16V cold and hot start problems - PeachParts Mercedes-Benz Forum

#1 09-10-2002, 11:16 AM

My 87 190E 2.3-16V has been in the shop repeatedly for start and idle problems. My mechanic doesn't seem to know how to correct the situation. Please help.

Cold start: car starts up and dies immediately, as if out of fuel. This continues until I give some pressure to the throttle, but the engine will not idle without continuous pressure on the throttle.

Hot start: after car is hot and engine is turned off, same starting problem resumes.

First drive: when the car is first driven, for about a quarter mile it coughs and chokes as if there is vacuum loss. (I am not mechanically inclined so "vacuum loss" may be incorrect description and may be misleading. Apologies, if this is the case.)

Once the car has been driven for several minutes the idle settles down at 1300 RPM (not at the 900 +/- 50 specified by the factory).

Above problems occur regardless of a/c being on or off.

My mechanic has already replaced 1) throttle valve; 2) air flow position sensor; 3) potentiometer and then my a/c compressor had to be replaced (????) when the a/c stopped working during one of the repair trips.

It is most frustrating. Thanks in advance for your comments and help.

mbdoc · #2 09-10-2002, 12:38 PM

How about valve clearance? Has the valve adjustment been checked? That could cause the STARTING problem.

The idle circuit needs imput from 4 sensors to operate correctly.
Idle contact switch, decel switch, air flow position sensor, & speed sensor(hall effect) imput.

#3 09-10-2002, 02:16 PM

M.B. Doc.

Thank you so much for your prompt reply!!! I am going to give a hard copy of your suggestion to my mechanic right away.

I don't think the valve clearance has been checked. Now I am concerned that my guy is way over his head with this very special car. Should I be taking this car to the local M-B dealer to fix this problem?

Regards,
YF Yin

#4 09-18-2002, 11:48 AM

M.B. Doc:

You asked about valve adjustment in your last message. I heard this is a big job and should be done by M-B dealer service technicians. Is this what you would recommend?

My start problem continues. I am killing the battery now, I think, because I have had to crank the starter so many times each time I try to start the car.

The idle is now at 1500 rpm when the car is finally started. I want to get both the start and idle problems solved but I want to make sure I take the car to the right place.

Please advise.

YF Yin

mbdoc · #5 09-18-2002, 04:56 PM

The valve adjustment requires SHIMS that come in 19 sizes. ANYONE must have the needed sizes OR they won't be able to adjust the valves!! ALSO the cams must come out if the valves need adjustment.

Most idle speed problems on the 16V engine are from the air flow housing SENSOR! It can also cause starting problems.

#6 09-18-2002, 06:39 PM

I notice no discussion here of fuel system issues such as leaky injectors. With a start-stall or long crank before start, isn't a quick leakdown test helpful?

#7 09-18-2002, 09:18 PM

M.B. Doc: Thank you.
Richard: Thank you.

I've decided not to take my car back to the mechanic who has not been able to solve my start-stall and long crank problems after repeated attempts. My problem is how to proceed. Is my best option to take the car to a M-B service center and have them try to fix the problems?

M.B. Doc:
I've noticed one more thing: when I shift to neutral (my car is a manual shift model) the RPM does not drop right away but stays at about 2500, then gradually settled down at my current idle rate of 1400-1500. Does this help you to further diagnose what could be my problems?

Yee-Fun Yin
'87 190E, 23-16
'84 Alfa Romeo, GTV6

190dee · #8 09-19-2002, 02:58 AM

MB.DOC: Are there any special tool requiered otherwise? I would appriciate if you could tell us the metods on how the measure what shim to use.

I got some clattering valves and would really get rid of the noise as quickly as possible.

mbdoc · #9 09-19-2002, 08:10 AM

Valve adjustment on a 16V isn't a diyER. Just having enough shims to make an adjustment will cost $150. Plus most people wouldn't have the expertize to remove & reinstall the cams to exchange these shims when needed.

Again MOST idle problems are related to AIR flow SENSOR problems.

#10 09-19-2002, 09:23 AM

I agree with the doc on all issues noted here. Used to do Jaguar and VW OHC adjustments and taking cams out and back in, sometimes twice, is no Saturday party under a tree. To the guy in Finland, US version 8V engines are hydraulic autoadjusters, so valve noise is a larger issue than adjustment.

If your local guy doesn't have MB tools and serious training, the road to fining the problem can be long and expensive. European system philosophies, combined with MB's almost isolated approach to vehicle systems offers problems to the average technician that are not easily solved, even with the right manuals. If you don't have a serious indepenent shop, pay the fees for dealer service. It will likely save your sanity in the long run.

#11 09-19-2002, 10:35 AM

M.B. DOC: Once again, thank you!
Richard: Thank you for your advice.

I was debating whether to take the car to an independent shop or to the dealer, but now I am certain to take the car to the dealer. All of your advice and suggestions are well taken and I do appreciate the discussions. I don't want to go down that long and expensive road to fixing the start and idle problems because I am not confident that my independent mechanics are familiar enough with this car.

I will post the results later when the car is fixed.

Sincerely,
YF Yin
'87 190E, 2.3-16

Tinker · #12 09-21-2002, 07:37 PM

I have to disagree with the opinion that adjusting the valves on a 16V is difficult or beyond the skill of an average do it yourselfer. I adjusted mine a month ago when several of them were tight. I know there is a few other members on this list that have also adjusted their own. It is more complicated than a typical motor where there is an adjustment nut. But if one proceeds carefully and measures the clearance before and after there should be no problems. You can usually juggle the shims around so you will only need to buy a few. They are about $3.00 a shim.
The intake will usually be ok, but the exhaust will get tighter.

My $.02.

Tinker

mbdoc · #13 09-22-2002, 08:15 AM

The shims list for $6.00 & dealer cost is $3.80. Also as stated this isn't a DIYer for most week-end mechanics. Have seen seen several techs BREAK camshafts trying this job.

meek · #14 09-22-2002, 07:19 PM

M.B. Doc-- stupid question, but where is the AIR flow SENSOR located and what do I look for? thanks.

190dee · #15 09-23-2002, 03:36 AM

The air flow sensor is located under your air filter housing. The air filter housing is directly attached to it. You can't miss it. It's the funnel with a plate in the middle. The plate in the middle is sucked down by the air that passes it and this gives info to the ecu on how much air the enging gets.