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 Post subject: rough idle
PostPosted: Fri Feb 04, 2011 5:18 pm 
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I am merely driving my van
I am merely driving my van

Joined: Sat Dec 25, 2010 5:32 am
Posts: 14
got to love new projects:). i have acquired a rough idle. but it only idles rough at a stop light or stop sign. it started after i changed the air filter and pcv valve. is the a simple solution to fix this? ty for any tips or suggestions. this is in my 1990 astro van.


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 5:34 pm 
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check for leaks in your intake and vacuum system.


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 6:39 pm 
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Also pull and check the EGR for carbon deposits.

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2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

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Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 6:42 pm 
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LiftedAWDAstro wrote:
Also pull and check the EGR for carbon deposits.

that's got my vote (depending on how rough)

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vans owned: Image
97 Astro AWD (selling by summer .. i think) SOLD
99 Astro LS Sept 08 ASV VOM
94 Astro LT
93 Astro LT
96 Astro LT AWD * parts van*


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 8:49 pm 
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I am merely driving my van
I am merely driving my van

Joined: Sat Dec 25, 2010 5:32 am
Posts: 14
what is the EGR? still learning terms also.


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 9:16 pm 
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I finally get the smurf thing

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Exhaust Gas. Recirculation


I allows a bit of your exhaust to go back into the intake to burn off some of the extras that get through the first burn.>> ( i think.... could be wrong....Been a while since i splained this stuff)

Its part of the emissions system..

Should be able to trace it as a pipe that comes off the exhaust manifold an goes over to the intake manifold. There is a valve in there that regulates how much gets back in based on the sensors in the exhaust.

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1999 Safari SLE. Stock. Proud owner since May 2010. So far I love it..

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The old cars - my progression to here (most recent first)

1996 Honda Passport
1988 BMW 320i touring
1989 BMW 520
2005 Chrysler Sebring Convertible
2002 Dodge 1500 Quad Cab
1989 BMW 320i
1990 Toyota Tercel EZ
1991 Mitshubishi Mirage
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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:12 pm 
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I get chills without my van.
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My take on EGR a little different.Using hot detonation prone air lacking oxegen from its first trip through the cylinders.To try to burn gas.Causing that fuel to misfire causing worse emissions and robbing power.Maybe I wrong but I never heard any goverment agency ever claim carbon monoxide and hydrocarbons would burn gasoline.I just dont know how good the LSD was when they thought that was a good idea.Surely the first engine with it was a clue.They eventually did away with them on most engines.Think it was the poor mileage and emissions?Okay I a smart aleck.But these facts are so obvious a blind man can see them.

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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:26 pm 
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EGR lowers the combustion temperature to reduce NOx emissions. Excessive EGR can cause misfires and partial burns, but properly tuned, it can improve efficiency.


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:32 pm 
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NOX emissions actually are from improper air fuel mixture.To lean.I got mine blocked better milage and alot more power not seeing downside.

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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:37 pm 
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Try searching through any EGR posts to see if you can find a pic of where it is and what it looks like. I will do the same.

EDIT: found some pics.

These are of Lockdoc's 93. Not sure if your 90 is in the same location or not.

Image

See the little chunk in the hole?

Image

Here it is!

Image

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Current rides:
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition

Mileage spreadsheet

Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:49 pm 
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I get chills without my van.
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Posts: 96
this to a 90 van my 94 electronically controlled.On tbi it behind Injector unit On w motors it under the plastic intake.There are two openings on one pictured had to have center hole to work.On my 94 just a flat plate with th bolt holes.I can dig up a picture of w Motor placement
Attachment:
EGR Block.jpg
EGR Block.jpg [ 211.96 KiB | Viewed 1612 times ]

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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:56 pm 
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chevymaher wrote:
NOX emissions actually are from improper air fuel mixture.To lean.

Precisely. The exhaust gas displaces oxygen making the mixture richer, and lowering combustion temperature. Nitrous Oxides form when Nitrogen and Oxygen from the air combine at high temperatures. Unsophisticated 1970's EGR systems had side effects, but modern EGR systems improve performance and economy without affecting drivability.
A malfunctioning EGR will trigger the trouble light, and you may not pass emissions testing.


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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 10:59 pm 
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I get chills without my van.
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This my spare motor it in the back of intake between intake and distributer.My 94 has same EGR valve as you show on that CPI motor But on TBI it located in rear as 90 motor shown
Attachment:
EGR placement.jpg
EGR placement.jpg [ 216.81 KiB | Viewed 1611 times ]

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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 11:04 pm 
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I get chills without my van.
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Joined: Thu Jan 20, 2011 11:50 pm
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timelessbeing wrote:
chevymaher wrote:
NOX emissions actually are from improper air fuel mixture.To lean.

Precisely. The exhaust gas displaces oxygen making the mixture richer, and lowering combustion temperature. Nitrous Oxides form when Nitrogen and Oxygen from the air combine at high temperatures. Unsophisticated 1970's EGR systems had side effects, but modern EGR systems improve performance and economy without affecting drivability.
A malfunctioning EGR will trigger the trouble light, and you may not pass emissions testing.

I dont have emissions testing,and I got older garbage style.I will go with delete and setting air fuel mixture correctly.Getting rid of hot intake air and adding more oxegen a power adder.More fuel and more air more power. And 800 degree air is not good for combustion.They may have improved it but it better without, if again the key is tuned correctly

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 Post subject: Re: rough idle
PostPosted: Fri Feb 04, 2011 11:29 pm 
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EGR is supposed to improve combustion as well. It's not as simple as more air=more power.
There's other effects to consider like:
Reduced throttling losses.
Reduced heat rejection.
Reduced chemical dissociation.


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