A whole lot of shakin' and knockin'...starting issue. [Forums - C4 Technical]

C4 Technical > A whole lot of shakin' and knockin'...starting issue.
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95Vert	A whole lot of shakin' and knockin'...starting issue.	#1
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	When completely cold, the car starts without issue. Driving around, not a problem. If I leave the car and then come back after 5 or 10 minutes, the car will start ok. Again, not much of an issue. If I leave the car outside at work and come back after 8 or 9 hours, it likes to crank over before it finally starts. Might take several sequences of turning off and cranking again. Anything over 10 minutes or so and the car was shaking, idling very rough and sounded like knocking. The last time it did this, something came on line and the idle settled in and it idled naturally. Do these things have an IAC that needs to be cleaned? Do I need to clean the Throttle body? Fuel issue?
	Posted on: 2012/3/14 21:50
	_________________ Ralf "Send lawyers, guns and money..."
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bogus	Re: A whole lot of shakin' and knockin'...starting issue.	#2
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	it really sounds like either the opti or PCM is failing. Can you get any codes? When my dynaspark died, it did something very similar to what you are describing.
	Posted on: 2012/3/14 22:36
	_________________ 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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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#3
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	Oh for goodness sake, does it ever stop??? Thanks Andy. What's the PCM? Have not checked for codes at this time...
	Posted on: 2012/3/14 22:50

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bogus	Re: A whole lot of shakin' and knockin'...starting issue.	#4
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	PCM = Powertrain Control Module - the engine controller. And no, it never stops. Also, check the following: Coil Coil wire for chaffing Ignition Control Module The coil and ICM are both heat sensitive, and when they get over heated and start to fail, they do weird things.
	Posted on: 2012/3/14 23:01
	_________________ 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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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#5
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	OK, thanks. I replaced the Coil wire when I did the wires at the time I did the water pump. I'll check again. I know where coil is, but I don't know where PCM or ICM is...always learning...Is one of those the big unit over the battery?
	Posted on: 2012/3/14 23:06
	_________________ Ralf "Send lawyers, guns and money..."
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bogus	Re: A whole lot of shakin' and knockin'...starting issue.	#6
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	The PCM, yes, is over the battery. The ICM is between the coil and the head. If the wire is new, I would be shocked if it was already damaged, but you never know.
	Posted on: 2012/3/14 23:21
	_________________ 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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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#7
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	This is getting expensive sounding. That PCM does not look cheap. Same for the ICBM I'll see if there are any codes, but I have no check engine light. Coil should not be too bad, but what is the recommned brand or factory?
	Posted on: 2012/3/14 23:47
	_________________ Ralf "Send lawyers, guns and money..."
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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#8
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	Hi Ralf, If that were happening to me.....and getting no codes....first (only because it's free) I'd remove/clean/re-adjust the IAC (Idle Air Control). Second, the thing I'd replace is the CTS (coolant temperature sensor). It's about $50.00 and would of been my first suspect, but I'd do the free stuff first. Good luck!
	Posted on: 2012/3/15 1:07
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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#9
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	When you leave it outside at work for 8 hours or so is it sitting in the sun baking? IE, getting hot under the hood? If so I could see it being ICM related or fuel related.
	Posted on: 2012/3/15 1:12
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#10
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	Great suggestions! Thank you!!! Matt, it sits outside, yes, but it really hasn't been that hot! It will, but not right now. How does that change the equation?
	Posted on: 2012/3/15 1:24
	_________________ Ralf "Send lawyers, guns and money..."
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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#11
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	I've heard of cars sitting in the sun and getting so hot in the sun that the fuel in the rail turns to vapor and the car won't fire. I was thinking that for your cranking issue. Less likely the heat from the sun would affect the ICM, but anything is possible. It's just strange that if it sits overnight (ie cold) it's fine, but sitting for 8-9 hours outside (more than enough time to cool off) it has a problem cranking. I think a fuel pressure test would be a good idea when you have to crank it multiple times to fire.
	Posted on: 2012/3/15 2:10
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#12
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	Quote: Matatk wrote: I think a fuel pressure test would be a good idea when you have to crank it multiple times to fire. Agreed!
	Posted on: 2012/3/15 2:29
	_________________ 1995 Forged 385 ZF6 227/234 1.6 FIC30# MSD BBK SS SLP Bullets X-Pipe DynoMax
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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#13
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	Quote: Matatk wrote: I think a fuel pressure test would be a good idea when you have to crank it multiple times to fire. Agreed![/quote] Re: ICM....The Ignition Control Module most often fails when hot, thus Matthews suggestion.
	Posted on: 2012/3/15 2:32
	_________________ 1995 Forged 385 ZF6 227/234 1.6 FIC30# MSD BBK SS SLP Bullets X-Pipe DynoMax
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tjpreul	Re: A whole lot of shakin' and knockin'...starting issue.	#14
Elite Guru Columbia, MO 1103 Posts Member since: 2008/9/16 18:12	Quote: Matatk wrote: I've heard of cars sitting in the sun and getting so hot in the sun that the fuel in the rail turns to vapor and the car won't fire. I was thinking that for your cranking issue. Less likely the heat from the sun would affect the ICM, but anything is possible. I was having this issue with my car last summer. However mine was sitting in the sunlight during the day. Before I would try to start it I would open my fuel cap. Later I found my fuel tank vent line and purge valve were clogged. If I didn't relieve the pressure it could take 2-3min for it to clear up.
	Posted on: 2012/3/15 2:52

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bogus	Re: A whole lot of shakin' and knockin'...starting issue.	#15
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	hm... don't these have crank triggers?
	Posted on: 2012/3/15 3:57
	_________________ 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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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#16
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	Quote: bogus wrote: hm... don't these have crank triggers? '96 and up.
	Posted on: 2012/3/15 4:14
	_________________ 1995 Forged 385 ZF6 227/234 1.6 FIC30# MSD BBK SS SLP Bullets X-Pipe DynoMax
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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#17
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	(p.s.......I learned that from you Andy)
	Posted on: 2012/3/15 5:44
	_________________ 1995 Forged 385 ZF6 227/234 1.6 FIC30# MSD BBK SS SLP Bullets X-Pipe DynoMax
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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#18
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	Quote: tjpreul wrote: Quote: Matatk wrote: I've heard of cars sitting in the sun and getting so hot in the sun that the fuel in the rail turns to vapor and the car won't fire. I was thinking that for your cranking issue. Less likely the heat from the sun would affect the ICM, but anything is possible. I was having this issue with my car last summer. However mine was sitting in the sunlight during the day. Before I would try to start it I would open my fuel cap. Later I found my fuel tank vent line and purge valve were clogged. If I didn't relieve the pressure it could take 2-3min for it to clear up. Good tip! Problems with the EGR or EVAP system might be related to this. I forgot to ask, did you check for codes?
	Posted on: 2012/3/15 11:41
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#19
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	I still need to, so have to dig up Bill's explanation of how its done again. I want to clean that IAC as well. I'm so invested in my Jap stuff and Ford, I feel sheepish about checking, but there's a throttle body to clean, right? I really need to get more acquainted with this car, but it seems I'm just chasing issues instead of doing preventive stuff...I think its getting better.
	Posted on: 2012/3/15 14:53

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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#20
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	The IAC is attached to the bottom of the throttle body. There are a bunch of little passages underneath and in there to clean out with an old toothbrush and some carb/TB cleaner. Be careful with the IAC itself, there is a pintle on it. You are technically not suppoed to soak it in solvent. You really need to pull the codes for proper diagnosis. It will give us an avenue to look at...for example you might have and EGR or EVAP code, then we know where to start.
	Posted on: 2012/3/15 18:26
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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1Fast04Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#21
Elite Guru The hills of N. Georgia 2424 Posts Member since: 2007/12/30 0:00	Quote: Matatk wrote: The IAC is attached to the bottom of the throttle body. There are a bunch of little passages underneath and in there to clean out with an old toothbrush and some carb/TB cleaner. Be careful with the IAC itself, there is a pintle on it. You are technically not suppoed to soak it in solvent. You really need to pull the codes for proper diagnosis. It will give us an avenue to look at...for example you might have and EGR or EVAP code, then we know where to start. On his LT series the IAC is mounted on the passenger side of the throttle body with two Torx head bolts.
	Posted on: 2012/3/15 21:39
	_________________ 2004 Vert. 475hp. Built by Vengeance Racing
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95Vert	Re: A whole lot of shakin' and knockin'...starting issue.	#22
Senior Guru Aiken, SC 440 Posts Member since: 2008/6/2 1:15	Ha!!! So there is a throttle body!!! I've got tomorrow off. Will pull some codes, do some cleaning and publish what I find. It was doing the rumbling again after being started after 15 minutes. Coming from work, hard starting. Three go arounds turn key off then on. When it was doing its shaking, something was catching it, then couldn't keep up and it would start shaking again. Weird...
	Posted on: 2012/3/16 2:21

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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#23
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	Quote: 95vette wrote: On his LT series the IAC is mounted on the passenger side of the throttle body with two Torx head bolts. Thank you for the correction...I'm not an LT expert Ralf - those codes are really step one, so post up what you find!
	Posted on: 2012/3/16 2:39
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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Calm	Re: A whole lot of shakin' and knockin'...starting issue.	#24
Senior Guru Vancouver, Canada 608 Posts Member since: 2007/12/27 0:00	Quote: Matatk wrote: Quote: 95vette wrote: On his LT series the IAC is mounted on the passenger side of the throttle body with two Torx head bolts. Thank you for the correction...I'm not an LT expert Ralf - those codes are really step one, so post up what you find!
	Posted on: 2012/3/16 2:49
	_________________ 1995 Forged 385 ZF6 227/234 1.6 FIC30# MSD BBK SS SLP Bullets X-Pipe DynoMax
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RickAnthony	Re: A whole lot of shakin' and knockin'...starting issue.	#25
ASE Master Certified Downers Grove, IL 703 Posts Member since: 2006/8/2 0:00	Check for codes, Check fuel pressure, both good places to start... I'd check the fuel pressure regulator as well, make sure you are not having fuel leaking into the vacuum line... just a though not real hard to check.. IAC not a bad idea either to check..
	Posted on: 2012/3/16 12:33
	_________________ My Automotive Blog autoserviceupdated.blogspot.com CORVETTE SERVICE & REPAIR RickAnthonyMotorsports.NET
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Matatk	Re: A whole lot of shakin' and knockin'...starting issue.	#26
Webmaster SW Chicago Burbs 22805 Posts Member since: 2008/1/7 0:00	Any update with codes?
	Posted on: 2012/3/17 2:55
	_________________ 2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP
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