Ignition problems after driving for a few hours

[caduceus2001]

1996 Lexus LS400 with 1UZ-FE. Car when cold starts just fine and can drive around town, even trips less than an hour and it has no issues. Drive it for about 2 or 3 hours on the Highway, then stop and turn it off and it will not start again. It will crank and at the first turn of the key it sounds like it might fire, then it cranks like it has no compression and it will not start. Leave it for about an hour and it will start, but has very low idle and no throttle response. It will run for maybe 30 seconds then stalls. Leave it overnight and it will start just fine the next morning. Seems to only be a starting issue, since while the car is running it keeps running with no problems, but as soon as it is turned off, it will not start until it has completely cooled down. Temps are perfect and it has a new MAF, fuel pump, fuel filter, rebuilt computer, and front O2 sensors. I haven't replaced the rear O2 sensors yet, as it seems to be a very big job just to get to the plugs (unless someone knows a trick to get at them without having to remove the carpet) I do have a flashing engine light, but it just flashes continuously without showing any codes. My first thoughts are the Ignition modules, but I am just guessing. Any insight to the problem and help would be greatly appreciated.

 

[ivan129]

There are 5 essential things for an engine to run well, fuel, air, spark, timing and compression. However if the ECU has spat the dummy, it might not want to play. So next time you have the problem you need to start checking things. Is there fuel in the rail, do you have fuel pressure in the rail, should be around 40psi if the fuel pump is running. Do you have a fuel recirculation / breathing problem causing a vacuum in the fuel tank? Lift the fuel cap and listen for suction. This could starve the engine of fuel. Is the throttle butterfly opening (not sure if your engine is drive by wire or cable throttle). Make up a couple of plug leads with spark plugs you can hold against the cam covers so you can push them on the coils to check for spark. Use a timing light on No.1 and see where the timing marks are. See how you go from there.