hi rpm problem

[rhd240]

i have a 89 240sx with rb20 swap . the car runs great but at about 6000rpm it starts breain up. i didnt have this problem with my last one. can any 1 help me figure this out?

[Joe]

check your timing and plug gap.

also for boost leaks.

[DriftX]

I would check for ignition problems first! Pull out your plugs, inspect them for debris, clean, regap.

Now check the condition of your coilpacks. Clean the button/spring with med grit sandpaper and look at the sides for any 'arc bleeding', they they look fine, put them back in.

Check to make sure the ground for the ignitor is tight and that the coilpack plate ground is hooked up.

Make sure all connections are tight on the coilpacks

Now, your ignition system should be fine..

Check for base voltage on the battery. Put it under a small amp load (flick the lights on) and test what the battery voltage is putting out. If it is under 12.5 or so, then perhaps your charging system isn't up to par.. if that checks out, then it's fine.

Now, check for any fuel leaks, and then test for fuel pressure. Should be 36ish at idle.

Now visually inspect your couplers on your intercooler piping. If you have ring worm clamps one could have come loose or a coupler has split indicating a boost leak.

Hopefully this helps!

I myself had incorrect base timing and a bad coil pack.. both of which will do what you said.

[rhd240]

just did a grand national coilpack conversion,new plugs and had timing checked and still does it but if i let of the trottle just a very lil bit it is running good. dont know why . i thought something could be adjusted wrong . also i have very little mechanical skills so that dont help either. i can make them look good though.

[DriftX]

Well if you have to let off the throttle to get it to run right, your either getting too much fuel or not enough spark energy. make sure all your grounds are clean on your coil conversion, all plug wires are tight, set tps to factory spec, check base timing and go from there.

[shally2186]

my guess would be to check ur fuel pressure..i have a 89 coupe w a RB20DET and it was giving me the same problem sept around 5k...do u have an upgraded fuel system?

[papachrizzle]

im having this same problem with my car right now..when im driving it and gets up to about 5 to 6 grand rpms its start bogging a lil and wont pick up speed,,.... thats crazy....

[rhd240]

only motor upgrade is a rb25 turbo , and grand national coil setup. havent had it 2 long

[shally2186]

ic..well mines about the same sept i have a bigger fuel system. i just played with my fuel presssure and reset my ECU.

[matafied]

only motor upgrade is a rb25 turbo , and grand national coil setup. havent had it 2 long

with the coil pack conversion it is necesary that you run a differant power wire to the coil packs, the one on the factory harness (white wire ) can not supply the needed power for the much larger coil packs. ( towards the end of the coil conversion thread ) oh and change those plugs to some AC delco's plats gapped to .8 and you should be fine

[rhd240]

think i found my problem. i have a rfl bov that is sucking air at an idle. i was told i probably just need a new bov.

[DeclareYrWar]

just recirculate it like factory