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Discussion Starter #1
Hi there, I drive an 87 pulsar nx xe with an E16i, every thing is stock except for the AT-MT swap performed recently. As you may know this motor is TBI, and pretty simple.
I've done quite a bit of searching over the past week or so on this forum, just trying to figure out what is happening with my pulsar. I am pretty familiar with the car inside and out but now I'm stumped. When I am driving regardless of my current speed the engine feels like it suddenly gets a boost of power when it hits around 3000 rpm. It's almost like hitting V-tech in a Honda. Not to complain about my new found power but it is a little unsettling, because cars just don't start making extra power for no reason.
However in the last few months I have replace the AT with a MT. I did replace the ECU at the same time and had to reset the idle speed when I finished. Also last year I replaced the mass airflow sensor and the throttle position sensor. Both appear to be operating normal still.
On top of that I am also having another intermittent problem while driving. Once in a great while I can be just cruising down the road and all the sudden my rpms drop and the car starts to buck wildly, as if it were having a fuel cut issue. However if I let off the throttle immediately the car will just coast but not allow me to maintain speed or accelerate. When it does this the engine never stalls and idles just fine. When I press on the accelerator, while in neutral, the rpms will jump to just about 3000 again but then will not go past that and the motor just cuts out until the rpms drop down to 2500 and then back up, repeat. If I let it idle for about 1 minute then its fine, and doesn't happen again for about another month.
So I think that the two problems are connected somehow, and I know its not due to the new transmission swap because it did this once before I swapped it.
If anyone has any suggestions or thoughts I would greatly appreciate it!
 

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possibly a TPS thats out of adjustment?
 

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Discussion Starter #3
Could be I suppose. I did swap out my ISCV two days ago, since I had an extra one. That seams to have fixed most of the issue. However once in a great while it still does it. I think I will check that tomorrow. Thank you for the heads up.
 

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So after about a week or so the problem returned and got even worse. The car would run great when it was cold, but once it warmed up it just wouldn't allow me to rev past 2500 rpms. So I did some real in depth looking around and found that the plug that goes to the coolant temp sensor on the rear of the intake manifold was broken. I have no idea how it broke but it was just barely on there and if I were to wiggle it just a little bit whilst the engine was at idle the rpms would jump up. So today I braved the local pulln'save wrecking yard, with several feet of snow covering all cars out there, and found myself an unbroken plug. Also went to Napa auto parts store and bought a new sensor. came home installed it, and all the sudden the idle speed smooths out and it seems to be problem solved. However since I had recently adjusted the idle speed I now had to readjust it and bring it down some. Which also means I got to readjust the Throttle Position Switch lots of fun!.
So to sum up this long drawn out solution. The coolant temp sensor with a loose plug seems to have been the problem all along.
 

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yes i also have had to replace my old rotten coolant plug. glad to hear you have found the problem.
 
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