M119 Badly Misfiring & Running Very Rough

[Smoky400E]

New member here, this very neglected '92 400E will be my next MB project. It runs/drives somewhat, but sounds awful of course, but wondering what I should work on first besides the basic tune-up stuff. Car has likely be sitting for 10+ years. I was planning on these basic steps, but very open to opinions and recommendations:

1. Check and likely replace battery and clean terminals.
2. Replace all fuses with new, good quality ones.
3. Inspect engine wiring harness, it appears to have been replaced, but need to verify.
4. Inspect and possibly replace engine grounding wires (not sure where these are on an M119).
5. Drain all old gas, refill with like 5 gallons of fresh premium.
6. Replace fuel filter, inspect fuel lines.
7. Run engine to operating temp (monitoring it carefully), change engine oil, filter, filter housing gasket, drop oil pan, inspect bottom end, and replace oil pan gasket. (should I consider using the LiquiMoly engine flush? I have had good results with that on old BMWs)
8. Replace spark plugs and inspect spark plug wires (they appear to have been replaced previously).
9. Inspect ignition system and plan for a full replacement depending on condition.
10. Remove and replace drive belt and tensioner.
11. Inspect cooling system and plan for at least a partial replacement of main components.
12. Replace air filters, clean airbox, replace intake ducts (bought the M117 ones, hopefully they can be made to work without too much hassle.
13. Test run engine...and likely find more issues that need addressing.
14. Replace motor mounts, inspect transmission mount.
15. Flush power steering system, replace filter and refill with fresh fluid.
16. Plan for the upper timing chain guides, cam oiler o-ring, valve cover gasket project. It looks like it is recommended to only use Genuine MB parts for this job.
17. Change transmission fluid and filter, inspect flex discs.
18. Replace rubber brake lines (might go SS lines), flush brake fluid, refill system, plan for complete brake pad/rotor replacement.
19. Clean horribly dirty car for moral support.
20. Test drive car...find more issues.

 

[gsxr]

Sounds like a good plan. If it really has been sitting for 10 years the fuel system is suspect. After draining the tank only put in 2-3 gallons non-ethanol premium to start with, so if you need to drain it again or otherwise remove the feed hose, you're dealing with less fuel. The high pressure fuel hose exiting the filter is a common leaker, if it's cracked or looks bad, replace it with OE only. Details on all the fuel system components are in this thread.

The belt tensioner may not need replacement if it's still tensioning, but inspect that. The adjustment procedure is a bit finicky, remember to loosen the cener bolt before adjusting, and tighten it afterwards. Don't over-tighten.

Before refilling the power steering system, inspect the hoses, in particular the short hose between the reservoir and pump - VERY common leak point. Ditto for the S-hose to the frame rail. If either one is not dry, replace them.

Definitely only Genuine MB parts for the chain rails and valve cover gaskets. Cam oiler O-rings are likely not necessary. Plan on having to replace all the PCV hoses from intake to valve covers (Genuine MB for those also).

Brake hoses may be OK but new stainless steel is always a good idea. Pressure bleed with DOT 4/4+ fluid.

Good luck, and welcome to the forum!

 

[Smoky400E]

Sounds like a good plan. If it really has been sitting for 10 years the fuel system is suspect. After draining the tank only put in 2-3 gallons non-ethanol premium to start with, so if you need to drain it again or otherwise remove the feed hose, you're dealing with less fuel. The high pressure fuel hose exiting the filter is a common leaker, if it's cracked or looks bad, replace it with OE only. Details on all the fuel system components are in this thread.

The belt tensioner may not need replacement if it's still tensioning, but inspect that. The adjustment procedure is a bit finicky, remember to loosen the cener bolt before adjusting, and tighten it afterwards. Don't over-tighten.

Before refilling the power steering system, inspect the hoses, in particular the short hose between the reservoir and pump - VERY common leak point. Ditto for the S-hose to the frame rail. If either one is not dry, replace them.

Definitely only Genuine MB parts for the chain rails and valve cover gaskets. Cam oiler O-rings are likely not necessary. Plan on having to replace all the PCV hoses from intake to valve covers (Genuine MB for those also).

Brake hoses may be OK but new stainless steel is always a good idea. Pressure bleed with DOT 4/4+ fluid.

Good luck, and welcome to the forum!

Thank you for the input and advice, much appreciated. I've worked on a fair amount of old BMW's but not that I've grown up and got a MB, its somewhat new territory. Based on the available info (somewhat limited of course) the car was owned by one person for the first ~150k miles in NJ and was regularly serviced by a MB dealer. It then came to MI and was regularly serviced by an indy shop to ~211k miles. Then in 2010 it went somewhat dark and not much history and probably was not driven much. It is interesting to look at some of the older dealership service notes; mostly routine maintenance, but it does show that the transmission was replaced at only 89k miles (no idea why) and there was an episode of back-to-back spark plug replacements with <1,000 miles between the services.

Are there any good aftermarket engine mounts? I see RockAuto has some Rein brand mounts, and some of their products are considered good on classic BMW's...not so sure though.

Should I consider some kind of engine flush when I change the oil the first time or bad idea?

 

[gsxr]

The Genuine engine mounts are best, but are spendy at ~$200/ea from discount dealers. Otherwise, pick your favorite SuperChina brand, they should last a few years at least.

NO engine flush. Use your favorite synthetic oil if you want some internal cleaning. 10W-40 is a good viscosity for the M119, and will be fine in Michigan winters if it's fully synthetic. 5W-40 or 15-40 are also ok if you prefer those for some reason.

 

[Smoky400E]

The Genuine engine mounts are best, but are spendy at ~$200/ea from discount dealers. Otherwise, pick your favorite SuperChina brand, they should last a few years at least.

NO engine flush. Use your favorite synthetic oil if you want some internal cleaning. 10W-40 is a good viscosity for the M119, and will be fine in Michigan winters if it's fully synthetic. 5W-40 or 15-40 are also ok if you prefer those for some reason.

OK, sounds good. I will not drive this in the winter most likely (have junky BMW's for that). It already has some rust issues that I will fix after the mechanical stuff is somewhat sorted, but I hate fixing rust so don't want to do it again Thank you for the very prompt reply!

 

[Smoky400E]

Does this mean that the upper engine wiring harness was already replaced with one from ~2003?

 

[gsxr]

Yup! The insulation on that harness should be good.

 

[Smoky400E]

Finally made a deal on this '92 400E and dragged it home. It of course needs a lot of work, but I changed the oil, started cleaning it up and reconnected some displaced vacuum lines and it's somewhat better. The EGR valve is completely corroded to the point that the vacuum connection is broken off. I've been reading some old threads about deleting the EGR, wondering if anyone has done this and if it caused other issues? This is at beast just a weekend car for me.

 

[gsxr]

EGR can be deleted if desired. You'll get a constant fault code stored on the LH module for EGR, but just ignore that. If your car has a CEL, the CEL will stay on as well. If you have a 49-state car without CEL, nevermind.

 

[Smoky400E]

EGR can be deleted if desired. You'll get a constant fault code stored on the LH module for EGR, but just ignore that. If your car has a CEL, the CEL will stay on as well. If you have a 49-state car without CEL, nevermind.

Got it. I'd replace it but it looks like they are unavailable anywhere new. I don't even see any used ones on eBay. There are some slightly different ones from 500 SL's on there, but not sure they'd work (vacuum port appears to be on the side instead of the top). I found once company in Germany that makes a kit with the three metal block-off plates and gaskets, long lead time of course. Do you have any advice on this? Is the deleting the EGR a dumb idea?

Would I also need to remove the smog pump and get a different length belt?

 

[gsxr]

EGR is strictly an emissions item, and dumps exhaust into the intake where it mixes with oil vapor and generally deposits crud into the intake manifold. Deletion is a good thing IMO, although not legal for street use in USA.

No need to remove the smog/air pump, that is totally separate, all it does is heat the catalysts faster after a cold start. Deleting the air pump is much more complicated as you need a different bracket with idler pulley ($$$).

 

[Smoky400E]

EGR is strictly an emissions item, and dumps exhaust into the intake where it mixes with oil vapor and generally deposits crud into the intake manifold. Deletion is a good thing IMO, although not legal for street use in USA.

No need to remove the smog/air pump, that is totally separate, all it does is heat the catalysts faster after a cold start. Deleting the air pump is much more complicated as you need a different bracket with idler pulley ($$$).

Thanks! Did you make your own block off plates? Seems like they'd be easy enough to make and then just buy some OE gaskets and be done with the EGR valve.

 

[gsxr]

I have never deleted EGR as my M119 cars are all street legal, and I don't want the CEL disabled. However, it's pretty simple to delete. You can replace the factory gasket with a piece of flat sheet metal cut to the same shape. Just needs to block the ports. This leaves the EGR valve in place, but non-functional.

 

[Smoky400E]

Thanks!

 

[Smoky400E]

Are there any current recommendations on a reasonably priced OBD1 code reader? I looked thru some of the older threads on this topic, but was wondering if anyone had any recent experiences? I’m currently learning towards just getting a cheap ($45) code reader with the 4mm leads and a 38 hole breakout box ($45) off eBay or similar. I’d like to get a digital code reader that has an adapter to the 38 pin connector but I can’t seem to find much so far (this might also be outside the budget right now too).

 

[gsxr]

The 4mm blinker box with 38-pin breakout box is the cheapest solution. This will allow you to read and clear fault codes.

A digital scanner is needed for live data, but as you noted, that will cost a lot more. A C4 or M6 Star Diagnostic System (SDS) from China is the best solution, but make sure it has HHT-Win support, and also has a fully-populated 38-pin cable. It's been difficult to find a reliable vendor that provides a turnkey, working solution. Read the long threads on the SDS systems for more info. These will likely run you $750+ and if anything doesn't work right, the seller could ghost you. I'd use something like AliExpress where you have a 30-day window for a refund if anything goes south after delivery.

 

[Smoky400E]

Thank you, great info. I for some reason haven’t read those SDS threads yet. For such an expensive option though I’ll just get the breakout box and blinking code reader.

 

[gsxr]

Live data is really nice, but generally only needed for advanced diagnostics when the engine is not running properly and there are either NO fault codes, or the codes are unhelpful. Investing in SDS makes more sense if you plan to own Mercedes for many years to come, and/or own any newer MB which requires DAS or Xentry for full access to diangostics.

 

[TerryA]

@gsxr & Smoky400E,
Will Smoky get or need the proper 38 pin connector w/ all 38 pins populated for $45.00?

 

[gsxr]

@gsxr & Smoky400E,
Will Smoky get or need the proper 38 pin connector w/ all 38 pins populated for $45.00?

He's just getting a breakout box to use with a blink code reader. So far, nobody has reported a breakout box that doesn't have all 38 sockets functioning.

The problem was with crappy Chinese manufacturing, where someone got the idea to eliminate half the wires inside the 38-pin cable for SDS C3 / C4 / M6, rendering the cable useless. Idiots!

 

[Smoky400E]

He's just getting a breakout box to use with a blink code reader. So far, nobody has reported a breakout box that doesn't have all 38 sockets functioning.

The problem was with crappy Chinese manufacturing, where someone got the idea to eliminate half the wires inside the 38-pin cable for SDS C3 / C4 / M6, rendering the cable useless. Idiots!

Yeah, just ordered some Chinese stuff yesterday from sellers on eBay that had good ratings so we’ll see.

 

[Smoky400E]

I tried unsuccessfully yesterday to remove the instrument cluster. It kind of loosened on the right side but still doesn’t want to come out. I watched a couple YT videos, so not sure why it’s being so difficult. Any tricks to get it out without damage? I’ve got a set of the hooks off Amazon recommended by a MB mechanic on YT.

 

[gsxr]

Something might be sticking. Keep pulling, carefully... it should pop loose.

 

[Smoky400E]

What aftermarket replacement antenna mast have others had good luck with? I see that FCP has one from URO but of course I typically avoid that brand. Thanks

 

[gsxr]

What aftermarket replacement antenna mast have others had good luck with? I see that FCP has one from URO but of course I typically avoid that brand. Thanks

I avoid almost everything from ÜRO, but the antenna mast is one of the extremely few exceptions. The ÜRO mast is - sigh - almost cromulent. And, I don't know of any alternatives. At least this isn't a mission-critical part.

 

[Smoky400E]

I avoid almost everything from ÜRO, but the antenna mast is one of the extremely few exceptions. The ÜRO mast is - sigh - almost cromulent. And, I don't know of any alternatives. At least this isn't a mission-critical part.

Thanks! Putting it in the next shopping cart from FCP

 

[Smoky400E]

Got the cluster out finally and it's rough looking to say the least; will disassemble/clean and see what happens. Replaced all of the spark plugs with the correct Bosch ones, but then remembered some with these cars are gaping the plugs to 1.0mm from the factory spec of 0.8mm. Should I pull them and expand their gap to 1.0mm or good enough to get the car functional with factory spec?

 

[Smoky400E]

Also, realized I bought the wrong belt from FCP. Apparently I got the 6-rib version and since it's a '92 I need the 8-rib belt. It does not seem to be readily available from a number of suppliers, but I did find one on RockAuto (of all places) that is an 8-rib and may be the correct one. Can anyone confirm this is the one I need and/or suggest a supplier that has the correct one available? More Information for CONTINENTAL 8PK1289

 

[gsxr]

If the car is running well on 0.8mm gap you can leave it alone. Next time the plugs are out, open it up to ~1.0mm.

Rock Auto is a good vendor, if you stick with name-brand manufacturers. They sell a lot of cheap SuperChina crap, so be careful.

The 8-rib serpentine belt should be 2465mm long, MB p/n 009-997-87-92. Your Conti number above is incorrect (wrong length). Pelican claims to have one in stock...

 

[Smoky400E]

If the car is running well on 0.8mm gap you can leave it alone. Next time the plugs are out, open it up to ~1.0mm.

Rock Auto is a good vendor, if you stick with name-brand manufacturers. They sell a lot of cheap SuperChina crap, so be careful.

The 8-rib serpentine belt should be 2465mm long, MB p/n 009-997-87-92. Your Conti number above is incorrect (wrong length). Pelican claims to have one in stock...

Thanks for the very quick check on the belt, much appreciated! I thought I checked Pelican, but I'll look again

 

[gsxr]

Pelican link:

https://www.pelicanparts.com/More_Info/0099978792.htm?pn=009-997-87-92-M21

 

[Smoky400E]

Pelican link:

https://www.pelicanparts.com/More_Info/0099978792.htm?pn=009-997-87-92-M21

Thanks, I think I found my mistake, was searching for a genuine MB belt last night and that does not seem to be available. New belt on its way!

 

[Smoky400E]

Dumb question: any harm in starting the car just to see how it runs with new plugs, etc. without the cluster installed? Will it even start without a cluster? I've done it on old BMW's but that's another matter...also cluster is pretty rough inside. Going to try cleaning it up for now, but it probably needs at least portions of it replaced.

 

[gsxr]

No problem at all starting without the cluster, you just won't have any warning lights or temp gauge.

I have NEVER seen a cluster with that much rust / corrosion on the back side. Or any corrosion, for that matter... wow. Was this parked near salt water with the windows open for long periods of time?

That tach looks pretty rough. Only another M119 tach will work. If the fuel/oil/temp pod is defective, you can use one from any other W124 sedan or coupé. (If the donor gauge is from a wagon or cabrio, the fuel gauge will need to be adjusted via a pot on the circuit board, as those models have different fuel level sending units.)

 

[emerydc8]

I have NEVER seen a cluster with that much rust / corrosion on the back side. Or any corrosion, for that matter... wow. Was this parked near salt water with the windows open for long periods of time?

That looks horrible. Is there a quick and easy way to determine if the car has ever been in a flood?

 

[gsxr]

That looks horrible. Is there a quick and easy way to determine if the car has ever been in a flood?

That was my second thought, but flood waters that high up - eeeek!

 

[gerryvz]

I avoid almost everything from ÜRO, but the antenna mast is one of the extremely few exceptions. The ÜRO mast is - sigh - almost cromulent. And, I don't know of any alternatives. At least this isn't a mission-critical part.

Thanks! Putting it in the next shopping cart from FCP

 

[Smoky400E]

That looks horrible. Is there a quick and easy way to determine if the car has ever been in a flood?

I agree, I think what issue was is that the car was stored outside under a tree for like a decade and it seems to have a small leak at least on the right front footwell, maybe the left too. There are signs unfortunately that the car was very moist inside for some time. I knew some of this when I picked it up but it's always worse than you think lol. The car does have a clean carfax but I think it was very neglected for the last decade+

 

[Smoky400E]

No problem at all starting without the cluster, you just won't have any warning lights or temp gauge.

I have NEVER seen a cluster with that much rust / corrosion on the back side. Or any corrosion, for that matter... wow. Was this parked near salt water with the windows open for long periods of time?

That tach looks pretty rough. Only another M119 tach will work. If the fuel/oil/temp pod is defective, you can use one from any other W124 sedan or coupé. (If the donor gauge is from a wagon or cabrio, the fuel gauge will need to be adjusted via a pot on the circuit board, as those models have different fuel level sending units.)

Good to know, I found this one on eBay that physically looks like the rusty one I've got but maybe it won't work. Seller hasn't gotten back to me on it yet. This car is definitely very rough, which to me makes it all the more impressive that it will just start up after sitting for so long. I was hoping to at least get it roadworthy for this all-German car show near me in a month, but we shall see.

 

[Smoky400E]

Pulled the EGR valve, going to make a stainless steel plate and just use a thin bead of high heat RTV to seal up the two holes. Also cleaned and put first stage of leather conditioning on the front seats. Discovered some scary looking rust around one of the rear up shock mounts…

 

[Smoky400E]

Making an EGR delete plate out of some misc SS plate I had laying around.

 

[Smoky400E]

What are others running for replacement springs? Saw some older posts about H&R lowering spring being a good upgrade.

 

[gsxr]

I forget if H&R offers a 400E-specific set of lowering springs. The 500E springs will not work, and the 6-cyl springs are too short/soft. Sadly, the 400E Sportline springs are NLA.

If you just want the car a bit lower, cut the stock springs, 1/4 coil at a time until you get the ride height where you want it. Measure ride height from fender lip to wheel center. Set ride height with a full tank of fuel so the measurement is the same front & rear. With an empty tank the rear will lift up 1/4" to 1/2".

Click here for photos of our 1994 E420 with stock springs all around, ride height is 14.25" from wheel center to fender lip front & rear, with a full tank of fuel. Those are #39 front springs w/ blue stripe, cut 1/4 coil, with 1-pt rubber pad... rear springs are #12 w/ red stripe and 1pt rubber pad. Note the top of the tire is *not* tucked up inside the fender.

I don't recommend going much below about 14.0" all around with a full tank, for normal street use. Bilstein Yellow B8's or KONI's work well for dampers.

 

[Smoky400E]

Thanks for the awesome response! I’d like to go a little lower when I get that point, but nothing crazy (MI roads aren’t awesome). Good to know that cutting the old ones might be a realistic alternative to new. I was considering these but maybe they’re not correct since they seem to be for all W124s, including the 6 cylinder models: https://www.fcpeuro.com/products/mercedes-benz-lowering-spring-kit-h-r-295692#fitment

 

[gsxr]

Yeah, those are the infamous "one size fits most" H&R springs. They are very likely to drop the 400E too much. You don't want it in the weeds or sitting on the bump stops. They only offer chassis-specific springs for the 500E and cabrio, and sort of the wagon, per their nebulous application chart.

If you aren't planning to autocross, cutting the stock springs is the cheap/easy/effective method to drop the car a bit. Works great.

 

[Smoky400E]

I assume I should try and replace the lower windshield cowl pieces? They look pretty bad, especially the right side. Any chance they’re available anywhere? I’ll do some searching…

 

[Smoky400E]

I think a found a good replacement cluster for a decent price so I’m leaning towards just trying that since the existing one is so corroded.

 

[gsxr]

Ouch, your lower windshield trims are fried pretty bad. Look for good used ones. They are NLA new. I've seen good used ones at the junkyard in the past. Takes a lot of sunshine time to get them looking that bad...

 

[Smoky400E]

Ouch, your lower windshield trims are fried pretty bad. Look for good used ones. They are NLA new. I've seen good used ones at the junkyard in the past. Takes a lot of sunshine time to get them looking that bad...

Yeah, I popped them off this evening and they’re really trashed!

 

[Smoky400E]

My little SS EGR delete plate turned out ok I think…