This problem first presented in October 2002. The history is copied below.
An update:
This engine is still running rough, the tach reading is jumping and erratic, and code 18 is setting nearly all the time. Occasionally code 17 also sets.
Against my belief that the cam sensor was bad, I replaced it anyway. No improvement.
Since the last round of troubleshooting, I have just completed the following:
Checked all wiring continuity between the cam sensor, crank sensor, ignition module, and the PCM. All were under 1 ohm and with no intermittents when the wiring was moved.
All pins on the PCM were checked for pushed pins and grip tension. No problems found.
The ignition module was replaced with a brand new unit. No change. Original swapped back.
PCM was removed and the MEMCAL removed and reseated. No change.
Removed both serpentine belts and ran the engine. Still ran rough but no mechanical engine noise. Replaced the belt driving the supercharger and the previously observed engine rattle resumed. This same belt drives the A/C and water pump. The A/C was not engaged and the water pump spins silently. I conclude that the supercharger has serious internal problems.
I also conclude that the noise from the supercharger is not causing the knock sensor to produce a 'false' signal which would cause the PCM to retard the timing. I was conserned that this was a cause of the poor running.
I further disconnected the knock sensor and ran the engine. The rough running was present and I set the code for a knock sensor circuit failure. Reconnected and reset the code.
I grounded the bypass signal output of the PCM that instructs the ignition module to run in the 'module' or fail-safe mode with a fixed
10 degree ignition advance. The engine still ran poorly, no change detected.I have 148K miles on this engine. Original timing chain. I put a timing light on the engine and found that at idle the timing mark jumped back and forth at least 10-15 degrees.
QUESTIONS: Is this a clue that the timing chain is shot? Could a bad timing chain cause my poor running? Can it also set a code 18 (cam/crank sensor)?
Is is possible that a fuel problem (clogged filter, clogged/dirty injectors, other) could cause a code 18 to be set? There don't appear to be any codes that get set for fuel problems.
On the old cars (before computers) both fuel and ignition problems often presented similiar running characteristics.
I have an old scope but it is hard for me to see if there are any substantial changes in the waveforms since my last look. The scope I used previously was a much better unit and I am going to try to borrow that one back to take another look at all the waveforms.
Robert Hancock- any suggestions?
Anyone else have any ideas.
All ideas for troubleshooting and suggestions are greatly appreciated.
Rich
----------------------------------------------------------------------------------------------- Previous thread from last October:
I would suspect that the cam sensor is just bad, it shouldn't have those spikes.
-- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from snipped-for-privacy@nospamshaw.ca Home Page: