SR cutting out under low throttle.

[Dolby109]

So I just finished installing a new SR20DET (with stage II cams) in my 240.
I got it idling decently and got it to stop stalling every time I let off the gas (from load).
However I am having one major problem. The engine keeps trying to cut out from 2500-3500rpm under low throttle. If I accelerate semi hard it drives fine, but as soon as I get up to cruising speed and left off the gas it starts having problems. The problem is most noticeable if I accelerate slowly in second gear the car abruptly stops at 3000rpm and sputters there.
As soon as I give it more gas the sputtering stops and it accelerates out.

Any ideas for what this could be are much appreciated!

[Dolby109]

Come on...doesn't anyone have an idea?

I checked and the spark plugs looked good except slightly white on the tip. The O2 sensor was slightly dirty so I cleaned it, and there was no change.
If I unplug the MAF the car runs like crap.
If I unplug the TPS the car idles very high, but the problem remains.

So far it drives completely fine except when you are essentially at cruising speed between 2500-3500rpm. When I took it on the highway I had to keep accelerating then coasting.
When it happens it feels like fuel cutoff, sounds sort of like a launch controller for drag racing.

It has to be something the computer is doing with one of the sensors...any ideas?

[240dream]

sounds like my ka-t, it would mis/bog when i hit boost it turned out to be to rich flooding it out, whats your afr?

[Dolby109]

No idea what the AFR is...I may have to hook up a wideband.
However my problem is not quite the same...when I give it more throttle it acts fine. As long as its enough to accelerate at a decent pace the car feels completely normal.

Also the plugs if anything suggested it was running lean, which is unusual because my last SR (with the same computer and most of the sensors) ran rich most of the time.

Would an SR act like this if the timing was off? When I got the engine the CAS was turned as far as it would go to the right. I centered it out. At one point I tried to play with the timing (just by sound, I dont have a light), and any way I would adjust it the RPM would lower and then correct itself and run normal again.
I have a friend with a timing light, so I'd like to try and make sure its timed right (to 15btdc) but given its performance under heaver throttle I doubt timing is the issue. One other thing is I have heard reference to timing mode, so I looked up how to put the car into timing mode, but never found out exactly what timing mode does. Does it keep the timing from advancing when you raise the RPM? Does the computer go out of timing mode as soon as you shut the car off?

[ultimateirving]

Mr dolby109. You probably jacked up the timing if under low load its getting real bucky/cutting out. Please research there is a process to setting the timing in SR's, you cant just starting spinning the CAS.
To make sure 100% the timing is right, its recommended to remove the VC and verify the links on the timing chain match up to the marks on the cam.
There are about as many writeups how to set the timing, as mcdonalds has served worldwide.

[KoukiMonsta]

Originally Posted by Dolby109

No idea what the AFR is...I may have to hook up a wideband.
However my problem is not quite the same...when I give it more throttle it acts fine. As long as its enough to accelerate at a decent pace the car feels completely normal.

Also the plugs if anything suggested it was running lean, which is unusual because my last SR (with the same computer and most of the sensors) ran rich most of the time.

Would an SR act like this if the timing was off? When I got the engine the CAS was turned as far as it would go to the right. I centered it out. At one point I tried to play with the timing (just by sound, I dont have a light), and any way I would adjust it the RPM would lower and then correct itself and run normal again.
I have a friend with a timing light, so I'd like to try and make sure its timed right (to 15btdc) but given its performance under heaver throttle I doubt timing is the issue. One other thing is I have heard reference to timing mode, so I looked up how to put the car into timing mode, but never found out exactly what timing mode does. Does it keep the timing from advancing when you raise the RPM? Does the computer go out of timing mode as soon as you shut the car off?

Haven't played with sr in a while...timing mode as I recall can be done by turning the ecu screw. I agree with ultimateirving. Do a bit of readi g on timing. I do not see it being related to any other sensors, besides CAS. Especially since u said it was way cocked when the motor arrived. Make sure she didn't jump a tooth. get back to us.

Originally Posted by ultimateirving

Mr dolby109. You probably jacked up the timing if under low load its getting real bucky/cutting out. Please research there is a process to setting the timing in SR's, you cant just starting spinning the CAS.
To make sure 100% the timing is right, its recommended to remove the VC and verify the links on the timing chain match up to the marks on the cam.
There are about as many writeups how to set the timing, as mcdonalds has served worldwide.

[fliprayzin240sx]

Get a timing light and check your baseline timing...sounds like its too far advanced.

You can still re-stab the CAS in with the valve cover off and make sure the dots on the CAS line up. Doing that gets you close to 15* but its still not always 100% guaranteed. I always stab the cas with the cover on, then still shoot it to make sure its at the 2nd line from the right (15*) on the main pulley.

[jdm213]

i f i were you i would check my fuel pump unless u have a walbro 255, then if all is good check the fuel pressure regulator