No power when accelerating

[SWISS MIKE]

Hello,

Hopefully I can get some het from the Forum.

My car was in storage for a couple of years (1992 500E). When I stored the car, everything was working perfectly fine. Once out of storage, engine would only crank but not start. It ended up being clogged injectors. Details in the thread at this link.

After replacing all 8 Injectors, engine starts up perfectly and runs great in idle. The problem I am having is, as soon as I accelerate, the engine lacks power and stalls out. If I let go on the gas pedal engine runs nice and smooth in idle. I barely made it to the gas station and back. I am pretty sure it's not misfire.

Since my fuel system was contaminated, I replaced the following parts: 8 Injectors, 2x Bosch fuel pumps, Bosch fuel pressure regulator, fuel filter, drained the whole tank and filled with fresh gas.

Other maintenance items replaced: All spark plugs, air filter, Beru Wire Set, Oil and Filter. Removed caps and rotors multiple times, they look good. I replaced them roughly 2k miles ago with Bosch parts. Upper engine harness was replaced in 2015. Checked compression, chain timing ok. Fuel Pressure is good. No high back pressure. Disconnect MAF sensor, same thing, engine stalls. With my blink code reader, no codes in system. Smoke tested intake manifold, no leaks.

I feel like it's not getting enough air... could the throttle body be defective?

Please see video below, once the RPM goes up, engine just stalls out. Any advice is appreciated

 

[gsxr]

You've done some good work so far, eliminating a lot of possibilities. If the rail pressure remains steady as the engine loses power and dies, it's not fuel delivery (to the rail anyway). There's no hint of misfire in your video, so you can rule out ignition also. Same with MAF disconnected, so it's not MAF. Compression & cam timing ok, so it's not an internal mechanical issue. Seems like it has to be engine management, or blocked exhaust.

Can't tell if it's lacking air or fuel, but no, the throttle body should not cause this. A throttle body issue would still let the engine idle, not shut it off.

You blink-code tested all modules, including LH / EZL / E-GAS, correct?

What was the reading (in psi) on the exhaust backpressure gauge, and did the reading increase (vs remain the same or decrease) as the engine dies?

Can you drive the car at light throttle, or is it not drivable at all?

Do you have spare modules to swap in for testing (LH, EZL, etc)?

Live data from HHT-Win would be VERY helpful.

 

[SWISS MIKE]

Yes, I blink code tested all the modules, with no codes.
Today, I installed the back pressure gauge again and drove around the neighborhood. Under load the max back pressure I get is roughly 0.6 PSI. In idle it's at 0 PSI.
What I noticed today, with a cold engine I get full acceleration and torque. After running the engine for a few minutes, engine starts to surge and loose power while accelerating. Today, engine didn't stall out only started to surge and loose power under load.
Yes, I can drive the car with light throttle as long as I don't need to drive up an incline.
Unfortunately, I don't have any spare modules or access to Win.

 

[gsxr]

OK - backpressure sounds normal, that should not be an issues (which is good news - you don't want to replace factory cats, ever).

Lack of power under load only seems like fuel supply, but this is impossible to test without a remote fuel pressure gauge.

Can you still make the engine die out while parked in the driveway, as shown in your video? If so, can you observe the fuel pressure when it dies?

I'm running low on ideas.

 

[ArauzMotoring]

Did you ever replace the eta in this car?

Can you have someone check if the eta is working (opening and closing) when you depress the throttle pedal?

 

[gsxr]

Did you ever replace the eta in this car?

Can you have someone check if the eta is working (opening and closing) when you depress the throttle pedal?

Really need to test this while the problem is occurring, by viewing the throttle position in live data. It's possible the ETA could be causing issues, but 99% of the time there will be fault codes stored on the E-GAS module. However! That other 1%... you can have zero codes and seriously weird problems, caused by a failing ETA.

If the ETA is old or original, it is definitely a suspect.

 

[gerryvz]

Yes, I blink code tested all the modules, with no codes.
Today, I installed the back pressure gauge again and drove around the neighborhood. Under load the max back pressure I get is roughly 0.6 PSI. In idle it's at 0 PSI.
What I noticed today, with a cold engine I get full acceleration and torque. After running the engine for a few minutes, engine starts to surge and loose power while accelerating. Today, engine didn't stall out only started to surge and loose power under load.
Yes, I can drive the car with light throttle as long as I don't need to drive up an incline.
Unfortunately, I don't have any spare modules or access to Win.

I hate to say it, because I know you have replaced the ignition components, but this sounds like you have the classic "moisture in the distributor caps" situation, where the car starts and runs fine initially, and then after a bit stumbles/surges/hesitates/loses power/stalls when you are accelerating.

Have you considered cutting the slots into the distributor caps, and cleaning the entire area -- the insides of the caps, the insulators behind the caps, and checking the cam seals to ensure there is no oil leakage or moisture in the area?

The HOW-TO for cap slotting is here:

Thread 'HOW-TO: Solving M119 Stumbling at Ignition Distributor Caps'

Sep 5, 2025

It is a common malady to nearly all M119 engines with dual-distributor systems, sooner or later, that the engine will suffer stumbling and cutting out. This condition is because there is inadequate air circulation inside the closed environment of the distributor caps, which causes condensation to form inside of the caps, effectively electrically "shorting" the flow of electricity to the spark plugs inside of the cap.

There is MUCH more background about this condition here on the forum, in this thread: FYI - Essential M119 Ignition "Tune Up" mods [Distributor cap vent / slot] | M119...

• gerryvz
• Replies: 57
• Forum: "HOW-TO" Tutorial Articles

• 
• 
• 

This changed my car from misfiring every time I drove it, back to a normal operation....EVERY TIME I DRIVE IT.

 

[SWISS MIKE]

OK - backpressure sounds normal, that should not be an issues (which is good news - you don't want to replace factory cats, ever).

Lack of power under load only seems like fuel supply, but this is impossible to test without a remote fuel pressure gauge.

Can you still make the engine die out while parked in the driveway, as shown in your video? If so, can you observe the fuel pressure when it dies?

I'm running low on ideas.

No, I wasn't able to die out the engine while parked. Driving around the neighborhood, once the engine starts to surge under load, if I don't let go on the throttle, the engine will die. I am searching for a longer fuel hose to connect to my fuel pressure gauge, so I can drive around and monitor the pressure.

 

[SWISS MIKE]

Did you ever replace the eta in this car?

Can you have someone check if the eta is working (opening and closing) when you depress the throttle pedal?

I never did any work on the ETA since my ownership (13 years). Before that the car was mainly serviced at the dealership, no records there regarding work done on the ETA.
I will try that out, to see if the throttle plate moves. Thank you

 

[SWISS MIKE]

I hate to say it, because I know you have replaced the ignition components, but this sounds like you have the classic "moisture in the distributor caps" situation, where the car starts and runs fine initially, and then after a bit stumbles/surges/hesitates/loses power/stalls when you are accelerating.

Have you considered cutting the slots into the distributor caps, and cleaning the entire area -- the insides of the caps, the insulators behind the caps, and checking the cam seals to ensure there is no oil leakage or moisture in the area?

The HOW-TO for cap slotting is here:

Thread 'HOW-TO: Solving M119 Stumbling at Ignition Distributor Caps'

Sep 5, 2025

It is a common malady to nearly all M119 engines with dual-distributor systems, sooner or later, that the engine will suffer stumbling and cutting out. This condition is because there is inadequate air circulation inside the closed environment of the distributor caps, which causes condensation to form inside of the caps, effectively electrically "shorting" the flow of electricity to the spark plugs inside of the cap.

There is MUCH more background about this condition here on the forum, in this thread: FYI - Essential M119 Ignition "Tune Up" mods [Distributor cap vent / slot] | M119...

• gerryvz
• Replies: 57
• Forum: "HOW-TO" Tutorial Articles

• 
• 
• 

This changed my car from misfiring every time I drove it, back to a normal operation....EVERY TIME I DRIVE IT.

I will remove both caps and cut the extra slots and clean them to eliminate that problem a 100%. Thank you

 

[SWISS MIKE]

I hate to say it, because I know you have replaced the ignition components, but this sounds like you have the classic "moisture in the distributor caps" situation, where the car starts and runs fine initially, and then after a bit stumbles/surges/hesitates/loses power/stalls when you are accelerating.

Have you considered cutting the slots into the distributor caps, and cleaning the entire area -- the insides of the caps, the insulators behind the caps, and checking the cam seals to ensure there is no oil leakage or moisture in the area?

The HOW-TO for cap slotting is here:

Thread 'HOW-TO: Solving M119 Stumbling at Ignition Distributor Caps'

Sep 5, 2025

It is a common malady to nearly all M119 engines with dual-distributor systems, sooner or later, that the engine will suffer stumbling and cutting out. This condition is because there is inadequate air circulation inside the closed environment of the distributor caps, which causes condensation to form inside of the caps, effectively electrically "shorting" the flow of electricity to the spark plugs inside of the cap.

There is MUCH more background about this condition here on the forum, in this thread: FYI - Essential M119 Ignition "Tune Up" mods [Distributor cap vent / slot] | M119...

• gerryvz
• Replies: 57
• Forum: "HOW-TO" Tutorial Articles

• 
• 
• 

This changed my car from misfiring every time I drove it, back to a normal operation....EVERY TIME I DRIVE IT.

Hello Gerry,

I followed your thread and inspected the cam seals (completely dry), cut the slots into both caps and cleaned the caps.
I am still experiencing the same issue with no power/surging under load.

One thing that came to my mind, since all my injectors were clogged from having old gas. How about if I have a restriction in one of the fuel lines. Fuel pressure is good, but how about if I am not getting enough flow...

 

[gsxr]

One thing that came to my mind, since all my injectors were clogged from having old gas. How about if I have a restriction in one of the fuel lines. Fuel pressure is good, but how about if I am not getting enough flow...

If there was a lack of flow, this would appear as a pressure drop at the rail under load. But, you can't see this unless there's a gauge you can view while driving.

 

[SWISS MIKE]

If there was a lack of flow, this would appear as a pressure drop at the rail under load. But, you can't see this unless there's a gauge you can view while driving.

I am traveling for the holidays; the car is covered up and parked in the garage. I will figure out the issue next year ! I will arrange a longer fuel hose to connect to my pressure gauge so I can drive around and monitor the pressure.

 

[SWISS MIKE]

Update on my lack of power under load issue: Inspected ETA, per sticker the ETA has a manufacture date 00M11. Therefore, was replaced under previous ownership. Inspected the wiring, looks great. Cleaned throttle body built up with throttle body cleaner. Installed fuel pressure gauge and tape to Windshield to road test. Pressure is steady between 40-50PSI. Drove coach for 30+ minutes with no issues. Runs great, even on the freeway with 80mph.
I guess the car fixed itself while I was in Europe for the holidays
Next week, I will take the car on a nice long drive and get the smog test done to register the car. Hopefully the issue doesn't return.