The car is a well maintained 1995 E320S with 171k. The idle in drive (air on or off) always had the needle on the tach resting on top of the five, now for some reason the needle is just under the ten mark on the tach(in drive) . It has no rhyme or reason. This is what I have tried so far, airflow sensor, idle actuator and the temp switch for the EFI computer. Any ideas? When I come to a stop sometimes it drops to its normal mark then sometimes it just jumps up, no bouncing around or anything, it just jumps up. Your thoughts are appreciated.

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

Does anybody have any thoughts on this? When I did a search I found one case like mine, that was a vacuum leak. I just had the head gasket replaced and the idle was doing this before, so if it was a vacuum leak I assume it would have been fixed with new gaskets. Also my tech got a code 35 on his hand held tester. He is stumped over this.

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

Common causes are the OVP relay failing and leaving you in limp-home mode, the idle valve failing and ending up in its no-power position, or wiring to the idle valve is bad.

I would check to see if the valve is getting power when the idle jumps up.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Dirty throttle body?

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95 E320 Cabriolet, 159K

HHT -code 35 is O2 sens at rich limit , lean condition.
[assuming he got the HHT from the HFM-SFI module]

Possibles are fuel pressure regulator or vac leak,
Because it does it at certain times, I would check for vac leaks AFTER the switch-over valve at both air pump and egr valves.
Also purge valve..and all hoses...
On the reg., look for fuel drip when removal of vac line to reg.....

I had a problem where the idle was 1500-1800 in neutral & park, and about 1000 when in drive. Turns out it was an ECM of some sort...there is one on the front passenger side floor...I believe that is the one replaced. I get my car back tonight, so we'll see if it's 100% again, but word on the street is that it's fixed.

My idle tended to seem to be high only in warmer weather conditions or after I drove it awhile - and lately, since the weather has been warmer, the idle was always high. Cruise control didn't work when the idle was high. And once the idle was high, it wouldn't go back down under any circumstances, unless I restarted the car (and then it only went back down rarely).

My high idle started right after I had the throttle acutator replaced...not sure if something maybe got shorted when that was put in, or if the ECM was always screwed up and I just never realized it because the throttle actuator was also screwed up...

Not sure if this helps at all, but at least that's my experience from a similar sounding problem.

Matt
1994 E320
167k

Thanks guys for your help. I did check the vacuum hoses around the intake and everything held vacuum. I did not check the fuel pressure reg. or any vacuum lines going to it. Not sure where the fuel pressure reg. is on this car. If one can point me in the direction that the reg. is, I will check its hoses for leaks. By the way reset the computer yesterday and today I got the same code again (35). By the way what is a ECM?

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

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How did you reset it ? Do you have HHT?

It would help if you were to tell me where you are getting this code from..
The HHT codes are completetly different than the Flash codes...

Arthur

My friend who is a tech has a hand held device that allowed him to reset the system. The part of the system he checked would not have turned the "check engine" light on. I hope that makes sense, if not I can call him and ask him.

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

OK , I see ..

Had me confused as to how you were clearing.
Anyway, you want to ask him which pin he is getting the code from
It will be #8 or #14..
Then I can tell you more,

I assume it was #8, but assuming never works..

Arthur

I called him and he said it was # 8 and 3. I hope this helps. Thanks!

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

OK

8 is HFM module and 35 code is digital code for HHT .
So, again, check fuel regulator as my other post.
It is round, silver valve with a vac line attached. Between the thermo housing and the dip stick...

Thanks for all your help, I will let you know as soon as I do!

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

Well we still don't know what is wrong with my car. We tried a "purge valve" because they can have a slow leak and its hard to find, that did not change anything. We tried a O2 sensor, that did not work either. The only vacuum leak we found was the transmission vacuum modulator, which we will replace tomorrow. But when we blocked the line it did not change any readings on the O2 sensor. After a couple of days of driving I am still getting a code 35 (lean). The manifold does sound like it has a air leak but no starting fluid has found it if its leaking. It feels like its getting worse because if your in a parking lot and you hit the gas and then the brake it feels like it wants to stall then the idle jumps back up. The fuel pres. regulator was checked and no problem was found, so what is wrong with this car?

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Mike

90 300D 511k
95 C280 133k
14 BMW 528i

My 94 E320 had a 035 code. Replaced the Engine Control module and that fixed the problem. You should have a check engine light with code 035.

You can start with the O2 sensors, mass air flow sensor, vaccum leaks, fuel pressure, if everything checks out, replace the ECM and see if adaptation numbers change.

Your DM should be giving you a code 19, along with 3 and/or 4.

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Zafar
94 E320 58000 Miles