Warm idle too slow - occasionally stalls 300E

[jaymanek]

Great read, you answering all your own questions!

[Brabus3.6]

Okay, now a question perhaps someone else can answer . After the alternator upgrade I've just noticed that when the ignition is switched on the ABS light comes on then goes off after a second or so, the hand brake light is on (as it should be) but NO other dash light comes on. I removed an indicator bulb then put the ignition on & triggered the indicator. The bulb warning light came on as it should so I think all the warning lights are actually working, but just not coming on at ignition to be checked except for the ABS light. I've checked all the fuses, they're fine. Also, with the car idling in P at 1000RPM I slowly turned the volume of my stereo up to max. RPM decreased and became more erratic as the volume increased. I've charge & load tested my battery with a multimeter & it's fine. Is there any sort of external voltage regulator?

[Will]

IIRC, they sound like possible symptoms of a faulty OVP relay?

Do you know of somebody who can check it with yours (either substitute your relay into theirs or vice-versa)

Couldn't tell you which order the ABS and other warning lights come on and go off in etc, (long time since I sold my last W201 - similar to a W124) but I do know that the OVP relay is responsible for a few key functions whilst the ignition is first switched on, in particular the ABS system and for the ECU.

Obviously ignore this if my memory is lying to me!

HTH,

Cheers,

Will

[Will]

Just read that you have been working in the vicinity of the OVP!

Maybe check that you have not disturbed something here, and that the relay is properly seated?

Cheers,

Will

[Vlad]

If your car is still running on its original OVP it's only a matter of time before it fails.....the originals had a design flaw in them that results in the internal soldering failing and causing intermittent faults....normally the fuse on the top is fine even though the relay is faulty.

For the sake of £60 or so I would get it changed....both my 280 engined C and E class have had failed OVP's. The flickering ABS light is an OVP failure hint as is a nasty idle.

If your leave a failing OVP for too long you run the risk of frying your ECU.

Good luck

[Brabus3.6]

Vlad & Will thanks for the replies. If it is serious enough to fry to ECU I will change OVP. The ABS light isn't flickering, it just happens to be the only light that 'self-tests' when the ignition is switched on. I thought however that if it fails it gives no power to the ECU, not allowing it to fry. Of course if I did fry my ECU I'd be screwed because Brabus have remapped it so it wouldn't be a simple swap! I believe I have a temporary 'fix'. The car is sometimes hard to start requiring some cranking & throttle to get it going. Sometimes it splutters to life misfiring. I put the lights on & observe the interior lights, they'll be dim. A few seconds at 3000RPM idle & the lights will brighten up with a good solid idle ~ 600RPM in D where it should be. I thought it must be the battery which is a 66Ah, 510A cold crank Bosch Silver. I had Halfords test it & it passed with exactly 510A & 12.75V. I thought that it required the 3000RPM after starting to recharge the battery, seemingly not. Once it is running the idle is good, not 'rock' steady like an ECU controlled S500 but stable, no hunting. I think the idle of my car will be rougher than a normal 300E due to the adjustable, not hydraulic, tappets. I spoke with George Fraser who said he'd book his electrical specialist in for me. I guess I'll do that in a couple weeks once I've settled into Uni.

[Brabus3.6]

I replaced the OVP with the new, updated, dual fuse one from MB. No difference to my problems but peace of mind that I won't have to do it in the near future I guess. The car is hard to start, sometimes requiring a couple of long cranks & accelerator depression. This happens cold or hot. When it's working seemingly properly the idle in neutral is ~1000 which seems high.

[Brabus3.6]

Okay, finally back from Uni I took it in to see George Fraser today. Three parts were immediately mentioned, OVP, ICV & ECU. I told him the OVP had been replaced, the ICV cleaned & also checked by replacement at a breakers. A spare a ECU was on hand but thankfully that didn't change anything. I say that because my ECU has been remapped by Brabus and I dread to think of the difficulty in getting one of these now, so long after the cars production.
Well, the mechanic who looked over it slightly readjusted the mixture but told me that KE-Jetronic system diagnosis is basically trial and error. I showed him the proportionalty of current draw and idle speed. He and then George who glanced over it at the end told me to get a high capacity battery to match the 150A alternator, about 100A battery I was advised. I think I'll add an Optima Yellow Top in addition to my Bosch Silver 66Ah to deal with the audio system.
After inspection the car now has a new problem! During mid-throttle acceleration the car stutters, the power delivery is no longer smooth. This behaviour does not seemingly manifest itself after 3500RPM when it begins pulling cleanly to redline. I can only assume it is something to do with the air intake system which I will remove and carefully reassemble later. Anyone had this problem before? Could this possibly be the gearbox? P.S. George didn't charge me for the diagnosis as he couldn't pinpoint the problem.

[Brabus 300E 3.6]

Hi, i have owned a W123 230CE 1981 and it had the same symtons your descibed
1. hard to start
2. low idling to stall.
3. bad pulling untill 3500RPM after that it seams to be ok.

The problem was a lose hose under the intake system witch caused a lot of falls air to interfear with odd behavour ass result.
The hose was neer imposiple to reach from any angel, and therfore hard to find, but it was under the so called spider.!

By the way im looking at a Brabus 300E-24 3.6 from 1991
Can you give me some pointers to look after/fore.
What can the car do at topspeed? is it limmited to 250?

[Ian B Walker]

Originally Posted by Brabus 300E 3.6

By the way im looking at a Brabus 300E-24 3.6 from 1991

Arnt we all

[ADY1983]

Originally Posted by Ian B Walker

Arnt we all

Yep...

[Brabus 300E 3.6]

Hehe well. i acturaly found one for sale BRABUS 300E-24V 3.6 285HP
so therefore i ask here what to look after when bying this special car.

i know the 300E because my father has one, but it´s a regular 300E-12V 188HP model and im prety sure i want to by that BRABUS i found because i love that E model so much.

Compared to the new model that came after in 1993 this "old" model W124 is much more well crafted and there is not all these eletronical problems/faults as with the model that came afterwards.
That is what i have been told from all the mercedes owners, clubs etc. it´s commond knowlage between the pioneers in mercedes.

Btw.
Does enyone know what to be aware for, in a BRABUS tuned version of this beutifull car?
What is the engines week spots if there is eny?

[Brabus3.6]

Originally Posted by Brabus 300E 3.6

Btw.
Does enyone know what to be aware for, in a BRABUS tuned version of this beutifull car?
What is the engines week spots if there is eny?

I have the M103 engined 12V variant which I do believe shares the same bottom end. I can only say ensure all Brabus specific items are working. It may have the Brabus Tempamatik system allowing oil or outside temperature to be viewed. If this is innoperative I know first hand that just the oil temperatue sensing bolt is over £130!
The biggie to watch out for is the head gasket. At 155,000km it may have already been done but if not it's only a matter of time. While the heads off you'd be mad not to do stem seals and valve guides. If you do your own work be prepared to be set back around £1,000 as just the head gasket is £440, valve guide work is expensive too as it's best left to the engineers. If you don't I wouldn't like to estimate the cost involved in doing this.
My experience with the car, having clocked up over 30,000 miles on it doing a water pump and a couple of head gaskets plus much more along the way is that provided you don't abuse it, it's little more trouble than a standard Merc. There is a dude on this forum and others with a Brabus 190E who has I believe, your engine. He would be better informed about your particular M104.

With regards to my problem last year of the dash lights not coming on it was because I had the wrong alternator. I had one from a 2003 car which used a new style voltage regulator incompatable with these cars. I swapped it for another 150A one from a C43 which has the single bolt VR and all is fine. I also managed to cut back down to one battery. The massive 975CCA optima can be doused (just!) in the original battery position of the 124 with slight modification (read - smashing) of the battery tray.

[Brabus 300E 3.6]

Thank you so much.

My first question is:

Why do the head gasket need to be changed/done after only 155.000 Km.
could it not only have to do with a regular abuse of the car or is it because the head gasket is a regular quality and not made specialy to the stronger engine specs,
i know litle about cars that are tuned use another meterial wich are more solid, made of complet alaminium i think.

Normaly you would´n ekspect a head gasket change on a car unless you abused the car or am i wrong?

and by the way, did you solve your engine problems with the odd idle and what where the problem?

[Brabus3.6]

Well the first head gasket went around the 96,000 mile mark. My uncle had the car at that point and the water pump blew out on him, head expanded causing head gasket failure. I'm not sure why the second only lasted around 15,000. It may be that the head wasn't properly checked for tollerences although I did give it in to an engineering company recommended by Mercedes. It could also be that it was a faulty head gasket, these things do happen. I believe both the M103 and M104 engines had head gasket problems. The Brabus head gasket seems to be of a different material to the Mercedes one although it's still just a reinforced, glorified piece of paper!
Of course prior to our purchase of the car at around 90,000 miles I don't know how it was treated. It's over 129,000 miles now though and still running strong (touch wood). The idle problem was solved with a 150A alternator from a C43 AMG and a massive 975CCA Optima yellow top battery. It still occasionally idles around 500RPM but more steadiy and has not (and I think will not) die on me. The worst thing about these low idle speeds that the engine was not designed to hold as it is NOT ECU controlled is that the oil pressure can dip bellow 1bar in the searing heat! I dread to think what it would drop to if it wasn't Mobil 1 motorsport oil and didn't have an oil cooler!
Idle problem now seemingly completely solved by a new set of Beru HT leads. This is combination with the 150A alternator was the key for me. I haven't tested my old leads but all my new leads were well within spec as they should be, ranging from 0.93kOhm - 1.08kOhm. The specs are 1kOhm +/- 20%. Engine is now slightly more responsive too, as if that was needed