a PROFESSIONAL for 40 years on auto and aircraft (ASE, A&P certified) so don't let someone convince you because they are a service writer and don't really do the mechanic's part, just like most shops will throw a $130 tune-up that you didn't need, and that doesn't include fuel filters,air filters, spark plud wires, the MAF has to be tested and cleaned,
Understand that the bad MPG is from either a weak spark (bad coil, wires, spark plugs) or retricted air flow, (bad MAF, vacumn leak, including bad injectors), I have a 95 civic that gets 40 MPG, Cirrus gets 29 MPG, Achieva 27, El Camino 10, but it's my rat rod. 383 CID backed by a 2 spd powerglide, 373 gears
All the gaskets were shot the intake manifold was the worst
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This may seem obvious, but the first thing you should do is make sure you don't have a fuel leak.
Do a compression check on all cylinders. In most cases when I see this the problem is either a compression issue or the vehicle is only running on partial cylinders instead of firing on all cylinders. Make sure the plugs aren't fouled and the coil pack is actually working properly. If the compression is low or extremely high on one or more cylinders in comparison to the others then you have a more serious problem that needs a rebuild. Another issue could be the fans themselves. Make sure they spin freely with the ignition off. If they aren't then you are having to overcome that resistance as well as the normal resistance the motor was designed to beat. Most likely your going to find a compression issue.
One thing I forgot to mention and it kind of depends on your situation. It kind of sounds like you may have someone helping you with your gas. That is to say they maybe using what was referred to in my area as a Missouri Gas station Hose. This is a hose with a specially designed tip on the end that they use to siphon the gas right out of your tank. Before 1990 they the car manufacturers didn't put crimps in the filler tubes that go to the tank from your fill point. Because of the way gas prices where going in the 90's they started putting a crimp in the tube to to stop people from using hoses to easily drain your tank. A 20 gallon tank can be emptied in about 5 minutes. If they hit you up for 4 to 5 gallons a night you probably wouldn't notice that someone was siphoning your gas off. You have two choices to test for this. Put a small piece of paper under the cover where your gas cap is so it falls when the cover is opened or put a locking cap on the cover. I only mention this because I recently caught someone trying to do this to one of my vehicles.
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Try paying 7 dollars US a gallon then this vehicle would be scrapped and a nice diesel manual bought ,right looking at the comments i would remove the air filter and see if its dirty the i would check to see if a plastic bag or a bird or a mouse have gone into the air intake ,if a quick look didnt reveal anything then i would look at the autochoke and how it works ?? because as this vehicle is american market vehicle of this age then it would have different sensors and bits to out europeon vehicles of the same age but if the exhaust is black then its a sign of excess fuel and i would suspect the temperature sensor for the autochoke and check the voltages out with a automotive multimeter on the temperatures first ,now if all the plugs are black then this is a possibility of your problem but if only one is black then a suspect injector is a a most viable cause .But in all honesty i can only make suggestions as without my head under the bonnet and good look around i have no idea .Please remember that here in europe big monster gas burners are not used that much but most vehicles are small petrol units and most american makes of vehicles are diesel with manual transmissions .which appear to be only made for the europeon market from i read on here as no one ask questions about them on this web site .
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