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Base timing unstable with timing pin grounded in Link - ranges from 5* to just past 1 T mark...???

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Gremo87

Proven Member
128
2
Mar 14, 2013
Decatur, Illinois
Been chasing a low vacuum/low power/hard cold start/cylinder 2 lean/etc issue.
(see here if interested in backstory: http://www.dsmtuners.com/threads/my...new-perspective-still-troubleshooting.495724/)

I checked base timing and it's at 5* a lot of the time, but jumps (a lot) just past the TDC (1 T) mark. I'd say 55-60% 5* and 40-45% about 1/8"-1/4" past the 1 T mark.

What could cause this?

Could this be causing my issue, or vice versa - could the issue be causing the jumping?

If it's causing the issue, what are some things that could cause the base idle to be so unstable?

(I'm doing my own searching but wanted to get something going on here in the meantime)

Also - once the timing pin is grounded, idle surge begins and gets progressively worse the longer the pin is grounded. So if I understand correctly, that means there would always be an idle surge if the ECU wasn't constantly adjusting timing at idle to compensate and keep it from surging. (and I can't get the idle any lower than 800-850 even with the BISS bottomed out, so there's something going on with too much air getting in, and it seems to be focused at cylinder 2 as evidenced by white spark plug.)
 
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Quoted from http://www.dsmtalk.com/forums/archive/index.php/t-197695.html in response to someone who's base timing was wandering from 0 to 10*:

"if you got that much wander, I would suspect timing belt adjustment has loosened up, CAS connection to the exhaust cam is worn, or worse yet, timing belt is ready to go."

My engine was rebuilt less than 3000 miles ago by the original owner....so timing belt is fairly fresh.

?
 
Intake gasket leak.... weak timing belt tensioner? Isn't the power brake vacuum line there too check that. But I would start with checking the timing belt tensioner and making sure that it's set up correctly... if the t belt is that new you should be able (if set correctly) almost if not be able to slip the grenade pin back in or close to.... hope that helps
 
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Thank you for your ideas!

I've completely disconnected the brake booster vacuum line and everything connected to that vacuum source in the IM and it didn't change anything, and boost leak tests don't indicate a leak at the manifold gasket.

As for timing belt tho, I've done nothing in that direction. Never messed with a timing belt on these cars so I'll have to do some research on that.

Thanks again
 
I've also heard that ground the pin in link, and leaving the cable plugged into the obd port, can cause it to jump around. I've tried it both ways:
1. leave link plugged in, car running, ground the pin;
2. ground the pin in link, remove link cable

and i haven't come to a conclusion that MY car acts differently, but someone's must have for some reason for them to have said that.

Also, if you're surging, then i'd think your base idle rpm is off. before doing base timing, you should set the biss by ground both the timing and diag pins and adjusting the biss until the ISC reads around 30 in link.
 
Hey tmoney20g - I've tried what you first mentioned and it didn't make a difference.

As for BISS adjustment, it's weird. BISS is set for ISC position 30 at idle. If I leave BISS there and ground the 2 pins, the car will die. Not with just one or the other, but both will cause it to die. I have to back the BISS way out for it to stay running with those pins grounded, which takes it way off the 30 position.

luv2rallye, it's not a 2g - it's a 1g. (94) And the IPS is working according to Link, and simulating it makes no difference. Thanks though! The base timing shouldn't wander with the timing and diagnostic pins grounded, but, it does...it jumps from 5* to just past the TDC mark - a lot.
 
I just checked base timing again today and it wasn't jumping NEARLY as much as it was the other 2 or 3 times I've checked it. Weird......it was at 5* for probably 95% of the time with maybe 5-6 jumps over a 30 second period. Before it was constantly jumping back and forth.

Another weird thing is that grounding the diagnostic pin doesn't stop the ISC from making adjustments....yet it definitely has some effect, because if the timing pin is already grounded, the car will die when I ground the diagnostic pin - every time. (unless I back the BISS way out, far off from the ISC pos 30 and bring the idle way up) So it's definitely doing something, but Link shows the ISC still making adjustments when I ground the diagnostic pin.
 
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