I just bought my 91 Maxima...starts right up everytime but there's a few things wrong with it like needs a complete radiator flush(gunked up), I think it has a dead #1 cynlinder, boots on the rack is busted but I'm mainly stuck on one, which is the tranny. It seems like it doesn't want to shift out of 1st like it winds all the way out. I have to let off the gas to make it shift but also it only seems like it drives it only two gears. When I take off I have ok pick up but when I make it shift it has nothing. Its like I'm going from 1st gear to 6th. If I drive in O/D the rpms go up but the car doesn't really go anywhere? Any advice would help thanks

 

if you have a dead cylinder, that will make you have to push the gas pedal harder to get the same amount of power, which might be throwing off the shift points, but it could also be something else.

Do you have a video of what the car's doing? Preferrably narrated..

 

No but I can make one tomorrow and post it... the dead cylinder is I believe the 1st or 3rd its the one closest to waterpump...yea when I take off if I ease on the gas petal it acts like it wants to die but once I get past about like 1200rpms its fine.

 

I'm betting you have one or two bad injectors...

 

also check your codes to see if there's any diagnostic codes stored. Most of them do NOT light up the check-engine light for whatever reason, so you could have one stored and not be alerted to it without a manual check.

Put the key in "on" with the engine stopped. Stick a flat-head screwdriver into the ECU screw, turn to the right. You'll see 2 dual-LED flashes, then 3 dual-LED flashes. Turn the screw to the left after the 3 flashes. Then watch the single-LED flashes after that. Red = 10's place, green = 1's place. 5 red + 5 green = 55 = normal. Anything else is a trouble code.

video of how to check:

 

No codes found as of now when I bought it yes it was the O2 sensor replaced it check engine went away hasn't came back on yet. Now the injectors I don't if they every been replaced and the injector harrness or whatever that plugs into the injectors are old and very loose. I have cleaned them off as best I could I plan on replacing soon. I've replaced the MAF and Throttle postion sensor fuel filter I've flushed the tranny using a flush machine (t-tech) at a shop, and a few more things ill have to think of

 

did you check the resistance between pins on the injectors? Supposed to be between 10 and 14 ohms. Anything higher and the wire on the inside is likely thinning/corroded.

 

No I haven't check that yet b/c honestly I don't how...I really have no clue about injectors but ill take back to my uncles shop and have him check it when he gets a chance. But the injectors wouldn't have nothing to do with they why its shifting. That's what my problem is at the moment. I think its the shift sensor but not sure.

 

"shift sensor"? what exactly would the "shift sensor" be? The gear selector position switch? Throttle position sensor?

The shift points are controlled COMPLETLY by the TPS (throttle pos sensor) and VSS (vehicle speed sensor), which are fed to the TCU, and the TCU determines what gear you should be in for that much throttle at that speed. If your engine is significantly weaker than normal, you'll be pushing the pedal down farther (as if climbing a mountain) which could cause the RPM to linger. Or perhaps just your TPS is mis-cablibrated.

You say the car eventually goes into O/D (1700rpm-ish at 4500rpm steady on flat ground) after a while?

 

I was told by oreilly's auto parts that the "shift sensor" coukd be the problem. So I'm taking it that shift sensor is the vehicle speed sensor? Idk but I replaced the TPS with a brand new one I don't think that's the problem. Now the TCU I haven't got to yet so it could be the problem. If so where is it and how do I replace it?

I can't drive in O/D. If I do the car will move but only do like 10mph and the rpms are like at 4 grand... basically the engine is running way higher then the actual speed of the car...I'm trying to get around to making a video but I work two jobs so its kinda hard...

 

the guys at Advance Oreillyzone don't know squat about any particular car except maybe a Chevy half-ton pickup, and a bubble-butt Civic....

Their mythical "shift sensor" could either be the TPS or the VSS. TPS has to be calibrated for idle. There's a switch in the TPS that should have continuity between pins at idle... and lose continuity the instant the throttle moves at all. On the body of the TPS i believe (midddle and bottom pins?) not the external wired connector that comes out the side of it. Also if you have bad wiring for the TPS, then I think that can cause the TCU to default to "speed-only shifting" which might cause your driving experience to be rather..... interesting...

VSS is just a little cylindrical thing the diameter of a half-dollar held in with a single bolt, on top of the rear-top of the transmission. If the VSS was messed up then your speedo/odometer/cruise would be messed up also.

TCU is a mini pizza-box thing sitting on top of the ECU.

 

Ok ill have to check into TPS again and ill check out at the VSS also...my speedo/odo/cruise work just fine all the gauges but the temp gauge but I think that's a short. I can flick it and it wroks just fine...I've made a video but its in the dark u can see the dash and here me but I don't know how to post it...

 

If the TPS is fine, then it could be the wiring/connector. Do you have a multimeter to verify the TPS is fully functional? The embedded plug is an idle switch and a WOT switch..... and the wired plug is the variable potentiometer for the TCU. I think it sweeps from 1k to 9k from the outer pin to middle pin.

For example my o2 sensor had a bad harness. I replaced the sensor and predictably it didn't do a darn thing. Until i fixed the wiring... (hard to see but the black wire is totally cut/loose)

 

The wiring harness to the TPS was a little bit corroded when I replaced it but I took a SOS brillo pad and cleaned it the best I could. It looked as if I got all the corrsion off but you never know so ill be checking that out 2ma. No I don't have a multimeter to test it. Where can I get that done? My uncle might be able to its just whenever he gets time and I'm trying to get that fixed now. I feel like I'm gunna blow a rod or something one day b/c of the way it shifts. I don't think it'll happen b/c I baby it but its just the wear and tear on the engine.

 

they're $3-7 at Harbor Freight http://www.harborfreight.com/7-funct...ter-98025.html

I'm not talking about the contacts on the connectors, i'm talking about actual broken/corroded/damaged wiring inside the harness bundle somewhere. As you saw in my o2 connector, the issue was on the backside of the connector where a wire was actually cut completely, there was nothing at all wrong with the contacts.

I'll see if I can make a video of me doing the same tests on my car.... it's no longer a/t but it was when it was built (did a 5spd swap on it) so all the a/t connectors are still there.

 

ok mybad I read your post wrong. I see what you mean now. So basically I need to check the whole wiring harness to see if I see any weak/corroded spots on the harness. If I do I need to just replace it? Another thing is my MAF sensor...is the connector prongs (four little silver prongs) suppose to be soddered together. B/c I went through three MAF's trying to figure it out. I just replaced the whole air filter housing that connects to the MAF. Its fine now I just want to know for in the future.

 

Well, first thing I would do is find out if that's the problem to begin with. If the problem is wiring, you can "wire around" the stock harness and just stuff the wires through the firewall hole where the rest of the wires go, and tap them in on the other side where they need to connect. The FSM for our cars is here: http://www.nicoclub.com/FSM/Maxima/1994/

in 'ec' and 'at' you'll find info on checking the TPS circuit and other circuits, tho for some of the checks you might need REALLY long leads on the multimeter aka some extra wire and some alligator clips. that hold onto un-twisted paper-clips. Like some things want you to test inside the car and outside the car at the same time.

Another thing you can try, is unplug the TPS (both connectors) and see if the car drives/behaves any different. Without TPS signal, the TCU will use a "default shifting logic" that is not related to engine load, only speed. IE it will shift from 2-3 at "x" mph no matter if you are coasting, or have the pedal floored.

 

can't see the video yet... is it still uploading?

 

http://m1354.photobucket.com/albumvi...l?o=0&newest=1

 

you must have it set to private.... i can see "2 uploads" but the only one i can see is a small picture of your face when you get on a PC later see if you can set it to public.

 

It done uploading...just trying to figure out how to post it

 

i still can't see that the file even exists... are you always posting from your phone or do you ever get on a PC to do it? The link you provided is a mobile link anyways, but either way I can't see the contents.

 

Yea always from my phone. Can you to to my photobucket and see it? Otherwise I cant figure it out I can post it on facebook also

 

I can't get to your photobucket main page.. can you go down and click "view full site" and get the non-mobile link, maybe?

also youtube would be better than facebook, as far as an alternative method.

 

Did you find out anything about your transmission? Cause mines does the same thing. It goes past what it is suppose to in RPMs with the first to second gear. But after that, it shifts normally. I sometimes lift off the pedal, or I sometimes press it harder to get it to shift more quickly. I don't know if it harms the engine but Im not sure as of what else to do..

 

still can't see that video OP posted.... must be set to private or "friends only" or something. Gonna need to log in on a PC instead of a phone and actually see what's up with the video's privacy settings. And/or post it to youtube.

Anyways depdupp, first thing to check is your TPS. Speed and throttle position are the only things the TCU uses for shift-points, so since you haven't also said your speedometer is broken, then it's fair to assume there's an issue reading your throttle position. That or your engine runs like crap causing you to use more throttle than you should actually have to.

http://www.nicoclub.com/FSM/Maxima/1994/ec.pdf

Do the test on EC-145 (throttle position sensor), EC-148 (closed throttle position switch), and EC-149 (wide open throttle position switch). With the test on pg148, the idea is to get the switch to open the instant you are off idle, which is why it's adjustible. And make sure that the transition from low to high resistance is smooth and continuous on the test on pg145.

 

Idk about whats going with the video??? Anyways no nothing on the transmission yet but heard from a few buddies of mine that it mosts likely the TPS stuck in 'safety mode'. Meaning that its takeing off in second and shifting to Sixth. I just bought a TPS and MAF from a Junk Yard. Im about to change them out now to see if thats one of my problems... I'll let yall know the results later tonite... thanks for the help.

 

lol there is no "sixth"... we have a 4spd auto. Remember that the TPS has to actually be calibrated in order to be accurate, it's not hard to do, as long as you have a test light or multimeter handy (basically you want the idle switch to be ON at 0% throttle and immediately turn off at more-than-0%).

Safe mode on the Trans Control Unit (not on the TPS) is 3rd-gear-only, which looks like this (my speedo was flaky, it was only showing 33% of true speed in the video) http://s164.photobucket.com/user/cap..._1165.mp4.html

did you ever sort out the misfire or whatever was wrong with the engine? Remember that if your engine is running badly, it will cause you to use too much throttle (for what you normally would) and can therefore alter your car's shift points.. similar to climbing up a mountain.