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Discussion Starter · #1 ·
Hi, I have been driving this 1991 240sx le, auto (canadian car if there is any difference), and I sometime drive it hard, ok often drive it hard. But I always waited until the engine was warm. Until the other day I was in a hurry so, I just started the car, waited a min or two and went. It was a busy day and lot of traffic. So to get in I didn't have to, but I gess habit, so I just floored it, and to my suprise when it hit about 5000 or maybe a little bit before the car just pulled like crazy. First time ever that I felt it pull like that. I'm now asking my self if the dohc is working at all. Because it would explain a couple of things like: the feeling of floating valves at around 6500 to 7000 in second gear.

What could be causing this ?

Also, if anyone could tell me how exactly the dohc system works in these
cars it could help find the trouble, or narrow down the possibility.

Any feedback would be appreciated.

and does any one now if there is a difference between the ECU of a auto and a 5 spd 240 sx, for example could a 5 spd 1989 trans, be put in a 1991 auto car and keep the auto ECU. Cause I have a 5 spd trans, and I would like to put it in this car. It's from a part car I bought, the person that owned the car before fried the ECU. The clutch in the auto trans are going and If I take it out I would really consider putting the 5 spd. I hate auto.

I live in Canada there aren't a lot of 240sx around my place, Atlantic province.
 

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Discussion Starter · #3 ·
What I mean by more power, is the needle went from 5k to 7k, at least twice has fast has it normally take. I'm sure it's not cold air. The temp here is below freezing, And the day it append, it was actually a nice day.

Almost burned some rubber lol.

Felt like a shot of nos almost.

But thankx
 

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Did you do any type of tuneup prior to this new power discovery? There is nothing mysterious about the DOHC working different at low RPMs verses working at high RPMs. There is no VTEC type of mechanism on these motors.

IMO, I would refrain from running the motor at 7,000 RPM or higher often; good way to stress the rods. Power drops off at around 6,200.
 

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I don't know about your problem but with the tranny as far as I have been told you need a dohc tranny I have no proof behind this or reasosn why so I'm probably worung with the ecu I would suggest keeping your suto ecu because there is a speed limiter on the 5 spd ecus yes you can keepp your auto ecu my budy keep his when he did his swap and I plan on donig the same
 

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Discussion Starter · #6 ·
I'm going to check about the trans. and try to find the specs (gear ratio) and try to put the bolt pattern on a piece of cardboard to see if it match.

I'm going to find the specs for the head, It might give me a better idea of what could be the problem. I don't want to take that head apart for noting, It's not leaking, or anything, and I had problem whit the water pump a will ago and the girlfriend drove it, I'm not sure if she over heated the head. I wouldn't thing she would have, but I gess you never now.

Thankx for the feedback.
 
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