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busup

91 still not running right

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Ok, so my 91 is still not running right, I have been a backyard mechanic for almost 23 years & now I am a licensed airplane mechanic, but this is stumping me really bad. Ready to go back to school or get rid of my path, heres my issue again,

 

My 1991 pathfinder has some issues, when I start it cold it always starts right up. At times when it is warm it wont start unless I pull out the fuel pump relay. My compression when warm is over 180 per cylinder, and cold is over 150. It also blows black smoke intermittently but not sure if that is from the sea foam I put into the tank. I changed the MAF sensor ( bought it used)but I still get the ECU code for it, even reset the ecu. new plugs, cap, rotor, wires & fuel pressure regulator & pump. I had a friend tell me my computer is bad but not too sure about that. This truck sat for over 5 years before I bought it so I drained the fuel tank, replaced timing belt & double checked that twice. Cleaned the injectors & the TB, any ideas out there????? :headwall::scratchhead:

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Huhm.

 

The only code it throws is the MAF sensor huh.

 

I wonder if it's your ECU Coolant Temp Sensor...

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Actually, that code does show up also.

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That's what mine did. Ran great when it's cold, but when it warmed up the sensor would freak and dump a crap load of gas into it. I used a half a tank of tank of gas in 13 miles. The sensor is in the valley of the block. It was an $800 repair at a local shop. I didn't have time to do it myself, or I would have. I think the sensor its self listed for $56.

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Ok, so I changed the coolant sensor TWICE, (broke the first one...oops) Seems to run a little better, still no power though and the ECU code is gone except for the MAF, Sooooo.....looks like I may try & fork out the $$ for a brand new one, gotta wait til next paycheck though. Woulda thought the MAF would be fine if the sensors are both intact though. I did try disconnecting the CT from the coolant sensor & the idle jumps up just a bit but still no power, so still searching for ideas, hopefully something not entailing buying a new MAF.

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I have a MAF off my 93 if u rather buy that? PM me

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Aloha all, been a while since I posted about my pathy. Needing some help here. Heres my updated story, so far I've changed the timing belt, cap rotor, plugs fuel injectors fuel pump fuel pressure regulator, fuel filter, MAF (was used) coolant sensor, drained & cleaned the fuel tank. I was having problems before with absolutely no power after the belt change so I actually bought a Nissan belt & tried it again. Now I have power up the wazoo but it is still missing a bit. I can actually drive it on the road now though, the weird thing is, I found that if I set my distributor in the 9 oclock position it gives me that power I need, at the 11 it is a dog, I checked the timing belt numerous times, I have 40 teeth between cams, & 43 between L/H & crank shaft so I know it's set right. I still get some black smoke out the exhaust but not sure if that is from the sea foam or not. ANY IDEAS??? Oh yeah, if I disconnect the MAF it runs very smooth but governs as it should. I also replaced that harness.

Edited by busup

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the weird thing is, I found that if I set my distributor in the 9 oclock position it gives me that power I need, at the 11 it is a dog

 

What does this equate to as degrees advanced using a timing light?

 

Oh yeah, if I disconnect the MAF it runs very smooth but governs as it should.

Did you try a different MAF? The ECU occasionally fails, but not often. Only a few times that I can recall in 5 years. At least check the connection there??

 

B

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This is going to sound bad... and I doubt it's it...

 

have you tried using different / higher quality fuel? I had something similar to this happen once when I filled up at a cheapo gas station out of state... I guess they watered it down or something cause it ran like hell even after a second top off... finally had to run her near-dry and then refuel + water remove and it ran like a champ after that *shrugs*

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OK, I changed the end of the maf harness hoping that would be my issue, when I took a voltage reading going in I get 12v, and 12 going out on both the other wires. I thought I read somewhere that it is supposed to be only 5 in and something like 1.3 out? any ideas?

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I got a 94 and had dramas since i bought it. started fine but when it warmed up it ran like @!*%. I got on forums and searched hi and low for solutions to the problems and it ended up being the o2 sensor, easy to change it screws in the exhause between the headers and the cat and the wires run up near the battery on the right side. Nissan use bosch so if you go to your local parts supplies and insist on bosch they should get it.

I did all the plugs leads filters fuel checks and maf and it ended up being the o2 :my2cents:

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