3.2 60 days sitting, bad miss under load

[198491132]

New CHT installed. Orginal issue still remains. A bit smoother running, with improvement, but still not drivable. Next test is fuel delivery system, as suggested earlier.



Dave

[198491132]

Just may have found something. Idle position switch tests closed all the time. When I remove it from the harness, I have free revs and no further mis issue. Runs great but high idle. Could this be the root cause of my misfire? DME still thinks car is in idle mapping tables?

Dave

[scarceller]

If the idle switch is always closed you would not likely rev past the fuel decel cutoff set at 1200RPM. But a problematic intermittent idle switch would result in fuel cut at RPMs above 1200. I have seen bad idle switches, actually just saw one last week.

If you unplug the switch you will just remain in the Part Throttle maps and idle high, other than that no harm done.

If you want to see exactly how a shorted out (always closed) switch behaves, simply unplug it and jumper the 2 pins in the harness. Then try reving it past 1200RPMs, I bet lunch it dies and sputters right around the 1200RPM area.

[198491132]

Sal, I think you got it. I can rev past 1200 but only once or twice then breaks up. Must be hitting the limit. The switch tests continuity 100% of the time. Needs replacement. Seems PP can not get me one, do you know a source?

Dave

[scarceller]

If PP does not have it, here you have a OEM factory part:
Throttle Body Switch Micro Switch 100 Genuine Porsche for A 911 Carrera 84 89 | eBay

This is the cost of this switch $200 crazy expensive for what it is. I've never seen anything but the factory part available. They run about $200 all the time.

While at it remove the WOT switch, most are easy to open up. Open it up and clean the contacts with 600 grit sand paper. If it's the newer sealed unit I suggest testing it as well to be sure it closes (reads 0 ohms) at about 80% throttle, once it closes it needs to stay closed all the way to 100% throttle.

Also be aware that the idle switch has a very specific procedure for how to adjust it. You DO NOT ever want the idle stop to become the switch! The idle stop must be the stop screw and the linkage must NEVER hammer on the switch. At idle stop you move the switch just enough so it activates (red button plunger) clicks on. You do not want excessive pressure against the switch as it will damage it, very likely what damaged that switch you have now. I usually remove the TB entirely from the car to properly set the stop screw and the switches, I also look very carefully at the throttle plate to be sure it's not hitting or rubbing inside the throttle body. Basically a good time to look over the entire throttle body.

[198491132]

Thanks Sal.....I will do some additional searches as well tomorrow. How difficult is this to instal? Looks impossible!

[scarceller]

Read my prior post, take the TB out of the car. Much easier to do this on the bench.

Originally Posted by 198491132

Thanks Sal.....I will do some additional searches as well tomorrow. How difficult is this to instal? Looks impossible!

[steely]

Dave,

here is a pic of my intake removed, you can see 2 screws holding the switch plate (circled) at 9 o'clock. It might be easier to remove that plate and then replace the switch - not sure - it may be a 'blind' mate.

[198491132]

Sorry Sal, read your post on my cell phone only. Crap, never took the TB out. Steely...Thanks....this makes me think this a bit more of a job......

Dave

[198491132]

Got IT!!##

Thanks All for your guidance and support. I have a lot to learn....but,

My issue was a sticky idle microswitch. There was gunk holding the switch from opening upon throttling up. After 15 times of pushing on the switch with my finger, it loosened up.

Checks good and issue is resolved. Thanks again, you guys are great.

Dave

[198491132]

Running and happy...

[CCM911]

Wow! A most impessive finale!!

How are Dan and Sal so smart???