sohc is running really rough with very little power

[supreme_1]

i am completely stumped, went through all relevant threads and tech posts.

i have a 89 sohc ka24e 240sx, i bought it like this so i am not sure what the problem is. the car was sitting for a bit but starts up and runs really rough.

when i pull injector harness #1 and #4 the car runs the same ( like crap) i changed out the injectors for another set and still it runs the same. i have approx 13 volts at the power wire on both injectors, and nearly nothing on the other (im guessing this is normal since the cylinders that are running do this also). i pulled my plugs and it doesnt look like cylinder 1 and 4 are firing.

i have consistent spark through all cylinders and my plugs are all firing.

i also pulled codes and there are no codes

can someone help me out

[supreme_1]

alright, so i just swapped cylinder 2's injector which i know is working, with cylinder 1. and it still runs the same. i know the injectors are good bc upon swapping them with another they run the cylinders which i know are firing.

[supreme_1]

so i figured the problem out.

i jumped the pulsating wire from the working cylinder to the non working cylinder, and it made the non working cylinder's fuel injector finally fire. so since i ruled out all other problems, the only thing left was continuity and ecm.

i used my volt meter to figure out that i had continuity on the wire. so lastly was the ecm. i swapped the ecm for another. and vuala, she works cherry.

cheeeeeeeeepono

hope this info helps

[jasaniceguy]

i think i have the same problem, but not sure. My car runs rough, No code, all injector seems to work. only runs rough on low end. what other things do you check?

[h2v7]

nice one on figuring it out sounds like a pain.

but im sure a comeup if that was all that wrong with it

[supreme_1]

i checked for vaccume leaks iwth a can of carb cleaner. just spray it around all vaccume lines and if you hear your idle change you have a vac leak there.

check your check valve going to the brake booster. can do this by pressing your brakes the load of times and watching for an idle change, or you can plug the line and see if the idle changes.

does your car sound like a wrx? if it does your running on one or two less cylinders. check this by unhooking your injector clips one by one. til you find the one that runs the same when you unhook it. from there isolate whether it is spark or fuel that you are missing. unhook your spark plug wire and put a screw driver in it and put the metal part of the driver about a mm away from a solid ground. dont touch it tho your going to get zapped.

clean your maf, and possibly change your plugs, make sure you gap them correctly.

does your exhaust smell foul?maybe one part of your exhaust system is plugged?

hope this helps

[jasaniceguy]

i checked for vaccume leaks iwth a can of carb cleaner. just spray it around all vaccume lines and if you hear your idle change you have a vac leak there.


check your check valve going to the brake booster. can do this by pressing your brakes the load of times and watching for an idle change, or you can plug the line and see if the idle changes.

does your car sound like a wrx? if it does your running on one or two less cylinders. check this by unhooking your injector clips one by one. til you find the one that runs the same when you unhook it. from there isolate whether it is spark or fuel that you are missing. unhook your spark plug wire and put a screw driver in it and put the metal part of the driver about a mm away from a solid ground. dont touch it tho your going to get zapped.

yes it sound like a WRX when i drive. all injector click, all four cylinder fire, with the used of a timing light.

clean your maf, and possibly change your plugs, make sure you gap them correctly.

all plug are new.

does your exhaust smell foul?maybe one part of your exhaust system is plugged?

hope this helps

other suggestion

[jasaniceguy]

check all four compression and came out 1=180 2=175 3=175 4=175.
runs fine when disconnected vac hose between BPT and EGR.

[supreme_1]

ok so if you sound like a wrx your more than likely running on 3 or less cylinders.

engines need a few things to run: air, fuel, spark and compression.

judging from your numbers you have compression.now on to the rest.

more than likely you have air coming into the cylinders if your engine still runs.

what i think is that you more than likely dont have fuel or spark.
to check for spark, you can either get a spark tester that conducts current through your spark plug wire, or you can get the one that plugs into the boot. check for consistant spark. it doesnt matter if your plugs are new, if there is no current going to the plug to make it fire, you will not have spark in that cylinder. are your plugs all gaped correctly?have you looked inside your cap and rotor for any signs of arcing in the cap, or possibly worn contacts. the center part of your cap has to have a spring and a conduit. im pretty sure thats how it looked, dont quote me on this tho.

how did you check for fuel?if you just put your hand on each injector while feeling for a click, that more than likely will not work. either get a hose and put it to your ear, while the other end is on the injector; or you can start your car and pull injector clips one by one. this is the easiest way to check which cylinder is down. so pull until the motor remains running the same.

you can also get a volt meter and probe each injector clip. i believe the red wire is consistant voltage (12.6-14.4) while the other pulsates at i believe the same voltage. iirc mines read 8.6 bc my volt meter couldnt keep up with the pulse.

another way you can check for fuel is to pull your rail form the block and either prime the engine by putting the key on the on position, or you can crank it. make sure to remove your ignition module so you dont get spark and light yourself on fire.

lastly, did you check to see if your grounds are connected. i dont remember exactly where they were on this motor, im pretty sure theres one or two on the back drivers side corner of the head and possible one on the back or front side of the head on the pass side.

check your injector clips for corrosion and correct contacts. if they are coroded clean it.more than likely these old motors have wiring or contact issues. start by lightly shaking all wires around the injectors and plug wires while the car is on. then go the more agressive route and shake the shit out of the large wire loom going from the motor to your ecu. shake it throughout the whole harness.

if you have an injector problem do what i did and jump current from a good cylinder to a bad one. if that changes your idle it is more than likely your ecu.

these are the main problems that i incurred while working on ka motors. of course there are other problems that you may have, but im basing my inferences on the fact that your car was running fine while daily driving it.

in the worse case you could have a bent valve, leaky head gasket, loose head bolt, and or cracked head or block.

disclaimer: i am not infront of a motor, nor am i infront of your car. each car is different and it could be anything, but this is my opinion of what i feel is wrong with your car, along with my remedies that helped me fix my projects.

[supreme_1]

did you scan for codes before you started diagnosing anything? theres do it yourself write ups