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Car runs Rough when cold

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Dready

15+ Year Contributor
68
0
Apr 30, 2008
NMB, South_Carolina
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.
 
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.
 
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?
 
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
 
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??
 
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.
 
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 :cool:

:dsm:
 
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.
 
There is the FIAV
http://www.dsmtuners.com/forums/newbie-forum/315778-fiav.html

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.
 
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
 
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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