W201 M103 - Power/Idle/Starting Issues

[JamesDean]

Hi All,

So I've been trying to do some rebuilding on my 190E.

I'm not quite sure where to start but I appear to be having a power/vacuum related issue.

A few weeks ago I replaced:
-Fuel Injectors
-Fuel Injector holders and seals
-IACV Hoses
-AFM Boot

All of these parts were original to the motor and had about 125K on them.

My primary goal was to make the car idle smoother. It had rough and hard at idle.

When I start the car up, engine vacuum sits at about 15". I put the car into drive and it falls to about 12".

I plugged up every vacuum connection on the manifold, with the exception of the brake booster, and it was 15". Putting it into drive nets 12" of vacuum.

I had my meter connected to the X11 diagnostic port during all of this. When I first started out today it was sitting around 70-88%. I adjusted it back to 45-50%.

I reconnected each of the vacuum lines, monitoring the duty cycle and vacuum.

None of them resulted in significant vacuum loss at idle.

HOWEVER

One of them resulted in a significant drop in the X11 port duty cycle. When connected the engine ran rich, in the 30% area. When disconnected/plugged the engine sits in the 45-50% area like it should.

Does anyone know what this line services? I have to dig into the FSM to see if I can find it. Vacuum diagrams are not centralized as much as I would like.






Beyond that issue...

I still have

1) 12" of vacuum in drive at idle.

2) Lots of cranking to start up. I would say 6-10 seconds? Then it meekly starts up and is fine after a second.

[lsmalley]

I think that goes to the economy gauge.

[JamesDean]

Originally Posted by lsmalley

I think that goes to the economy gauge.

On the 93 model year there isn't an economy gauge. At least when I bought it it didn't have one. Later I added one and ran a line directly to the manifold. As best i can tell this line runs off to the passenger side or something. I'm not sure. Its hard to tell.

[optimusprime]

Vacuum runs at a peak, if engine performance is spot on. Poor engine performance will lower the vacuum.

[Duke2.6]

You need to be more specific about idle vacuum. With a manual transmission it should be specified as "Hg @ RPM in neutral. My 2.6 manual is about 15" @ 700.

Idle vacuum for an automatic should be measured with the transmission in Drive, and both RPM and vacuum will usally be lower than the same engine with a manual idling in neutral.

I don't have any data for a 2.6 automatic idling in Drive, but if you post yours, perhaps someone with a 2.6 automatic can chime in with their reading.

Duke

[JamesDean]

You bring up a good point about idle speed. It looks like when I am in drive, the engine is about 550 RPM. Vacuum is about 12-13" Hg.

[lsmalley]

Here are my readings from my 2.6 (pics included)
N= 750± @15mmhg
D= 550± @12.5mmhg

[JamesDean]

Originally Posted by lsmalley

Here are my readings from my 2.6 (pics included)
N= 750± @15mmhg
D= 550± @12.5mmhg

Thanks for this. So maybe I am barking up the wrong tree looking at vacuum?

Hmmmm

[lsmalley]

Make sure when you find out what the issue is at cranking you let us know because I am having the same issue. I'm having to crank the key for about 7-8 seconds. But runs fine and idles perfect. I'm wondering if it's my starter because sometimes during the cranking it doesn't even crank so I back off and retry and it catches.

[JamesDean]

I will definitely post up if I figure it out.

So far if I crank for 7-8 seconds it will barely start but once it catches a few cylinders running it will pickup and idle @ spec.

In drive or partk, my idle feels rough.

Potentially related to this, I managed to burn out a catalytic converter. At least thats what the muffler shop said. I am not sure if it was burnt out or joke broken somehow from physical force..

Have you checked your cold start valve/injector?

[lsmalley]

Haven't checked csv because problem occurs on both cold and hot engine.

[Duke2.6]

I had a similar starting problem for nearly two years - long cranking time, then very rough operation for several seconds, then all was normal, but it was intermittent. Sometimes it would happen cold and sometimes warm after only sitting for an hour or two. As time went by the problem became more frequent.

I finally traced it to an internal leak in the fuel accumulator. Search for a thread started by me, "fuel accumulator failure analysis" that also describes a simple test to determine if it has an internal leak, which will not allow proper fuel pressure to build up.

Duke

[lsmalley]

Originally Posted by Duke2.6

I had a similar starting problem for nearly two years - long cranking time, then very rough operation for several seconds, then all was normal, but it was intermittent. Sometimes it would happen cold and sometimes warm after only sitting for an hour or two. As time went by the problem became more frequent.

I finally traced it to an internal leak in the fuel accumulator. Search for a thread started by me, "fuel accumulator failure analysis" that also describes a simple test to determine if it has an internal leak, which will not allow proper fuel pressure to build up.

Duke

Vacuum tested fuel accumulator and had a leak. Replaced with another and problem still persists

[Duke2.6]

Was the replacement new? Whether new or used, you should retest it. I'm not sure what you mean by "vacuum test", but the on-the-car test I described in the thread I started on this issue will easily detect an internal leak due to microcracks in the fiber reinforced elastomeric diaphragm.

Duke

[Stretch]

Have you got the charcoal cannister arrangement on your fuel tank?