[Giving It Another Shot] Stall Under Very Specific Conditions [Forums - C4 Technical]

C4 Technical > [Giving It Another Shot] Stall Under Very Specific Conditions
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j3studio	[Giving It Another Shot] Stall Under Very Specific Conditions	#1
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	[early 1985/A4/3.07/very stock] I get an occasional stall from the 1985 under these conditions: 1) After running for a while at highway speeds 2) Very slow or stopped 3) Warm conditions Bulletin 85-91 (Minimum Idle Speed Revision) suggests simply increasing the minimum idle to 500 RPM from 400 RPM. Is it this simple or am I missing something else?
	Posted on: 2008/6/30 16:56
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bogus	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#2
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	I would think that the IAC is a little slow... maybe the TB is a bit coked up, too.
	Posted on: 2008/6/30 17:54
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#3
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: bogus wrote: I would think that the IAC is a little slow... maybe the TB is a bit coked up, too. Andy, Thanks for the response. TB is clean as of a month ago (cleaned while putting in new injectors). IAC was set to original spec less than a year ago. Issue has been a constant for the four years I have had the car.
	Posted on: 2008/6/30 18:40
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bogus	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#4
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	raise the base idle up to 500 rpm and see what happens. it is very possible that the TSB was never performed.
	Posted on: 2008/6/30 18:41
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#5
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: bogus wrote: raise the base idle up to 500 rpm and see what happens. it is very possible that the TSB was never performed. That's what I thought - I can't believe I didn't catch this when I did the adjustment...
	Posted on: 2008/6/30 21:07
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#6
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Does it restart fine after stalling? Does it stumble at all before dying?
	Posted on: 2008/6/30 23:27
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#7
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: Does it restart fine after stalling? Does it stumble at all before dying? Hello CC! :wave: Restarts very quickly and cleanly after stalling. Occasionally will have a slight stumble shortly before stalling, but about half the time there's no warning at all.
	Posted on: 2008/6/30 23:54
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#8
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Any other thoughts?
	Posted on: 2008/7/1 17:28
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#9
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Beats me. I was hoping for some cooked ignition parts. But if it restarts without missing a beat, that can't be it. Now on mine on very hot restarts, it sometimes stumbles for a bit. I blame that on injectors flooding the intake after shutdown and the computer chasing its tail for awhile until it clears up. Does the engine feel healthy around 4500 rpms? Does it hit an early ceiling? Does the fuel pump give out a healthy hum when you prime it? Have you checked fuel pressure at hot idle? Is your torque converter pulling the engine down too much? What does it idle at in park vs drive with your foot on the brake? Is the brake booster check valve leaking a bit?
	Posted on: 2008/7/1 18:38
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#10
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: Beats me. I was hoping for some cooked ignition parts. But if it restarts without missing a beat, that can't be it. 3 years on the alternator, 1 year on the starter, 2 years on the plugs and plug wires, brand new rotor, cap is good. Quote: Now on mine on very hot restarts, it sometimes stumbles for a bit. I blame that on injectors flooding the intake after shutdown and the computer chasing its tail for awhile until it clears up. Does the engine feel healthy around 4500 rpms? Does it hit an early ceiling? Healthy under hard acceleration up to around 4500 RPM - no early ceiling. Quote: Does the fuel pump give out a healthy hum when you prime it? Have you checked fuel pressure at hot idle? The fuel pump hums nicely when I prime it. I have not checked the fuel pressure at hot idle - cold fuel pressure is good. This may not be related, but I'm pretty sure the fuel pressure sensor is bad - it spends most of its time maxed out at 80 PSI. Quote: Is your torque converter pulling the engine down too much? What does it idle at in park vs drive with your foot on the brake? I think it's two or three hundred RPM down from park to drive, but don't hold me to that. I'll check. Quote: Is the brake booster check valve leaking a bit? I'll check...
	Posted on: 2008/7/1 18:51
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#11
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	A booster check valve can introduce unmetered air and make it stumble. Oil pressure sender at 80 psi is no biggie. I know you had said the coil and ignition module were original, those are both parts that tend to fail under heat. It increases the resistance in the solid-state circuitry, or opens up windings in the coil. But usually this won't recover until after letting the car cool down.
	Posted on: 2008/7/1 18:57
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Woodstock	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#12
Senior Guru Bremen/Germany 369 Posts Member since: 2008/1/15 0:00	Don't know how it relates to the 85, but isn't the ECM between a rock and a hard place when reaching 400rpm and lower? At 400rpm and higher the ECM takes over for computer controlled ignition, below it's controlled by the iginition module.
	Posted on: 2008/7/1 20:06
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#13
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	The ignition module isn't used over 400 rpm?
	Posted on: 2008/7/1 20:10
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SpectatorRacing	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#14
Elite Guru 1721 Posts Member since: 2007/12/29 0:00	On the LT1 it is. The ignition module gets it's timing signal from the ECM. However, I suppose it could be completely different on an L98.
	Posted on: 2008/7/1 20:49
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#15
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Quote: SpectatorRacing wrote: On the LT1 it is. The ignition module gets it's timing signal from the ECM. I wouldn't expect any different on any computer controlled small block. What else is there besides telling it what timing the ecm wants? The distributor does the rest. But with that said, advancing the base timing a bit on a carb'd vehicle tends to raise the idle a bit and smooth it out. That probably won't accomplish much on a computer controlled car though. What is your timing at idle with the car in drive with the brake on?
	Posted on: 2008/7/1 22:19
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#16
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: j3studio wrote: I think it's two or three hundred RPM down from park to drive, but don't hold me to that. I'll check. Completely wrong. Park 550 - 600 RPM Drive 510 - 540 RPM
	Posted on: 2008/7/1 23:27
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#17
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Why so low? Mine idles between 600-700 rpm.
	Posted on: 2008/7/2 2:31
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#18
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: Why so low? Mine idles between 600-700 rpm. Looks like JP and I will be doing another IAC adjustment this weekend...
	Posted on: 2008/7/2 11:13
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#19
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Gordon killebrew had some modified setting for the TPS, .65V I think. What is the base idle setting? 450? 550? You can always experiment a bit and bump that up. I presume you get the higher cold idle at 1100 rpm or whatever it is until it hits closed loop?
	Posted on: 2008/7/2 14:34
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#20
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: Gordon Killebrew had some modified setting for the TPS, .65V I think. What's the theory behind that?
	Posted on: 2008/7/3 21:17
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#21
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	From the factory, there's a window to adjust it in. That setting just puts it on the edge of the window, supposedly for better throttle response. I'm not sure of the effect on idle. You should also be setting the base idle with the timing advance disconnected.
	Posted on: 2008/7/3 21:23
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#22
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: You should also be setting the base idle with the timing advance disconnected. I'm away from home without my manual - am I correct that Lars' original instructions referenced below do this? http://corvetteforum.com/techtips/vie ... p?SubTopicID=55&TopicID=2
	Posted on: 2008/7/3 21:29
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#23
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Geez that's painful to read. Do this on a warm engine: 1. Jumper ALDL A+B. 2. Turn key on for 60 seconds. 3. Disconnect IAC and EST connectors. 4. Unjumper ALDL, start car. 5. Adjust base idle to 450 rpm (I cheat and do 500) 6. Shut car off, reconnect IAC and EST. 7. Adjust TPS to 0.65V.
	Posted on: 2008/7/3 21:37
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#24
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: CentralCoaster wrote: Geez that's painful to read. (I cleaned the text up when I did it) Did you do this with your ride? Did you see any changes?
	Posted on: 2008/7/4 2:29
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CentralCoaster	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#25
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	I do it that way everytime, except for disconnecting the EST. That's apparently more necessary on an A4.
	Posted on: 2008/7/4 5:00
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#26
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	JP and I did this (again) today - we'll see what happens... ...thanks to all who advised on this thread.
	Posted on: 2008/7/4 21:32
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bogus	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#27
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	I will be curious to hear the results. How frequently would it stall? If you go 3 weeks, will you assume the problem has been resolved?
	Posted on: 2008/7/5 1:18
	_________________ The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me
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j3studio	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#28
Elite Guru Western Philadelphia Burbs 4247 Posts Member since: 2007/9/2 0:00	Quote: bogus wrote: I will be curious to hear the results. How frequently would it stall? If you go 3 weeks, will you assume the problem has been resolved? Normally, I would say no - but over the next three weeks we're going to do close to 3,000 miles in Lauren, so if we don't stall in that period I will be very happy...
	Posted on: 2008/7/5 1:37
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bogus	Re: [Giving It Another Shot] Stall Under Very Specific Conditions	#29
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	that's the ticket!
	Posted on: 2008/7/5 6:10
	_________________ The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me
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