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Newbie Forum: Beginner/newbie/general DSM modification questions. First mods, how to run 10's when you haven't run 12's yet, any tech question that doesn't fit in another tech forum. Probationary Members must limit their tech posts to this forum and sub-forums.

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Old 11-25-2008, 05:22 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #1 (permalink)
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Car runs Rough when cold


My car runs rough and kinda bucks a little when the coolant temp is still low.

I let the car warm up for atleast a minute but it still runs rough WHILE DRIVING until it gets to Normal operating temperature.

Could the coolant system be too full of coolant?

Would sparkplugs help this issue?

Any Ideas?

Like i said the car runs perfect after it gets warmed up..its just really annoying for the 1st few minutes.

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Old 11-25-2008, 08:24 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #2 (permalink)
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Do you have a aftermarket boost gauge? If so what's your vacuum read?
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Old 11-25-2008, 09:26 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #3 (permalink)
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I have the same issue... I'm assuming it's fairly commen but I just bought some new plugs... I need to get a gapping tool first but I'll post back with my results.

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Old 11-25-2008, 11:48 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #4 (permalink)
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its not common ( it should be smooth even when its cold) try changing your OIL also it may help

check the spark plugs and the wires

good luck


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Old 11-26-2008, 01:20 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #5 (permalink)
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In my car I'll leave it as common since I already changed oil,coolant,spark plugs/and wires,and the vacuum is the same as when is at temperature so I give up at least is only like that for a minute or two but no more.
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Old 11-26-2008, 02:26 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #6 (permalink)
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Check the ECT (Engine Coolant Temperature) sensor.


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Old 11-26-2008, 06:35 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #7 (permalink)
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The reason I ask about the vacuum is because if you have a vacuum leak, then you'll be running rich, and while the car is starting cold it's gonna idle high. Add that high idle to the richness caused by a vacuum leak and your car's gonna feel very bogged down and run like crap. So again, what's your vacuum reading?
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Old 11-26-2008, 07:10 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #8 (permalink)
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Thats kinda weird. Whe i cold start my car in 20 degree weather it will have a 1100 rpm idle, vacuum gauge runs a 20 out of 30.....then when it warms up, idle drops to 850rpm and vacuum gauge goes to 15/30. my A/F gague shows lean. I have a vacuum leak and i fixed it.

When you start your car cold...rev in neutral..does it sputter and spit? I thot at first it was spark plugs. went out and put like 150 on MSD ignition, MSD wires, and NGK Iridium plugs and it didnt help the problem.

GLuck

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Old 11-26-2008, 11:24 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #9 (permalink)
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My car vacuum is also 20/30
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Old 11-26-2008, 11:47 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #10 (permalink)
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Quote:
Originally Posted by habitatguy187 View Post
The reason I ask about the vacuum is because if you have a vacuum leak, then you'll be running rich, and while the car is starting cold it's gonna idle high. Add that high idle to the richness caused by a vacuum leak and your car's gonna feel very bogged down and run like crap. So again, what's your vacuum reading?

How do you check your vacuum reading??

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Old 11-26-2008, 12:04 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #11 (permalink)
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Originally Posted by SexaiPander View Post
How do you check your vacuum reading??
An aftermarket boost gauge that shows negative (vacuum, -hg) and positive (boost) pressure. This should be the first thing that you buy.
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Old 11-26-2008, 12:05 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #12 (permalink)
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Originally Posted by cano86 View Post
My car vacuum is also 20/30
Your vacuum reading should be higher when the car is warming up. (higher when idle rpms are higher) If it's the same when idling high as when idling normal, there's something wrong.
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Old 11-26-2008, 12:15 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #13 (permalink)
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mine is kinda funny like that to i think its normal

when i first start it and drive it, like start it put it in gear and go it is kinda weird

but if i let it idle for like 35sec. then it is all good

which when it is cold out side you should let you car warm up just a little, and get pretty close to fully warm befor boosting. thats what i do no boost untill its warm.


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Old 11-26-2008, 02:56 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #14 (permalink)
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Quote:
Originally Posted by ApexVIII View Post
mine is kinda funny like that to i think its normal

when i first start it and drive it, like start it put it in gear and go it is kinda weird

but if i let it idle for like 35sec. then it is all good

which when it is cold out side you should let you car warm up just a little, and get pretty close to fully warm befor boosting. thats what i do no boost untill its warm.
+1 Mee 2. I do it a lot more though. I turn it on put it on the turbo timer and then I go back inside my house and finish getting ready. When I come back I know the car is ready for whatever I throw at it

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Old 11-26-2008, 04:21 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #15 (permalink)
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From what I know it's fairly common, more so when you do the vacuum mod. When you delete the sensors on the drivers side of the engine bay it really does it.. All of my cars have done it. One of the sensors on the firewall on the drivers side is a cold start vacuum solenoid that actuates vacuum when the ECT is low so it won't run as rich and buck.
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Old 11-26-2008, 04:29 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #16 (permalink)
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It seems like its pretty common
I have the same exact problem. The vac gauge reads 20/30, and it only runs smooth once it warms up...my bo0st leak that i cant seem to get rid of doesnt help very much either
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Old 11-26-2008, 04:41 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #17 (permalink)
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There is the FIAV
Fiav?

The ISC, and a few other parts that affect how it runs. Mine didn't start the same after I got rid of the fuel pump solenoid. I've more or less tuned it out though. Still rough, but much less so. I don't know a whole lot about all that, but there's much more that can go wrong besides the CTS and a vacuum leak : )

When you let your engine idle to warm up, it will be ready for anything. Your transmission however, will still be cool at best, and your rear differential (if you have one) will still be at ambient. From everything I've heard, the best way to warm up a street car is to drive it normally. This brings the engine up to operating temperature more quickly and makes sure all the other things that need to heat up are good to go.


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Old 11-26-2008, 08:30 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #18 (permalink)
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Yes, its common. The ECU adds more fuel when the car is cold. It isn't as noticeable with a stock FP but if you have a higher flow FP esp. with a stock FPR then you really notice it. The ECU stays in closed loop operation until the coolant temp reaches normal temperature. Once this happens the ECU goes into open loop mode and stops dumping the extra fuel.

This article may help: The Essential Primer on the Diamond-Star Engine Control Units - Chapter 5

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Old 12-01-2008, 11:41 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #19 (permalink)
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Quote:
Originally Posted by habitatguy187 View Post
An aftermarket boost gauge that shows negative (vacuum, -hg) and positive (boost) pressure. This should be the first thing that you buy.
Ok well i already have that so thanks

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Old 12-17-2008, 06:58 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #20 (permalink)
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Sorry to bump an old thread, but I said I would post back after installing new plugs and I just got around to doing it. Turns out the old plugs weren't OEM, they were NGK but a different model. I put in the OEM ones and it runs much better when I first start off. Used to sort of bog if I got on it at all, now it hardly does. So try swapping out the plugs.

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