400E Poor Running 1992 400E / Extended Crank / Lagging initial throttle performance at times

[dreaming.haze]

Been diagnosing an issue with a 1992 400E that used to be owned by JDAMG (Owners Thread). Sounds like he had similar issues at times and also faced the classic secondary ignition issues related to moisture within the distributer caps. I resolved the secondary ignition issues with some used distributors that had slots cut into them / fresh rotors / New camshaft solenoids that weren't leaking oil. JDAMG had already gone through a few different fixes to try and get the ignition issues resolved including Camshaft seals + new distributors / dust shields. On top of this work, there was a replacement of a camshaft adjuster + timing chains / etc completed (link to this work)

Issue description / faults:
1. On initial start, input into the throttle can cause car to stall and die at times. This could be if reversing out of a space -> shift from R -> D -> input of throttle = car dying out. This can also occur when initially driving the car away from a stop light ~maybe 1-2 minutes post start up. If the car has been running for a minute, then you will not see this issue, but can still occur randomly.
2. Also on initial start, I am not hearing the Fuel Pumps prime the system when putting the key into position 2. *If I unhook the battery and reconnect things, I can hear the system prime on first start.
3. Extended Crank on start up. Compared to my 500E, the crank can be 1 to 2 seconds longer
4. When accelerating, you can sometimes feel like the car is lacking fuel / doesn't have the same push as just moments prior in the rev range. Imagine accelerating from 2500 rpm -> 5500 rpm and having certain parts where the power doesn't feel as linear and will dive down vs. continuing to build.

Troubleshooting so far:
First off, I focused on the fuel system. This was a bit of a rabbit hole in trying to fix a rusty tank / deciding that wouldn't work and trying to find a decent condition one used / then replacing all the parts (fuel pumps / filter / fuel lines / etc.). I also tested out the Fuel Pump Relay to see if swapping things helped / didn't help - no change.

In further troubleshooting, I had a code produced indicating a bad camshaft position sensor. Swapped across the CPS from my 500E to test and this code disappeared, so I replaced things with a good used OE unit.

Next focusing on the LH module itself, I decided to swap to another LH module I had around. No fix, but it did feel like it reset some level of the fueling table so it drove better on the initial driving, but didn't fix things long term. I then re-capped both the original to the car unit + my test module. Same results occurred with a slow initial crank.

Codes:
As of Oct29 2024, here are the codes I am able to grab that will not disappear post a 5 mile drive around my area.
LH: Code 8 ( CMP sensor (L5/1) signal, open/short circuit )
ASR: Code 11 & 15 (ABS/ASR hydraulic unit, solenoid valve relay (A7/3k1) / ABS/ASR control module (N30/1) )
EZL: Code 5 & 6 (Knock sensor 1 and/or 2 defective / CMP sensor (L5/1) defective )


From here, I look for more advice from the community on next troubleshooting steps.

 

[gsxr]

Will, you may have a couple of different issues occurring simultaneously.

1) Initial start issues / stalling: Has the ETA been rebuilt / replaced? Date code? Do you have a spare to try out? Any fault codes on the E-GAS module?

2) Fuel pumps should prime for ~2 seconds every time the key is cycled. If not, the LH module is the root cause. I've never had this particular symptom cause problems with starting / driving / etc, but you have swaped in a spare module, which should cure this particular malady.

3) Extended crank: Connect a fuel pressure gauge to the rail and view pressure while starting. If fuel pressure is at the normal ~55psi and it still cranks excessively, something electronic may be going on. Is the CKP (crank sensor) original? I'd expect a fault code if the CKP was flaky.

4a) Knock sensor faults can cause a noticeable power loss under acceleration. If you have a spare EZL, swap that first because it's soooo much easier. If you get identical fault codes on the spare EZL, next up is replacing the knock sensors... which of course are NLA. If you don't have a spare used one, I think Kurth might sell a retrofit harness that uses the replaceable round sensors from the .98x engine?

4b) The CMP fault shouldn't be coming back with a good sensor. Try the EZL swap first. Next up is pulling the valve cover to check cam timing on the driver intake cam, along with confirming the air gap from CMP to sprocket tab is within spec. This could also be causing power losses if the EZL isn't reading the CMP correctly.

 

[dreaming.haze]

Hey Dave,

Thanks for your replies, will take me a bit to get towards proper testing on a few of your notes, but I can give some notes to your questions thus far.

1) ETA hasn't been touched as far as I know. It was taken off / put back on by the previous owner during an upper intake manifold removal, but that would be the extent. No spare right next to me, but I could source one as a test. No codes on the E-Gas module in my testing yesterday. Also need to check the date codes on things.

2) Agreed, Feels like spare module swap would be a cure for things. For this specific failure of no fuel pump prime, could I test out using a 5.0L LH module to see if it improved things as well?

3) Can do, have a pressure gauge purchased but haven't put things together just yet, I can likely get a reading on this later today. CKP is original to the car as far as I know. Took a look through the maintenance notes / history and can't see the part number there. Looks like Bosch is NLA, but direct from MB is still available for ~$170 from discount revparts dealers.

4a) I do have a spare EZL that was provided by the previous owner, he was likely going through the same error codes / troubleshooting - so likely why it is around. I can swap things over and see if the codes follow. Kurth does sell a replacement knock sensor harness (Here)

4b) Will see what EZL swap does first, but I do know they had the drivers side apart to replace the camshaft adjuster and re-did a spread of things while in there. Curious if there was just a botched segment to the job then.

Will report back!

 

[gsxr]

Sounds good, Will!

1) Definitely inspect that ETA and look for a spare to test with.

2) Yup, you can test the pump prime with a 5.0 module. I expect it will return to normal with a different module.

3) I thought the CKP (A0031534928) went NLA, but my memory was off... the OEM vanished from aftermarket, but Genuine is indeed still available - phew. I think Genuine is AB Electrik, more info here. I doubt this is your issue, and the CKP can last a very long time.

4) Cool - swap EZL first since it's easy. If the same codes pop up, you'll need to see if the previous techs botched something inside.

 

[dreaming.haze]

A couple blinks, and now it is months later. LIfe is like that sometimes.

1. Still haven't broken out a spare test ETA, have a couple of parts cars that I will scavange from over the next weeks to grab one.

2. Pump is now priming and I can hear things working as expected, likely the capaciter fix + just keeping my ear up and listening is good to go.

3. Still need to measure fuel pressure on start up / generally.

4. Tested out a 95 E420 EZL that the previous owner had provided with the car. Looks like things are running better with this EZL and there isn't as much of a drop off in the mid range performance + it revs out a bit better. After the swap, I was still seeing issues with initial throttle input off the line and having the car fully stall out and need to be restarted. This occurred earlier on in my test drives, but didn't happen as often as the car was drivig more.

5. I also tested out disconnecting the crossover exhaust pipe to see if the Catalytic Converter/s are clogged. With how loud everything was, couldn't really confirm how things were feeling. Felt like there was less of a 'wall' in performance, but I did this before swapping the EZL. Hooked things back up and will report back on performance tomorrow.

6. Decided to check and see if the timing was done correctly on the drivers bank by the previous owner/ MB. Was able to get the valve cover off and measure things at the '45' mark on the balancer. TIming checked out and all was good there - so can rule that off the list of potential things.

With the EZL swap / clearning old codes / etc. , I still saw the following codes pop up:

LH: Code 8 ( CMP sensor (L5/1) signal, open/short circuit )
EZL: Code 5 & 6 (Knock sensor 1 and/or 2 defective / CMP sensor (L5/1) defective )

Dave, to your previous note of `along with confirming the air gap from CMP to sprocket tab is within spec` - How should I be going about this? I searched a bit, but wasn't able to come up with the correct terms in seems.

 

[gsxr]

LH: Code 8 ( CMP sensor (L5/1) signal, open/short circuit )
EZL: Code 5 & 6 (Knock sensor 1 and/or 2 defective / CMP sensor (L5/1) defective )

This is unusual. I assume the upper engine harness has been replaced. Wouldn't hurt to test the wiring to the CMP. Remember the EZL connects through the body harness to the engine harness, so there's a slim chance you have issues with the body harness... nibbling rodents might have wreaked havoc somewhere not easily visible.

After confirming the wiring to CMP is good... what part number LH and EZL are installed, and have you tried others with identical fault codes appearing? I've seen weird incompatibility on certain non-standard engine + LH + EZL combinations, and one of the failure modes was LH code 008. This is unlikely, but worth looking into if the wiring checks out.

Dave, to your previous note of `along with confirming the air gap from CMP to sprocket tab is within spec` - How should I be going about this? I searched a bit, but wasn't able to come up with the correct terms in seems.

The FSM procedure here is beyond useless, because it lacks the referenced document about clearance. Grrr.

I know I've seen the "good" FSM procedure somewhere, that shows the correct gap, and the shims to adjust. From memory it's 0.5mm air gap? I just can't find it!

 

[gsxr]

Found this spec buried in the EZL overview:

 

[dreaming.haze]

Update from today's testing so far.

Decided to replace the spark plugs that were in there and gap things to 1.0-1.1mm, seems to have smoothed out the idle + haven't had the initial bog off the line in my testing so far. Curious if that was just a plug that wasn't working as expected OR the plug wires not fully seating correctly on one cylinder.

Cleared out the EZL codes for 5&6 related to knock sensors, came back after the test drive of course.

To your questions:
Date code on upper wiring harness is 2012, so it is good.
LH = 015 545 34 32 / 92M11 for date
EZL = 015 545 60 32 / Unsure how to tell dates on an EZL as I've never looked for it picture attached.

I've swapped LH module / EZL and the codes have followed.
The other LH module = 014 545 15 32 / 92M02 for date.
The other EZL module = 013 545 63 32

I'll check into the wiring and see if there is anything noticable along the way + check the air gap, pretty sure I kept the shims when swapping sensors last round, but never hurts to check.

 

[dreaming.haze]

Update: Wiring from CMP -> EZL is good. Measured from CMP -> Coax connection behind Module box then again from Coax connection -> EZL / and finally the whole run just in case. For future searches the run can be found in Camshaft Sensor and Crankshaft Sensor persisting code. | M119 Engine thread post. So the communication looks to be active and no mice nibling away at things.

For the air gap measurement, I need to get the engine turned over to the correct point it looks like. I was doing my measurements and getting annoyed for awhile until I saw this image to help me along on where I should be measuring to.

 

[dreaming.haze]

Well that took some effort, but was able to get the engine turned over to the correct point and measure the triggering nubs on the camshaft. Both with our without the shim things are good and within the 0.4-0.6mm air gap needed.

Now to experiement further with module swapping it seems. Going to test back with the older LH module that I re-capped and already swapped a month or two back. It hasn't been tested with the EZL currently in the car.

Update: Was able to swap over the LH module and code 008 on LH went away - Now, I'd like to drive it around more to see if it comes back with time or if it is fully gone. I will say the previous LH module felt like it drove better than this one, but again it was a shorter drive and likely needs to adapt more.

Codes 005 / 006 on the EZL still are active after a test drive.

 

[dreaming.haze]

And another update today, Was able to get the o2 sensor out of the car easily (previous owner replaced it in the past 5,000-10,000 miles or so) and then hook up an exhaust back pressure guage to the o2 sensor bung. Sadly, looks like the cats have seen better days and are all clogged up. Pretty terrible readings pressure wise (photo is at ~4500/5000 rpm and had multiple runs where it maxed out the guage even more). Going to sit on the diagnoses for now and decide how I'd like to proceed as there are multiple paths forward.

 

[dreaming.haze]

Finally an update after some vacation + sourcing some parts.

Took an exhaust off a friends parts E420. Was a bit of a pain in the ass due to the tires being flat + the car having been sitting in the same spot for years, but was able to get it all out. Probably should have just cut out the Catalytic area, but wanted to make sure the exhaust guy had more metal to work with. Sadly, after getting the parts Cats welded in, they were clogged as well. On one set you could hear some of the catalytic materials rattling around, and the on another there was a large chuck of material that fell out after removal. So it goes.

Getting fed up and annoyed, I now have some straight pipes put in the car. The exhaust already had a non-factory cat back segment (without resonator) installed, so didn't feel too bad. Car is back to feeling great and with proper power. Only did a single test drive so far, but need to likely install some fresh exhaust rubber under the car to help with some of the NVH.

From here, I'll do another code read and report back. Still working to get my M6+ machine going for some HHTwin troubleshooting.

 

[dreaming.haze]

Another quick update.

Installed a fresh o2 sensor that had a bit longer wire vs. the OE sensor. Helped properly allow for the 'click' in of the wire connector for the sensor. Also removed the Crank Position Sensor and gave that a good clean, looks like it had been installed since manufactoring with a 91 date code on it. With reinstall I added a bit of a gasket to space things out ~0.4-0.6mm, didn't notice anything with a shorter or longer start up, but figure it was worth a clean and test. This was after reading a bit on the following thread: Crank Position Sensor: Adding Shim | M119 Engine

Also, I was able to get my M6+ machine working with HHTWin and was able to read out / clear all codes pretty easily. Game changer after years of the blink box... After clearing all codes on the LH module, I was able to reset adaptations properly and this resulted in a bit of running performance adjustments on a test drive. Resulting in a smoother idle and what felt like a more proper running machine.

Sadly, two codes are still coming back:
Codes 005 / 006 on the EZL - Which would point towards the Camshaft position sensor and then the knock sensors. Knock sensors would be a bear of a job due to needing to pull the motor mounts out so I am still hesitant on getting into this job.

Car itself is now running great, but would love to get it to that 100% mark that I know the 4.2L is capable of.

 

[gsxr]

Will, do you have a spare EZL to try first? If another EZL coughs up the same 005/006 codes, they may be legit.

You can test the cam sensor wiring and the sensor itself (compare to your other cars).

The knock sensors, I don't know of any 'test' to check the sensors via the 3-pin connector. And yes, the knock sensors aren't fun to replace. Easier with a lift, but still not fun.

If you can set up the M6+ to be viewable while driving, watch the EZL/DI live data for ignition retard per cylinder while driving. Normally all cylinders should be zero, or at full load, low single digits (maybe 1-3° retard on random cylinders). I don't know what the EZL does to the timing if it thinks the sensors are bad, i.e. if it goes into a default "safe" mode with reduced timing?