95 E420 Quarantine Project Needs Help!

[mnessari]

Hello as the title states, I bought myself a little project to keep myself busy during the pandemic since I got laid off.

When I got it, the car was a bit neglected by the second owner. Upon pickup, the engine was very shaky, under powered, and sounded like a misfire. I thought, OK, I'll replace caps, rotors, wires, and plugs, but its still running like absolute garbage. I did get the sulfur smell so I am guessing the cats are toast. No CEL on the dash but decided to press the button on the 8 pin DTC and got codes 9/10. One for the intake air temp sensor and the other for the MAF voltage too high or low. Luckily the upper harness has been updated already.

Any ideas on what to do next? Clean MAF? Replace IAT? I really like the car and don't want to sell it! Any help would be appreciated!

 

[gsxr]

IAT sensor is located behind the driver side air intake housing. This sensor does very little, it reduces ignition timing at very hot ambient temps, that's about it. The IAT won't cause any of the problems you describe. If the sensor is not defective, most likely it was disconnected when the key was turned on or engine started, which stored the code. Make sure it's plugged in, if the same code keeps returning, it might be bad. They are a rare failure.

The MAF code could indicate a defective MAF, but first check if the engine wiring harness is original and crumbling apart. The degraded insulation is obvious at any exposed connector. Replacement harnesses should have insulation that looks brand new. If the harness is good, and MAF connection is tight, disconnect the MAF completely and go for a test drive. If the car runs normally, your MAF is probably defective. If the harness is bad, replace that first, you can find good late-datecode harnesses for less than half of new.

The sulfur smell is from unburned fuel, either from a bad MAF reading, or a misfire. Since there's a code for the MAF, start there. Also, make sure the plugs are non-resistor (Bosch F8DC4, or equivalent from Beru / NGK). These engines don't like resistor plugs, and open the gap up to 1.0mm (spec is 0.8mm). This won't help with the problems you describe though.

ALSO - your cats are probably not toast, if they are stock/OE. The incorrect mixture OR misfiring will cause the smell.

 

[Kyiv]

I had IAT sensor fail. It triggered a check engine and car had, what seemed like half the power, yet sounded and operated otherwise normal

 

[gsxr]

I had IAT sensor fail. It triggered a check engine and car had, what seemed like half the power, yet sounded and operated otherwise normal

Interesting! I wonder if it was reading max temperature. This is the first I've heard of a bad IAT causing a noticeable power reduction. More accurately, first I remember, as we probably discussed this back when it happened - LOL.

 

[mnessari]

I had IAT sensor fail. It triggered a check engine and car had, what seemed like half the power, yet sounded and operated otherwise normal

Thanks for the input, mine has half the power at best and sounds just as bad

 

[Kyiv]

Thanks for the input, mine has half the power at best and sounds just as bad

so, at least you know a definitive cause for the reduced power Next, as GSXR says, try disconnecting MAF and going for a drive

IAT sensor part # A0095426817. It's under $20. You may or may not be missing its bracket/holder, part #A1245280340. Funny, this holder is more expensive than the sensor ~$25

 

[mnessari]

so, at least you know a definitive cause for the reduced power Next, as GSXR says, try disconnecting MAF and going for a drive

IAT sensor part # A0095426817. It's under $20. You may or may not be missing its bracket/holder, part #A1245280340. Funny, this holder is more expensive than the sensor ~$25

Gotta love the pricing lol. I did follow the recommendation and cleared codes, drove with maf plugged in, no codes popped up. When I unplugged the MAF the code came back.. STUMPED

 

[Kyiv]

I'll replace caps, rotors, wires, and plugs

Have you replaced or inspected the insulators behind the rotors?

Mercedes Distributor Dust Shield - Bosch 1191580188

Mercedes Distributor Dust Shield - Bosch 1191580188

www.fcpeuro.com

 

[mnessari]

Have you replaced or inspected the insulators behind the rotors?

Mercedes Distributor Dust Shield - Bosch 1191580188

Mercedes Distributor Dust Shield - Bosch 1191580188

www.fcpeuro.com

I have not, I removed them to get to the cam seal on driver side but didnt inspect them... The worst part to this is Im not getting a CEL either because the bulb in cluster is out or I dont know. The code I pulled was when the MAF was unplugged

 

[Kyiv]

I have not, I removed them to get to the cam seal on driver side but didnt inspect them... The worst part to this is Im not getting a CEL either because the bulb in cluster is out or I dont know. The code I pulled was when the MAF was unplugged

The consensus on this forum is that, unless you definitively know this dust shield/insulator has been replaced before, it must be replaced to baseline your car. I'm not saying this part is the culprit of your current problem, but it's a known, often undiagnosed, cause of ignition issues.

To see if CEL might have burned off, twist the key to ignition, to see if it lights up along with other lights.

Lastly, exactly what is the behavior of your engine. Be a bit more descriptive

 

[Kyiv]

very shaky, under powered, and sounded like a misfire.

This could also be caused by the coils. When I had one of the two coils go bad, the above describes how my engine behaved. I replaced both and that fixed the problem

 

[mnessari]

The consensus on this forum is that, unless you definitively know this dust shield/insulator has been replaced before, it must be replaced to baseline your car. I'm not saying this part is the culprit of your current problem, but it's a known, often undiagnosed, cause of ignition issues.

To see if CEL might have burned off, twist the key to ignition, to see if it lights up along with other lights.

Lastly, exactly what is the behavior of your engine. Be a bit more descriptive

The consensus on this forum is that, unless you definitively know this dust shield/insulator has been replaced before, it must be replaced to baseline your car. I'm not saying this part is the culprit of your current problem, but it's a known, often undiagnosed, cause of ignition issues.

To see if CEL might have burned off, twist the key to ignition, to see if it lights up along with other lights.

Lastly, exactly what is the behavior of your engine. Be a bit more descriptive

Thank you! I will pop off the insulators tomorrow to inspect. As for the CEL it def doesnt light up when turning the key so that answers that. As for the car, it idles really rough and shaky at 500 rpm while in park. Lacking power, shaky acceleration but coasts fine after it takes about 20 seconds to get to 30 mph. Lastly the sulfur smell after a quick drive.

View attachment Rev1.mp4

 

[Kyiv]

If you don't know whether the coils were replaced before, I'd order Bosch units from FCPeuro (they are not terribly expensive) along with insulators for behind the rotors. Coils last long time in our cars. If you look at yours and have have MB star on them, they are extremely likely to be 25 years old at this point

Does engine behavior worsens with it warming up or is it stably bad from the get go?

 

[mnessari]

If you don't know whether the coils were replaced before, I'd order Bosch units from FCPeuro (they are not terribly expensive) along with insulators for behind the rotors. Coils last long time in our cars. If you look at yours and have have MB star on them, they are extremely likely to be 25 years old at this point

Does engine behavior worsens with it warming up or is it stably bad from the get go?

Gotcha the coils definitely look old so that can be a good possibility...

The engine behavior is bad to begin with, cold start and after being warmed up.

 

[gsxr]

Idle should be 650rpm in P/N and 500rpm in gear. If not, your NSS / gear position switch on the transmission may be defective. A "rough idle" can sometimes be caused by engine mounts which are collapsed, see image below on how to measure, but based on the video I doubt this is your issue (but worth checking for grins):
http://www.w124performance.com/images/M119/engine_mounts/engine_mount_measure.jpg

You really need to pull codes from all modules, with a hand-held blink code reader. Since your car has ASR and doesn't appear to be in limp mode, that's a good sign.

Without codes from the LH / EZL / E-GAS module, you're stuck throwing parts at it, which isn't ideal. If the O2 sensor is old or original that's another item to look into, but the engine would run normally at cold start since it's in open-loop (ignoring the O2) until it warms up. The video showing the engine revving appears to be smooth and without misfiring.

Poor acceleration can also be caused by failing fuel pumps, but this won't cause "shaky" acceleration, just very low (smooth) power. Clogged catalysts are another long shot, you can test by disconnecting the crossover pipe ahead of the cats and test-driving. I'm still suspecting something related to fuel or ignition though.

If you plan to keep the car long-term, and/or own other 90-up Mercedes, investing in an SDS C4 with HHT-Win would be a good investment.

 

[gerryvz]

Yep, you are only running on four cylinders.

The shaky power until you get up to speed, and the sulfur through the exhaust, is 100% the classic symptom of only four cylinders burning gas. Raw gasoline is being dumped into the exhaust, hence the sulfur smell out the cats. DO NOT run the car unless absolutely necessary, otherwise you will poison the cats.

Guaranteed, you have ONE of TWO problems:

1) Your EZL is bad, and is in "one half" failure mode. I had this same thing happen in 2009, with the same exact symptoms. If your EZL is a "Bosch" unit it is even more likely that this is the problem. The "Siemens" units are more reliable and tend not to have as many problems. However with age and use, even the "Siemens" units CAN fail.

2) You have a failed coil, and it is not providing spark to one bank of cylinders (one half of the engine). You will need to determine the side with the bad coil, and replace it. Actually you should replace BOTH coils at the same time. They are different part numbers, so be aware of that.

Nothing to do with bad fuel pumps or clogged catalytic converters. You have an ignition issue. One half of the engine is not getting a spark.

 

[gsxr]

Gerry is better at hearing the 4 dead cylinders on the video than I am.

To test, disconnect 1 coil wire at a time. If 4 cylinders are not firing, with one disconnected the engine won't start at all, with the other it will run the same as with both connected. If that is the case, you then get to figure out if it's control (EZL) or secondary ignition.

 

[mnessari]

Awesome! Thanks to both experts with their recommendations. I haven't had the chance to look at the O2 yet but I unplugged passenger side bank and the car popped and cranked but didn't turn on, once I plugged that in she turned on running bad and unplugging driver side bank coil gave me no change so looking to replace them both while I'm at it. As for the EZL I double checked it and turned out to be a Siemens unit ***BUT*** I did notice a black hard plastic vacuum line that has a crack which leads into the intake manifold.

Regardless of outcome, the help I have received is very much appreciated. I have always loved the W124 bodies and am still determined to get myself a 500E since that and the E36 M3 have been childhood favorites for me. I got the E36 now falling for this 420!

 

[Kyiv]

A "while in there", you may want to replace this resistor. It's behind driver's headlight and makes aux fans come on when A/C is on:

Yeah, I meant the aux fan resistor. Part number: 000 158 32 45 MB Annapolis part price $33.60.

I replaced it here: RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

Old and new: RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

 

[mnessari]

Awesome!! Added to the shopping cart!

 

[gerryvz]

Most likely a bad coil, as you started to diagnose via the simple test. Definitely when you have this issue it’s going to be a coil or the EZL. More often the coil than the EZL.

I had it happen on my E500, and it’s also happened twice with the coil packs on two of my M104s (each of the three coil packs controls two cylinders).

The sulfur smell is a dead giveaway, as is the reduced power and rough running until you get moving.

I know immediately what it is.

 

[mnessari]

Since I didnt feel like waiting I went to my local pick and pull and was lucky enough to find a S500 with its coils still in it which I pulled one for testing purposes. Regardless, came home, took off driver headlight, replaced left side coil and voila. She is running smooth!!! Smooth enough for me to order H&R springs for her! Literally started her up in the last 10 mins! THANK YOU ALL!!!!

 

[gerryvz]

Glad that you preliminarily solved the problem. Hopefully you have the two coils on order, and also a new resistor for the aux fans. I HIGHLY recommend you replace both of your coils.

I did this over the summer on my COVID project, proactively. I was still using the original coils, and it was time to change them because of their age. Resistor, too.

 

[gsxr]

Good to hear it's running again! As Gerry noted above... +1 on installing a pair of NEW coils.

If that S500 is a 92-95 you may want to check for some other useful spares, like the MAF.

 

[mnessari]

Indeed! I have 2 coils, resistor, and an oil dipstick on the way. The S class was a 94 but the MAF was gone. I took a picture of one of the two identical coils and looks like it was the original production part. The thing looks OLD!!!

 

[gerryvz]

That is an original coil, yes. But if it works until your new ones come, that is great.

 

[Kyiv]

You have omitted to order insulators behind the rotors?

 

[mnessari]

Thank you! I'm in no rush so I might as well wait. I went with Bosch 00086/00087 but I was caught off guard of how many companies are out there.. Uro, Standard Motor, NGK, Facet, etc...

 

[mnessari]

You have omitted to order insulators behind the rotors?

Sorry I inspected both and they looked dry with no discoloration, I contacted the previous seller, he had done a tune up 40k miles ago, and recently, changed them less than 1000 miles ago. So they look good!!!

 

[gsxr]

Thank you! I'm in no rush so I might as well wait. I went with Bosch 00086/00087 but I was caught off guard of how many companies are out there.. Uro, Standard Motor, NGK, Facet, etc...

Read post #36 here... most all those brands you do NOT want to buy:

OWNER - hsumeet (400E) | Owners and Their Cars

ADMIN EDIT: This is the car hsumeet purchased, a 1993 400E in Nautical Blue, non-ASR: https://www.500eboard.co/forums/threads/fs-1993-400e-nautical-blue-cream-beige-tmu-5k-dallas-tx.12265/ I agree. Worth the gamble. I and others here have spare parts for E420 / 400E cars should you need...

www.500eboard.co

 

[gerryvz]

Sounds like you have been looking at the catalog at Rock Auto. STAY AWAY FROM ROCK AUTO.

Only use the following third-party vendors:

- RM European
- FCP Euro
- Autohaus Arizona

Or use an online MB dealer (getmercedesparts.com., etc.) if you want genuine MB parts.

 

[mnessari]

Sounds like you have been looking at the catalog at Rock Auto. STAY AWAY FROM ROCK AUTO.

Only use the following third-party vendors:

- RM European
- FCP Euro
- Autohaus Arizona

Or use an online MB dealer (getmercedesparts.com., etc.) if you want genuine MB parts.

You’re absolutely right I was looking everywhere to compare prices but I went through with AutohausAz even though they mentioned free shipping but I ended up having to pay for it lol

 

[gerryvz]

FCP Euro offers free shipping for orders over $49. Autohaus AZ used to be $50, then $75, and now they are charging shipping for all orders from what I can see. FCP also has a lifetime warranty on parts.

You will only find anything good on Rock Auto perhaps 1% of the time. I don't even bother to check their site but perhaps once a year, and that is only if I get a tip that a quality part is being closed out.

 

[mnessari]

Got it, I hope I won’t need much more but let’s face it, cars are a disease and I’m sure I will need to shop for goodies sooner rather than later

 

[gerryvz]

IF you stick to those three vendors, and comparison shop between them, you will be best off. The @gsxr doesn't like AutohausAZ as much as RM and FCP, because he feels they carry increasing amounts of URO and other brands. That may be, but the other vendors also carry cheaper brands. I have used AZ for probably 15 years and overall have been happy with them. But, I've only ordered known quality brands from them, ignoring the crap.

IMO, FCP Euro is probably the best deal going right now with their low shipping threshhold, lifetime warranty, and exceedingly fast shipping (often next day, or 2-3 days, for their free shipping option depending on where you live in comparison to their warehouses).

Five Rules for Successful and Happy Parts Buying:

1. Comparison shop between FCP, RM, and AHAZ and buy the best deal
2. Consult with the 500Eboard Parts Manufacturer Quality List. ONLY buy parts from the "Safe" (APPROVED VENDOR) list.
3. Buy MB Genuine Parts whenever and wherever possible. Use a discount online MB parts dealer (there are 10-15 of them) which offer 20-40% discounts off of factory list prices.
4. If an MB factory part is 10-20% more than an aftermarket part, it's often better to just get the MB factory part. MB factory parts carry a two-year warranty.
5. Study this forum carefully to determine where specific "aftermarket" parts are actually MB factory parts with the star ground off of it. Often times, the same manufacturers sell the MB part (with the star ground off) under their own brand name

 

[gsxr]

Gerry is right. AZ carries more junk, but more importantly, they often don't have an acceptable brand for the part I want to buy. Charging for shipping on top usually kills the deal. 10+ years ago I bought a lot from AHAZ, but after discovering Importec (now RM Euro) I switched to RME almost exclusively, until FCP appeared. Now I get most from RME or FCP.

Some other vendors are acceptable, but may only be price competitive for certain parts. Amazon sometimes has good deals on Bosch parts but it *must* be sold/shipped by Amazon, not a third party. ECS Tuning is another alternative. Pelican usually isn't competitive. Rock is only good for certain purchases, I do buy from them, but it's infrequently and typically something that none of the other vendors carry.

 

[mnessari]

Gerry is right. AZ carries more junk, but more importantly, they often don't have an acceptable brand for the part I want to buy. Charging for shipping on top usually kills the deal. 10+ years ago I bought a lot from AHAZ, but after discovering Importec (now RM Euro) I switched to RME almost exclusively, until FCP appeared. Now I get most from RME or FCP.

Some other vendors are acceptable, but may only be price competitive for certain parts. Amazon sometimes has good deals on Bosch parts but it *must* be sold/shipped by Amazon, not a third party. ECS Tuning is another alternative. Pelican usually isn't competitive. Rock is only good for certain purchases, I do buy from them, but it's infrequently and typically something that none of the other vendors carry.

That’s very informative and much appreciated! I made sure to screen shot tips from both! Thank you guys!

 

[mnessari]

Coils are in, and wow! It produced night and day difference!!! Idle smooth and revs smooth as well. Took her for a quick spin, got on it and downshifted properly but felt very restricted and under powered past 2500-3000 RPM. Vacuum leak? Did my cats die after having all that unburned fuel dumped? I do remember mini backfires coming from under the car when I would lightly rev the car before the coil replacement. Tried tapping the cats with rubber mallet, no noticeable noises. Should I buy a vacuum gauge to test vacuum from the booster? In the meanwhile, here is how she purrs::

View attachment Rev2.mp4

 

[gsxr]

Diagnosing plugged catalysts is a pain. If you don't have an exhaust backpressure gauge, disconnect the crossover pipe from the driver side manifold so it's "open exhaust" and go for a short test drive. If power is normal with open exhaust, then your cats may be plugged. If power is still weak past 2500rpm, something else is wrong.

 

[mnessari]

Diagnosing plugged catalysts is a pain. If you don't have an exhaust backpressure gauge, disconnect the crossover pipe from the driver side manifold so it's "open exhaust" and go for a short test drive. If power is normal with open exhaust, then your cats may be plugged. If power is still weak past 2500rpm, something else is wrong.

Thank you for the insight. I need to pickup new jack stands to get under the car to remove crossover, would you recommend hooking up a vacuum gauge into the brake booster and check that way for the time being?

 

[gsxr]

I'm not sure if the vacuum test will tell you much unless the exhaust is severely blocked. I also can't remember what vacuum readings to look for, but someone posted details years ago, I think. Shouldn't need to connect to the brake booster pipe, any vacuum connection on the intake should work? Again, if the engine will pull anywhere near redline and just has lower power than normal, I think the vacuum test won't show anything.