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Over 50 MPH runs like crap

kenny811

kenny811

NAXJA Forum User
Location
Damascus, OR
I have a 94 HO 160K. Took it to Seattle WA for the weekend and on the drive it ran fine untill about 50 / 55 and on any inclaine or up hill it just started spuddering, missing and spitting. it did it for a few seconds then was fine. It did it about every 5 to ten minutes. In town it ran fine, oil press, temp shifting everything was great. Just on the freeway. It felt like it was running out of gas....(kinda) Its hard to explain but thats as close as I can get to it. Any Ideas?????

Thanks
Kenny
 
Sounds like something isn't up to the job under a heavier load. Assuming no check engine light? If there is or was, pull codes for guidance.

Start by testing fuel pressure at the schrader valve on the fuel rail. Must use a gauge. Compare your readings to factory spec.

Be sure tuneup hardware is fresh. That includes plugs, wires, cap, rotor, fuel and air filters.

A weak ignition coil is another possibility. Coils can be tested for primary/secondary resistance.
 
Last edited:
collapsing catalytic clogging up the exhaust? Might be it. As well as all the other stuff listed above.
 
Well all great ideas. I did plugs cap, wirers about 12k ago, My first guess was fuel but I figured if it were fuel it would do it all the time not just at 55. Then the cat was a distant secont guess. I didnt want to to start throwing parts at it hoping to fix the problem. I have a ny 89, that I did too. It was $$$ but now the motor and everything on it is brand new. I have a gauge to check fuel so I will start there, them maybe swap pumps. I have 2 extra that have never been in the tank. I'll keep this posted.

Again Thanks.
 
rocknxj said:
Ever check or clean your throttle body?
Click to expand...

Or test the TPS with an analog ohm meter looking for a flat spot? It seems to recover as you give it more skinny pedal?
 
Update to this problem. I pulled the plugs to check & regap, the number 6 plug was completly covered in white carbon. There must have been enough spark at low speed to make it run, but not over 55. I replaced plugs, cap rotor & wires and it runs as good as it ever has.
 
kenny811 said:
Update to this problem. I pulled the plugs to check & regap, the number 6 plug was completly covered in white carbon. There must have been enough spark at low speed to make it run, but not over 55. I replaced plugs, cap rotor & wires and it runs as good as it ever has.
Click to expand...

Thanks for the update. Glad you found it.

Chalk up another one for checking TUNEUP hardware first when symptomatic.
 
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