Ever since I've switch from the b16 to the b20, I've been dealing with the car studdering/hesitating under regular throttle but only under about 3k rpms.

When you give it WOT, the car accelerates smoothly.
Any Ideas? Or has anyone else dealt with this in the past?

Fuel, vacuum, bad sensor, poor spark?

Thanks in Advance.

 

whens the last time u did plugs, wires, cap n rotor? also, are the o rings on the valve cover sealing? you could have a little oil down in the spark plug holes that is causing a misfire. if it runs fine and WOT i dont think its anything compression related. you could also maybe run some injector cleaner in there too. other than that....are you on a stock ecu or a chipped one?

 

Valve cover seals are perfect.. plugs have good color to them.
Haven't changed wires, I'll try that today. And I'm running an un-tuned P75 Ls ecu.

 

is the timing set right at 16* btdc? are you running adj cam gears and have you adjusted the intake cam at all? if so you would need to set the timing properly with a timing light. ie if you advane the intake cam 2* you need to also advance the distributor 2*. if your timing is off itl run ackward. also, have you had the timing belt off? you may be off a tooth in timing.

 

^I'm not running any cam gears or any modifications, its completely stock..I will have to get a light and time it tho. I changed the belt before installing it, but it runs too good to be off a full tooth.

It only studders at a constant throttle under 3k. If you give it anymore than 1/8th throttle it accels fine.

This is a weird issue.
I forgot to mention its throwing code 41 (o2 heater circuit)
Any ideas how to fix that? I have replaced the o2 with a new Denso, still same code and same studder.

 

maybe one of the grounds are loose?

 

When I had that problem I replaced the O2, fuel pump, spark plugs, and redid timing and idle...after all that it ran perfectly. My guess is the 02 sensor was what caused it all.

 

definately would know if you were a tooth off. had that happen once and the car goes crazy. try a different coil or get someone with the same parts and keep swapping till you find it

 

My LS was like 2-3 teeth off and had so little power that I could barely move the car in first gear. So yea you will know if your off on the teeth lol.

 

last or not least the ignitor can be going bad in the distributor