Rough idle HP down a bit after engine warms up

[newboyspo]

Hi,I bought a 90 240sx with the ka24e with 178000mi and am in the process of going through it front to back, the problem is that after warm up it tends to have a little bit of a rough idle (around 600-700rpm) and looses some (maybe 10-15 hp?) of it's power after it warms up, I read a thread about a 91 ka24de on this sight with the same prob. and he thought it was the knock sensor, under the intake, my question is does the ka24e have a knock sensor and could this be my problem, I have went through every vacume line I can get my hands on, checked and good, o2 sensor is new, plugs wires cap rotor maf egr all test good, also removed the aiv and plugged the holes. Thanks for any help youall can give

[Shift_Tommy]

Run the ECM in Diagnosis Test Mode II and check for any error codes. Also, check your iacv-air regulator by pinching the IACV-air regulator hose and see if the engine speed drops.

[newboyspo]

Thanks Shift_Tommy,I pulled the ecu out and checked the codes, if I am reading them right (ie:two slow blinks of both led's at the same time, a short pause, first set of blinks is slower and counts for 10's second set of led blink faster and counts for 01's)If this is true I get 3 longs then 4 shorts(34 = knock sensor)5 longs and 1 short (51=injetor analysis)

pinching the idle air control valve hose does drop the idle

Is there anywhere I can get a drawing of the intake side to be able to find the knock sensor? or a web page with a picture of the part, or somthing?

I don't know what the 51 injector analysis is all about and I also need to find out how to reset or clear the memory on the ecu (after my having pulled wires to several sensors and changing out the seals and O rings on the injectors it could be old data?)anyway thanks again and any help would be great!!

you guys are great.

[Shift_Tommy]

the knock sensor is on the passenger side, upper engine area, blow center of intake manifold, and mounted in engine block

to reset the ecm, while in Diagnosis Test mode II, just change it back to Diagnosis Test mode I.

Also, you should check your IACV-air regulator because pinching the hose shouldn't drop the idle. It probably is clogged.

[NISTECH]

if you pinch the iacv hose you starve the engine for air, so yes you should have an idle drop.Code 51 typically means injector leak into the engine. It means rich condition. Check your coolant temp conections and see if it has green corrosion in it. If so clean it best as you can and tighten the female pins in the connector so it fits tighter on the sensor terminal pins.

[newboyspo]

Thanks for the info,I found that the ecu is happy, I do have a leaky injector to deal with and I think this may be my whole problem.. I am going to check the iacv though newbie is as newbie does I always say

I read the codes just like a newbie would read them...

when the key is turned on the first thing the led's do is blink twice (I found out that this is because one has to choose the mode one wants.. ie: mode 1, mode 2 ...3....4....5), then read the blinks

becaues it starts out in mode one as soon as you twist the screwdriver switch it blinks twice for 2 then 3 times for 3, four times for four, 5 times for 5 and then blinks once for one again...... so I read it as 34 and 51 duh......

once I figured it out using a service manual I went into mode II then it gave me a code 55 =ok

thanks for all your help... I am learning, please have pitty on all us newbies..

P. S. which forum would I go to to find out how to best boost the hp on the ka24e besides turbo bolt-ons?

if you pinch the iacv hose you starve the engine for air, so yes you should have an idle drop.Code 51 typically means injector leak into the engine. It means rich condition. Check your coolant temp conections and see if it has green corrosion in it. If so clean it best as you can and tighten the female pins in the connector so it fits tighter on the sensor terminal pins.

if you pinch the iacv hose you starve the engine for air, so yes you should have an idle drop.Code 51 typically means injector leak into the engine. It means rich condition. Check your coolant temp conections and see if it has green corrosion in it. If so clean it best as you can and tighten the female pins in the connector so it fits tighter on the sensor terminal pins.