Rough idle and more...

[thysonsacclaim]

I mentioned something about the rough idle in another thread, but decided I would make a new one since I haven't gotten this problem corrected yet.

The problems:

1: Idle is rough and uneven. It will maintain idle though. It doesn't die and starts right up.

2: Revving the engine to about 1500-2000 RPM and letting off results in a near stall. RPMs briefly drop down to below 700

3: Acceleration lags. Badly.

4: Does not seem to shift gears at the correct time. That is, it's almost like in a manual where you run in one gear too long. You can just tell by the engine noise. Otherwise, the transmission seems fine. There are no loud sounds or clunking. Shifting between gears is smooth, so I *think* it is related to the obvious fuel issue. >>> Does that sound plausible?

5: When I changed out the oil that was in there when I got it, it had a scent of gasoline.

6: The scent of gasoline is very noticeable while running the vehicle.

7: There is no smoke coming from the exhaust. Exhaust is clear.

I have been checking out this post related to D Jet troubleshooting.


What has been done so far:
1: The ECU is new, so I don't think that is the problem and it probably wouldn't start up if it was.

2: Distributor and spark plugs and wires are new.

--- My thoughts are leading me towards:

1: Dirty fuel filter

2: Dirty/faulty injectors

3: Failure of a D Jet component (will test them as soon as I can).

4: Possibly the MPS?


I'm going to check the plugs and post a picture if necessary. I'm going to start with the fuel filter, since it should be changed anyway. Don't know when it was done last.

[thysonsacclaim]

Just checked the MPS via flashlight (near 10pm here).

Terminals 7 & 15 read: 95-96 ohms
Terminals 8 & 10 read: 370 ohms

The numbers should be 90 and 350, but I'm not sure about the tolerance. Based on someone's experience with a bad MPS, would my numbers function reasonably well?

Edit:

Dug up this from a post on here and may check it out. So much to learn and it's quite different from what I've worked on before:

Make sure your ignition timing is set right, D-jet it very critical due to the trigger point timing.

Make sure the mixture is set right at the ECU using an exhaust gas analyser.

Make sure all your ignition parts are in top condition (plugs, leads, coil, points, etc.) as a weak spark on 1 or more cylinder and it will still fire but not b a complete combustion, leading to a fumy smelly exhaust.

[oscar]

The numbers should be 90 and 350, but I'm not sure about the tolerance. Based on someone's experience with a bad MPS, would my numbers function reasonably well?

Personally I don't think there's too much for concern there.  I've tried a few and they've varied but all have been in the ballpark, or near the ballpark's turnstyles.  A new one of those is up around or over $1k so you'll be limited to used ones which will show minor variances.  I'd call the readings you got still in the ballpark.

IMO D-jet's can be a fickle phenomenon as there are often co-contributing factors that cause issues.  Nutz's troubleshooting guides are excellent but those type of guides, including ones in the Haynes manual, assume there's no other issues elsewhere.  I should rephrase a little, I mean to put the onus back on us.  When trying to diagnose FI problems or engine running issues and the guides fail to pinpoint the cause of a problem, I'd confidently guess that most of us skip the first piece of advice they give us like "ensure that the ignition system is in good shape ", or "the engine must be in good order", or "the rest of the FI must be working correctly".  For example, one might blame the FI system for poor idling when it's perhaps oiled up spark plugs or uneven compression between cylinders.  Two more likely causes.

With the engine, it's ideal then to be able to know what compression is like on each cylinder including leak down testing plus evaluating valve operation, condition of valves and timing of valves and timing chain condition and of course the ignition system including timing.  As daunting as it all sounds, realistically, most of us don't or can't do thorough testing to evaluate the engine.  So apart from basics we assume many other things are fine.  Just keep this in mind is all.

Your problems

1. rough and uneven idle
That PB Anders d-jet fundamentals site I posted in a thread somewhere will acknowledge that getting and maintaining a stable idle in a d-jet is a PITA, or words to that affect.  What to blame - spark plugs, injectors, compression, ignition leads ...there's so much more.  There's obviously better combustion happening in some cylinders that's not happening in others.  Check the spark plugs first for cleanliness and gap.  A question - is this uneveness during a cold start only or regardless of whether the engine's cold or warm? 

2 The near stall
When you take your foot off the accelerator pedal the injectors are shut off until a pre set RPM is reached.  Not exactly sure what the magic number is but presume it's partly a bunch of 70s electronics and partly the position of the TPS (throttle position sensor).  I think this issue may be due to the TPS  being either faulty or mal adjusted. 
Check these two links:
Describes faulty TPS 
http://forum.w116.org/mechanicals/a-warm-engine-running-issue/msg33804/#msg33804
First post has videos to test for faulty TPS   
http://forum.w116.org/mechanicals/d-jet-tps/

I have to go and will put thoughts up later if no one else does but just quickly with these last few easier probs.....

5: When I changed out the oil that was in there when I got it, it had a scent of gasoline.
Normal.  D-jets run a bit rich and with our older engines it gets past the rings.  No biggie, frequent oil changes is a good thing, but also refer to 6 re ECU and CO.
6: The scent of gasoline is very noticeable while running the vehicle.
Same kind of thing as above.  However, check all over for fuel leaks, all hoses and particularly remove the air filter and check those hoses to the injectors.  I also read the car had a new ECU.  Hopefully it's the right one for a 450.  It might be a bit hard to check the part number but what you should check is the tailpipe CO which should be around 1-2%.  There's a white or grey CO control knob on the ECU (check manual) which is accessed through a rubber or sometimes plastic access panel to the left of your left foot if sitting in the driver's seat (LHD of course).  Counterclockwise is lean, Clockwise is rich.  There's about 20 or 22 settings.  Rotating it slowly from one extreme to the other you'll note the change in idle,  it may even stall.   Just remember what position it was before you moved it so you can return it to that setting if need be.  I haven't measured my CO, I just set the knob in the middle and keep saying "one day I'll get that set properly".   
7: There is no smoke coming from the exhaust. Exhaust is clear.
Awsome, that's a good thing! But the only way you'll really know is if your in a different car following whilst someone drives your 450 and puts it through its paces, up and down hills etc.  There's bound to be a little.  No biggie.  But as long as there's no plumes, that's good.  If there's truly none during hard acceleration or high revs then damn good!

[thysonsacclaim]

Personally I don't think there's too much for concern there.

Phew! I saw those numbers browsing for parts (just in case) and about jumped. I can see it now: "I paid $900 for the car, $1200 for the MPS" (shock and awe). I was thinking it should be okay.

A question - is this uneveness during a cold start only or regardless of whether the engine's cold or warm?

Both. The engine was warm most of today as I was testing things, checking fluids, starting it up often. Afterward, I let it run for a good 15 minutes and the other day for 45 minutes of idling & around the block & hitting the gas to clear it out after an oil change.

When you take your foot off the accelerator pedal the injectors are shut off until a pre set RPM is reached ... I think this issue may be due to the TPS  being either faulty or mal adjusted.

Will certainly check out the TPS on the morrow.

Hopefully it's the right one for a 450.  It might be a bit hard to check the part number but what you should check is the tailpipe CO which should be around 1-2%.

Again, I'll check this straight away. Although, now that I think about it, it may not be the ECU that is new. The part I am referring to is in the engine bay (I was using the words of the guy who sold it to me, and he pointed to the box in the bay... perhaps he meant something else).

Awsome, that's a good thing!

Indeed! Thus far my repair bill is squarely at $68 USD, for the oil, filter, drain pan and a can of ether.


On a final note (the one that actually concerns me a lot): The shifting hesitation. Is my conclusion possibly valid that it is probably not shifting correctly because of the fuel problems and NOT because of the transmission?

There are no leaks, no hard knocks, no grinding, fluid is bright red, reverse is fine, running through the gears is fine, no clunks, and shifting is fine when the engine is behaving itself.

I'll keep an eye on it anyway, just would rather ascribe it to the FI than the tranny.

[s class]

Tranny shifting is strongly influenced by engine vacuum.  So until you get the engine running correctly, it is unlikely the tranny will shift properly.

[Papalangi]

My trans shifted oddly until I squared away the mechanical linkage from the throttle to the trans.

I don't know how to directly link to a PDF in the library so you'll have to do some navigating yourself,

http://handbook.w116.org/engine_75_l.htm
"More" until you get to Group 30
Click Sub-function 300
Look for control pressure rod

Michael

[thysonsacclaim]

I switched down the CO a bit and adjusted the idle speed. On my LHD SEL450, I found the ECU on the right side of the passenger foot area.



On the driver's side, near the E-brake, I found a series of relays which I didn't know about. I'm not sure, at this point, what they control, but I will check to make sure they all work.



It is the Ignition control unit which is new.



After pulling off the air filter cover, I found a fuel leak at a point where a rubber hose connects to the LH fuel rail. I tightened it up, which stopped it, but will replace the hose soon.



I check the hose to the MPS. It seems rigid and does not give in to pressure. There are no holes or cracks. Previously I checked the resistance, which seemed in tolerable limits.



After running a good 15-20 minutes, you can see the status of the gauges here. I think it looks okay, although does the oil pressure seem high? I read it shouldn't drop below 20 at idle, but where should it not be above?



So how does it run? Well, I didn't take it around the block. Just let it idle so I could inspect and check things out. There is more to do tomorrow as I didn't get to spend as much time on it today. However, I recorded a video of the idle. You can just barely hear the tappety knock I mentioned. Its hard to hear. Underneath the whirring sound. At this point, I'm not concerned about it because it is probably normal.

Listen to it idle.


Edit: One last thing. I checked the plugs and they were a bit carbonized.

[thysonsacclaim]

I was just reading this post about a faulty TPS. I tried to do some of the steps in the D-Jet troubleshooting post, but to no avail.

I did the following, according to the guide:

1: Set key to II, but engine off.

2: Opening throttle should give 20 clicks.

I tried opening the throttle manually (with my hand) but did not hear anything. So I took key out, moved back to II and pushed the gas pedal. I didn't hear anything, although I was partly in the cabin while trying to listen.

If indeed there were no clicks, you would think the engine would not fire at all? As per the video, you can see my runs.

Going to give it another try tomorrow and post my results. Perhaps I am missing something.

[oscar]

I'll have to come back to this later because I'm short on time but great job on logging the troubleshooting.  Sorry about the ECU location.  I thought LHD and RHD cars had them on the same side.  On the issue of the TPS, iginition to II and no clicks means there must be a discontinuation in wiring to the TPS or the TPS is faulty.  You can hear these clicks in the cabin as well, they are distinct.  However, the engine runs without the TPS connected.  The TPS provides extra shots of fuel to improve acceleration and counteracts slight lag for when the accelerator is depressed, the vacuum drops and it takes a fraction or so for the MPS to respond to enrichen the fuel for acceleration.

[thysonsacclaim]

Ah, I wasn't sure if it would run with it or not when making that post. It's rather late here, so I won't touch it until tomorrow anyway, although I'd like to. A Shame a I don't have a proper garage to work on it; would probably not sleep at all. I'm just searching the forums and printing up information I'll need for tomorrow. By the looks of it, I'll have an entire service manual printed by morning 

Going to check the compression, check wiring to the TPS and the TPS itself, pull out the ECU and inspect it further (the harness looked rather shoddy IMO), drain the radiator and run some vinegar through the cooling system and check that the MPS is keeping a vacuum.

I haven't a proper automotive pressure gauge... only a vacuum extractor for a Buchner funnel & flask with a gauge.

I'll try to fashion something to evacuate the air, but I want to be careful not to pull too much pressure (may damage MPS?). The vacuum system I just mentioned is for removing solvents from a medium, usually to wash and filter a final product of impurities. However, with the right rigging it should do the trick. 

Cheers

[oscar]

A thing about the TPS, there's two kinds.  280 and 450 d-jets have one type and it seems 350s have a different type.  If you noticed in one of my links or that PB Anders site, discussion on MPS and their tendency to have cracked diaphragms, well the 280 and 450 don't have these diaphragms.  These diaphragms provide the 350 with full throttle enrichment.  On the 280 and 450, full load enrichment is provided by the TPS.  From that info it's worth pointing out then that there's two kinds of TPS as seen in that last thread you've linked, where I've got the two types pictured side by side, the 350's with 4 pins, the 280 & 450's with 5. 

My suggestion from the above is don't go to too much trouble with diagnosing a vac leak in your MPS as they're much less likey to have one than those equipped with a full load diaphragm.  However, since you got a hand operated vac pump, it shouldn't take long to check it.  Only go to about 10-20psi and see if it holds for about 10 to 20 seconds is all.  Whilst there's no diaphragms there are two barometric cells that may stress under too much vacuum.  As crude as it sounds, all I do is suck on the MPS then stick my tounge to the end.  If it stays there for 10 seconds the MPS is good.  Haven't had a chance to check out wreckers for spare MPS but since I've read other guys do the same, I might have to purchase a hand pump afterall, or carry alcohol swabs.

Oil pressure is fine.  Side note: US gauges show pressure in PSI and temp in F, where everyone else's are usually in bar and Celsius, so if you see anyone talking of oil pressure as 1,2 or 3, just think of it as 15, 30 and 45 respectively. 
When starting cold, the pressure hits 45.  When driving with any decent revs (2k plus) it stays at 45 regardless of warm or cold engine.  When fully warmed up and idling or driving slow you might see it anywhere from around 20 to 40.  Yours is fine IMO.

I watched the idle video and I can hear the ticking.  A valve clearance/tappet adjustment (same thing) will minimise it.  You can do it yourself with a feeler gauge and a 17mm special spanner.  The problem is the spanner.   You can't really use a normal spanner because they're too long and there's not enough room to swing them. You need something like the pic below.  Available from samstagsales.com for $105, I got a used one from ebay but it's worn.  You should be able to find an open ended crow foot for little money and attach socket extensions to that.  They must be open ended since the flare wrench type crow feet wont fit.



About the whirr sound in the video.  Couldn't really pick that up but it's either the alternator, power steering fluid low or maybe even timing chain.  Whirrrs are usually power steering related IMO.

Sorry this is turning out to be a mammoth post but I gotta get all this out before I forget.

On to the transmision.  A few more things to add to what the other guys said.  I have to ask how you checked the AT fluid level?  If you do it whilst the engine's off you'll get a false high.  You're supposed to take the car out for a run, warming up the transmission in the process, moving through all the gears then return home, put it in Park, keep the engine running and immediately pull the dipstick, wipe, reinsert and take out again.  That way you'll get a proper reading.  Not sure if low fluid causes your issues but it's worth asking if that's what was done to assess fluid level.

I haven't had to adjust my control rod that papa mentioned but it's highlighted below in a grab from your vid.  Check that it's connected then adjust.  Unfortunately the manual only covers later verions with a spring clip whereas ours have a threaded adjustable shaft.  Procedure's still the same I presume.  I think lengthening it will make the gears change sooner.

Lastly on the transmission, a statement from an earlier post has me baffled.

On my shifter, I have the usual Park and Neutral and what not. However, I noticed there seems to be two places for Drive (as in, I can shift it in to either of these two spots) and the last one is Super/Sport. I tried the Super/Sport one once and it seems quite slow in that gear. Also, shifting down from Park, the first Drive seems to work best. I tried the other and it seemed a bit slow like the Super/Sport spot. Note, however, that it just says Drive. Not D1 and D2 or Drive 1 and Drive 2... just one simple Drive. Is that normal?

PRNDSL should be the markings with a shaped gate designed to aid as a lockout from going directly from D to R and/or P and/or vice versa.  Hence why there's no release button like you'd get on a T Bar auto.  The lockout and gate is also aided by the stick being constantly sprung to the left, so for example, whilst in P, if you push the stick to the right it will return to the left. 
I'll assume you know what PRN stands for but of the forward drive selections,
D is for Drive and will automatically go through 1st, 2nd, 3rd and back like any auto. 
S is for Slope and from a standing start will go through 1st and 2nd only, better hillclimbing ability and engine braking on descents.
L is for Load.  It only utilises 1st gear. For steep hillclimbs, descents, heavy load (manual says heavy traffic areas too).  Personally I think it's for traffic light drag races.
Hope that explains it but your comment about 2 selectable Drive postions and super/sport threw me as though someone's messed with the label.




Regarding the photo below.  My wire that attaches to the air filter housing temp sensor comes out of the harness highlighted.  It exits just south of the photo limits where the wires for the other two sensors come out.

PS: not sure what the relays are sorry but I did notice your ignition coil is upside down I doubt it matters but had to say so.

[thysonsacclaim]

Just getting ready to run out there so I figured I'd respond to some of your remarks.

A thing about the TPS, there's two kinds.

I did notice the different TPS and MPS variants based on the posts you mentioned. That Anders site is quite a thing! I didn't get a chance to cross-reference to see what I have in there, but thanks for letting me know. Glad I don't have that diaphragm. 

Oil pressure is fine.  Side note: US gauges show pressure in PSI and temp in F

That's good to hear. It was a little lower before I changed the oil, but I haven't any idea how old the oil was or what weight. Possibly they had something too thin in there.

Lastly on the transmission, a statement from an earlier post has me baffled.

Seems what was happened here is that the PRNDSL letter insert has fallen backwards. Upon further inspection, I was able to make out the beginning of the L (couldn't see it before, hence why I wasn't sure what things were). I'll have to open up the cover and move the label forwards a bit.

[thysonsacclaim]

Checked out the TPS and got it working. The outlet was quite corroded. Very green, indeed. Here is a video clip of the TPS going, which I will try to compare to the videos you posted, oscar.

TPS clicking in action.

[oscar]

Awsome job, glad you got the clicks happening.  I watched it just before I came to work but didn't take note of the number of clicks and the puter I'm on now doesn't have sound but from what I could tell, the acceleration clicks sounded good but there's inconsistent clicking on the return.  There should be no clicks on the return.  What this means is that on the overrun whilst decelerating you will experience a buck or slight surge in power anytime you take your foot off the pedal.  It wont send you through a red light or such, it's nowhere near that dramatic.  It will be interesting however to hear if you do notice a difference in power and driveability though.  I hope so.

Good news on the tranny labelling too. 

[thysonsacclaim]

Indeed. I haven't got the surge that you mentioned, but I've only gone about 55 km/h with it. All the gears shifted fine so I am attributing the shifting issue to the sticky linkage. I lubricated it well and adjusted the linkage on the throttle body. That and I cleaned all the gunk off of it. The flap was sticking a bit.

After doing that, when I shift in drive or reverse, the car begins to gently roll forward or backward. Before, I had to hit the gas a bit to make it move at all.

I need to still tweak the CO and idle speed. It doesn't seem quite right, but I haven't got a CO meter so I have to go by ear and RPMs for now, I guess.

There seems to still be an issue with the throttle at low speed. The response is lethargic and the RPMs drop a bit until it get to speed. I'm chalking this up to the TPS or maybe the linkage needs further tweaking. Will be looking at that tomorrow.

Oh and there is quite a bit less smell. However, I am getting quite a bit of fumes in the cabin. I could feel a warm breeze below my seat. Unfortunately it was dark, so I couldn't see, but I think there may be a crack in the floor just at the start of where the seat rails bolt into the floor where engine compartment fumes are coming in, or perhaps maybe the exhaust has a leak and is getting in there. Damn rust and humid climates.

I also noticed the lower AC/heat rotary switch (my label is gone, so I have to check a picture to see what it is for) gets quite warm. Perhaps not 'hot,' but it definitely needs a looksee. I don't think it should be as warm to the touch as it is.

So far everything seems to be coming together pretty well. The shifting issue had me a bit scared, though. I really was afraid the transmission was no good for a bit. 

Do you recommend any manuals besides the obvious one in the library? Perhaps Haynes? I was doing a bit of looking for a good review of one. I did see the one koan recommended about the D-Jet system, which I will probably purchase. I did find another good source of D-Jet info, as well: http://www.thebenzbin.com/mercedes-d_jetronic_1.html not sure if you've seen it.

Thanks for all the help. Not sure what you drink in Oz, but here's a cold Beck's on the house  :