View Full Version : RPM drop
Danger DANJ
10-05-2002, 05:20 PM
At the end of last winter and begining of spring, I started getting rpm drops when I started the car up in the morning. I would start the car and everything would be idling fine for a second or two, then the rpms would drop down real quick, then back up to normal again. Sometimes it would do that two or three times in a row, then everything would be fine and I'd drive the rest of the day fine. Throughout the summer I did not get this problem at all, but now that it's getting cold out again, the problem is back. It doesn't do it every morning yet, only when it's cold. Just recently I have also noticed that after a long run on the highway coming home from work, as I finally come to a complete stop at the bottom of the exit ramp near my house, sometimes the rpms will drop for a split second and the car gets a slight jerking feeling in it.
I have a '99 ES V6 with 49k miles on it and there is no ses light or anything like that coming on. I have an Infinity Basslink amplified sub in the trunk with an Optima Red Top battery which has been in well before the problems started. I can't figure out why it only did it when it's cold but now it seems to do it occaisionally after a long highway run.
Any ideas?
Auto-9
10-05-2002, 06:16 PM
I'm going to say I think it's something spark plug/wire related, but only because my old 4 banger did this and that was the cause. Other than that...I really don't have any technical proof and explanation I can base it on https://www.thegalantcenter.org/style_emoticons/default/sad.gif
Fishboy55
10-05-2002, 07:29 PM
It could be a problem with your throttle position sensor Dave. I'm sure manybrews will know exactly what it is. If it was my old 350 chevy, I'd tell you the automatic choke was sticking. LOL. https://www.thegalantcenter.org/style_emoticons/default/laugh.gif
Chip
chibisak
10-05-2002, 10:47 PM
DANJ u are not the only one,
i experience that as well every winter, these days getting cold the car do that to me so many time . make me worry about the winter....
any idea/
I get it every now and then but it's definitely related to the electronics in the car. The biggest factor seems to be the AC but other things also seem to make the idle up and down. And of course you never really notice these fluctuations when the tach is running high but when you come to a stop and the idle dips a little too low, your engine wants to quit and you sometimes feel a shudder. I just countered it by raising my idle speed a little and don't worry about it. Maybe you can do the same and it will be alright.
BTW, one thing I did noticed though was after I got a bigger TB put in, even at very low dips in the idle, the engine was smoother and it doesn't feel like the engine wants to die like before.
speedygalant
10-06-2002, 03:01 PM
I am having the same problem. but i live in florida. The thing is, i did the byo intake setup on my ride yesterday and i honestly did not like it. so i put everything back. i started the car an hour later, i let it run for about 10 minutes. then i drove it for twenty five miles on the highway. later on, it still kept on dying on me. the rpm's would drop and go up. it's weird and i'm getting worried now. any suggestions?
BlueESV6
10-06-2002, 03:22 PM
I had that problem... wasn't cold related though... clean the throttle body with carb cleaner and it may go away... especially if you haven't done it in a while. It fixed my idle problem!
https://www.thegalantcenter.org/style_emoticons/default/smile.gif
speedygalant
10-06-2002, 03:31 PM
okay, you are speaking in tongues to me now. what is the throttle body? and where should i pour the fluid in? do you mean a fuel cleaner?
Auto-9
10-06-2002, 05:41 PM
The throttle body is where your intake meets the intake plenum...it controls the amount of air going into the engine. Man I wish I had a link handy for a pic...as for the cleaner I'm sure you just swab it out...if you ever take a look at the throttle body and intake plenum you'd be surprised at how much gunk the EGR valve spits in there to control emissions...
Fishboy55
10-06-2002, 07:38 PM
okay, you are speaking in tongues to me now. what is the throttle body? and where should i pour the fluid in? do you mean a fuel cleaner?
Follow your intake tube all the way back toward the firewall. It connects to the throttle body. Remove the intake from there. I think it's just a clamp that holds it on. ( I havent had my stock intake for years, so I don't remember) Get some carbuerator and choke cleaner (not that fuel injector cleaner junk you dump in the gas tank) at the auto parts store. Spray it on a rag and scrub out the throttle body. Not the intake tube, but the metal part it connects to. Clean it real nice then put everything back together. Now you've just cleaned your throttle body and learned a little something about your car at the same time. I know for me, it's always a sense of accomplishment when I do something myself, even the simple things. Ask back if you have anymore questions. We're here to help.
Chip
speedygalant
10-06-2002, 07:41 PM
thanks, i'll try that tomorrow and i'll let you know.
Danger DANJ
10-07-2002, 02:06 PM
OK thanks guys.
So, let's say I clean out the throttle body and that fixes the problem, wouldn't that be a good sign to hook up a breather filter instead of letting all that debris get sucked into the intake pipe? We've discussed hooking up a breather filter before on the old board, but nobody seemed to think it was good for anything. Now it seems like a good idea.
BlueESV6
10-07-2002, 08:18 PM
I'm not sure what a breather filter is? I just sprayed carb cleaner in there and wiped out the liquidy/ oily residue with a rag. I especially cleaned around and behind the butterfly valve. One tip is to put a rag under the TB to catch any run off as your cleaning/spraying it out....
There was no debris really just the oily gunk from the PVC valve and emission junk.... https://www.thegalantcenter.org/style_emoticons/default/smile.gif
manybrews
10-07-2002, 08:26 PM
OK thanks guys.
So, let's say I clean out the throttle body and that fixes the problem, wouldn't that be a good sign to hook up a breather filter instead of letting all that debris get sucked into the intake pipe? We've discussed hooking up a breather filter before on the old board, but nobody seemed to think it was good for anything. Now it seems like a good idea.
HUGELY bad idea.
first, the breather IS using filtered air... thats why its attached behind the air cleaner element.
second, theres nothing coming OUT of the tube attached upstream on the intake pipe... its nothing more than clean air going into the crankcase due to the PCV valve and system. if you have vapors coming out of it, you probably have a clogged PCV valve.
NEVER, NEVER, EVER use a damn "breather" air cleaner. its a total and utter waste of money and resources.. and this is particularly true on a turbo car due to the physics involved (and the fact that a PCV system doesnt function under boost, but we'll not get into that).
the dirt on the throttle is normal combustion deposits from gas and heat. nothing more.
ALL throttle plates get dirty over time (except on some older throttle body injected cars due to the gas being sprayed directly onto the throttle plates, but no one had used throttle body injection in 10 years)...
HUGELY bad idea.
first, the breather IS using filtered air... thats why its attached behind the air cleaner element.
second, theres nothing coming OUT of the tube attached upstream on the intake pipe... its nothing more than clean air going into the crankcase due to the PCV valve and system. if you have vapors coming out of it, you probably have a clogged PCV valve.
NEVER, NEVER, EVER use a damn "breather" air cleaner. its a total and utter waste of money and resources.. and this is particularly true on a turbo car due to the physics involved (and the fact that a PCV system doesnt function under boost, but we'll not get into that).
the dirt on the throttle is normal combustion deposits from gas and heat. nothing more.
ALL throttle plates get dirty over time (except on some older throttle body injected cars due to the gas being sprayed directly onto the throttle plates, but no one had used throttle body injection in 10 years)...
I'm sorry but I have to totally disagree. If there was a way to filter it nicely I'm all for it but this is not the case in my experience. I've unplugged that hose and there is oil. Yes, oil and in both vacuum hoses. Which goes to show you that the PCV does it's job of letting airflow go in one direction but it does nothing for filtering. Also you know that air or liquid takes the easiest path out so what guarantee is there that the air is traveling from your intake hose to the valve cover and out the PVC when your PVC has oil in it. I guess to clear it, the vacuum does draw all of that stuff back into the engine and eventually gets burned up but no very efficient. I wish there was an environmentally safe and more efficient way to handle blow by but it's unacceptable by my standards after seeing the mess it makes in my intake manifold, intake hose, and throttle body. I guess clean environment or cleaner intake is your pick.
You know what, I just thought of something... If they were to design the valve cover with a built in splash shield right where the PVC sticks into the valve cover, that might keep unwanted oil from fouling the PVC. I don't know, just babbling now...
manybrews
10-07-2002, 10:12 PM
I'm sorry but I have to totally disagree. If there was a way to filter it nicely I'm all for it but this is not the case in my experience. I've unplugged that hose and there is oil. Yes, oil and in both vacuum hoses. Which goes to show you that the PCV does it's job of letting airflow go in one direction but it does nothing for filtering. Also you know that air or liquid takes the easiest path out so what guarantee is there that the air is traveling from your intake hose to the valve cover and out the PVC when your PVC has oil in it. I guess to clear it, the vacuum does draw all of that stuff back into the engine and eventually gets burned up but no very efficient. I wish there was an environmentally safe and more efficient way to handle blow by but it's unacceptable by my standards after seeing the mess it makes in my intake manifold, intake hose, and throttle body. I guess clean environment or cleaner intake is your pick.
You know what, I just thought of something... If they were to design the valve cover with a built in splash shield right where the PVC sticks into the valve cover, that might keep unwanted oil from fouling the PVC. I don't know, just babbling now...
there is SUPPOST to be oil in the pcv system!! its normal and, in fact, EXACTLY what its designed to catch!
blow by gasses and oil.
its suppost to catch and BURN all those vapors, and wether is doing it on the vacuum side (the PCV valve), or the intake side, it STILL IS being burned.
venting it to the atmosphere does NOTHING but pollute. it burns no less oil, it consumes no less gas, and in fact can cause poor idling due to the fact that at idle nearly 20 percent(!!!!!) of the air being combusted comes from the PCV!! if you dont have the intake filter attached, you are not metering that air through the airflow meter!
and incidently, ALL mitsus valve covers have had splash shields for 10 years +
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