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View Full Version : Setting timing on SR and idle RPM issues



_Def_
04-19-2005, 09:13 PM
I tried to reset the timing on my S13 SR tonight since I retarded it a small amount to check out a noise I was hearing(that I now believe to be an exhaust leak at high RPM).

The only thing is, when I disconnect my TPS sensor, the idle goes up to ~1.6k. My idle adjustment screw is almost all the way CLOCKWISE - which should lower it right? Maybe half a turn off full CW or something like that, and the car still idles high. It has always wanted to idle high in cold weather(high being 1k RPM or so after a little sprint down the highway or something), but sitting there dropped it back down to 800-850 RPM. I figured the water temp was getting too cold or the Walbro 255 was causing a slightly high fuel pressure condition at idle. No big deal. On really cold nights I'll lean it out a hair(like 5-7%) on the S-AFC2 and it'll make the idle drop down to 850 RPM pretty quickly after coming to a stop(2-3 seconds).


Well, this whole not being able to get the idle down with the TPS disconnected is concerning me. The only thing I saw in the FSM about it is that the fast idle cam should be aligned with some marks - are they talking about the idle control valve on the intake manifold plenum?

I did the whole hold the engine at 2k RPM for a while then race it a few times described in the FSM - and no change. It's been about a year since I set the timing, but I seem to recall being able to get the idle down with the TPS disconnected. I think it went up a bit, but then went down after turning on my electrical fans.

The only thing I found from a search is after unplugging the TPS -

"4. restart car. It may die on you, but give it enough gas to keep it running until it maintains a decent idle at around 750 RPM. If the idle *increases* during this step, then you will need to disconnect the AAC valve plug and manually adjust the idle screw to get the car to idle at 750 RPM."

Does that mean I have to disconnect the plug going to the idle control valve and then mess with the screw to get my idle to 750 RPM with the TPS disconnected? I don't think I can really tighten the idle screw anymore - at least not enough to make a difference like that.

Also - the timing light(cheap ass one on a section of regular plug wire from the No. 1 coilpack to the plug) shows 15*BTDC at an 800-850 RPM idle when the CAS is almost fully CW(meaning almost all the way advanced) - but that's WITH the TPS connected. Without the TPS connected, at ~1.6-1.7k RPM it'll show probably 25-30*BTDC, but that doesn't really mean anything with such a high idle.

If I set the CAS to the middle of its adjustment range, the engine runs like crap, and the timing is very obviously being retarded. I think I was measuring somewhere around TDC to maybe 5* BTDC with it in the middle of its adjustment range. Does that mean anything? I've mentioned it before, but some people say their SR is like that, while others say theirs is at 15*BTDC with the CAS in the middle.

A quick drive after adjusting it to 15*BTDC at 850 RPM with the TPS connected(almost fully advanced CAS) showed that there was WAY too much timing. I hit boost for just a second and there was definitely detonation(138 on the S-AFC).

I feel like a tard for not being able to set the timing(I did it just fine when I first got my SR), but I don't know why the idle won't drop with the TPS disconnected(so it's pretty hard to use a timing light then...). I haven't ever re-stabbed the CAS - should I do that and just call it a day?

The scariest thing of the night was that I heard something metallic bounce off the bottom of the car right before hitting it(didn't think anything of it). Well, turns out it was one of the bolts for my center support bearing for my driveshaft!!! The car would clunk like hell when starting out in 1st after that(but fine above 5 mph for the most part, but I was driving easy back to my place). The other side was almost out from the clunking. I torqued both of the bolts to spec, and haven't touched them in almost a year since I finished the swap. Guess the harmonic vibration from my solid 6 puck ACT clutch loosened them up over time. So I guess everybody with the dreaded 4th gear harmonic decel noise should check their driveshaft/center support bearing bolts. It would have really sucked to loose one of those on the track!!!

Luke
04-20-2005, 11:15 AM
This same thing is happening to me. I did restab the CAS and it seemed to center it, instead of fully clockwise. I still have problems with it idling up after disconnecting the TPS. I'm figuring it's part of another problem, just can't figure it out. http://forums.freshalloy.com/images/graemlins/confused.gif

pearlS13
04-20-2005, 11:45 AM
I was having issues setting timing on my sr aswell so i took off the valve cover and realized how off my timing was. I couldnt get the dots to line up even with turning the CAS all the way through its range so i took it out and re stabbed it. This way i know for sure the timing is correct.
If i were you i would this this, its very easy to do and it took me about 20 minutes to do.

_Def_
04-20-2005, 12:54 PM
I guess I'll have to restab the CAS when I get back in town. For now I'm leaving to go pick up my new daily beater - an E36 M3 Sedan. http://forums.freshalloy.com/images/graemlins/grin.gif

S13_fastback
04-20-2005, 11:05 PM
I had a very similar problem on my s14 SR. Couldn't get the idle to stabilize at ~800 rpms, it kept jumping around. I also removed the valve cover and set the timing that way