Hesiattion and oil leak! I'm close to giving up on her!

30csl

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In the garage till 5am saturday night/sunday morning. Took the inlet manifold off of my 3.0 csl to get at the oil sender which seemed to be leaking. Blanked it off and then reassembled and put in new injectors. I was hoping these better flowing injectors would cure the hesistation under full load at 4500 rpms.

No joy on either the leak or the hesistation! So sickening. I didnt get a chance to see if the leak is still from the sender location (maybe i didnt tighten the bolt up enough to crush the washer!?) but there it is so hard to see where it is coming from. I plan to power wash the whole area and then put it on a lift and run it to see where it appears first. Last chance saloon and if it doesnt work then it will be discovered in the corner of a shed when i die!

Any ideas on the hesistation at 4500 - I have made sure the screen in the tank is ok - fuel pressure is 32-34 at idle, new fuel filter. New injectors. New cap, new leads. It feels like it is fuel supply vs electrical as when it hesistates the gauges do not act up and the loss of power is not violent. Its like someone cutes the fuel supply in half? Should i be looking at the MPS? I checked the TPS a while back for WOT signal and it was spot on - will check this again I guess.


A few years ago it was working well and had 200bhp on the rolling road - went back again and it had 180bhp. I guess perhaps I should book it into one to get to the bottom of it but there are so few places that would be up to speed on the d jetronic.

Regards,

Rohan
 
Hi Rohan,

A very common E9-problem with hesitating +4500 rpm is a very easy one.

Replace the additional air slide with a new one (blocked filter). If already replaced, check if the new one still has the round filter inside. Unfortunately there was a production problem with some new air slides. The filter simply fall out after some few km. With no filter in the additional air slide, the engine will hesitate starting from 4500 rpm. I had this problem om all my injection E9.

Cheers
 
Hey CSL,

I don't quite understand - the auxilliary air slide is shut when the engine is warm though and therefore the air filter for this should not make a difference? I did replace the auxilliary air slide a while ago but I reused the air slide air filter.

Regards,

Rohan
 
If you re-used the air filter check that the round air filter itself is still there or not blocked. My aux air slide filter house looked fine at a glance but when I put my fingers inside (from the right), it was empty. The poor air filter-welding/glue was broken and the filter had fall out despite that the part was just a few km old. Same story with both my CSL and CSi. After another new aux air filter (improved version), the hesitation I had at 4500 was gone.

Don't ask me for the logic in this, I'm just happy that the hesitation was finally gone.

Cheers
 
Thanks for that - well perhaps I will take it off and block the auxiliary slider to try and see if this is the problem? It seems it shouldnt be the case but if it works then I am very happy to try it!

Rohan
 
Anyone else had this problem? I plan to try and block it off tonight to see if this helps matters.
 
I was hoping these better flowing injectors would cure the hesitation under full load at 4500 rpm.

I have made sure the screen in the tank is ok - fuel pressure is 32-34 at idle, new fuel filter. New injectors. New cap, new leads. It feels like it is fuel supply vs electrical as when it hesitates the gauges do not act up and the loss of power is not violent. Its like someone cutes the fuel supply in half? Should i be looking at the MPS? I checked the TPS a while back for WOT signal and it was spot on - will check this again I guess.


Deja Vu? http://www.e9coupe.com/forum/showthread.php?t=4781

I was unable to read through the various posts and responses to your problem, but having been there a few times, resolution usually amounts to something very very basic. At the risk of repeating some ideas, here are a few that come to mind.

Does this miss or loss of power occur all of the time? Cold vs. hot, etc.?

Since you have a few modifications (e.g., different injectors) have you considered tuning via your eyes, ears and nose? Different injectors would likely affect the mixture. Is it possible that you are now too rich at higher revs? Looking at your plugs and tailpipe (or rear view mirror) might be helpful. An engine being fed a rich mixture might, in turn, benefit from more ignition timing. Thus, have you considered setting the timing via ear or deviating from the stock recommendations? Conversely, you mentioned “It’s like someone cuts the fuel supply in half” - suggesting a lean mixture. Could it be that your ignition timing is now too far advanced? My point is that unless you have some empirical base line data to work with (a la an exhaust sensor) can you fiddle with the timing so that your problem disappears (even at the expense of poor running at a different speed or poor idle?) Have you tried altering the plug gaps or even the brand/style of plugs? Can you view your engine at night with little ambient light to look for any occult ignition arcing?

While I cannot specifically recall experiencing an outright ECU failure, swapping even identically numbered and color coded boxes can result in some differences. It sure would be nice if you could have someone else try your ECU on their platform or vice versa to eliminate this as a possibility. From memory, and as a long distance hunch, the more likely scenario is your pressure sending unit a.k.a. your map sensor. Checking to ensure it retains vacuum is the most obvious test, but it is far from the only one. The units are constantly moving under vacuum and susceptible to wear. Depending upon who you ask, they can be adjusted or modified. As with the ECU, swapping for a know good unit or trying yours on another platform would be nice. Some conventional wisdom suggests that disconnecting the air temp sensor at the forward part of the intake manifold log results in a default “rich” setting for a pressure sending unit that is out of normal specs. Have you tried this?

Regarding your oil leak, it is very common for the sending units to leak at the upper portion of the unit. Only fix of which I am aware is a new unit. I suppose that a poor crush gasket could also result in a leak, but I haven’t experienced one.

Lastly, in my limited experience, an open auxiliary air will undoubtedly result in a leaner mixture. However, if you can stick your finger in the intake orifice with the filter removed and engine running and feel no vacuum, it is unlikely that this has anything to do with your high rev issues. Frankly, plugging the “U” hose with the business end of a spark plug after the engine is at operating temp. While on the subject of auxiliary air valves, there are two nearby temp sensors should can affect mixture at different temps. If the sensors are not functioning or if the sensor wiring is loose or compromised, the ECU may function as though the engine has never reached normal operating temperature. Translation: double check the wiring and connections down there. Incidentally, there are filters commonly fitted to valve cover vents that will fit the auxiliary air valve in place of the stock Purolator paper filter. The added benefit is that these after market filters are often washable fabric elements.

knn-62-1560_w.jpg
 
Hi MMercury,

many thanks for the reply - and yes you are right on the deja vu! But each time I usually have a different take on the problem. The oil leak is annoying but the running problem is what is killing me!

As for the injectors - I changed them as the ones in the car were not correct and did not have the right flow etc.

I have checked the fuel pressure and this does not die when the hesitation appears.

I will now swap out the MAP sensor and the ECU and try that tomorrow.

Other than that I will also check for no vacuum when hot at the auxilliary air slide valve.

The temp sensor is an interesting check if it does default to rich - I will also try this.

Many thanks - will report back once I have tried these each in isolation.

Regards,

Rohan
 
TPS check...

Have you checked the TPS to make sure that it's set properly and does not have any contacts that are arching? From fuzzy memory... I think there are 21 distinct points you should be able to hear. If one contact is not functioning properly it could/would give you a hesitation- it would occur consistently at a given TP and be most noticeable under load.
 
I have checked the fuel pressure and this does not die when the hesitation appears.
I will now swap out the MAP sensor and the ECU and try that tomorrow.
Other than that I will also check for no vacuum when hot at the auxiliary air slide valve.

The temp sensor is an interesting check if it does default to rich - I will also try this.



I reread the deja vu thread and am more convinced there is something simple you have overlooked. You didn't loan your car out to someone named Hagrid? I feel uncomfortable having suggested swapping the ecu and/or map sensor/PSU - if you have already performed this exercise without any discernible changes. Not sure any of these suggestions are particularly on point, but here are some more scattershot thoughts. Forgive me if you previously addressed these questions or they seem easily dismissed.

Does the hesitation occur above 4500 R's - in all gears? How about before the engine reaches normal operating temps? (When things might be slightly richer than normal) In other words, is there an occasion where the engine does not experience the hesitation?

You mentioned the change in injectors, are you certain that you are currently using injectors with the same or similar flow rates as the OEM? Your previous observations regarding "pinging" and retarded ignition support the argument that you are running lean at higher revs. Not sure if this was before or after the change of injectors. Running on "the edge" can sometimes be good. Wonder what would happen if you increased the fuel pressure by tweaking the regulator. (Didn't you did have readings that were slightly low at one time?)

As suggested before, a sub par coil or condenser (or loose connection to either component) can mimic a bad fuel pump - and fuel starvation under load. Is it possible that your coil is marginal and that you are running wider-than-usual spark plug gaps? And how do the plugs look after a bout of hesitation? (Possibly "white hot" and overheated due to a lean condition?) (I know it sounds like a long shot, but is it possible you have plugs that are too hot for your current application. What type of plugs? (Copper core, silver, or . . . platinum tipped?) Possibly too much resistance in the ignition system? (Resistor'ed rotor, wires, plugs, plug terminals. This should not be an impediment to garden variety operation beyond 4500 rpm.)

On the subject of the auxiliary air valve, what is the condition of the "U" hose? Could it be the source of an unintended vacuum leak? Is anything going on with the cold start injector? Could it be leaking fuel or somehow contributing to unintended mixture instability? Seriously doubt any direct causation, and have no way of knowing this, but if it's dribbling fuel - who knows?

Possible vacuum leak at the throttle shaft or throttle body? (Again, this would more likely be an issue at idle or slightly off-idle and not upper operating range.) Casting the net even further, you mentioned before that your compression readings were somewhat reduced (180 ft/lbs vs. 200). Uniform, albeit lower readings across all cylinders seems acceptable. Yet, it begs the question, does your engine possibly suffer from extra-serious blow by (which might be affecting your mixture)?

You don't happen to have a severely restricted exhaust system (e.g., nasty crimp in the piping or an add-on catalytic converter that's plugged )? If you were employing carburetors, one of the first things to question might be whether your linkage is adjusted to ensure the FULL opening of the throttle shafts. Can you confirm that mashing the foot pedal downward results in the throttle being completely open? Along the same lines, any restrictions in the intake air feed? Is the air filter clean? (Have you considered trying to run the engine (temporarily) without the filter attached?

Regarding the sensors and the djet, in general, take another gander at these posts:

http://www.e9coupe.com/forum/showthread.php?t=6449

http://www.e9coupe.com/forum/showthread.php?t=2879&page=2

quoting: http://www.benzworld.org/forums/w11...-d-jetronic-k-jetronic-troubleshooting-2.html

http://www.e9coupe.com/forum/showthread.php?t=6674

We are anxious for some good news. Good luck!

plugdiag.jpg
 
Well guys, I havent had a chance to go after the hesitation yet. I am fairly sure now I have no vaccum leaks so first thing will be to swap out the MPS for another unit to see it that helps. Then the ECU.

Then if I have no joy I guess the TPS?
Thanks MM for your brilliant help. With it I have drawn up a hit list of which the abover are top three. The throttle itself is opening fine.

On the oil leak - i got it up on a stand tonight and cleaned it up - then ran it and watched - the leak is coming from the head gasket at the rear - not the oil pressure sender or the cam end cover plate. I am very surprised and dismayed! Has anyone else had this?
 
Hey Matthew, I bought a new dizzy cap but havent tried to lock up the rev limiter - its a good idea and i will try it also but as the car will very gradually rev through it I am unhopeful on this?

Thanks,

Rohan
 
Well i finally got hold of a borescope(sp?) and had a look at the car today - it seems the oil is indeed leaking from the head gasket. Very strange.

Looks like its time to pull the engine and fix it properly.

I reckon i will lift the car off of the subframe as I plan to change the steering box to manual at this time too.

Any tips?

Regards,

Rohan
 
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