190E 16v - car-shaking idle and hard cold starts

[lithium726]

Hi all,

I'm slowly going through my revamp of a 16v, but two problems persist. One, the car takes forever to start if it's been more than about 15 mins since it was last started. It will crank 10-15 times, try to catch every once in a while and finally start. When it's been sitting for 5 mins or so it will start much quicker. 2. when idling, the motor vibrates so much the car shakes. If my hand is hanging out the window it visibly shakes up and down.

Now, things I have already done, all of which have helped power and smoothness but those two problems persist (with the starting problem getting somewhat worse):

1. Valve Adjustment
2. Pulled fuel distributor, lines, injectors, idle valve and gave them an ultrasonic cleaning. I did not clean the EHA valve, I will do this next.
3. New, proper, non-resistor plugs. (NGK BP7EFS)
4. New motor, trans and subframe mounts
5. New cap and rotor

Motor is smooth as silk once I put my foot down, even if I keep it just above idle. It pulls smoothly to redline and will burn the rear tires easily. Sounds demonic at WOT.

Fuel pump is of unknown vintage, fuel filter was replaced within the last 3 years and I have a new one ready to go in.

Any thoughts?

[mbdoc]

How about the overvoltage relay, do you have power to the ECU?

[lithium726]

Originally Posted by mbdoc

How about the overvoltage relay, do you have power to the ECU?

if I did not have power to the ECU, the car would not start at all, yes?

I'm not super familiar with the CIS-E system or the ECU that MB used in this era... I'm much more familiar with EFI BMWs. How would I go about checking this?

MTI - responded to you on mbworld as well, but wouldn't a compression problem be evident in the entire revband?

The valve clearances were WAY off when I did the adjustment, but all adjusted to within spec with very similar sizes on intake/exaust, respectively, indicating that the seats are wearing evenly...

[duxthe1]

Yes the car will start without the ECU but it can run poorly and be stubborn to start depending on the basic setting . The car has a basic mechanical setting that will allow the car to run, the ECU just fine tunes it for the operating conditions. When the overvoltage relay doesn't power up the ECU its common to have the symptoms that you describe.

[MTI]

Originally Posted by lithium726

MTI - responded to you on mbworld as well, but wouldn't a compression problem be evident in the entire revband?

It won't be evident using the "seat of the pants" dynomometer.

Here's a picture of one of my damaged exhaust valves



Despite low compression values in that cylinder, the car ran like a champ when warm, but had a tendency to hesitate on cold start, vibrate and not hold idle. When warm, the idle might drift upwards, but a throttle blip would settle it back to 900 -1K RPM.

[lithium726]

Yikes. I hope that is not the case, I don't want to have to remove the head.

Just checked the OVP relay. It looks original, although it is no longer bolted on to anything... just flopping around in the battery try. The fuses are fine, and when I unplug the unit it absolutely will not start, so it seems to be functioning.

Guess I'll go buy a compression tester tomorrow and hope for the best.

edit: relay has the newer part number, so it has been replaced at some point.

[zhenya]

2nd on testing the compression. My 16v had many of the issues you describe (difficulty starting, erratic idling, occasional stalling, etc.) yet seat of the pants the car seemed ok.

A bad head gasket necessitated head removal this year, and all exhaust valves were bad (not cracked like MTI's, but replaced). With a full head rebuild the car now runs perfectly - smooth idle, starts every time - and the car is clearly much more powerful.

Hopefully this is not your issue - but don't ignore the fact that it well could be.

[MTI]

I'm thinking it could be a compression issue. I have similar symptoms and found it was a couple of toasted exhaust valves in one cylinder.

[jt20]

Those numbers are not accurate. You can use them in comparison with a WARM compression test to verify suspicions.

Remove ALL the plugs when testing. You need as many RPMs as you can get.

You might be jumping the gun on a full rebuild. Its probably just time to do the head like MTI mentioned.

Damage?... running lean is certainly not good for the cylinders and a shaking engine is bad for bearings. But both of those take time to do severe damage.


edit: I see you are planning on re-doing the comp test.

[lithium726]

oil change and hot compression test completed. Changed oil to some Valvoline VR-1 Racing 20w-50, which is helping it idle a little better. it's not jerking around as much, but still quite a lot. I did about 4 miles of several WOT runs and 60mph cruising to get the new oil warmed up.

compression results (all plugs out, fuel relay removed, WOT):

1: 100PSI
2: 120PSI
3: 100PSI
4: 132PSI

Head's gonna need to come off. Also noticed that I just started leaking some oil. HORRAY!

[duxthe1]

I didn't see the mileage mentioned. I recently did a valve job with all new timing parts on one that burnt 2 ex valves. Bill was over 6K$ The parts are real spendy and its huge labor to get the front cover off to replace the timing parts.

[lithium726]

Car has 155k miles.

I will be pulling everything. Got quoted $650 to refurb the head by the guy that the dealership contracts out headwork to - he's done a cosworth head before.

worst case, guides are about $18 and exhaust valves are about $90... so if i've burned a few this will likely run me 1k-1.2k with gaskets and all the other crap that goes along with it, "while i'm there" like the water pump. I already have a bag of brand new, OE timing components so I'll just do that while it's apart.