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more idle and fluctuating rpm problems

B

bobbyw

CEG'er
Joined
Apr 17, 2008
Messages
145
Location
Bloomingdale, IL
Lately my car(2k SVT) has been idling strangely. When I come to a stop, the rpms sit at about 1300 for about 3 seconds, then they drop quickly and catch at about 500 and shoot back up, dip down again, then settle at about 850. Sometimes when I clutch in to shift the rpms drop really quickly and do the same routine. I also have codes for banks 1 and 2 rich. I've reset the ECU, no help. Any ideas? Thanks guys
 
espguitarist91 said:
Lately my car(2k SVT) has been idling strangely. When I come to a stop, the rpms sit at about 1300 for about 3 seconds, then they drop quickly and catch at about 500 and shoot back up, dip down again, then settle at about 850. Sometimes when I clutch in to shift the rpms drop really quickly and do the same routine. I also have codes for banks 1 and 2 rich. I've reset the ECU, no help. Any ideas? Thanks guys
Click to expand...
Post the exact codes. Resetting the ECU without fixing the problem will not help.
 
P0172 and P0175
Its a strange problem. It was apparent during the summer and i reset the ECU and it drove perfectly until now. I recently had the ECU reset after checking the 02 sensors, and i believe that brought it up again.
 
Some reasons for P0172 and P0175 are:
1) Camshaft timing incorrect
2) Engine oil overfill condition
3) EVAP vapor recovery system failure
4) Fuel pressure regulator damaged
5) O2 sensor contaminated with alcohol or water
6) MAF sensor values incorrect or out of range
7) Fuel injector(s) leaking.
 
Ok thanks. I'm pretty sure 2, 5, and 6 can be eliminated. 6 qts oil, the 02 logged ok, and i unplugged the MAF and it got way worse, studdered, and died, which im guessing means its functioning properly.
 
[FONT=arial,verdana,helvetica,sans-serif]P0172[/FONT][FONT=arial,verdana,helvetica,sans-serif]System Too Rich - Bank No. 1. [/FONT]
[FONT=arial,verdana,helvetica,sans-serif]P0175[/FONT][FONT=arial,verdana,helvetica,sans-serif]System Too Rich - Bank No. 2. [/FONT]
 
I think you have a huge vacuum leak somewhere, listen for hissing noises in the engine bay. Also, if you did a UIM/LIM cleaning/rebuild recently and reused your intake manifold gaskets, those gaskets are probably worn out and causing a leak.
 
Nope, I havent touched the intake manifolds at all. It might be a vacuum leak, ill test it with spraying starting fluid around the hoses.
 
I tried unplugging the MAF with the car running and it sputtered and died. That would make me think its not the problem, but im not sure.
 
not necesarily. just because it died doesnt mean its not reading poorly. try taking the sensor off the housing and spraying it down with electrical contact cleaner.
 
Alright, thanks. I'll give that a shot, see how things are after. I hope is an easy fix, i need to have this running in good shape before winter hits. My ambition to fix problems disappears with subzero temperatures.
 
another thing to check is to see if your IAC (idle air control) is clean, and the hose is working properly. you would get a code if it were totally bad, but it could be getting old and un responsive. i deleted the IAC on my car (to make way for a 65mm TB on a 3L manifold) and it will drop rpm fast. that is usually due to the IAC not operating properly. if your engine is stock its located on the intake manifold at the drivers side rear. its got a two wire plug going into it. there is a hose from there going to the intake of the car, the biggest one going into the intake accordian. the IAC has two 10mm bolts holding it on, but if you take it off, note that its got a paper gasket and you'll have to be careful or buy a new one.
 
I had the same exact issue. Only my codes are p0171 and p0174 banks 1 & 2 running lean. My idle would sit at about 1100 1200 rpms coming to a stop, sit there for a few seconds and then bounce up and down. My car even died some times. :crazy: I cleaned my iac and that didn't seem to do much. I haven't played around with the maf. But I did get a fuel induction service at my work and so far the idle hasn't bounced around at all but the idle still hangs when you approaching a stop and the car is in neutral. I still have my codes all I know is that it's not a vacumn leak because I sprayed carb cleaner everywhere.
 
Hmmm....weird. Mine comes down to idle pretty normally now. The rpms still drop quickly at random times, but if i keep the clutch in, the car doesnt die now, the rpms drop to about 500 and then shoot back up. The high rpm problem is still there, it just sounds bad when it gets to around 5800 and the engine wont rev any higher. Ill try cleaning a few things and see what happens
 
sounds like you have a throttle hang issue, or you have IMRC issues. IMRC will give you top end problems, and on a 2.5L they can make the bottom end a little weird too, because it takes a few seconds to pull full vaccum when the secondaries stay open. sounds weird, but its happened to me.
 
I had a problem with my rpms idling at around 2000 and it would hold it's speed whenever I hit the accelerator. Basically it was accelerating for me and I had to drive with my brake. I replaced the mass air flow sensor and the problem was gone. May cost around $100 depending on the vehicle but that's with a core charge. They also said it may cause a misfiring cylinder code as well. Good luck, hope all this helps.
 
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