So my car, 93 KA24DE, has been running real rough when it warms up. So i replaced fuel pump, fuel filter, knock sensor, distributer, plugs, knock sensor, both coolant temp sensors, and maf. When the cart is cold it runs good, but when it gets to operating temp it hesitates when i use the throttle to maintane speed. If I full throttle it there is zero hesitation. i have checked for vacuum leaks and found one and fixed it but no help. Could it be fuel pressure regulater or TPS? TPS is with in specs and my fuel pressure seemed right but i might have checked it wrong. Could the EGR system be going out? The only mod on the car is a K&N drop in filter. I have looked everywhere on this site. Any help would be appreciated even if its a link on this site.
need help car has been down and out for 2 months
jdm240sx
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So my car, 93 KA24DE, has been running real rough when it warms up. So i replaced fuel pump, fuel filter, knock sensor, distributer, plugs, knock sensor, both coolant temp sensors, and maf. When the cart is cold it runs good, but when it gets to operating temp it hesitates when i use the throttle to maintane speed. If I full throttle it there is zero hesitation. i have checked for vacuum leaks and found one and fixed it but no help. Could it be fuel pressure regulater or TPS? TPS is with in specs and my fuel pressure seemed right but i might have checked it wrong. Could the EGR system be going out? The only mod on the car is a K&N drop in filter. I have looked everywhere on this site. Any help would be appreciated even if its a link on this site.
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16 Posts
Did you replace all those things with new ones or used? Katfan27 is right check the codes.
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28 Posts
Is it getting fuel, sparks, and compression
I doubt it's the tps if it looked to spec when you checked it. I would guess that it's either the MAF, IACV, or the injectors, but I'm leaning toward the IACV. It's pretty cheap to clean so you may as well start with that. I had the same problem and it ended up being the MAF and adjusting the idle on the IACV.
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I'm doing this on my phone so bare with me. Auto tech 101. When you first start your car your. Ar will run what's called "open loop" this means your ecu is running the engine on a preset fuel map and not looking at your sensors for any feedback to make adjustments. You say tour car runs fine when it's cold this is why. As you drive the car it warms up and when it reaches operating tempature it goes into what's called "closed loop" this now means your ecu has reached out and is now using signals from all your sensors to make adjustments to the fuel map and run the engine. Your car hesitates when you are in closed loop. This means you have a faulty sensor somewhere that involves engine control. The only way out of closed loop once the car warms up to operating tempature is to go WOT (wide open throttle). During WOT the ecu stops looking to the sensors andmaking adjustment to the fuel map. It goes back to a preset fuel map and gives it all it's got. Once you take your foot off the pedal or are no longer pushing the pedal through the floor your ecu goes back to using the sensors and your problem returns. The fix for this is not easy without the right tools. Idealy you would need a data logger to see what your sensors are seeing in real time. His way you would know why the ecu is doing what it is doing. If you don't have one your going to have to go old school or use your knowledge to solve this one. I'm not there with your car so I'm going to give you a sweep to check. First think simple. For the engine to run you need fuel, air, and spark. The ecu does not control spark. You can rule that out. Your ignition is your ignition. The plugs fire the same way in the same order at 500rpm or 5000.The ecu can though retard your timing in case knock is detected. This controls a delay in when your sparkplugs receive energy to fire. This could cause your engine to hesitate. This would really be noticeable below 3000rpm. You replaced your knock sensor so check your wiring. Make sure it is plugged in snug and the wiring is not torn Ar ripped out of the conector. Your ecu does not control air either. It icontrolled by rpm. The faster you spin the motor the more air it ingest, but the ecu does monitor the amount of you ingest. This is the job of the MAFS. It reads how much air flows past it and sends a a signal to the ecu. This information tells the ecu how much fuel to add to keep the running at optimal condition. He more you ingest the more fuel you will need to keep the engine running at optimal without going lean. If you run lean you will know it with a kaboom from the engine bay.
If you are running rich you will have black smoke coming from the back lf he car or built up on the bumper above the exhaust. You will see this on the bumper if you do a lot of wot runs. Remember every car runs rich from the factory to keep the motor safe at least for warranty reasons. You wot fuel map is pig rich. A faulty mafs will cause your hesitate bad even buck like a bronco in some cases. He beauty and agony in this is the fact that your car will not run over 3000 rpm if your mafs is not reading. If you unplug it and rev your motor you will notice you hit fuel cut at around 3000 rpm cause your ecu does not see the signal anymore. The agony is ifyour car revs and drives over 3000 rpm once at operating temp your mafs is sending a signal to the ecu. You have to find out if the signal is correct or not. You did the right thing by swapping it with one you know works. I'm going to rule it out if you swapped with a known good one. Your mafs also reads the temp of the air going by also just so you know. Your IACV (idle air conrol valve) is just a valve that allows air to pass your throttle plate and idle when the the throttle plate is closed. Your car idles well Imma rule that out. Then there is your good ol O2 sensors (oxygen sensor). These bad boys read how much oxygen is in air or exhaust as it passes by. His tells the ecu if it is getting a complete burn or not. Your only burning the oxygen in the air you ingest into your motor. This air then passes through your catalytic converter which slows the exhausg flow with a wire mesh inside the converter. This wire mesh is hot from the exhaust going by therefore heats the air hotter than he rest of the exhaust piping causes it slows the flow. The air then pases a second O2 sensor. This second sensor reads the air again. If the oxygen content is lower then lower then first reading your catalytic converter is good and doing it's job. If it is the same as he first reading you get a CEL (check engine light) for catalytic converter malfunction. If your o2 sensors are reading a lot of oxygen your ecu interpets this as a lean condition and and adds fuel to the mixture. His to would cause your car to hesitate. Just cause you don't have a code for o2 sensor does not mean they are working correctly either. They can get "Lazy" they will send a delayed sigm to the ecu or a faulty reading due to carbon build up. Your TPS (throttle position sensor) als sends a signal to the ecu. This signal tells the ecu how far open your throttle plate is therefor the amount of fuel you need. This not being adjusted right will send a faulty signal to the ecu. It will read your throttle is open further or lesser than what it really is. This will cause more or less fuel being added to the mixture. His will cause the car to hesitate or even stall.I'm going to rule this out just for the fact that the car will idle fine till you hit the acclerater, and you are capable of hitting WOT. What you did not mention was your fuel pressure regulator. As rpm increases so does your fuel pressure. I'm betting this is your problem. I'm not at your car so don't hold me to it, but check it. You will not see a cel for this ever. Your car will hesitate, stall, even buck if this is not working. Your ecu has no idea if this works or not cause it does not report to the ecu. Your ecu will see a rich or lean condition from the other sensors though. It will attempt to adjust fuel eiher way and cause a cycle of mayhem. No matter what it does it will not be able to correct this problem. It will not give up though, it will keep trying. To rich you hesitate, to lean you either hesitate and stall if your lucky or your unlucky go lean engine keeps running you go kaboom. If your fpr is stuck open your ecu will see a rich condition and start trying to lean the mixture. If it is closed it will add fuel. This being based on the other sensors not the fpr itself. By the way I almost forgot. Your CTS (coolant tempature sensor) sends a signal to the ecu so it knows what temp your engine is at. His tells the ecu two things. It says I am at tempature I can go into closed loop and I'm getting to hot I need to turn on the radiator fans. There are two sensors also. One that does this and one that operates the gauge the dash. All in all, think of your ecu as a fuel controller. I'm going tonsay your problem is your fpr. The one thing you forgot. You will need a gauge to check this or you can swap it with one you know works. Don't forget to relieve the fuel pressure before replacing. Happy hunting. Class dismissed. :beer2:
If you are running rich you will have black smoke coming from the back lf he car or built up on the bumper above the exhaust. You will see this on the bumper if you do a lot of wot runs. Remember every car runs rich from the factory to keep the motor safe at least for warranty reasons. You wot fuel map is pig rich. A faulty mafs will cause your hesitate bad even buck like a bronco in some cases. He beauty and agony in this is the fact that your car will not run over 3000 rpm if your mafs is not reading. If you unplug it and rev your motor you will notice you hit fuel cut at around 3000 rpm cause your ecu does not see the signal anymore. The agony is ifyour car revs and drives over 3000 rpm once at operating temp your mafs is sending a signal to the ecu. You have to find out if the signal is correct or not. You did the right thing by swapping it with one you know works. I'm going to rule it out if you swapped with a known good one. Your mafs also reads the temp of the air going by also just so you know. Your IACV (idle air conrol valve) is just a valve that allows air to pass your throttle plate and idle when the the throttle plate is closed. Your car idles well Imma rule that out. Then there is your good ol O2 sensors (oxygen sensor). These bad boys read how much oxygen is in air or exhaust as it passes by. His tells the ecu if it is getting a complete burn or not. Your only burning the oxygen in the air you ingest into your motor. This air then passes through your catalytic converter which slows the exhausg flow with a wire mesh inside the converter. This wire mesh is hot from the exhaust going by therefore heats the air hotter than he rest of the exhaust piping causes it slows the flow. The air then pases a second O2 sensor. This second sensor reads the air again. If the oxygen content is lower then lower then first reading your catalytic converter is good and doing it's job. If it is the same as he first reading you get a CEL (check engine light) for catalytic converter malfunction. If your o2 sensors are reading a lot of oxygen your ecu interpets this as a lean condition and and adds fuel to the mixture. His to would cause your car to hesitate. Just cause you don't have a code for o2 sensor does not mean they are working correctly either. They can get "Lazy" they will send a delayed sigm to the ecu or a faulty reading due to carbon build up. Your TPS (throttle position sensor) als sends a signal to the ecu. This signal tells the ecu how far open your throttle plate is therefor the amount of fuel you need. This not being adjusted right will send a faulty signal to the ecu. It will read your throttle is open further or lesser than what it really is. This will cause more or less fuel being added to the mixture. His will cause the car to hesitate or even stall.I'm going to rule this out just for the fact that the car will idle fine till you hit the acclerater, and you are capable of hitting WOT. What you did not mention was your fuel pressure regulator. As rpm increases so does your fuel pressure. I'm betting this is your problem. I'm not at your car so don't hold me to it, but check it. You will not see a cel for this ever. Your car will hesitate, stall, even buck if this is not working. Your ecu has no idea if this works or not cause it does not report to the ecu. Your ecu will see a rich or lean condition from the other sensors though. It will attempt to adjust fuel eiher way and cause a cycle of mayhem. No matter what it does it will not be able to correct this problem. It will not give up though, it will keep trying. To rich you hesitate, to lean you either hesitate and stall if your lucky or your unlucky go lean engine keeps running you go kaboom. If your fpr is stuck open your ecu will see a rich condition and start trying to lean the mixture. If it is closed it will add fuel. This being based on the other sensors not the fpr itself. By the way I almost forgot. Your CTS (coolant tempature sensor) sends a signal to the ecu so it knows what temp your engine is at. His tells the ecu two things. It says I am at tempature I can go into closed loop and I'm getting to hot I need to turn on the radiator fans. There are two sensors also. One that does this and one that operates the gauge the dash. All in all, think of your ecu as a fuel controller. I'm going tonsay your problem is your fpr. The one thing you forgot. You will need a gauge to check this or you can swap it with one you know works. Don't forget to relieve the fuel pressure before replacing. Happy hunting. Class dismissed. :beer2:
Well I'm back. The car started doing its thing again. Replaced FPR and sparkplug wires. It now has a real jumpy idle. 500-1000. Car wants to die and partcial throttle and at partcial throttle wont rev past 3000 rpms unless I let up then WOT it. Is it possible the IACV is messed up? Im going to have a buddy come look at it this week. hopefully its something stupid that i just overlooked cause i have been looking at this car forever. I cant find a good forum for removing or adjusting the IACV. Any help would be greatly appreciated.
http://youtu.be/WTWTmZjdOao
video of it.
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34 Posts
ok guy i just wtched the youtube clip , i would definatly check your mass airr flow . iacv wont make you ping at a rev limiter neither will fuell problems, (injector, FPR) Thats all computer doing that... You could unplug the mass air flow and it would do the same thing
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34 Posts
Check electronics, your thinking too mechanical
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28 Posts
Check your fuel injector, fuel pressure regulator, exhaust gas sensor, and compressrio check.. You could check those out..
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