Coil firing problems

Tiny
TOBO1201
  • MEMBER
  • 1994 LEXUS ES
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 204,000 MILES
I have a 94 lexus es300 the car ran fine until the trans went out I pulled the motor and trans as a unit replaced trans with rebuilt one and installed motor and trans back into car the car will start and run now but only on three cylinders I think it is the 1 2 & 4 that are firing I put a code reader on it and it has no codes and the check engine light is not on I have replaced computer ignighter crank sensor cam sensor
coils spark plugs I do have 12 volts to all coils I think I am getting constant ground to the 3 cylinders that are not firing can you tell me what breaks the 12 volt current so the coil sends power to the plug
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Monday, January 17th, 2011 AT 5:32 PM

5 Replies

Tiny
KHLOW2008
  • EXPERT
TRIGGERING SIGNALS
Two camshaft sensors (one camshaft sensor) and a crankshaft sensor provide the triggering signals for the ECM, which uses these signals to control the ignitor(s).

The camshaft sensor contains a pick-up coil. A reluctor is mounted on the camshaft. As the camshaft rotates, a protrusion on the reluctor passes near the pick-up coil. This induces AC voltage in the pick-up coil. ECM interprets this AC voltage signal as TDC of cylinder No. 1.

The crankshaft sensor contains a pick-up coil. A reluctor is mounted on the crankshaft pulley. As the crankshaft rotates, protrusions on the reluctor pass near the pick-up coil. This induces AC voltage in the pick-up coil. The ECM senses the AC voltage, and uses it to determine incremental crankshaft position and engine speed.

IGNITOR(S)
Ignitor keeps the ignition coil primary circuit grounded, allowing a magnetic field to be built up in the ignition coil. When the ECM signals the ignitor, the ignitor interrupts the primary circuit, causing the ignition coil to fire.

Are you sure it is 1, 2 and 4 that is not firing? Recheck wireharness and connectors for loseness and contaminations.
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Tuesday, January 18th, 2011 AT 3:23 PM
Tiny
TOBO1201
  • MEMBER
1st cylinders from front of engine front bank and rear bank and 2 or middle cylinder on rear bank I know that it is either 1, 2 4, or
1, 2, 3 other than checking connections that I will do again but have checked over and over is there anything else you might recommend
trying if I took this car to a shop would their diagnostic equipment be able to find the problem sense there is no engine codes showing
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Tuesday, January 18th, 2011 AT 5:13 PM
Tiny
KHLOW2008
  • EXPERT
If no engine codes are showing, test equipment would not show anything but they can be used to check if any of the circuits are not functioning correctly.

One way of checking if it is a wiring fault, is to perform contuinity test between the ignition coils and PCM.

From what you described, it should be 1, 2 and 3 that is not firing.

Try swapping coils with known good firing cylinders to test if problem migrates. Is it confirmed that it is sparks that is missing and not a fuel problem.

Check the spark plugs as well.
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Tuesday, January 18th, 2011 AT 5:30 PM
Tiny
TOBO1201
  • MEMBER
The cylinder I described are firing it is 456 that are not firing
i have swapped coils and plugs with known good ones with same problem it is definitley spark problem not a fuel problem does each cylinder have its own closed circuit or do two oppisite cylinders use one circuit I think some fords fire opppisite cylinders at the ssame time so one cylinder is on comprssion during spark and the opposite cylinder iis on exhauststroke
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Wednesday, January 19th, 2011 AT 5:11 AM
Tiny
KHLOW2008
  • EXPERT
The coils are individually controlled by the PCM and firing specifically for designated cylinders.
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Wednesday, January 19th, 2011 AT 5:52 PM

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