WELL after throtle body clean its still there.

AT IDLE RPM'S GO DOWN THEN BACK UP WHILE IN DRIVE AT STOP LIGHT AND IDLING, NOT EVERY TIME. OTHER THEN THAT NO PROBLEM WITH ACCELERATION AND CEL NOT ON. AFTER ENGINE IS REALLY WARM IT WON'T DO THIS. INDY MECHANIC SAID DIDN'T DO IT TO HIM SO DOES NOT WANT TO JUST START REPLACING PARTS.

WHAT WOULD CAUSE RPMS TO FLUCUTATE AT IDLE?

SPARK PLUGS CHANGED 6 MONTHS AGO AND NOTICED IT AFTER ONE MONTH. CAN THAT DO IT.

1998 C 230.

HELP, TIRED OF PAYING THESE GUYS THAT HAVE NO IDEA, OR NO EXPERIENCE.

Did you install the correct sparkplugs?

__________________
2007 C 230 Sport.

Air pump self test. Normal. Didn't we have this conversation already? Turn your caps lock off, it's annoying.

If the car experiences a 1-2 second dip in the idle, with a "shudder," then runs fine the rest of the time and no CEL, then what you're experiencing is the air pump self test. I've owned my C230 since new, for 240,000km now, and it has done it since new, and always will as long as the air pump is working properly.

You can keep throwing time, money and effort at solving this problem, but I doubt you will ever be satisfied. The car has a normal system operation that causes a slight idle drop. Get used to it.

Don't clean the Air Mass Meter. You're asking for trouble. They were not meant to be serviced, and even if it was failing, at best you bought a little time. The failure of the AMM causes a fuel trim adapation problem and is easy to diagnose. First, 95% of the time it will throw a CEL then you'll have a terrible hesitation at 4500rpm and above. Driveability will be effected.

Now that you screwed with the AMM, I'll bet that sometime in the not-too-distant future it will go out on you. If you get code P0170/P0171, then have the adaptations read and I'll bet they be maxed at 1.32 and you'll need a new AMM. BUT, the symptoms are different than what you're describing.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

YES

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I cleaned T.B. and not M.A.S.

COULD incorrect plugs or not tight enough cause this same symptoms?


Sorry for capital letters, just tired of mechanics who are supposed to know about abnormal and normal variants.


I AM asking because for 100,000 miles this vehicle has not done this self pump air test SO not a normal variant and very noticeable! Only real change are spark plugs.

COULD IT BE PLUGS, NOT RIGHT SIZE,OR TIGHT, LOOSE?

What plugs did you install?

__________________
2007 C 230 Sport.

See my post above.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Lore, it seems to me that Will already told you, that it's a "normal" self test to have an idle surge during long idles. Spark plugs won't do it, because it would do it all the time, or at random times. The fact that Will's car does it at exact intervals means it's some sort of computer self check. Your car has a very complex computer, that tries to get past emmissions, while making lots of power, and maintains drivability around town.

Several people have said the only way to find out is to hook it up to the right computer (SDS) and see if it has a problem. If the computer says it's fine, live with it. Without the computer, buying parts because someone told you is a waste of money.

Please, please turn your caps lock off, it's really anoying to try to read your posts.

Chuck

__________________
2000 C230 Kompressor "Frosty"

2007 PT Cruiser
2001 VW TDI Beetle
1999 Landrover Discovery II
1971 Corvette

Gone: 97 Cabrio, 83 240D, 93 VW Eurovan, 95 Volvo 850, 93 Chevy Astro Van, 77 VW Bus, 99 VW Jetta, 74 VW Bus

Mine is random and does not need loong intervals to idle.

Had not done this for over 100,000 miles and noticed it now.

Complex and expensive parts yes, throw money at it, H*** NO!

Will did not mention THROTTLE actuator.

If mine was cyclical like ac surge, I can understand. But it isn't.

Therefore asking opinions and got a few.

A SURGE IS UP, MINE IDLES R.P.M. DOWN THEN BACK UP!

TODAY it didn't do it once after over 60 long stops, this can happen the next day 2-3 times though.

This is why I asked question of what could it be for people who really know how these machines work, no novice please???

[QUOTE=N41EF;1707142]Lore, it seems to me that Will already told you, that it's a "normal" self test to have an idle surge during long idles.

I never said it wass normal. Doing it for excessive lengths of time would tell me that something is wrong with the pump or emissions system, but in 100k miles there have never been any diagnostic codes related to these symptoms.

I have learned to LIVE with it, but it's not normal

__________________
former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL

YOU got PROFESSIONAL advice a LONG TIME ago partner.

See post #13.

Many of us don't get that in our posts, you did. Use it to your benefit.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

GOT EXACTLY same advice at other post, I know both of these guys are not
newbees!!

I think you have what I have. Here are my exact symptoms:

Once (or maybe twice) a day, at a stop, after fully warmed up, the rpm stumbles for about 1/2 sec. That is it. No other symptoms. It is a curiosity.

Is that exactly as what yours does?

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I think both Lore and I have the same issue Mike - mine will do it for 2 minutes, the quick "blip 'n dip," multiple times, ryhthmically. It's not a 1 or 2-time deal at first startup. It's a lengthy annoyance that is definitely abnormal, but again, in the OP's defense, the "great advice" of checking the system with SDS is probably futile. Neither of my local dealers could determine a "problem" in teh past

So, now it comes down to ingenuity - and I would think a failing throttle actuator would cause the problem ALL the time, not just for the first 20 mins

__________________
former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL