96 240sx Sporadic idle, and bucking when warm

[Yasko]

Problem started when i hit 100mph, then drove home. Not sure if that helps at all, but ever since then ive been having these problems.
PROBLEMS ONLY OCCUR when the car is warm (30min drive)

-Sporadic Idle, fluctuates from 100-800, completely random. One redlight it will act up the next it will idle perfect
-When pulling out it will bog down and if you dont rev it past 2.5k it will start bucking.
-When cruising the bucking will sometimes happen, and the rpms will drop a little when it happens (only seems to happen under 2.5k-3k rpms)

Any ideas?

Edit: Forgot to mention that no codes are being thrown.

[biggie]

Could look for vaccum leaks. Doubt that's it though, just look at the free options first.

Then try replacing the ECU Temp sensor (the 2 wire on one on the front of the engine).

[Yasko]

Could look for vaccum leaks. Doubt that's it though, just look at the free options first.

Then try replacing the ECU Temp sensor (the 2 wire on one on the front of the engine).

Wouldn't that throw a code if it went bad? just curious. Could this be a fuel problem?
No vacuum leaks, already checked. could it be iacv or even maf? Its just weird it only happens when the engine gets hot, it will drive fine at operating temp for like 25min then the problems start to occur.

[liquid_cool]

there are a few things this could be...#1 loose dizzy ...#2 possible timing chain slip due to tentioner or guide..#3 fuel pump and or regulator..#4 blown head gasket casin failed spark in 1 or 2 cylinders..check those symptoms and get back to us..hard to tech a ride over the net when the cars not infront of you.

[Yasko]

-Distributor is tight,
-If timing chain slipped wouldn't it run bad even when its cool?
-Going to replace fuel pump first then fpr, because i have one lying around.
-Dont think I have a blown headgasket, Oil color looks good, and coolant doesnt come out of cap when i first start to test, nor air bubbles, but after about 15sec of engine running it does start to overflow just a little, not sure if thats normal.

[walperstyle]

come on guys teach him how to isolate the problem first

When its bucking and running bad, if it does this at an Idle, try un-plugging a spark lead (wire). See if the problem gets worse, or A LOT WORSE.

why? This might help you locate what cylinder is having the issue. You unplug one, listen for a moment, feel the engine see if anything changes for better or worse. (it still can be all of them, so don't feel bad if you don't get any different results). You can kinda judge where a problem is happening by the reactions of the engine.

Try swapping out injectors, or at the minimum, clean them. (you can search google on how to do this)

Take off your fuel lines, and make sure there is no debris. Air hose works great for blowing crap out.

Check your fuel pump sock. AKA, its in the gas can, pull your fuel pump and take a look for any rust, or bad gas. I once had some 'orange' looking junk from a gas station once. I was pissed, had to clean out a carb for 2 hours the next day... as well as the gas tank.

anyways, that should help you get started. The problem could also be a bad ground wire, or lead wire, or something along those lines. Try shaking wires in the engine bay to see if anything gets better.

[4cefed]

Not sure if the OP fixed this, but it could also be related to the TPS. Search the site for tips on how to test and "adjust" the TPS. I was having simillar problems and ran through the tests today, it turns out a terminal was loose in the sensor side of the connection to the harness. I think it was making intermittent contact and confusing the ECU.

Mine exhibited hunting for idle and severe bucking when cruising when it got warm. Under deceleration or acceleration it was fine. I'm thinking the torque on the engine in these two conditions forced the lose wire to make contact with the harness. Make sure all the pins are firmly inserted into the connectors.