2004 GX with rough idle, surging, and misfire (1 Viewer)

[langsen]

Our 2004 GX470 with 180,000 miles has suddenly started to run rough at idle and sometimes stall. I have not driven it anywhere like this, since it can barely idle. It started yesterday morning, when I started it for the first time after it had been parked for about 10 days while we were out of town.

It initially started up and ran fine, but I remembered I left something in the house, so I turned it off, went back in the house, came back out, tried starting it again and it wouldn't fire. The engine would turn over just fine, but it never started. The CEL came on and I scanned it with Torque and got only a P0335 Crankshaft Position Sensor A Circuit code. I went under the car and removed the crankshaft position sensor (one of the most awkward jobs, btw), and tested it according to the FSM. It tested OK but I swapped in a new sensor anyway just to see if it would make the car start. When I tried starting it again, it did the same thing as with the old sensor, cranked but didn't start. So I put the original sensor back in, cleared codes, and saved the new sensor for another day.

When I tried starting it after re-installing the original crankshaft sensor, it started fine, but after 10-15 seconds of idling, it stumbled and died and the CEL came on again. I scanned it and this time the only code I got was a P0230 Fuel Pump Primary Circuit code. So I went to the fuse box and swapped the relays around, and tried starting it again, but it still didn't idle smoothly. I cleared the codes again. Tried starting it a couple more times, and it would only run for 2-3 minutes at the most before stalling. Scanned codes again, and this time there are none.

The engine runs like when there is a bad MAF sensor, bad gas, or a bad coil pack. I cleaned the MAF sensor and the throttle body, and checked all the connectors on the coil packs just to be sure. I scanned it again, this time with TS and still found no codes. The TS live view shows intermittent misfires on all cylinders in roughly equal numbers, so it doesn't seem to be just one bank that's having problems.

Currently, the CEL is off. If I scan for codes, there are none, but it still runs terrible.

Any suggestions on what I should take a look at next?

UPDATE: It looks like the problem was caused by the sensor wire getting rubbed through by the serpentine belt, see pic below.

 

[Infinity00]

I’ve had trouble with aftermarket sensors, and now always buy OEM. Also, check all the wires going into it to make sure they aren’t damaged. If you know how to check the signal from the crank shaft sensor, try to do that.

 

[GXO]

It sat for 10 days. Have you tested your battery? Have you checked under the intake for rodents? Sitting for a while usually ends up with a charging issue due to a drain on the battery and that will give you all sorts of odd things if the alt can't pump enough juice. Rodents can damage the wiring to those sensors as well as the coil packs. You are doing all the right things, so it has to be something different.

 

[langsen]

UPDATE: I charged the battery this morning just to be sure. There are no rodents or droppings, or chewed bits of plastic that I could find anywhere. All the sensors are OEM. I did not scope the crankshaft sensor yet, since that code hasn't returned.

It seemed ok this morning while the engine was cold, but after a couple minutes of idling it starting to have a rough idle. The problem seems to be worse when the A/C compressor is on, it will bog down and stall after a couple seconds. I drove slowly around the block, with A/C off, and notice a slight knock or pinging that would happen if I gave it gas too quickly. Still, no CEL and no codes.

Is there a way to check the timing without removing the timing belt covers?

 

[GXDude]

tested fuel pressure?

 

[langsen]

Where is that wire supposed to be so that it will stay away from the belt?

 

[GXDude]

View attachment 2026365

Where is that wire supposed to be so that it will stay away from the belt?

based on mine, i believe its supposed to route along the right, outside of the AC condensor...

 

[GXDude]

Code P0230 Lexus: Fuel Pump Primary Circuit

The Engine Control Module (ECM) provides ignition positive voltage to the coil side of the fuel pump relay. When the ignition switch is first turned ON,

www.autocodes.com

1)check your fuse AND relay. 2) check your fuel pressure - if pressure is low, could be faulty pump (assuming fuse and relay are good.)
Let us know.

 

[GXDude]

based on mine, i believe its supposed to route along the right, outside of the AC condensor...

compressor...** hehehe

 

[langsen]

Thank you. I think I got it taken care of. That wire in the pic had been worn through and was causing a very intermittent crank sensor signal that wasn't throwing codes but still caused a misfire. The wiring itself wasn't damaged, only the insulation, so I patched it up with layers of liquid electrical tape, regular electrical tape, foil tape (for shielding!), and wire loom. I routed it behind the oil pipe and now it seems out of the way of the belt. All is good!

 

[Infinity00]

Is your original problem gone now? Really great if you found the problem wire!