91 240sx running sluggish after head rebuild

[ranismo]

I just bought a 91 240sx hatch that has been sitting for 10 years. The previous owner overheated the car and it wouldn't start again, so he just left it in his garage. Anyways, we rebuilt the head, replaced water pump, thermostat, flushed and cleaned the radiator. We also replaced the starter, fuel filter, and fuel pump, and of course the spark plugs, wires, oil ect. There is spark, fuel, and air, but it still runs very sluggish. When i turn it on it idles fine, but when im driving on any gear, it will run very sluggish, very little power. And also when i try accelerating on any gear, it will force itself and not accelerate very much at all. When it warms up to half ways, it will not start, and the starter is brand new. I tried checking everything, even the maf sensor. The only code it pulled was the Detonation (knock) sensor. When i looked at it, it looked all melted. I was wondering if anyone has had the same problem and knows if the knock sensor will affect the driveability like this, and also will keep the car from starting when warmed up. Thanks in advance.

[navysnail]

a bad knock sensor will cause the car to be sluggish.

[carps13guy]

ya man i had a bog @ around 1.5k rpms and i changed the knock sensor and it went away. also it might be a fuel pump. only reason why i am saying this is because ive had a couple of older cars that when warmed up to operating temp and then shut off, would not start again until the temp lowered to like 120 or something

[carps13guy]

oh and

ya man i had a bog @ around 1.5k rpms and i changed the knock sensor and it went away. also it might be a fuel pump. only reason why i am saying this is because ive had a couple of older cars that when warmed up to operating temp and then shut off, would not start again until the temp lowered to like 120 or something

it turned out to be the fuel pump, cuz when they get old they get hotter than there suppose to and they would seize from the heat. im not sure how to explain this properly, its just what my mechanic buddy was tellin me when he replaced it.

[SullivanRacing06]

did it sieze on you or was it sized from the beginning? what pump did u replace it with?

[carps13guy]

did it sieze on you or was it sized from the beginning? what pump did u replace it with?

na man it wasnt seized from the beginning. for some reason when the in tank fuel pumps get old they start to get hotter than norm. and i think that some metal part in the pump expands more than a diff type of metal and it causes the pump to bind. and this happened to me on a jeep grand cherokee and an exploder i used to have. i replaced them w/oe cuz they were piles of crap.

[ranismo]

Thanks for your input everyone. I took out the knock sensor and it turns out that the harness was all messed up. It didnt connect. and the sensor.... well it was melted into the connector. I am going to try to fix it. Does anyone know how the wiring should look like? A diagram might help out. Where can i get the harness at? Thanks.

[schanne]

I have that harness and an extra knock sensor. E-mail me at [email protected]

[ranismo]

Thanks. I was able to fix the harness and i bought the sensor on ebay for 28.00. doesnt throw the code anymore. I changed the rotor (it was very corroaded) it made a difference performance wise. I changed the distributor brand new, doenst make a difference, so i returned it. the only thing i need now is to find out why my car doesnt start when hot. And recently it doesnt start when its very cold outside. I was searching and found something about the grounding. Could that be true?

[SullivanRacing06]

good

[ranismo]

Ok, i checked all the ground connections and sanded them down. I checked the ECU wire for the ignition and it was good. My car is still not starting! It is frustrating the crap out of me. First, it didnt start when it was hot, then it didnt start when cold. Now it doesnt even start at all. Could it be like the temperature sensor or something else? Can anyone help please, im at a loss. Thanks

[rockinthefans]

i hate to be the only one to say this but i can almost guarantee that your timing is off. i had the same thing happen to me. double check everything from the timing chain to the dizzy. its free and would be well worth the trouble. just my .02 bro

[ReX2SX]

Yeah maybe you messed up your timing abit when you replacved it. Make sure everything is the way it should be and connected and see where your at.

Exactly what happens when you try and start the car anyway?

[ranismo]

Thanks for the input. I will most definately double and triple check the timing. I also checked the ignition module and it was fine. Well, before it would start right up. It would run great, just a tiny tiny bit of a shake. When i have the heater on and the engine warms up, it will start right back up fine, again and again. If i don't have my heater on, and warm up the engine, it will not start, just crank and crank and crank, but no turn over. So recently, i tried turning it on, and it just cranks but not turn over. It is just sitting there now. Unable to start up. Let me know if you guys think of anything else that could be wrong. Thanks again.

[ranismo]

Ok. I found the problem. For some reason the compression is like at 60 on each cylinder. I guess the piston rings wore out after 10 years of sitting and a few days of use. Oh well... off to remove the engine and rebuild block. Thanks guys for all your help.

[UNVMY240]

u could have washed out cylinders... try pouring alittle bit of trans fluid in each spark plug hole and run the car for a little. Then recheck compression and see if that helped any before u go rebuilding. Pour about 2 cap fulls or so into each cyl.

hope this helps.

[ranismo]

Thanks for the reply. That was actually the first thing i did before taking everything apart. It smells like gas when i try cranking it. The spark plugs get full of gas right away. Do you think it might be the fuel pressure regulator?

[UNVMY240]

Regulator no, It could be a shorted/high resistance in your injectors. Also could be an ECM telling your injectors to spray more than they should. Do you have an adjustable fuel regulator on the car? Take a pressure reading there after the fuel filter and see what you have out of the pump. Mass air flow can cause injectors to dump as well, if you know anything about checking them their is a 5v reference to the ecm, 12v power and then a ground. I dont think you have bad rings yet.. lets try and fix the fuel dumping first before yanking out a motor.

60psi on all cylinders......... If you were off on timing like I have seen on a 3.3L Xterra was off 2 teeth on one bank and all of those cylinders were less than half of what they should have been. I am truely not sure if it would be the same on our 2.4L. If your cams were off one or 2 teeth then you may have the same symptom. Pop off your valve cover and see how your marks are lining up.

Hope this may help some... you got my gears turning in my head now!!

[lil_ben_20200]

one of the vaulves might be ajusted wrong !!

[ranismo]

I'll check if my FPR is adjustable. And i will check my MAF sensor as well. Also check the timing on the cams and all of the markings this weekend. I will let you guys know what happens. Thanks.