Tuning the Timing Advance

[jonheslop]

When I ground the timing plug and set my base timing to 5BTDC I have problems. Once I unplug the ground and start the car the idle surges or stays at about 1300rpm. However, if I ground the timing plug and plug in my logger, which I believe doesn't even set the ECU to timing mode, and then set it to 8 BTDC it is fine. Once I unplug everything and start the car again it idles at a perfect 850rpm and no idle surge. However, I know the timing must be way off. Does anybody know what I'm doing wrong here? Also...does anyone have a chart or something to tell what the base timing should read for different idle rpms? Because I know if it idles higher than 1000 rpm the timing won't be at 8BTDC. Thanks.

 

[Spoolio]

are you using a timing light?, cause if not, just go ahead and check the timing marks after you set the timing should be 5btdc, then when u unplug it like you said should be at 8degrees btdc, idk if your guessing its correct? idk, you didnt mention anything about a timing light im just checking.

 

[LT1andDSM]

I had the same problem before when my crank was off 3 teeth the best I could get was 10-13 degrees btdc. Make sure timing mark are line up. With the ground on should be set to 5deg btdc with it off u should get +/- 3-5deg. Hope this helps.

 

[steve]

Unless you have DSMlink or a custom EPROM the only idle speed is 750 RPM.
Plugging in your logger and grounding the timing connector put the ECU into BISS adjustment mode. You may need to go back and forth between setting the Base Idle Speed and setting the timing until you can get the car to idle at 750 RPM and get the timing with the connector grounded to 5* BTDC.

Steve

 

[jonheslop]

To answer your question, I am using a timing light. I understand about the computer going into BISS mode. I'm just wondering why it's acting so wierd. I have checked the timing marks many times and they are dead on so I know that's not the problem. I set the timing to 5BTDC but when I unplug it, the timing is nowhere near 8BTDC. I believe it ends up being at 0 or something. I can't remember but I know it's way wrong. However, the closer I set the timing to zero degrees the lower the idles goes. That's normal obviously, but if I try to set the idle the way you're susposed to it idle surges and sometimes idles at 1500 rpm. When I set the idle towards zero everything acts fine and it works like a dream. It's almost like my car likes different timing settings. Maybe you've already answered my question and I just didn't understand what you were saying, but from what I've read so far my question is not answered.

 

[jonheslop]

This is a question for STEVE...what do you mean by going back and forth between the BISS and timing? I already set my BISS which is screwed down all the way in because that is the only way to keep my idle down and keep it from surging. From there I started to work on the timing. I don't understand what you mean by going back and forth with them. I understand that when I finally get the timing right I might need to adjust the BISS again but I don't understand why I would need to go back and forth a lot. Explain to me what you mean by that.

 

[steve]

If your BISS is screwed in all the way you have some other problem that you need to fix.

The reason I said you might have to go back and forth is because as you have noticed changing the timing also has an effect on the idle speed. So often you have to set the idle speed, set the timing, reset the idle speed.

Steve

 

[jonheslop]

Ok, I understand that I might have to go back and forth but I can't figure out what my idle problem is. I have the BISS in all the way, the FIAV blocked, EGR blocked, the IAC tests fine, throttle body is clean, gm maf so no leaks in the intake system, all emissions blocked, all vacuum line on top of the throttle body blocked, no vacuum line leaks, I've checked everything. I know that the BISS could help my idle once I get the timing set right but it's screwed all the way in and it seems like I need to screw it in further because when I set the timing right the idle goes way up. I have to advance the timing a lot to keep the idle down. I can't think of where all that extra air is coming from.

 

[steve]

I have to advance the timing a lot to keep the idle down.

I think your retarding your timing to keep the idle down. Normal timing at idle will be around 8* BTDC with additional advance for altitude. If you set it as described with the logger attached you would be retarding it.

Steve

 

[jonheslop]

ok, , well then I have no clue what I'm doing. If I want to just completely start over and reset my timing, can I do it as the service manual says, like described before, or do I have to reset the computer's memory somehow?

 

[jonheslop]

One other question. This is going to sound dumb but I want to make sure. If my idle is too high, say 1200rpm, do I still set the base timing a 5 before? I know that it will always change when you take the ground wire off and check with a timing light, but as far as setting up the base timing do you always make it 5BTDC regarless of the idle rpm?

 

[missouri_dsm]

sounds like a vacuum leak. time for you to do a boost leak test.

 

[jonheslop]

I don't think I have a boost leak because I have the maf blow through setup which as you know places the maf about 3 inches away from the throttle body, so there is no room for anything to leak. I have tried this with the stock maf too and have always had the same problems. I have the results from my latest testing I just did. Ok...I reset the timing, it's at 5BTDC with the timing wire grounded. But just to make sure, what color wire is the timing ground wire? Mine is yellow with some other stripe, I forget what color. Anyways...the idle is around 1200rpm when I set it at 5BTDC. Then when I unplug that wire and start the car up again, it idles at around 1300rpm and the timing stays steady at about 20BTDC. I can't read it exactly because it is off the scale but it's around 20. Can someone tell me why the timing is jumping so much once I set the base timing? Do I need to advance it towards 0 to get a better idle? Even if I do that it will still jump a lot and I can't figure out why it doesn't only jump a few degrees like it's susposed to. I checked the timing marks and they are all lined up. Is it possible that my crank angle sensor is bad? If so, is that a symptom of it? Any ideas would be appreciated. I know somebody has to have this same problem that can help me out. I have been battling this high idle and timing problem for 6 months now. It is the only thing keeping me from having fun with this brand new motor I've had sitting for 3 years. By the way, my biss screw is still all the way screwed in which I know means something is wrong because it's still idling so high. Thanks.

 

[steve]

If my idle is too high, say 1200rpm, do I still set the base timing a 5 before? I know that it will always change when you take the ground wire off and check with a timing light, but as far as setting up the base timing do you always make it 5BTDC regarless of the idle rpm?

No the ECU drops out of the set timing mode if the idle speed is too high. So you have to get the idle RPMs below 1k.

Steve

 

[missouri_dsm]

you have a leak at the throttle body. TB gaskets, fiav, vacuum line. Even with a blow through set up you can have boost leaks and vacuum leaks and they will affect the idle(vacuum leak) or performance(boost/vacuum leak). since the throttle body is after your translator it will still affect your idle if you have a leak.

 

[jonheslop]

Well here is what I've done at the throttle body. I've replaced both gaskets, I even replaced the intake manifold gasket. I blocked off the FIAV, I blocked all four vacuum lines on top of the throttle body, the ISC seems to be working fine because I checked it out with a multimeter according to the manual. The BISS has a new o-ring, however I am missing the rubber plug, but I don't think that would bring the idle up to 1300 would it? Ummm....that's all I can think of. Would it be worth the trouble to replace both gaskets again with some silicone gasket maker added on top of the gaskets? Should I replace the throttle body? I've heard that there are some seals in the throttle body, mainly around the throttle plate rod, that can wear out and leak. I've starting to think about getting an aftermarket throttle body but I have a feeling it would only cause more problems with tuning. What do you think? I can't think of anything else that would leak on the throttle body. If the PCV valve is bad will it leak in air? Or does it close shut?

 

[larsrya8]

Your throttle cable isn't stuck is it?

 

[steve]

If the PCV valve is bad will it leak in air?

Yes, it's open under vacuum and what it bypasses normally is part of the total but if it's bad it may be leaking more than designed for. Just clamp down on it's hose and see what happens.

Have you pressure tested at the throttle elbow?

Steve

 

[jonheslop]

No, the throttle cable isn't stuck, it's fine. I haven't done any pressure testing or boost leak testing. I don't know how for one. Also, I've had the PCV valve system completely blocked off before so that won't be the problem. Tomorrow I am going to replace all the gaskets and put some gasket maker silicone on them for extra insurance, then I'm going to buy a new BISS set. Also, I will try to find a new oring for the ISC. Basically rebuild the whole TB. Does anyone know if the tps has any sort of seal or oring?

 

[steve]

Does anyone know if the tps has any sort of seal or oring?

Nope, the only seals are the ones on the throttle shaft for both sides of the throttle body.

Steve

 

[jonheslop]

where can i get replacements for those throttle shaft seals? I didn't know there were any because mine doesn't have them. Would those make much difference in the idle though? It seems like those would be a very very small leak.

 

[jonheslop]

ALSO...is it common for ISC motors to be bad even if they check out to be fine when tested? Because I'm thinking about buying a rebuilt one even though mine seems to be fine.

 

[steve]

Throttle shaft seals. http://www.machv.com/throtbodseal.html

Think about how much the BISS moves to get an idea how sensitive the idle circuit is.

The ISC is part of the system. If the ISC coils measure right both the wires and ECU still could be bad. About 25% of the 1G ECUs I see turn out to have bad ISC drivers that are not burned up and obviously bad.

Steve

 

[jonheslop]

I'm thinking I might need to look into getting a new ECU then, because I've tested that ISC three times and it tested fine all three times. And I can't seem to think of anything else. I am going to replace those seals first and see. However, I had no idea that if your idle is above 1000 rpm then the ECU won't adjust the timing. I think that might be my problem. It's the only reason I can think of that would make my timing so wierd. So I'll have to do those few things real quick and keep everyone updated.

 

[jonheslop]

I have one more question for you, wiseman. In the factory service manual, it says to take the ISC out and have a friend turn to ACC on and off with the key and make sure the ISC motor moves in and out. It tests fine when I do that, so does that mean the ECU is working properly? Or does that not mean anything?