Engine sputter

Alright, 00 XJ with the 4.0, 140,000. My problem started out with the engine just running rough after exterded high rpm (hillclimb, mudpass...). If the rpm's never go high the problem does not exist. The engine will sputter at idle, but clear up with any applied throttle. Sometimes upon startup it will have a misfire which clears up with a little throttle, or a re-start. Recently it has also been acting as if there is a rev limiter around 3,000rpm when you get on it . Now goin down the road it is kicking and bucking, If I baby it it will get goin but have to be very gradual with the throttle, All the time engine light flashing. Yesterday it did it's bucking episode just gion down the road on the way to work. Once parked for a little while the bucking is totally gone. It was giving a code for a misfire on cyl 1. All pugs are new. I put an injector in cylinder 1 and the rough startup totally went away, but it is still doin the sputter, and occasional bucking. Any ideas? I did a good amount of searching the forum and nobody seems to have the same problem.

Any useful info will be greatly apprecieated!

check spark plugs, fuel filter, injectors, vacume lines, .... take a magnet and stick it down in cylinder number one to see if u swallowed a screw or somthin. check ur oil to see if theres water mixed in. what have u checked so far?

plugs r new, injector is new, vacuum lines are good. It has to be a sensor of coil i beleive. Just wanted to see if anyone else ran into something similar before i start throwin parts at it since the scanner is showing nothing but cyl 1 misfire

swap ur coils around to check that. do a compression check on that cylinder

Keep in mind the symptoms described may or may not be caused by different issues.

What spark plugs are installed ? the 00-01 distributor-lees ignition runs best on plain Champion Copper Top plugs or Autolite APP-985. Sputter on start up and when hot can be a fuel delivery issue. Test the fuel pressure after sitting all night and when running. Running you should have 49 +/- 5 psi fuel pressure. Search "Check Valve" and "Heat Soak".

Test the Throttle Position Sensor. Test the O2 sensors and inspect their wire plugs and wires. Both can cause flat spots in acceleration, sputtering, and/or bucking.


TPS

You may have one or more of these Physical Symptoms:

1) The engine loses power and is stalling.
2) The engine will idle, but may die as soon as you press the gas pedal. When driving, it seems as if all power is gone.
3) Sometimes it feels as if the transmission is failed or isn't shifting properly, if at all. If you quickly jump on the gas you might be able to get the transmission to shift, but it won’t shift properly by itself. Shifting manually, the transmission goes through all the gears.

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics. The TPS function should be verified early in the troubleshooting process, when a transmission issue is suspected.

TPS TEST

You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.


The TPS is sensitive to heat, moisture, and vibration, leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following:

-Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".

- High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.

-Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.

-Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.

- Engine Misfire: A faulty TPS can report values outside the acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.