Biting the Bullet - ETA - what else?

[Prime]

Due to a surging idle problem under load, I've instructed my mechanic to order a new Electronic Throttle Actuator and put it in next week. I'm having the motor mounts done at the same time, and the notorious power steering return line. Is there anything else I should consider? I'm looking for things for which access might be made easier by the work I'm already having done. Does it make sense to replace vacuum lines if they are not causing any problems?

I think I'll have him power-flush the tranny (did the whole, more involved service last time) and replace the brake fluid while he has the car, but those are unrelated - it's just time.

 

[500ESpain]

Sorry about my poor english but what you mean with "power-flushing" the transmission?

 

[gsxr]

Some repair shops have "power flushing" machines which connect to the transmission cooler hoses near the radiator. They suck out the old fluid from one while pumping fresh fluid into the other. This is intended for transmissions which lack drain plugs on the torque converter, such as many older American cars. On those cars, you can't fully drain all the fluid out of the tranny - draining the pan only gets about half the fluid out.

On a Mercedes, this isn't really needed, as MB torque converters have drain plugs so you can drain over 90% of the fluid from thet transmission via the two drain plugs (converter drain and pan drain). Some places may not like doing this on a 400E/500E because you have to remove the exhaust crossover pipe to access the torque converter drain, which is a nuisance. It's easier for them to connect a "flushing" machine.

Personally, I would prefer draining the trans + converter properly, and not using the machine... even though it's more work.

 

[500ESpain]

Understood. Thanks!

 

[gsxr]

Due to a surging idle problem under load, I've instructed my mechanic to order a new Electronic Throttle Actuator and put it in next week. I'm having the motor mounts done at the same time, and the notorious power steering return line. Is there anything else I should consider? I'm looking for things for which access might be made easier by the work I'm already having done. Does it make sense to replace vacuum lines if they are not causing any problems?

Almost forgot the original question! Oooops:

1) There are TWO hoses for the power steering pump low pressure circuit... one is an "s" shape formed hose, the other is a short section of straight hose. The shaped one is a pain to replace, the straight one is even worse. If you're paying a shop to do it, have them do BOTH. Click here and here for photos. The second photo is pointing to the straight hose which disappears behind the heat shield.

2) If the engine harness is not original, plan on doing it soon. The starter / alternator harness is also worth inspecting (check the wires at the alternator, as well as oil pressure/level senders).

3) If the P/S pump hasn't been replaced or resealed before, this wouldn't be a bad time to consider it, if there is any evidence of minor fluid leakage. If it's dry, I'd leave it alone. The short hose above the pump (to the reservoir) often leaks, so change that if it's not perfecty dry.

4) Definitely replace any and all vacuum tubes which are fossilized. If they snap like twigs when you try to bend them, they are overdue for replacement. Vac tubing is cheap - don't pinch pennies here. Vac leaks can cause all kinds of annoying little problems.

 

[Prime]

Had this done today. Here's the grocery list:

- new Electronic Throttle Actuator
- new motor mounts
- replaced side mirror glass (it had broken off the mount that moves it by the motor)
- transmission drain & fill
- brake fluid replaced
- addressed loose hose clamp on power steering return line

The surge at idle is gone (I hope - it was intermittent), but most noticeable is the smoothness created by fresh motor mounts. Once again, Uncle Gerry was right on the money. I didn't think my engine vibration was that noticeable, but now that it's gone, it's like night and day. At idle I can't even tell that the car is running, and even cruising is smoother and quieter. I've lost some of that muscle car feel, but that's just another way of saying I've lost the noise, vibration, and harshness! It was an expensive day, but well worth it, I think.

 

[Sacco_Fan]

Can you share the cost of the ETA and labor for that installation? I'm asking b/c I'd like to have a baseline in case I need to replace mine.

 

[Prime]

ETA was $1270. You can get rebuilt ones cheaper, but I was told it was not recommended. Labor was about 3 hours, I think.

On a related note, my tech gave me another option that might interest someone here. He said that sometimes you can lengthen the threaded rod that connects to the ETA by pulling it out (not easy - you need to fish it around several obstacles) and giving it a turn or two. According to him, this will sometimes stop the throttle from sitting in the position that's giving you the surge problem. The idle, being electronic, is not affected. Obviously I decided to go with the more extensive fix, but especially for someone doing it themselves who doesn't need the car on the road right away, this might be worth trying.

 

[Prime]

UGH!

This cold-weather problem has now returned, 9 months later. WTH? As described above, the ETA is NEW, and when installed, seemed to fix the problem temporarily. But today it was below freezing outside and the surge at idle, under load, reared its ugly head.

Any ideas???

 

[gsxr]

I'd start looking for vacuum / intake leaks. What condition are the caps/rotors/plugs in, btw?

 

[Prime]

Funny you should ask. I was thinking that it's probably about time for new caps, rotors, and plugs, but I thought to myself that this couldn't be causing the cycling surge (vroom, vroom, vroom) I'm experiencing. Was I wrong?

 

[gsxr]

I wouldn't expect this symptom to be caused by ignition issues, but you might as well rule out the easy stuff. I wouldn't necessarily replace the caps/rotors without inspecting & cleaning them first however - if they look bad, then replace them. If they look ok or clean up nicely, I wouldn't waste the $$$. Rumor is the original non-resistor plugs may be out of production and are becoming more difficult to locate, so if you have the proper ones, I wouldn't change those either until they are worn (center electrode rounded).

 

[gerryvz]

Just a wild hair on this, but there are a number of sensors that have input to the computers, such as intake air sensors. It would probably be a good idea to check that these are all operating properly.

I agree with Dave with regard to caps, rotors and plugs. If they are not in bad condition, or clean up well, they they should be fine.

Are you getting any codes (and not just the blink codes for the CHECK ENGINE (DM)? It's really a good thing to check all of your codes, erase them, and see what comes back. VERY telling and can generally give you a heads up (or at minimum a directional indicator) on what is going on.

Cheers,
Gerry

 

[Prime]

Update - haven't had the chance to check any codes. I know this needs to be done. In the meantime, while the surge continues, I have not experienced any LHM or dash lights that might give me a clue.

I've seen other threads here with a similar problem, but everyone else with a surge seems to have it in Park or Neutral, and it goes away under a load. Mine is the opposite - only under load. If I put the car in P or N, it goes away. The other thing peculiar to mine is that it only seems to happen when the ambient temp is below freezing. In warmer weather the car runs beautifully.

I have read that others have solved their problem with a new crank position sensor and I've also read something about the brake light switch. I wonder about the brake light switch because I DO occasionally get a bulb out light on the dash when braking, but have never been able to find a bad bulb. I have replaced the air temp sensor (009 542 68 17), the water temp sender (008 542 45 17) and the Coolant temp switch (008 542 32 17), with no improvement. (On a side note - the coolant temp switch seemed strange. It's a 4-pin round connector. The plug has numbered connections and a flat spot on the housing as if it's intended to go on only one way, but the switch itself has no corresponding flat spot and no numbers so no way to tell how it's supposed to line up. Both the old and new switches were like this. Does anyone know if it matters?)

So now I'm thinking about the crank position sensor, but can't understand why it would act up only in cold weather. Any genius diagnosticians out there that might have a theory? I'm open to any wild hairs at this point.

 

[gsxr]

The other thing peculiar to mine is that it only seems to happen when the ambient temp is below freezing. In warmer weather the car runs beautifully.

Has the MAF or ETA been replaced yet?

I have replaced the air temp sensor (009 542 68 17), the water temp sender (008 542 45 17)...

This 2-prong sender is for the HVAC system, and triggers the electric fan high speed at ~105C... it has nothing to do with engine management (fuel/spark).

...and the Coolant temp switch (008 542 32 17), with no improvement. (On a side note - the coolant temp switch seemed strange. It's a 4-pin round connector. The plug has numbered connections and a flat spot on the housing as if it's intended to go on only one way, but the switch itself has no corresponding flat spot and no numbers so no way to tell how it's supposed to line up. Both the old and new switches were like this. Does anyone know if it matters?)

The 4-prong sensor is for the LH and EZL, it sends them coolant temp information. The diagonal pins are what matter, so it's impossible to plug it in 'wrong', and since both are supposed to have the same data, it doesn't matter which pair go to which system.

So now I'm thinking about the crank position sensor, but can't understand why it would act up only in cold weather. Any genius diagnosticians out there that might have a theory? I'm open to any wild hairs at this point.

Issues with the CPS will trigger a code, and may cause intermittent starting problems. I wouldn't replace it unless you had either or both of those issues. I also wouldn't throw any more parts at it without pulling codes, clearing them, and seeing which ones return...

 

[Prime]

Thanks Dave. The sensors were original, to my knowledge, so I figured it was good insurance. Got all 3 for under $60.

ETA was replaced last spring to correct this issue. It seemed to work at the time, but that also coincided with warmer weather, so it's hard to know for sure if it had an effect. When cold weather returned last fall, so did the surge. I had the car stored all winter, which is why I'm only getting to it now. MAF has not been replaced. Is there a clean/cure procedure I can try before replacement?

Previously my mechanic told me to bring it by while it was happening. The one time I tried, it evened out before I got there (of course). But even if it isn't still surging when I get there, the codes should remain and he should be able to read them, right?

 

[gsxr]

Stored codes will remain in memory until cleared, but make sure that codes are pulled from all six systems (LH, E-GAS, EZL, BM, DM, ASR) although ASR isn't likely to have anything to do with the issue. The main thing is to clear all the codes and see which (if any) return quickly, i.e. after a couple days of driving.

 

[Prime]

No codes. Everything reads clean. What now??

Mechanic says that sometimes a crank position sensor will be bad and not throw a code - as long as it's sending a signal, it might not throw a code, but the signal could still be wrong. Still, even he says replacing the CPS is a shot in the dark.

 

[autoworrks320]

is there any updates to this post. i seem to be having similar situation with my 93 after it was parked for the winter.

 

[Prime]

Sorry, but I still haven't solved it. Since there were no codes, my mechanic says the only way for him to move forward (short of randomly replacing parts) is to get his hands on it while the surge is happening so he can test some components for wacky signal. Every time I've tried to drive it over there while it was happening, it smoothed out before I got there. Now with the weather warming up it is happening even less often, so I may have to wait until autumn.

 

[RPB81]

Sorry, but I still haven't solved it. Since there were no codes, my mechanic says the only way for him to move forward (short of randomly replacing parts) is to get his hands on it while the surge is happening so he can test some components for wacky signal. Every time I've tried to drive it over there while it was happening, it smoothed out before I got there. Now with the weather warming up it is happening even less often, so I may have to wait until autumn.

I have the EXACT issue you are experiencing and no one can diagnose it. My car got a new actuator before the surging started, so most assume this part is the culprit but my current throttle actuator only has 5k on it. Then I read your post stating that you replaced the actuator w/ the problem persisting, now I am almost positive its not. Glad I did not throw another new one at it! My mechanic thinks I am crazy but like Prime stated by the time I get there it smooths out. Are we the only ones who have experienced this, weird. :?

 

[gsxr]

Could you define "surge at idle, under load"...? What exact conditions are present when the surge exists?

Also - you checked codes from all systems, with either a hand-held LED code reader, or digital scanner, right? Not just with the built-in LED on the CAN box?

 

[RPB81]

Could you define "surge at idle, under load"...? What exact conditions are present when the surge exists?

Also - you checked codes from all systems, with either a hand-held LED code reader, or digital scanner, right? Not just with the built-in LED on the CAN box?

Not under load, when I pull up to a light or pulling out of my driveway its surging between 500-800rpm until warmed up. Hesitates a little when I try to accelerate when this is happening. Seems to be present when temp is below 70 degrees but exacerbates the colder it gets, seriously! Seems like a little longer crank time too before it catches. Codes were checked w/ Star machine that did throw an actuator code but I did replace this not too long ago and my harness is coming up on needing a replacement soon. Just kind of odd how this only happens in certain climates as stated by Prime. Caps, Rotors, Coils, EZL, Fuel Pumps...all replaced.

I just went out to crank it to see if there were any other observations I could make. It started up perfectly, runs like a gem now! As is should when started the rpm now starts around a 900-1,000 then drops rights between 6-700 and when I start to drive ends up around 550 @ idle. In the cold right after the initial crank it would start rough, then when put in D/R would immediately drop to 600 then start surging till I have driven about a mile. My crank time still seems a little extended, is this usual after it has been sitting overnight? Definitely not 3+ seconds but takes its time or maybe its just me. :roll:

 

[DerFuror]

Re: Biting the Bullet - ETA - what else? Wiring Harness!

...and my harness is coming up on needing a replacement soon.

Could actually be overdue.

The harness is the first electrical item to seriously address during PPI or immediately after purchasing one of these cars. A deteriorated harness is often the root cause of everything else that ails ya. Strange things can occur when exposed/deteriorating control wires expand & contract under various temperature ranges.

A new wiring harness will provide you the proper baseline for conducting your diagnoses (many existing problems may actually go away).

 

[Prime]

Sounds similar but not EXACTLY the same as my issue. RPB81 states that his surge goes away when the engine warms up. Mine does not. Mine only occurs when the ambient temp is at or below freezing - not 70 degrees. Engine temp seems to have no effect. In other words, it sometimes happens upon start-up, sometimes happens after I've been driving for a while and the engine is warm. It can last anywhere from 5 minutes to an hour or more (don't often drive the car more than an hour without shutting down). But the common denominator is the cold outside temp. Now that it's wamer ourside I haven't experienced the problem at all.

Replaced my harness about 3 years ago when I got the car. Replaced the 116 motor (ETA) last year to solve this surge. That obviously didn't work, although that was in March, and it usually doesn't stay away from freezing here until later than that, so it's a little odd that I didn't experience the problem until the following autumn. Pulled codes from all systems last month and everything came up squeeky clean.

I'm enjoying driving the car in the warmer weather since it's running perfectly, but there's still this cloud hanging over my head with the surge I know will return...

 

[gsxr]

One very long shot is the adaptation could be way lean for some reason... if the O2 sensor is not recent, I'd replace that, then reset the LH adaptation and see what happens. Better yet to check the adaptation values but that requires a digital scanner / SDS / HHT to view the numbers. I've seen a car that had a bad O2 and the adaptation was near max lean, and it had this weird surging idle problem. Went away with a new O2 and adaptation reset.

Note: The 93-up modules should reset by disconnecting the battery cable for 15-30 minutes. The 92 modules will not reset via this method, you need to use either a digital scanner, or a hand-held LED blinker (connect to pin 4, check codes, then "clear" code #1 which indicates no-fault... this resets adaptation to the mean/average value of 1.000). This is explained in the code list from the WIS (click here), see page 6 of 25, on the lower/right side of the page.

 

[RPB81]

Sounds similar but not EXACTLY the same as my issue. RPB81 states that his surge goes away when the engine warms up. Mine does not. Mine only occurs when the ambient temp is at or below freezing - not 70 degrees. Engine temp seems to have no effect. In other words, it sometimes happens upon start-up, sometimes happens after I've been driving for a while and the engine is warm. It can last anywhere from 5 minutes to an hour or more (don't often drive the car more than an hour without shutting down). But the common denominator is the cold outside temp. Now that it's wamer ourside I haven't experienced the problem at all.

Replaced my harness about 3 years ago when I got the car. Replaced the 116 motor (ETA) last year to solve this surge. That obviously didn't work, although that was in March, and it usually doesn't stay away from freezing here until later than that, so it's a little odd that I didn't experience the problem until the following autumn. Pulled codes from all systems last month and everything came up squeeky clean.

I'm enjoying driving the car in the warmer weather since it's running perfectly, but there's still this cloud hanging over my head with the surge I know will return...

Agreed, my idle surge typically ceases after a little drive or is very hard to detect, but outside temp def seems to be a factor. For right now the car is running nice! Was getting an intermittent ASR light one day, then I changed my battery out to an MTP-93 and no ASR recurrence, not sure if this was the fix for that. Harness is next on the list.

 

[Prime]

Update

Took the car to a new mechanic this week for some other service and told him about the surge issue. They seemed to have much more extensive testing equipment, and they found one thing that came up wonky related to the ASR. I haven't spoken to them about it yet, but I'm not sure if/how this could relate to the surge problem. Any ideas?