I have no idea what this is. Ive replaced everything except the o2 sensor. WHenever my car approaches 3k under light to medium throttle it pops in the exaust and the cars ride becomes a constant back and forth hesitation...not a drastic hesitation, but still noticeable. ANd whenever im crusing in any gear, under 3k, it hesitates and pops, so cruising is anything but smooth. Does anyone have a clue as to what this could be?? Thanks in advance...John.

Might want to try here:
http://www.se-r.net/car_info/problems/index.html#Erratic Idle and jumping idle

Also, do a search on the digest for surge and bucking. You should be able to find some stuff there.

Could be your EGR and BPT are clogged. Or if your EGR daiphragm is bad, it is the same thing as a vacuum leak and will casue those symptoms.

Other possibility is your fuel injectors could be clogged and at low throttle are causing the bucking and exhaust fluctuation which in turn would cause a possible backfire sound like you had stated.

Here is some more info on this:

http://www.se-r.net/faq/problems.html

Have you checked your plugs? My O-Rings on the valve cover went bad causing the plugs to soak up in oil. The car would drive fine with no load, but studder when accelerating fast. Check that.

Originally posted by NismoNx2000
WHenever my car approaches 3k under light to medium throttle it pops in the exaust and the cars ride becomes a constant back and forth hesitation...not a drastic hesitation, but still noticeable. ANd whenever im crusing in any gear, under 3k, it hesitates and pops, so cruising is anything but smooth. Does anyone have a clue as to what this could be??

John,

I have had the same problem since I bought my 92 NX a year ago. I have replaced spark plugs, spark plug wires, dist cap, fuel filter, the EGR and BPT and clean, and also the throttle body has been cleaned.

I do not notice the problem under WOT and when off the throttle. The only time that I notice the problem(surge and hesitation) is when trying to hold a speed under 3K RPM's.

Also, I found that when the weather is warmer (above 60F), that the problem is more noticable, more surge and hesitation while holding a speed. I don't know what a fix is for this yet:( , but the day I figure this one out, I will be much happier!

Good luck on finding the problem.

Monty

Even if you clean the EGR, the actual diaphragm can be busted from age.

This will cause low RPM bucking and crappy engine idle under 3000k, but it will run ok at WOT, etc.

My old '91 NX2000 did this and I finally had it with the bucking, so I cut a plate out of thick aluminum stock using the EGR as a outline, drilled two holes in and put it between the EGR and plenum blocking the EGR off completely from the intake plenum.

I don't recommend this method, but it did the trick for me. A new EGR is quite expensive and at the time that was the only alternative I had.

have you tried using some carb cleaner and cleaning out the metal tube that leads up to the bpt tube? my car has the same problem and has since i bought it. I have a new egr and bpt valve as well as new hoses sitting in my room, i plan on cleaning the throttle body and all the little metal tubes that lead off the intake (i think theres only 1) but ill let you all know how it goes when i get it all fixed.

As a side note I had my exhaust worked on *** i busted a hole in my resonator racing my friends prelude. I had new gaskets put on around the cat to stop a leak and a new resonator, this helped calm down the bucking and surging alot!! didnt cure it though.

i have the same problem with et poping and teh odd surge on my NX i have pluged off the EGR completly and i stil have it a bit and i have started replacing all my vacume hoses and its bin geting better since i have started doing that so i must have some vacume leeks some were in the system. and i think i might have a falty PVC valve or just sluge that might be seeping in over time so im going to replace it and vent it in a catch can to see if it helps.

I want to get to the bottom of this popping thing. I noticed that after i drive the car for a long trip, say 40 miles or so straight on the higway, the popping and surging is pretty bad. However, i didnt try what they recommended on se-r net, and taht was too unplug the hose going from the bpt to the egr and plug both sides, i will see how it works on my drive home this evening. I appreciate everyones help though, its nice to know others have this problem, but its not cool that we cant figure out a solution. Im going to try and clean my throttle body this weekend as well, and who knows, maybe the o2 sensor needs to be changed.

well to me for a car with this much originallity and being 10 years old a little surge and hesitation doesnt bother me that much but yeah it would be nice to know what causes it.

WEll, i did what they suggested on se-r.net. All i did was unplug the small hose going from the bpt (left most disc shaped object) to the egr (right most disc shaped object). I pluged both holes, one with masking tape, and the hose end with a screw that sealed it nicely. I did this yesterday, and i drove home from my 45 mile trip home and the hesitation and popping under 3k seems to be gone now. Which makes me very happy, and it seems like that is the solution. I suggest you try this and see if it helps. A while ago i also removed the hose going from the egr into the intake hose going to the throttle body. That needs to be plugged as well on the intake hose. ONce again, i hope this info proves helpful. Thanks to everyone. John.

Originally posted by NismoNx2000
WEll, i did what they suggested on se-r.net. All i did was unplug the small hose going from the bpt (left most disc shaped object) to the egr (right most disc shaped object). I pluged both holes, one with masking tape, and the hose end with a screw that sealed it nicely.

I did the same on my old NX and after about 2 years or so, the diaphragm as stated earlier went bad, casued a vacuum leak and I was back to square one. Shitty performance. That was when I blocked the EGR totally with the aluminum stock plate.

Just keep that in your mind if you plan on keeping the car for a few years and do not want to replace the EGR with a new one. So when it possibly happens to yours, you'll know what to do next.

Glad to hear the blocking of the tubes worked I used standard rubber nipples from Advance Auto. they worked great, but would dry rot every few months.