Lost Power - 1993 500E

[Modpryor]

Lost Power

I have a 500E 1993 Mercedes the engine was running very sluggish I took it to my mechanic he put new spark plugs new wires new distributor caps I get the car back and it feels like the engine has lost half of it's power. The mechanic told me he think it is the ECU so I replaced that it's running smoother but still has no power. Im not sure what to do at this point.
Please Help Thanks

 

[gerryvz]

Did he also replace the rotors, and insulators behind the caps/rotors? Did he use the right plugs and wires? Are all the wires reconnected to the correct plugs (something you can double-check).

Before you do anything, pull the codes, clear them, drive It for a bit (20-50 miles) and see what codes come back.

This sounds a bit like limp-home mode at first blush. Do you have any dashboard lights showing?

Do all the dash lights show up when you turn the key to the first position?

 

[gsxr]

Need more info to diagnose. If you don't have a code reader, buy or build a blink code reader.

If the engine is running smooth but is low on power, and it's not in limp mode / no fault lights, it *might* be a fuel delivery issue. This is especially true if it seems to run normally at light throttle but has no power at heavy throttle (but is still smooth / no misfires).

 

[emerydc8]

There is only one plug that I know of that will work in these cars without any problems -- Bosch F8DC4 (A 003 159 67 03 26). If the plugs are the wrong plugs, it could cause serious performance issues. I bought a car that had the wrong plugs in and the problem didn't show up unitl I brought it out to the desert with 110F temperatures. It ran okay if you didn't push it, but under heavy throttle it almost seemed that the ECU was pulling the timing back to keep the engine from detonating and was a real dog. Changed the plugs and it solved the problem.

 

[Modpryor]

Lost Power

I have a 500E 1993 Mercedes the engine was running very sluggish I took it to my mechanic he put new spark plugs new wires new distributor caps I get the car back and it feels like the engine has lost half of it's power. The mechanic told me he think it is the ECU so I replaced that it's running smoother but still has no power. Im not sure what to do at this point.
Please Help Thanks

 

[gsxr]

Merged duplicate threads.

 

[Modpryor]

Did he also replace the rotors, and insulators behind the caps/rotors? Did he use the right plugs and wires? Are all the wires reconnected to the correct plugs (something you can double-check).

Before you do anything, pull the codes, clear them, drive It for a bit (20-50 miles) and see what codes come back.

This sounds a bit like limp-home mode at first blush. Do you have any dashboard lights showing?

Do all the dash lights show up when you turn the key to the first position?

 

[Modpryor]

I attached the invoice. So you can see what he did. Thank you for your help!

 

[gerryvz]

Those are the wrong plugs they installed. They put in resistor plugs. They need to be F8DC4s, not FR8DC4s. Not fatal, and the car will run with them, but they should be changed to non-resistor plugs for proper operation to spec.

 

[TerryA]

Wrong plugs on invoice and no mention of new insulators that go behind the rotors.

 

[gsxr]

Gerry and Terry are both correct. The wrong plugs and old insulators won't cause a low-power problem, but both items should be remedied. The correct plugs are not expensive and are easy to swap. Most mechanics don't know that original insulators should be replaced with the caps/rotors after 25+ years. Shoot, nobody on the forum knew either until Klink showed up a few years ago and explained it to us!

Is the low power problem always present, hot or cold, all the time? Or only cold, or only hot, or intermittent...?

 

[Kyiv]

it could also be an ignition coil. there are 2 on our cars. When one went bad on my 400E it lost half of it's power, but was drivable. It's a cheap part, around $80 a piece

 

[Modpryor]

Is the low power problem always present, hot or cold, all the time? Or only cold, or only hot, or intermittent...?

Yes it drives like a 4 cylinder instead of a 8
Thanks

 

[gerryvz]

If the coils check out, it also could be the EZL, which has one of its failure modes only running one bank of cylinders. Putting the car on an oscilloscope (which any garage/mechanic should have) would tell you immediately what is happening with the engine electrically in terms of the power distribution to the cylinders.

 

[gsxr]

You need to determine if the car is actually running on only 4 cylinders (which results in a rough idle, and rough acceleration)... or if you mean it feels like it only has 4-cylinder power output (low power, but runs smooth at all RPM). These are VERY different scenarios.

 

[gerryvz]

If the car is running on four cylinders, you will also smell the unburnt gas coming out the exhaust. This is from the fuel being injected into the cylinders, but not being burned because of no spark (i.e. bad coil or bad EZL).

 

[Modpryor]

If the coils check out, it also could be the EZL, which has one of its failure modes only running one bank of cylinders. Putting the car on an oscilloscope (which any garage/mechanic should have) would tell you immediately what is happening with the engine electrically in terms of the power distribution to the cylinders.

It feels like it’s only running on 4 cylinders.
The strange part is I work at a Mercedes dealership and majority of the techs have no clue about my car. I’ll get the EZL checked out.

Thanks

 

[gerryvz]

This is the exact reason why many of us do our own work, or use qualified independent shops. There are fewer and fewer people at dealerships these days who actually know how to deal with these non-computerized cars.

If you work at a dealership,

1) Have them attach the Star Diagnostic System (with HHTWin software mode) to the 500E 38-pin diagnostic connector, and run the car. The HHT software will tell you what is happening with the engine in real time.

2) Have them put the car on an oscilloscope (or a clamp around each plug wire) to see what is happening with that wire.

3) Have a tech pull the codes while the SDS/HHT is attached.

These are things that ANY elementary technician should be trained to do. Either or both of these steps will tell a technician everything they need to know about what is happening.

 

[Modpryor]

Gerry and Terry are both correct. The wrong plugs and old insulators won't cause a low-power problem, but both items should be remedied. The correct plugs are not expensive and are easy to swap. Most mechanics don't know that original insulators should be replaced with the caps/rotors after 25+ years. Shoot, nobody on the forum knew either until Klink showed up a few years ago and explained it to us!

Is the low power problem always present, hot or cold, all the time? Or only cold, or only hot, or intermittent...?

Loss power it’s all the time. I work at a mercedes dealership had it checked out two
techs seem to think it’s the throttle body not working.

 

[gsxr]

If you work at a dealer, have the techs connect Star Diagnostics, run HHT-Win, and pull all the codes. There's no need to guess about what is wrong, there are 6 powertrain computers, and all of them provide both codes AND live data for troubleshooting.

If the throttle body was "not working", the car would be in limp mode, with ASR light on in the dash... and the first half of accelerator pedal travel would do nothing. Which could be considered "power loss", sort of.

So. Are there any lights on in the cluster when driving?

 

[NotaBene]

I've found this thread through a search. I have a 1994 E420 which suddenly began running rough. It feels as if only one bank of cylinders are firing. It is roughest at idle, and seems to smooth out as the RPMs approach 2000.

Power is poor at idle as well, and that seems to improve also as RPMs approach 2000.
ASR light is on.

I have another car which I can use as a DD, so my first inclination was to take the car to a mechanic. He was ultimately stumped. I think it was Gerry above who said this is why we have to learn how to repair our own cars.

So, this is what has been done;

Replaced spark plugs. (Mechanic. I'll have to check they are correct)
Replaced Dist caps and Rotors. (Myself. Did not replace but inspected insulators.)

To be checked; Coils, EZL.

Before I go much further, though, I've ordered a Code Reader from E-Bay. This is the one;

Mercedes Diagnostic Code Reader Tool OBD1 W124, W126, W140, R129 E320 1988-1995 | eBay

Find many great new & used options and get the best deals for Mercedes Diagnostic Code Reader Tool OBD1 W124, W126, W140, R129 E320 1988-1995 at the best online prices at eBay! Free shipping for many products!

www.ebay.ca

So, any suggestions about order of procedure?
Is this an appropriate Code reader?
Any other advice?

Thanks for any help.

 

[Kyiv]

@NotaBene, if coils (there are 2) have never been replaced, I would do both of them. That way you can cross them off a list of future troubles if it doesn't resolve current one. They are not particularly expensive - $80 a piece or so - and relatively easy to access even for a novice.

Your description of the problem sounds very similar to when my coil went bad, although my car does not have ASR. Car run on one bank of cylinders, then, it seemed it would regain footing, only to revert back to 70 hp mode. By the way, my "mechanic" was also stumped

 

[NotaBene]

@NotaBene, if coils (there are 2) have never been replaced, I would do both of them. They are not particularly expensive - $80 a piece or so - and relatively easy to access even for a novice.

Your description of the problem sounds very similar to when my coil went bad, although my car does not have ASR. My "mechanic" was also stumped

Thanks. I'll try that now, since e-bay estimates 15 days before my code reader arrives. I'm not exactly sure if the ASR light is a symptom or something more sinister.

 

[gsxr]

Before I go much further, though, I've ordered a Code Reader from E-Bay. This is the one;
Is this an appropriate Code reader?

That code reader will only work if it has 1mm pins. The photos show 4mm pins, but the description claims it will work with the 38-pin diagnostic socket. I'd contact the seller and confirm it include adapters for 1mm sockets. If not, you'll need a separate breakout box, which makes things much easier... but adds to the cost. Whatever "code chart" comes with it, toss it out, unless they stole mine. Click here to download the code chart specific to the 400E/500E. Click here for the De-Coding subforum, read the "sticky" threads up top.

Any other advice?

If the engine smooths out and runs on all 8 cylinders, with full power, at higher RPM... the EZL is not at fault. Otherwise, it could be a number of different things. I'd start by pulling the insulators to inspect the back side, as your symptoms sound a lot like the insulator issue.

The ASR light on should be totally separate from the engine misfiring. You'll need codes to diagnose that further.

 

[NotaBene]

That code reader will only work if it has 1mm pins. The photos show 4mm pins, but the description claims it will work with the 38-pin diagnostic socket. I'd contact the seller and confirm it include adapters for 1mm sockets. If not, you'll need a separate breakout box, which makes things much easier... but adds to the cost. Whatever "code chart" comes with it, toss it out, unless they stole mine. Click here to download the code chart specific to the 400E/500E. Click here for the De-Coding subforum, read the "sticky" threads up top.



If the engine smooths out and runs on all 8 cylinders, with full power, at higher RPM... the EZL is not at fault. Otherwise, it could be a number of different things. I'd start by pulling the insulators to inspect the back side, as your symptoms sound a lot like the insulator issue.

The ASR light on should be totally separate from the engine misfiring. You'll need codes to diagnose that further.

That code reader will only work if it has 1mm pins. The photos show 4mm pins, but the description claims it will work with the 38-pin diagnostic socket. I'd contact the seller and confirm it include adapters for 1mm sockets. If not, you'll need a separate breakout box, which makes things much easier... but adds to the cost. Whatever "code chart" comes with it, toss it out, unless they stole mine. Click here to download the code chart specific to the 400E/500E. Click here for the De-Coding subforum, read the "sticky" threads up top.



If the engine smooths out and runs on all 8 cylinders, with full power, at higher RPM... the EZL is not at fault. Otherwise, it could be a number of different things. I'd start by pulling the insulators to inspect the back side, as your symptoms sound a lot like the insulator issue.

The ASR light on should be totally separate from the engine misfiring. You'll need codes to diagnose that further.

I understand. To be honest, I'm not sure the power or smoothness are 100%. Both are better. I'm going to try replacing the coils first, to see how that is.
And frankly, it looks like I need to do a bit of research before ordering the coils. I've generated a list on eBay, and half of them come from Lithuania, and maybe another 25% from Australia. Not ordering either of those. I'm in Canada, but anything from US works as well, as far as timely shipping. I'm also finding coil packs in threes or more looking physically different, which look like a post '95 application. I believe I'm looking for quantities of 1 or 2.

I mentioned the ASR light just in case there is a connected issue with limp mode and the ETA, although the cruise control seems to work.

I tried to see if the pin size was specified, hoping they were 4MMS so I could order the breakout box. They look like 4mm, so I'm reassured by your input.

Thanks,
Rob

 

[gsxr]

Rob, your E420 has two coils... they are different part numbers, because the orientation of the terminals are different on each. It's MUCH easier to replace the coils if you first remove the driver side headlight. That sounds like a lot of work, but it's far less painful than attempting the job with the headlight in place. Coils are Bosch p/n 00086 and 00087, under $100 USD each from most US vendors. Photos here:

Index of /images/M119/EZL/ignition_coils

The ASR light on without limp mode would be unusual, but could be a failing brake pedal switch. If you're in limp mode, you need fault codes if to avoid throwing parts and $$$ at it. Cruise control will not work in limp mode.

 

[NotaBene]

Rob, your E420 has two coils... they are different part numbers, because the orientation of the terminals are different on each. It's MUCH easier to replace the coils if you first remove the driver side headlight. That sounds like a lot of work, but it's far less painful than attempting the job with the headlight in place. Coils are Bosch p/n 00086 and 00087, under $100 USD each from most US vendors. Photos here:

Index of /images/M119/EZL/ignition_coils

The ASR light on without limp mode would be unusual, but could be a failing brake pedal switch. If you're in limp mode, you need fault codes if to avoid throwing parts and $$$ at it. Cruise control will not work in limp mode.

Ironically, I had intended to ask the question about the two coils being different when I got home from work today. I actually ordered coils from Pelican today. I didn't see any indication of right bank/left bank, so ordered quantity 2. I'll see if I can contact them to see if the situation can be rectified before shipping.

Yes, I thought limp mode would disable cruise; that's why I mentioned it. I discovered that a couple of years back when I had to replace my ETA.

Thanks for your guidance, then and now. I'll post updates!

Rob

 

[NotaBene]

I'm getting ready to order a breakout box from eBay. I've got some questions because some of these boxes suggest they work with OBD2 systems. Do they work with both?

The one that I'm most sure of claims to be genuine Mercedes:

Mercedes 38 pin impulse counter breakout box diagnostic tool W140 W124 R129 W202 for sale | eBay

Find great deals on eBay for Mercedes 38 pin impulse counter breakout box diagnostic tool W140 W124 R129 W202. Shop with confidence.

www.ebay.ca

It's more expensive, but that may be worth it.

Input?

Thanks

 

[gsxr]

These breakout boxes do *not* work with OBD-2 systems, at all. OBD-2 connectors are totally different.

The OBD-1 breakout box allows easy access to each of the 38 connections of the OBD-1 diagnostic socket, which are otherwise a real pain to access (tiny 1mm sockets, no numbers). And, these allow using a hand-held blink code reader with 4mm 'banana plug' pins.

Aftermarket / cheaper breakout boxes should work fine if they have the proper connector to plug into the 38-pin socket in your CAN box.

 

[northNH]

My inexpensive blink code reader came with a set of 4-to-1 mm wound copper adaptor pins for the banana plugs,
Work fine, with care...

 

[NotaBene]

These breakout boxes do *not* work with OBD-2 systems, at all. OBD-2 connectors are totally different.

The OBD-1 breakout box allows easy access to each of the 38 connections of the OBD-1 diagnostic socket, which are otherwise a real pain to access (tiny 1mm sockets, no numbers). And, these allow using a hand-held blink code reader with 4mm 'banana plug' pins.

Aftermarket / cheaper breakout boxes should work fine if they have the proper connector to plug into the 38-pin socket in your CAN box.

Thanks. That's what I thought re OBDII vs OBD1. I have an OBDII scanner for use with my other cars.

But it's this eBay entry that gives me pause:

Fit Benz MB OBDII 38 Pin Breakout Box Diagnostic Scanner Pinout Box Tool for sale | eBay

Find great deals on eBay for Fit Benz MB OBDII 38 Pin Breakout Box Diagnostic Scanner Pinout Box Tool. Shop with confidence.

www.ebay.ca

Why does it mention OBDII?

I think I'll order the used MB genuine box.

Thank you so much for all your advice.

 

[gsxr]

But it's this eBay entry that gives me pause:

https://www.ebay.ca/itm/Fit-Benz-MB...3d48d49ee2:g:eE8AAOSw~QRaNPAS&redirect=mobile

Why does it mention OBDII?

I think it's a typo. They don't seem to make any other claims related to OBD-2. Weird!

 

[Jlaa]

Thanks. That's what I thought re OBDII vs OBD1. I have an OBDII scanner for use with my other cars.

But it's this eBay entry that gives me pause:

Fit Benz MB OBDII 38 Pin Breakout Box Diagnostic Scanner Pinout Box Tool for sale | eBay

Find great deals on eBay for Fit Benz MB OBDII 38 Pin Breakout Box Diagnostic Scanner Pinout Box Tool. Shop with confidence.

www.ebay.ca

I have this exact model. I use it with my OBD1 1993 500E. It works fine. The big round 38 pin connector makes things a snap. The banana plug breakout box is good for fisher-price / playskool types like myself, who are clumsy with fine electrical contacts.

 

[NotaBene]

I think it's a typo. They don't seem to make any other claims related to OBD-2. Weird!

Yes, I think so too. Pardon me for asking so many questions. I didn't ask enough before ordering the coils and it's going to cost me $150 to fix the situation. But still, I'll come out ahead of having a mechanic solve the issue. And the knowledge is a bonus.

Again, many thanks.

Rob

 

[NotaBene]

I have this exact model. I use it with my OBD1 1993 500E. It works fine. The big round 38 pin connector makes things a snap. The banana plug breakout box is good for fisher-price / playskool types like myself, who are clumsy with fine electrical contacts.

On your input, I'm going to order this one.

Thanks,
Rob

 

[NotaBene]

Coil replacement update;

I took advantage of the day off today to begin replacing the coils.

After getting the headlight out, I could see how the bolt placement had been a problem for everyone. Kudos to those who managed to do the job with the headlight in place; I couldn't have done it.

I changed the passenger side first. It looked easier, and my gut said that was the faulty unit anyways. After completing the left side I reconnected the battery and coil wire and started the car to see if the problem still existed. It does.

At this point I removed the coil wire from the driver's side. The car would not start at all. Replaced d/s wire and removed the passenger side coil wire. Car would not start.

I'll replace the d/s coil on the weekend but I'm not optimistic. We'll see where to go from there but still waiting on the Blink code reader and Breakout box.....

Rob