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Thread: Cold running car bucks on light throttle.

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Posts: 1-10 of 13
2012-03-27 04:08:54
#1
Cold running car bucks on light throttle.
Got a odd issue with a mates Primera, Sr20ve with cvt removed and manual conversion. Running a b13 style ecu and daughter board. Drives fine when warm, but when cold it bucks and kicks on light throttle.

Got to take it out with wideband on tonight and see if i can data log everything and spot what its doing, but it kinda feels like fuel cut? I can adjust this and see what happens. Maps are fairly conventional, but will check where its running and see if its doing anything odd.

Thought it might need more coldstart fuel, but didnt change anything.

Any ideas i can look for while im out?
2012-03-27 06:20:50
#2
Originally Posted by Evlnxr
Got a odd issue with a mates Primera, Sr20ve with cvt removed and manual conversion. Running a b13 style ecu and daughter board. Drives fine when warm, but when cold it bucks and kicks on light throttle.

Got to take it out with wideband on tonight and see if i can data log everything and spot what its doing, but it kinda feels like fuel cut? I can adjust this and see what happens. Maps are fairly conventional, but will check where its running and see if its doing anything odd.

Thought it might need more coldstart fuel, but didnt change anything.

Any ideas i can look for while im out?

Mine does the same thing. Letting my VE warm up for a solid 5mins before I move her solved this problem.
2012-03-27 06:22:48
#3
Have you checked the maf? If it is only happening cold it prob isnt the maf but checking if it is dirty is free crc maf clear is $10 so worth a shot. Most of my idle/ low throttle issues seem to end up being maf related.
2012-03-27 06:47:39
#4
My B14 had this issue before. I cleaned the MAF, nothing changed, except I got a light increase in MPG's. Cleaning it had good benefits. But after doing research and talking to a bunch of people, I came to the conclusion that my spark plugs were bad. So I replaced them and gap'd them properly. I rarely have this issue now. My mechanic was suggesting that it was my IACV going bad, but everything seems fine for now.

So in conclusion, It may be:
1. Spark Plugs
2. IACV (Idle Air Control Valve)
2012-03-27 19:48:21
#5
i am having this same problem and was told it cauld be the tps? i have yet to pull it because the bottom screw is stripped but hopefully soon and ill let you know
2012-03-27 21:35:34
#6
I think eveyone has this problem, lol.. I used the same method Swagzb14 uses.. Runs like a champ afterwards..
2012-03-28 10:54:02
#7
Running more fuel helped, but the maf sugestion has merits, as it was not running lean a few weeks ago, if the maf is dirty it could explain that.

Plugs and TPS are a bit unknown too, although consult does acknowledge throttle closed position i havent checked the voltage.

Cheers
2012-04-02 13:55:59
#8
Any time I have idle and/or stumbling issues I set TPS, set base timing, set idle RPM and then verify vacuum leaks. Once all that is done, you can move to the MAF or O2 sensor and so on.

Brent
2012-04-03 05:15:11
#9
my car does this with my tuned JWT ecu for my DET. I've heard about it from another thread with JWT ecus. I let it warm up for 5mins as well and runs fine.
2012-04-03 05:26:10
#10
Originally Posted by sr20fan
my car does this with my tuned JWT ecu for my DET. I've heard about it from another thread with JWT ecus. I let it warm up for 5mins as well and runs fine.


Yeah, I'm running a JWT ecu as well. But it's not as before since I fixed/adjusted a couple of things.
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