R129 SL500- It never rains but it pours -Transmission, Injection, Thermostat...

[E55BOF]

Just out of interest, when you got the loom done by Si-lec, did you also get the throttle body harness done? I only ask because on mine the TB harness was way worse than the injector harness and could account for the sort of symptoms you describe.

Just read your post, Chris. Do you know, I'd rather forgotten about the TB... No, I only had the injector harness done. Si-lec only charge £80 for the TB harness, so: how easy is it to remove the throttle body?

 

[E55BOF]

Dennis, if you're not 100% bothered about originality, half the time these days its cheaper to have a bespoke stainless exhaust made. Doesn't have to be loud or brash, but may be cheaper and will outlast the car !

Thanks John. Not bothered about originality; I bought the car on a whim, to drive not restore. As it happens, I already have a stainless custom-made back box for the car - a member was advertising one on here for £50, so I bought it on spec. No front pipework on it, though, just a three-bolt flange.

Unless the cat section is goosed, which would doubtless be a whole new world of wallet pain, all I would need would be the centre box, and a pipe made up to connect it to my rear box. I wouldn't want anything too loud - it's not that sort of car, and I'm not that sort of owner.

I did a little desultory research on SL500 exhausts, and found more than one comment that they just didn't sound 'right'. Does anybody on here have a stainless system, and would care to venture an opinion on this?

 

[Doodle]

Unless the cat section is goosed, which would doubtless be a whole new world of wallet pain.

Circa £1500 from Mercedes, and stock was very low last time I enquired. A custom made replacement would be 1/3rd that.

I did a little desultory research on SL500 exhausts, and found more than one comment that they just didn't sound 'right'. Does anybody on here have a stainless system, and would care to venture an opinion on this?

The standard systems are very strangled on sound.

I have a stainless sports cat and straight through centre section, connected to an AMG backbox. Still refined and civilised, but with enough growl to let it be known there's a v8 under the bonnet.

 

[190E 16V]

sounds like it could be Throttle body Actuator, to me as well.

Is your battery putting out the correct voltage consistently.

Your car sounds like it is in "LHM" - Limp Home mode.

Low voltage, or sitting a long time without running properly will cause the computer to lose its 'learned' settings, and default to LHM.

The Throttle Body wiring tends to 'go bad' as well as the harness. This can cause false signals and trigger LHM.

It used to be possible to used reconditioned ones, on a swap basis, or take a gamble on eBay.

Hope this was some help.

 

[ray_hennig]

sounds like it could be Throttle body Actuator, to me as well.

Is your battery putting out the correct voltage consistently.

Your car sounds like it is in "LHM" - Limp Home mode.

Low voltage, or sitting a long time without running properly will cause the computer to lose its 'learned' settings, and default to LHM.

The Throttle Body wiring tends to 'go bad' as well as the harness. This can cause false signals and trigger LHM.

It used to be possible to used reconditioned ones, on a swap basis, or take a gamble on eBay.

Hope this was some help.

I'm a bit confused. The original post said that "distributor caps and rotor arms have been changed". In that case, it sounds like a KE Jetronic setup with separate ignition/injection.

I don't think that degraded wiring was an issue with these cars.

Clarification please?

RayH

 

[Will]

I thought all the SL500s of that age had caps and rotors - M119? Early cars ran KE jet and the later cars EFI afaik.

 

[brucemillar]

Hi

My two bobs worth:

You need to get the temperature issue sorted. Change the stat and the engine temp sender. Until that is correct then your fueling is likely to be unknown. I had this on my Pajero and the engine temp sender (£15) was the culprit, telling the ECU's lies about the true temp and so miss/over fueling causing poor idle and no hot start.

 

[E55BOF]

Thank you Doodle. £1500? Yours sounds like a MUCH better option, and of course I already have a back box.

Degraded wiring certainly can be an issue on a car of this age (about '92-'96 were the years affected, I believe); my injection harness was a mess. TB wiring could be the same; I haven't looked yet. Si-leck will recondition it for about £80.

It is not in Limp Home Mode (unless LHM will let it rev to over 4000 rpm). The battery is brand new.

The R129 M119s pre-facelift (d/k about post-facelift) all had distributors and rotors arms, but after I think the '93 MY they had EFI rather than KE-Jetronic; mine certainly has.

Bruce, I DREAM of there being nothing wrong other than poor idling and hot starting. I'll be surprised if changing the 'stat and the temp sender sorts it out, but as soon as an ordered 22mm box spanner (for the sender)
arrives I'll be able to crack on, and we'll see. Of course, the leaky exhaust won't be doing much for the gas flow at idle and low revs, but it isn't running right at higher revs either.

More anon.

 

[bing]

Your M119 has several ECUs/modules in the CAN box. It's not as simple as, "oh it could be the ecu!". You've done the basics by replacing most ignition parts, but it's really time to plug it in and see what fault codes come up. Otherwise you're guessing and throwing parts unnecessarily. Your ETA is highly suspect, so is the MAF, so is the kick down switch...etc etc.

What you're experiencing is very common with M119.97XXX engines, so nothing new here or never heard of. Pull some fault codes, clear 'em, see what comes back and concentrate on those.

 

[BTB 500]

The standard systems are very strangled on sound.

I have a stainless sports cat and straight through centre section, connected to an AMG backbox. Still refined and civilised, but with enough growl to let it be known there's a v8 under the bonnet.

Similar setup here.

I started by replacing the standard back box with an AMG one ... this made no difference to the sound but looks nice! They cost a fortune new (well over £1000) but I got one cheap on eBay.de and the in-laws picked it up and brought it over for free



Then I had the centre muffler replaced with a straight-through pipe and 200-cell sports cats fitted.

It's not remotely loud or raucous ... cruising it's still virtually silent, but there's a bit more exhaust noise when you put your foot down. Part of me would like it to sound more 'TVR like' but it wouldn't really suit the character of the car.

It's worth noting that M-B dropped the centre muffler themselves in the '99 facelift, so presumably the exhaust note was recognised as being an issue.

Of course a non-standard exhaust has to be declared for insurance but IIRC there was no increase in premium when I had mine done. Nor have there been any MOT issues, and it gets done by a main dealer (because they only charge £10!).

 

[Flyinspanner]

Isopropyl Alchohol is the best solution for cleaning your MAF, as it leaves no residues.

I'm not yet aquainted with MB mafs, but it was a common need on Subaru GTBs (my last car) when/if they started running rough, or threw a CEL / fault code.
I very carefully took it apart until I could reach the 'strip' and carefully and gingerly used a q-tip and IA, worked a treat. Clean the electrical plug whilst you are there.

 

[E55BOF]

Your M119 has several ECUs/modules in the CAN box. It's not as simple as, "oh it could be the ecu!". You've done the basics by replacing most ignition parts, but it's really time to plug it in and see what fault codes come up. Otherwise you're guessing and throwing parts unnecessarily. Your ETA is highly suspect, so is the MAF, so is the kick down switch...etc etc.

What you're experiencing is very common with M119.97XXX engines, so nothing new here or never heard of. Pull some fault codes, clear 'em, see what comes back and concentrate on those.

And if I was at home, I could tell you what each of those ECUs does, and the part numbers. The exhaust can wait until the rest is sorted - it's not blowing enough to be the culprit at higher revs.

It makes sense to me to fix what's known to be broken before I get the codes read and cleared. It takes five minutes and costs nothing to check the TB/ETA loom for degraded insulation and clean the plug contacts, and if it hasn't been replaced, it is highly likely that it needs to be. Though I've never seen the MAF loom mentioned, that too could be duff; again, five minutes to check. I have a new temperature sensor, which cost buttons, so I might as well change it.

As it's a hydraulic 'box, I would have thought the kickdown was a mechanical linkage, not a switch, though I stand to be corrected on that. Either way, that too can wait until the engine runs properly.

The codes will have to be read and cleared in due course, but not yet, I think. There's method in my madness...

 

[E55BOF]

Isopropyl Alchohol is the best solution for cleaning your MAF, as it leaves no residues.

I'm not yet aquainted with MB mafs, but it was a common need on Subaru GTBs (my last car) when/if they started running rough, or threw a CEL / fault code.
I very carefully took it apart until I could reach the 'strip' and carefully and gingerly used a q-tip and IA, worked a treat. Clean the electrical plug whilst you are there.

Thank you for that. I have a can of proprietary aerosol contact cleaner; I'll check what the chemical makeup is - it might well be isopropyl alcohol anyway.

 

[BlackC55]

The MAF's on those 119 engines are super reliable. I would be surprised if it was faulty.

 

[E55BOF]

Thank you very much for that. I take it, then, that they don't suffer from the biodegradable insulation wiring problem?

It will have to come off anyway if I need to remove the throttle body to have that rewired, of course, but I live in hopes. Not expectations...

 

[BlackC55]

Thank you very much for that. I take it, then, that they don't suffer from the biodegradable insulation wiring problem? It will have to come off anyway if I need to remove the throttle body to have that rewired, of course, but I live in hopes. Not expectations...

They do suffer from the loom issues too.

 

[Terry_]

The MAF's on those 119 engines are super reliable. I would be surprised if it was faulty.

I have changed only one ever!
On Bill Abba's first 500e.
And it made it run like dog turd

 

[E55BOF]

Thanks Terry. Mine runs like a dog turd already....

Still polishing, though. I'll get there...

 

[JCW1]

Just read your post, Chris. Do you know, I'd rather forgotten about the TB... No, I only had the injector harness done. Si-lec only charge £80 for the TB harness, so: how easy is it to remove the throttle body?

I just thought you were ignoring me

My view is that getting the TB harness done is a 'no brainer' for the charge SiLec make as there seems little point in looking at components until any issues with the signal pathways are eliminated.

As to how easy it is to get the TB out, I would say that it is a straightforward job but there are a couple of annoying hurdles along the way if you don't have the right tools. To get the two jubilee clips undone that hold the MAF to the TB requires a long flexi shaft socket.

Not having a workshop manual, I checked out U Tube and came across an 8 part series of videos posted by a Russian guy called Viktor which I found extremely helpful in assessing the complexity of the task, prior to committing to it. I would recommend watching although it's a bit tedious, as he makes a bit of a meal of it. Google 'M119 Throttle Body removal' and the vids will come up.

Hope this helps

 

[E55BOF]

I was watching Viktor for a while night before last; he certainly does go on a bit, but a very useful set of videos. I'll check the wiring for insulation issues before I start dismantling, but I expect it's all still original. I always knew I'd find a use for that 1/4 in. flexi socket drive one day...

It's a shame they didn't use those bodger's friends, nylon cable ties, to secure the MAF in the first place. Easy to remove with side cutters, and work perfectly in an application like that.