1990 Maxima SE AUTO:

Well first off I noticed that when driving at about 65-75 my RPM is at roughly 2500 with overdrive on; with it off, it is about 3500...is this normal for this big of a difference?

I just noticed today that I got roughly 140 miles off of half a tank of gas...now I will confirm how many MPG I actually got when I fill up my tank on friday, however I I don't believe 140miles off of 1/2 tank of gas (15 MPG) is normal for 75-80% of those miles on freeway driving passivly at 2500-3000RPM (MOST of the time it is right at 2500RPM). This then leads me to believe it might have something to do with my next problem...

The car SOMETIMES idles rough. I mean it will drop down to about 600RPM and it just feels rough. However, other times it will run just fine and be as smooth as a baby's butt.

What is going on here The engine was swapped out about 7000 miles ago by professionals, so I was thinking maybe I just need a tuneup to get the air:fuel ratio back to where it needs to be, but would this explain the entire situation? O2 sensor perhaps? MAF?

If pictures or video is needed I will be more than happy to provide them, however catching the rough idle will be tough because it only does it some times. Otherwise, it seems to run OK.

 

Start with the simple stuff..how's your vacuum line situation looking?

 

1. yes that RPM difference is totally normal. when you turn OD off you are putting your car into 3rd gear rather than 4th.
2. it's possible one or more of your injectors is failing. I've had an intermittent miss before from an injector, never did get it fixed though. It fixed itself

 

I will check the vacume lines ASAP. There was a hissing sound somewhere....so perhaps. I know for a fact my injectors are old and were a cause of many problems previously, however like you said internetautomar...they seemed to fix themselves :X Would these explain the bad gas milage though?

 

yes, even if they "fixed" themselves they may still be sticking open and allowing excess fuel into the cylinder.
oh and exhaust leaks hurt mileage

 

I will let the pictures and video do all the talking for me:


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Here is a video of the exhaust when reving some...thought it might help:




My dad...i swear he is such a cheap bastard sometimes!

 

I would definately start by replacing those hoses.

 

How much do you think I would be spending replacing them?

 

if you're talking vacuum hoses, you can usually just go down to the hardware store or auto parts store and by however many feet of each size you need and then cut them to fit, usually it's very cheap where i live.

 

U'z got a VG

 

Yes I do

 

I dont get much better MPG then he does. I tipically get 280 to 300 off one tank of 89 octance. Wat should be normal?

 

Mine is only rough on acceleration off from a stop. ex stop light or stop sign. 2500 RPM is 82mph for me 2300 is about 75.

 

normal?
I was getting 17mpg, then when I started driving a 1/2 hour to work it went up to 20. now that I'm not employed again

 

I drive at roughly 75-80MPH on the freeway for a good 25 miles a day, then again to come home. Sometimes I will drive an extra 10 'city' miles, but its hardly concidered 'city' when each stop light is at least 1 mile away from each other...and I drive fairly lightly right now, only actually giving it gas to get on the freeway.

So again, vacuum hoses...doing that tomorrow and while I am at it I think I might also check for exhaust leaks, check timing, and just a basic tuneup I think. How can I check the fuel:air ratio and change it?

 

Yet another 'Problems Production'. I thought I would put another audio clip of the exhaust after I drove home tonight. The sound is what we are after here....so please help me find out what this thing is! FYI: I am going into the dealership tomorrow to find out the sizes of the hoses I need so I can go and get some to replace them ASAP!

I am sitting just a couple feet at first from the exhaust then move up to within a foot of it:
http://conclaves.net/audio/exhaust2.mpa

 

Dumbass deal**** didn't have the listed sizes, only part numbers of what I needed and the cheapest hose was $14! This simply means, I have to cut back on my driving because I can not afford to replace them atm...

 

I just replaced a lot of my hoses, they cost like 79c per foot at autozone. So its very cheap, just get 2 feet every every size. Sometimes they are hard to match so you think what you're getting will fit and then cant get it on, in these cases it helps to have extras.

Have you checked the air filter? A dirty one will do wonders with your gas milage. I just filled up today from a few long highway trips and some city: 24mpg w/AC on.