Crappy throttle response at low rpms 1990 240 sx

[Airmanspecial]

ok heres the info, on this 1990 240sx, the motor starts up fine idles high at like 1k...we just finished retiming , its at 20 degrees, nad the idle screw is all the way up(low as it can go..), once the motor gets over round 3k rpms, shes starts to fly, but gettin goin from a start she sputters and hesitates. even just revving from parked with the hood up does the same thing. weve looked for vacumm leaks and whatnot, checked grounding, and voltage from the alternator, (im used to workin old fords..) nada..the only weird thing is when we disconnect the collant temp sensor it seems to run better...not to much, but a minor improvment. Im think that the coil is on its last leg...but not to familair with these motors....befor i start the swaptronics routine can anyone help?
Modified by Airmanspecial at 11:36 PM 1/16/2009

[fun240]

Man it probably needs some TLC.

Do your proper tune up, spray the TB with TB cleaner, clean the MAF.. you know the usual stuff

Pics? How many miles on the chassis?

Welcome to Nico!!

[Airmanspecial]

Thanks for the Welcome!

Me and my buddy are both experienced Aircraft Mechanics in the US AF were just new to this car( I couldnt find an early bronco to work on...)anyhow.....weve redon cap plus rotor,wire, fuel filter, reset timing changed that temp sensor, ive checked the ground on the motor...less than 1 ohm... regapped spark plugs.. did a compression check and all were at 150(all within 5psi of each other but not lower)it has a new throttlr position sensor, cleaned the maf...all of the above...would dirty/clogged fuel injectors make for sputter/no power comin out of idle through 3k rpms?would a faulty coil do the same? we also noticed the idle doesnt drop down below a grnad...and we cant adjust it anylower....oh and spark plugs looked good...(ie..brown...not wet or fouled, with a little white(very tiny...))do these motors have any wierd nuances i should know?. THanks again!

[GO240]

The whole timing system in these motors can be a nuisance but thats it really

[PDavis40]

when you time these motors you need to get idle below 850-800 i think and take off the tps sensor connector. I don't know if this will help you but its worth a shot. Hope im not wrong but thought I'd share my .02

[Airmanspecial]

Fixed IT!!...we hope...have to wait till monday!

it was the alternator of all things!!!, yes we checked it at idle it was puttinout 13.5-7 volts....which is ok.....BUT!!! after much head bangin ...a cleaned out idle sensor we check it again!!! with lights on and in gear...she dropeed to 11.5 ish...not good! why it was almost stalling at idle to 3k rpms..!! alternator wasnt putting out the amps at low rpms!!Thanks! for all your guys's help! ill let you know how it goes tomorow!

[Airmanspecial]

OK it helped!, but didnt fix it, throttle response at idle/park is workin right,The old alternator was gunked up from a valve cover gasket that had leaked over the year/years..(I just got this thing..)when i put it in gear it sputters and gets running good after 2-3k rpms but throttle response is crappy when yo let off the gas,... It does idle wierd, it fluctuats between 700-1300. if we pinch off the hose comin from intake tube goin to the back of the idle unit, the engine calms down(ie. idles nice)

[stutterr]

sounds like a vacuum leak

[Airmanspecial]

ive looked at all the vaccum lines and there all conncted/no leaks, the only line i havent checked would be the smog lines goin to the carbon canister, would, i seriously doubt that would casue this severe of a problem..

[liquid_cool]

greatings airman..and thanks for your service..now to the meat..im not to shure..dont quote me..but im thinkin you might have a problem with your butterfly set up..you know..the diaphram that opens and closes em may be bad..and i think that runs off of vacume too...im looking at my intake now..and it looks possible..the part cant run more that 20 bucks im shure..try changin that..hope this gave ya another area to look in..good luck

[Airmanspecial]

like the throttle body butterfly valve? or the EGR diaphram?

[liquid_cool]

ya..i suck with names of ****z but you got the idea..let me know if this helps.

[pj]

any more progress? because im having the exact same problem

[Airmanspecial]

yeah i just got it back, was sittin at a buddys shopbeen to busy getting to it for 2 weeks.Any how after some reinspection of the emissions systems, it looks like my egr valve is stuck open, lettin exhaust gas into eh motor at low rpms why it idles sucky im a take it off this weekend when it warms up a bit...(its 34 degress...suposed to be in the 60s!!! this weekend) if you havent checked you egr valve you can apply suction to the top vacum hose(suck on it if youdont have a pump..) or you can slip a finger underneath and gently push up to actuate the valve, it should take a few pounds to push it up and come right back down, mine doesnt even move, so im starting there. so if you get sucction, the diaphrms good, if it moves, its not siezed, a good sign. Mines got suction, but no movement, so its getting replaced, we werent getting anycodes of the ecu and theres no wires hooked up to the valve.

[liquid_cool]

rite on airman..glad to see the issue found..let us know how it ends up man.

[Airmanspecial]

got the egr off finally, its black as midnight and siezed with carbon/soot through out, i ordered a new one should be here tommorow....hopefully this fixes the big problems!! naturally theres gonna be more bug/tuneing....but i hope this gets it drivable..(its got a straight pipe with a resonator...form the manifold...so its quite loud...and i can t get goin withough puting it to full throttle....loud!!! im a have to put a new exhause on it....but a turbo is planned....so i dont want to by new stuff just to replace it laterz

[Airmanspecial]

ok changed out the egr, and it runs better...but not the night and day difference like I expected...theres more to this thing....im starting to go with more advanced timing issues...like whoever changed the timing chain missed a tooth....ohmed out the coil its fine..i couldnt check fuel pressure casue i lack the inline adapter to hook it to the fuel rail.... my buddy cleaned the MAF with brake cleaner so thats on my list to change as well...tommorow ima take the valve cover off and turn the motor and see where the chain is...its gettin there!! idle is alot better...just need to tune it!

[Airmanspecial]

looks like i found te culprit.....after removing the valve cover, found the timing chain guide busted in half just danglin there...no chain control on the right side(facing toward) of the chain....just loosey goosy. I picked up a complete timing set since ill have to rip into it to get the cover off. I bet the thing jump a tooth...lucky i didnt bend a valve, I keep you folks posted when i get r done..

[liquid_cool]

grats Airman...hope ya get it back on the road fast bro..post again if ya need a hand.

[Airmanspecial]

so....i did skip a tooth, the off colored chain link was not where it was supposed to be...i even managed to get the cover off without droping the oil pan...score!! im puttin it back together now, and will finsih it on monday(buddy who owns shop is outa town...grrr...) just down to pulleys puttin the radiator ect..back in and firing it up! and heresa handy tip for installing your distibutor........bolt it in....point toward number 1(assuming your at TDC>>) taka rubber band or whatever fasten it so the rotor doesnt move....then install the oil pump drive spindle.....and hen twist the oil pump into place...and BOOM! dont have to worry bout being a tooth off!

[tero404]

i have the same problem, i think i will try some of what u did like the egr and looking at the timing chain. let us know how it runs

[cbt240sx]

Welcome Airman, I see you're in my neck of the woods. Come on down to Downtown Music whenever you get a chance. I work the door there. BTW, what model engine are you working on? I see that its a 90, so KA-E?

[Airmanspecial]

yep, ka24e, after gettin her all put back to gether, it still has that throttle response problem...but it definatly idles alot better. i trouble shot it down to the crank angle position sensor...i can nurse the car into higher speeds...but i cant stomp on the gas and expect to go fast atm.,....motors not advancing the way it should, im a taake the dizzy apart and test the sensor...for some reason though all the replacment sensors(on partsamerica.com) dont look anything like the 1 thats in the dizzy, is that an upgraded OEM part? mines got the silver wheel with the holes at every degree mark...the new one looks like a solid black piece...and its 200 bucks..