HELP: SR20 bogging, horrible mileage, shuts off

[j0hn-0h]

So I recently bought my first 240sx with an sr20 swap and since then have ran into several problems.

It normally idles around 800 or so but sometimes it goes up to 1100 until i rev it, and sometimes it drops to around 500 and sits there for a while even when i rev it. Then it returns to 800 by itself.

The car gets horrible gas mileage. I'm not exactly sure because my odometer doesn't work. But I killed 25 bucks (appx. $3.17 per gallon) worth of gas just driving around town all day. I'm guessing that I drove about 100 miles or so.

Sometimes when I'm coming to a stop or just slowing down my car just shuts off on me. Usually it bogs first and then shuts off but yesterday as I was driving I was slowing down to a stop and it just shut off right when I stopped. If any of you know of the traffic circle in Long Beach, I've driven around it, and right before i got off onto N. PCH I slowed down, foot off the pedal, and the car shut off on me. Also, when I release the gas, the revs dip really low for a second below idle. (ex. I'm driving in 4th gear and I take it up to 4k rpm, then when I release the gas it goes down and hits like 400 or so and goes right back to idle.

There may be some things that I forgot to mention which I'll add later. Any help would be appreciated. Thanks.

[MomentumGT]

If you're running an aftermaket bov that vents into the atmosphere you might need to adjust it and tighten it up. Also check your MAF it may need to be cleaned.

-Jon

[s13rookie]

Also check your MAF it may need to be cleaned.

-Jon

Be careful with the cleaning of a maf. It doesnt take much to have them read wrong. Some people advise against it, some people have had no problems with it. There are quite a few writeups online about the best ways to do if you go that route. Just narrow down the possibiities before you screw with it though

[SexPanda]

See, im an NA guy. I could tell you damn near anything wrong with a ka. But an sr... My advice is to check the basics. Spark plugs, injectors, air filter, fuel filter, the usual. I actually had the same thing happening with my ka s13, but after a tune up it ran fine. And the MAF may be the problem, but like s13rookie said, i wouldnt screw with that yet. I would try to get your hands on a code reader. I'd say its OBD1, unless you have a newer s14/s15 sr20. I work in a shop alot, so I have one handy, but I know not everyone does. other than that, I wish I could help, but me talking about an SR is like a "cattle rancer helping you raise chickens, i tell you what boy. mmhmmm."

i heard a farmer saying that once. Laughed my *** off.

[s13rookie]

also you may want check your battery and alt. grounds

[j0hn-0h]

Thanks for the info guys. I forgot to mention that sometimes while I'm driving, I feel a loss of power as I gas it in first gear and sometimes in second as well. Also, occasionally, as I'm just cruising at any speed, the car bogs slightly. I just recently had my battery changed and alternator checked. Alternator was fine.

[silverarrow27]

Take pictures of your engine bay and post it up.

[yojimbo206]

check the idle air control valve(IACV) the easiest way to get to it is by taking off the intake manifold. it can get super dirty and the best thing to do is cean it out with brake cleaner and spray it clean with some compressed air. mine was idling like yours too and after i cleaned it it ran like a champ.

[RedtopTech]

The IAC valve is the first place to look, however a vaccum/boost leak, dirty Maf,or incorrect ignition timing could all cause these symptoms.
When i first did my swap i was having the same issue and founf that in its previous life someone had adjusted the small throttle stop srew on the throttle body. Also like previously stated, an open air BOV can do the same thing. hope this helps you!

[j0hn-0h]

I previously had a vacuum leak but had it fixed. I also had my timing done. I do have an aftermarket BOV. Oh and tonight as I was driving home on the freeway cruising in 5th gear at 3k rpm (I can only give rpms because my speedo doesn't work), I felt a sudden loss of power and the car would bog harder than normal. It would jump around between 3.1k and 2.9k at a steady rate and it kept going on and off for about 3 miles. I plan on getting a new MAF soon. Is this also responsible for my horrible gas mileage? I'm pretty broke and paying for premium is killing me.