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Discussion Starter · #1 ·
my car was showing symptoms of preignition (i.e. falling on its face under wide open throttle) and i put a heat riser tube back between the exhaust mani. and the air box and it didnt to it anymore...

it even seems to be getting up faster...sweeeet...:D:D
 

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That is wierd. But I guess it good
 

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Discussion Starter · #3 ·
might be a cure for the sentras that fall on their face under hard acelleration....which is odd because its forcing hot air back into the motor, which would bring the motor up to temp faster....what a cycle....heh...mabye these engineers wernt joking when they said 'You need this piece on your car' and we say 'eh..mabye...'


:D:D
 
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LittlebittaContact said:
my car was showing symptoms of preignition (i.e. falling on its face under wide open throttle) and i put a heat riser tube back between the exhaust mani. and the air box and it didnt to it anymore...

it even seems to be getting up faster...sweeeet...:D:D
That is not the description of preignition btw.
 

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My engine falls on it's face at wide throttle openings, but my car didn't have that tube from the factory. :(
 

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Discussion Starter · #6 ·
preignition or detonation

it would fake that the timing was off
 
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LittlebittaContact said:
preignition or detonation

it would fake that the timing was off
You said it was falling on its face - as in it had a flat spot.
The fix was to reinstall the heat riser tube. Increasing the air intake temp will make a preignition or detonation problem get worse.

Preignition can be heard because the engine PINGS.
Detonation causes knocking. You didn't mention either of those things happened.

More likely, the increased air temp helped keep your gasoline atomized thereby keeping the A/F ratio where it needs to be. This is what the heat risers function is.

Check that your coolant lines are going to your intake manifold. This also serves to heat the air mixture to keep the gas from condensing out of the air/fuel mix (also keeps the throttle plate from icing up and getting stuck).

http://www.hastingsmfg.com/Service%20Tips/detonation_and_preignition.htm
 

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Discussion Starter · #8 ·
It actually only does it when the motor is cold, so im going to try some different spark plugs, i have bosch +4 in there now and i dont like how it acts for about the first 10 minutes i drive it.

its fine after it warms up, i just need it to warm up faster.
 

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The Bosch +4 plugs are not good for our cars. Get the factory NGKs, they have been proven to be the best time and time again.
 
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Agreed, Bosch plugs are junk for Nissans. Put in OEM NGK's. Your problem of bogging/having a flat spot can definitely be ignition and a/f related.

Check that your heat riser door is working when the engine is cold. The door needs to block off the cool air intake so the engine draws heated air from your heat riser tube/exhaust manifold shroud. If the vacuum diaphragm leaks or your temp sensor is bad, you'll still be pulling in cold air when the engine is cold and have stumbling problems as you describe.
 

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RiceBox said:
The Bosch +4 plugs are not good for our cars. Get the factory NGKs, they have been proven to be the best time and time again.
Blah, Bosch +4!

Get some NGK V Series

Thats what im running now.
 
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Aren't the ngk platinum plugs better. By the way, do they make any difference ? Some people say they do, some say they don't. And since i haven't changed mine, i don't know. I also haven't changed mine because i would like to know which are best. Holla back people.
 

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Discussion Starter · #13 ·
well we all must be on the same brainwave because before i read these replys about the NGKs i actually went out and got some v power ones, the car runs a little better but thiers still a small flat spot, the timing light checks ok, i noticed the No.4 plug was carbon/oil coverd, but the only thing i can think of would be a leaking valve seal, as i have replaced every OTHER sealing component on the motor, and the car shoots no codes so im assuming this would not be a A/F problem, the MAF is brand new because i had to replace that when i bought it because it wouldnt turn over 2650 RPMs.

**takes a breath** ok im done for a few :)
 

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is your engine runnig some wath like unbalanced ??... cuz mine is like that now... seams to be a "flat spot" too.. but when i hit the gaz... it run strong and nicely... i even with the ngk it does it...
 
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