Engine Misfire At Idle 94 Sc400

[lexus082]

I have a 94 sc400. It has the same engine as the LS. Here's my problem:

I have a misfire that occurs I think just at idle. So basically to sum it up, I have replaced the plugs, caps, rotors, and the wires are only two years old. I pulled each wire (One by One) to make sure I didn't have a dead cylinder.

So heres the symptoms:

--The idle speed is within spec. approx. 700 rpms in park and 583 in gear.

--Tachometer is not getting the proper tach. signal.

--Have a random misfire.

--Car shakes slightly after it warms up when the idle comes down to 700 rpms.

--Engine mounts have never been replaced.

Any thoughts after reading those symptoms?

I have read that a misfire can be caused by a vacuum leak, leaky egr valve, weak fuel pump or fuel pressure regulator, dirty injectors, water in the gas...

[wmsfam]

I am having the EXACT same problem with my 94 SC400, 84,000 miles, still running fine.

My mechanic says that his diagnostics show the car thinks everything is just great. He cannot locate any problem whatsoever and is at a loss to even suggest what it might be.

Other than the "misfire", everything is wonderful. My symptoms are just a bit less demonstrative than yours:

--The idle speed is within spec. approx. 700 rpms in park and 583 in gear. (SAME FOR ME)

--Tachometer is not getting the proper tach. signal. (DON'T HAVE THIS ISSUE)

--Have a random misfire. (ONLY IN IDLE, EITHER IN PARK OR AT A STANDSTILL)

--Car shakes slightly after it warms up when the idle comes down to 700 rpms. (DON'T HAVE THIS.)

--Engine mounts have never been replaced. (SAME FOR MINE)

Would love to hear more about this....it is driving me crazy! Thanks for the great summation.

AJ

ajwms@hotmail.com

I have a 94 sc400. It has the same engine as the LS. Here's my problem:

I have a misfire that occurs I think just at idle. So basically to sum it up, I have replaced the plugs, caps, rotors, and the wires are only two years old. I pulled each wire (One by One) to make sure I didn't have a dead cylinder.

So heres the symptoms:

--The idle speed is within spec. approx. 700 rpms in park and 583 in gear.

--Tachometer is not getting the proper tach. signal.

--Have a random misfire.

--Car shakes slightly after it warms up when the idle comes down to 700 rpms.

--Engine mounts have never been replaced.

Any thoughts after reading those symptoms?

I have read that a misfire can be caused by a vacuum leak, leaky egr valve, weak fuel pump or fuel pressure regulator, dirty injectors, water in the gas...

[pishta]

I am having the EXACT same problem with my 94 SC400, 84,000 miles, still running fine.

My mechanic says that his diagnostics show the car thinks everything is just great. He cannot locate any problem whatsoever and is at a loss to even suggest what it might be.

Other than the "misfire", everything is wonderful. My symptoms are just a bit less demonstrative than yours:

--The idle speed is within spec. approx. 700 rpms in park and 583 in gear. (SAME FOR ME)

--Tachometer is not getting the proper tach. signal. (DON'T HAVE THIS ISSUE)

--Have a random misfire. (ONLY IN IDLE, EITHER IN PARK OR AT A STANDSTILL)

--Car shakes slightly after it warms up when the idle comes down to 700 rpms. (DON'T HAVE THIS.)

--Engine mounts have never been replaced. (SAME FOR MINE)

Would love to hear more about this....it is driving me crazy! Thanks for the great summation.

AJ

ajwms@hotmail.com

I have a 94 sc400. It has the same engine as the LS. Here's my problem:

I have a misfire that occurs I think just at idle. So basically to sum it up, I have replaced the plugs, caps, rotors, and the wires are only two years old. I pulled each wire (One by One) to make sure I didn't have a dead cylinder.

So heres the symptoms:

--The idle speed is within spec. approx. 700 rpms in park and 583 in gear.

--Tachometer is not getting the proper tach. signal.

--Have a random misfire.

--Car shakes slightly after it warms up when the idle comes down to 700 rpms.

--Engine mounts have never been replaced.

Any thoughts after reading those symptoms?

I have read that a misfire can be caused by a vacuum leak, leaky egr valve, weak fuel pump or fuel pressure regulator, dirty injectors, water in the gas...

Coil...Buy one and swap either out until you get satisfaction. I dont think ANY of those symptoms can cause a missfire, only a lack of high voltage to the plug, ie. coil, wires, rotor, cap, plug in that order.

[jzz30]

didnt i already tell you its the coil in the other forum?