Need Help. Car is running on 3 pistons and wont start at times

[-Tq-]

hey all. ive got a 90 240sx with about 149k miles. when i bought the car the problem didnt seem that big but now i that im trying to get it fix its become a pain. the problem its having is that the car will start if left alone over night fine. but when driven and left to park it wont start at times. it cranks so i dont think its the electrical. ive taken it to the shop and talked to a couple of mechanics. one guy said i was running only 3 pistons and showed me but pulling out one of the spark plug caps. he also said that the pistons have to be in the right position for it to start up. what i dont get though is why does it start up after letting it sit for awhile? i dont think the pistons would be turning on their own. other things ive been told is that ignition module is bad or the fuel problem. any thoughts would be appreciated.

[rogoman]

How does the car perform when you're driving it? If it's OK, then all the cylinders are most likely firing.

The problem with not starting when fully warmed up, may be due to fuel injector leakage after the motor is shut off which may be causing flooding.

[-Tq-]

at time the engine shake alot and the idle isnt steady. at one point today, i finally got the car started after a couple tries. drive it for a sec. it dies. got it started again but the idle kepting going from like 1.7 rpms to 2 over and over while i was driving it.

[KASilvia90]

The mechanic who said the pistons being "in the wrong spot" is very wrong, is bad at explaining problems or doesnt understand timing well. If your running on 3cylinders your car will kinda have a harley sound on acceleration (how they have an audible sputter/miss) and feel real weak.

Its hard to diagnose that, there can be many problems. It sounds kind of like a Crank Angle Sensor, mine acted similiar for a while. The car kind of loses its timing and the fuel/spark come at really random inconsistant times.

According to the factory service manual, things to look at are:MAF, Coolant Temp Sensor/Switch, Fuel Pressure Regulator.

Thats not everything but at least a start. And just because it cranks, doesnt mean it isnt eletrical. It just means your starter and battery are fine. What do you mean spark plug cap, do you mean spark plug or like spark plug wire boot? and what did the "odd bird" look like.

It also kind of sounds the throttle position sensor isnt working right or disconnected. I dont know about the 5-speed but when my car was auto, the tps got disconnected and it was just really nuts to drive in the rain (random shifting on apex's with bald tires FTW!).

Hope that helps some. If theres anything else you can add, definatly do it. That is unfortunatly a common problem with many things that can cause it, and the little things are better at determining it.

[180fan]

Hey do me a favor and wiggle your injector plugs. See if that changes your idle.

[-Tq-]

well friend came over yesturday and help me do a compression test on the first cyclinder. it was around 90-98lbs. he called up a friend and said normally it should be around 120-180. then i was like what the hell and decided to put in a new spark plug. it got the piston firing again from what we can tell. we did the same test of pulling out the spark plug boot while the engine was running and u can tell it cause it to run weaker. we might of fixed one of the problems but will need to run it more to be sure.

side note. we had some trouble install he spark plug (dont ask lol) but when it was loose we can hear gas spray pass spark plug and out of the engine.

this was all done while the engine started fine so the problem causing the engine to not start might still be hidden somewhere
Modified by -Tq- at 6:00 AM 1/10/2007