Clutch System Problems (T300) Help troubleshooting

[bp2000]

I have a T300 and I have a clutch problem, among other things. I know that I have a vacuum leak, on the check valve that supplies the intake manifold tuning valve actuator. This explains some of the symptoms but in their entirety just in case they are related, I have noticed the following.


1) Clunk in engine bay when on low throttle input sometimes. Associated with jolting/hesitating


2) Hesitating/jolting engine sometimes when at low throttle input. Like a resonance. Happens at a frequency of a couple of times a second.


3) Clutch pedal not fully disengaging (can’t activate cruise control). Related to clutch position switch – pulling back on clutch pedal with toe helps and allows neutral to be engaged.


4) Excessive engine braking when no throttle input (seems to be related to clutch position switch)[/TD]


5) When at standstill the stability control will come on[/TD]


6) Rough idle


7) Engine light related to engine too lean


5, 6, and 7 I'm 95% sure are related to the vacuum leak, the rest I suspect are a clutch problem. I made a post a while back about this issue Clutch pedal switch and increased engine braking. the vacuum issue came later and that's when symptoms 5, 6, and 7 appeared.


I for a long time thought it was the clutch pedal return spring. However that seems intact, and the free movement in the clutch pedal is only a small amount of its last travel, which I can't seem to reconcile with the spring being weak like I originally hoped.


Now I think there are a few options.


1) Something wrong with the pedal mechanism causing extra resistance in the last part of disengagement. Such as a worn plastic bushing.


2) A badly calibrated clutch position sensor.


3) Some strange air in the clutch hydraulic lines problem. Causing it to not fully disengage when released but not causing any other clutch slipping effect when accelerating.


4) Some mechanical hang up in the clutch doing the same thing as (3).


I kind of like (3) and (4) because it seems to link with the poor drivability (issues 1, 2, and 4) more than (1) or (2). I think (1) or (2) could cause drivability issues by the clutch position sensor doing something funky in the ECU, though I've found very little evidence of this.


Having said that (1) or (2) seems likely because I can fix the issues by pulling back on the pedal and if I'm always using a % of throttle input I don't really have any drivability issues. I feel (3) or (4) I should have more issues when the throttle input is high and the drive system is being stressed (i.e. clutch should slip more with more torque).

[GR1087]

Bleed the entire clutch/ brake system before you dive into checking the other issues. Check the master cylinder and clutch pedal, it might have air in the system or old degraded fluid. ReAdjust clutch pedal as needed.

Start by replace vacuum lines and the map sensor with a name brand unit from rock auto. Might as well change the air flow/temp sensor so everything is read properly by the ECU. Seems related to your issue #2.

Engine code for too lean can be oxygen sensor related, might need replacement for ECU to read properly. Adding to the other vacuum/sensor issues.

Clunking in engine bay under acceleration could be a failing or bad transmission mount, or engine mount.

Clean and tighten battery connections and terminals, erosion and poor contact can cause minor electrical issues and poor running conditions.