1990 Q fuel milage

[1990QOwner]

Hi all, I am new to the Nicco forums. I have 1990 q45 with 158,000 on it. The previous owner ran it out of engine oil and drove it for about 8,000 miles and the engine died. The body and inside were in perfect condition so I picked it up for $500 and replaced the engine with one that had 32,000 on it. I have been driving it for about 6 months and noticed that it wasn't getting that good of fuel mileage, so I clocked it and it was getting 10 MPG in the city when I am driving very very mellow never getting over 2000 RPM's. Is this normal? and if not is there anything I can do to improve the fuel mileage?

[qsiguy]

I would say you have something very wrong. It's not an economy car by any stretch of the imagination but you should be able to get 16-20 mpg depending on how you drive.

You need to do some diagnostics, if you don't already have it download the FSM. It will give you procedures to check the EGR, O2 sensors, MAF, and on and on. These cars have many built in diagnostics features.

How does it run? I'd think you could tell if it was running that rich. U sure your tach/odometer and your math is accurate?

[1990QOwner]

I have double and triple checked my math and it is accurate. I also have checked the mile odometer and it also is accurate. I recently replaced the fuel pump and fuel pump modulator. I also have noticed the fuel smell inside as other users have posted, could a small fuel leak under the plenum cause fuel mileage to drop much? I plan to do check over everything but want to get all of the facts together and see all of my options. Obviously, the previous owner did not take very good care of the engine or any other parts under the hood so I guess you can expect some trouble. Thanks for the help.

[1990QOwner]

One more question: Where do I go to download the FSM?

[96Qowner]

In the body of this thread, there are three places listed for downloading an FSM. The NICO site only has it for 1994 and newer. The other sites, you have to either register or pay for a one-day subscription.

Good luck with the problem. You should NOT be getting mileage that bad. It's gotta be running like crap.

[1990QOwner]

Ahh, I have been looking for about an hour looking for a FSM download. The only ones that I can find are for 94 on up. Can give me a link to find the FSM? Thanks

[96Qowner]

In the body of this thread, there are three places listed for downloading an FSM. The NICO site only has it for 1994 and newer. The other sites, you have to either register or pay for a one-day subscription.

LOL, body of what thread? Duh ... here it is:

Sources for Q45 FSM

[Q45tech]

Nissan never created PDF files until the 1994 FSM so FSM Books are normally used and acquired from ebay. Every Q came with a small print FSM in the trunk, most got lost or sold on ebay.

[qsiguy]

There is one small hose that has been known to leak occationally. It's behind the plenum near the firewall. It's a vertical hose. I don't have a photo of the said hose but if you start it up and look down there with a flashlight you should be able to see it. It's very tight to get in there but it's possible. I had to tighten up mine a few months ago. It would have to be leaking pretty badly to cause that much less fuel mileage tho. Mine was only an occational fuel smell.

[cccpman]

You can do all of the checking when you grab a copy of a FSM. Realistically you might be getting 14-18 mpg normally, maybe you are lucky and get 19 because of your 'mellow' driving. How strong is the fuel smell, does it make your passengers worry (leaky O-Ring on fuel pump) or is it just a slight odor (hose issue). Everyone gave you some pretty good information, its well worth the investment getting a FSM off ebay or looking to see if its hidden in the car somewhere

[1990QOwner]

I have looked all over in the car and cant find the FSM anywhere. I did find one on ebay and I intend on getting it and doing some fixing on my Q. The fuel smell isn't bad enough to knock you out or anything but it is noticeable.

I also had another question for you Q techs: I read something on the forum about the Transmission control unit. This Q wont start out in first gear, it usu. starts out in second unless you really punch it or if you physically shift it down. I am wondering if this is the transmission or if it is just another electronic part that is going out? I'm not a mechanic so bare with me. Thanks

[cccpman]

I think what you are asking is if you can just plug and play a replacement, the answer is yes. The TCU (transmission control unit) is what causes the car to start in second, your going to need something like a 93 (93-96 right?) TCU to force it to start in first. It is in pretty good demand, the secret is to pull it from a junked Q and that will save you even more money then the generous folks here at NICO in most cases (supply and demand usually here)

BTW I think the first start could actually help extend the life of your transmission somewhat, starting in first should help keep down on the heat right? (dont quote me on it, read it somewhere around here )

[1990QOwner]

Thanks for the info. Where is this unit on the car?

[Haitian_King]

I think the TCU is by your left foot on the driver's side. As for what cccpman said, I heard that too. IF you're going to keep the second gear start in the Q, you should invest in a Transmission cooler. There are write ups about it.

[maxnix]

If you're going to keep the second gear start in the Q, you should invest in a Transmission cooler. There are write ups about it.

Even if you install the 1993 TCU, you should add an auxiliary ATF cooler.

[Haitian_King]

Oh yeah? Did not know that. Thank you.

[maxnix]

Oh yeah? Did not know that. Thank you.

Yes, while there were gradual improvements to the early years G50, only the 1994+ had an adequate solution.

There again, it is wise to add an auxiliary cooler if you are not in the great white north.

[Jesda]

Ideally, you'd also have a trans temp gauge installed somewhere, like in the ash tray.

[Haitian_King]

Awww. I keep toll money in my ash tray.

How would I get the temp gauge in there? Do you have a picture of it?

[goody90q45]

Awww. I keep toll money in my ash tray. How would I get the temp gauge in there?

You could move the toll money to one of the many unused cup holders.

[1990QOwner]

Hey, I got under my Q and took a look at the transmission, I couldn't locate the TCU right off, but I did note a few things wrong with the transmission. Now I'm not a mechanic by any stretch but I did see something wrong with the picture. Check out these links of pictures of the transmission:

http://www.tronitek.com/1990Q/img_4466. ... g_4465.jpg

It appears that some of the bolts are missing for the transmission. How can I get this fixed?

[maxnix]

Order them form Jow or read the FSM and specify them locally.
Modified by maxnix at 9:24 PM 10/15/2007

[cccpman]

you can go buy bolts and put them in

[1990QOwner]

Do you think that it has ruined the transmission driving it like that?

[1990QOwner]

But what about the gasket that is hanging down? Wont I need to replace that? Or is that still good?

[cccpman]

the only person that could know that is you... Are you leaking transmission fluid? Do you even have any? Can you drive the car, shift into gears? If your not leaking and you do have fluid and you can shift just fine then the transmission is fine... I would probably replace the gaskets but thats an expensive job, your going to have to consult somebody more professional about this problem then myself

[1990QOwner]

Well sure, the transmission still shifts fine, but it was clear out of fluid. It is being held together by 2 bolts at the top. The reason that I didnt notice any fluid is cause it was clear out. What do you have to do to replace the gasket? I have taken it to a professional shop several times but they usually just keep if for a few days than give it back to me in a few days, with a bill for looking at it. and tell me that they can't touch it cause it is too foreign. Mabe I will just try to get that one back in place and see if it still leaks with all the bolts in it. I am still going to get a new TCU. Is the TCU inside the car or is it underneath it somewhere? Thanks for all the help.

[qsiguy]

The TCU is in the drivers side kick panel. Pop off the little cover and it's right there, really simple.

That is really crazy about the missing bolts. I'd be raising some serious crap with the transmission shop(s) that charged you to look at it. That is a major safety issue!

"Too foreign?" what...the domestics don't bolt on their transmissions?

[1990QOwner]

LOL. Yes, the domestic cars are designed to fall apart. It is very interesting how the bolts are just missing. I even had it in to be serviced less than a week ago and they didn't say a thing about the missing bolts.I think I will be replacing some bolts and fixing some leaks under there. Keep in mind that when the engine was replaced than they pulled it out from the top instead of lowering it from the bottom so i think a few other bolts prolly got forgotten also. I think by the time I am done with this car than I will be a Q expert like all you guys.

[maxnix]

You will surely put these guys on your so not use list.

What clowns.

"More damage is done to G50 by ignorant mechanics than even unknowning owners." - Q45tech