87 924S cold misfire
#1
08-23-2007, 09:17 PM
87 924S cold misfire
Hi all,
I have an 87 924S in my shop that is rather maddening. It starts fine, but within 3 seconds or so drops cyl #3, and then misses until the engine reaches operating temp. The owner replaced plugs, wires, dist cap/rotor, coil, fuel filter, fuel inj temp sensor, idle air control motor, etc. That made no change. I have checked compression on all cyls, hot and cold, no problems. Leakdown tests fine. Spark output is fine. Cam timing on. Fuel pressure is good. Switched fuel injectors, no change. Lifted fuel rail with injectors, all spray equally when cranking. Checked spark timing on each cylinder with timing light, all at correct time. Found no vacuum leaks. Substituted known good airflow meter, no change. Cam lobes look fine. Pulse width on adjacent injectors the same. Everything seems to check out fine, but it still misses on that cylinder until it warms up. Why??? I'm open to suggestions. Thanks for any thoughts..
I have an 87 924S in my shop that is rather maddening. It starts fine, but within 3 seconds or so drops cyl #3, and then misses until the engine reaches operating temp. The owner replaced plugs, wires, dist cap/rotor, coil, fuel filter, fuel inj temp sensor, idle air control motor, etc. That made no change. I have checked compression on all cyls, hot and cold, no problems. Leakdown tests fine. Spark output is fine. Cam timing on. Fuel pressure is good. Switched fuel injectors, no change. Lifted fuel rail with injectors, all spray equally when cranking. Checked spark timing on each cylinder with timing light, all at correct time. Found no vacuum leaks. Substituted known good airflow meter, no change. Cam lobes look fine. Pulse width on adjacent injectors the same. Everything seems to check out fine, but it still misses on that cylinder until it warms up. Why??? I'm open to suggestions. Thanks for any thoughts..
#2
10-14-2007, 03:54 PM
RE: 87 924S cold misfire
did you find the problem? Mine has a problem where it tends to want to stall when I move the accelerator pedal when it's idling from acold start - if you pressin more it catches - light tip-ins are a probelms though.
Steve
Steve
#3
10-14-2007, 03:55 PM
RE: 87 924S cold misfire
did you find the problem? Mine has a problem where it tends to want to stall when I move the accelerator pedal when it's idling from acold start - if you pressin more it catches - light tip-ins are a probelms though.
Steve
Steve
#4
10-14-2007, 07:09 PM
RE: 87 924S cold misfire
Are you sure its misfiring number 3? just a question. It could still be the injectors even if they sprayed equally, i would say change them around the 4 cylinders and see if #3 still misfires. Then try it with the plugs too. If it is still number 3, its something inside the motor. If it changes, It is one of the injectors or plugs. But you said if leak down and compression are fine i doubt its internal. But, there maybe some gunk on one of the valves that only happens to hang it up after the engine has gas in it or is firing, then the leakdown test wouldnt catch it. Im used to the supra, with the inline 6, so it sucks more with 6 cylinders to diagnose!
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