RPM problem

Dave · **RPM problem**

I began to have problems with my car since I had the dual exhaust installed. Whenever I have the car in park for longer than 2 minutes the RPM drop to 500 for a second then return to 750, it continues to do so for as longer as the car is on. The same thing happens when I come to stop when I am driving. I had the battery, alternator, spark plugs, and the air intake checked and none of these seem to cause the problems. I had auto zone run the test on the computer an no codes came up. I am thinking it might be the oxygen sensor.

Monkey · 09-09-2003, 10:25 PM

yeah, i think the welder got a little too close to the O2 sensor and one may be burnt out. I would just either take it to autozone to tell them which one is bad, or just buy a new set and replace the pair yourself.

Rellik · 09-09-2003, 10:32 PM

I kinda doubt its your 02 sensors. When they trip, it trips a CEL.
I would test them with a multimeter, or have someone test them for you.
Did you ever get a check engine light. You could haev an exhaust leak somewhere.. or even a vacumm leak.

Monkey · 09-09-2003, 10:37 PM

they dont always throw a code. if there is a small short that sometimes works and sometimes doesnt, it wont throw a code. he is saying that it works for about 2min before it kinda flucuates for a second. that split second wouldnt be long enough for the CEL to go on.

vacuum leak would hold the idle high. trust me, ive had about 5 of them, and can be in excess of 1000-1500rpm at idle

Danger Dude · 09-09-2003, 10:51 PM

It might be the O2 sensor but it might be the Idle sensor causing the fluctuation. But Monkey is right O2 sensors can be intermitten and unless they come on the computer will not store a code.

Rellik · 09-10-2003, 11:53 AM

When was the last time you changed or cleaned your air filter?

Dave · 09-10-2003, 03:04 PM

I took it the muffler shop a day after I got it installed and they said there wasn't any leaks. I recondition Mac filter about a month before the mufflers were installed. I quess I'll have the oxygen sensor checked.

Rellik · 09-10-2003, 04:08 PM

You re conditioned your mac air filter.

I'm going to assume that you re-oiled it. You may want to check to see if your MAF is gunked up with oil from the filter. :|

.:DarkEntity:. · 09-14-2003, 03:33 AM

I had the same problem...
except my 'Check Engine' light was on too, and it was the O2 sensor

zerauj · 10-22-2003, 10:14 PM

come to a conlusion of the problem? also have the same prob after dual install.

Dave · 10-24-2003, 08:38 PM

I took everyones advice on what was causing the problem, but nothing helped. My engine light doesn't turn on so I don't think it's the O2 sensor. I don't know if you have the same problem, but when I press on the brake I notice the rpm drop. Check out the discussion on the same subject:

http://www.v6stangs.com/forum/viewtopic.php?t=2616

mustangmeat · 10-24-2003, 09:20 PM

this has been discussed a thousand times. mine does the same thing with the stock exhaust. my guess is it's a coincidence with the exhaust and the real cause is the fuel delivery system. you didn't say what year car you had, but many people have this problem with 99 and newer cars.

mustangmeat · 10-24-2003, 09:21 PM

i would not buy an expensive ass o2 sensor if the light isn't on. i would think you would be wasting your money

Dave · 10-24-2003, 09:31 PM

I have a 2000 and I have pretty much given up. When I have enough money I'll take it to ford and hopefully they'll find the problem.

Extreme Effects.com · 10-24-2003, 09:32 PM

I think it is a vacuum leak.
Can you hear a leak at all?
A sort of hissing sound?

But it could be anything.

Dave · 10-27-2003, 03:00 PM

I went back to the muffler shop the day after I had the exhaust installed and they found nothing wrong. If anyones finds a solution please let me know.

Rellik · 10-27-2003, 09:59 PM

Did they test you 02 sensors?

Dave · 10-27-2003, 10:15 PM

No I haven't tested them because no codes come up and the engine light doesn't turn on.

Rellik · 10-27-2003, 10:17 PM

U should test them anyway.

Dave · 10-27-2003, 10:23 PM

How would I go about doing that?

Rellik · 10-27-2003, 11:36 PM

take it back to the exhaust shop.

Or take it to a shop that will do it.

Or pick up a multimeter, and a hanyes manual.

Fishers Stang · FDNY 343 9-11-01

my O2 is out (one of them, but it does not change my idle, the only thing its dowin now is soundin a lil louder cause its freazin cold here (well 32* right now

) but just my $0.02 worth, and thats very little)

Rellik · 10-28-2003, 12:55 AM

02's can hurt your idle. I had one out, and my car had horrible mileage, and a rough idle.