When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I need your help regading a problem on my car that I've tried to solve since 2 years ago.
I'm owner of a W126 500 SE 1982 european versione 170Kw with no catalitic coverter (Engine M117963)
After a thousand of jobs done, The engine is still shaking only in idle. I've swapped all this parts:
- Spark Plugs cables (Bosch)
- Rotor brush by Bosch
- swapped 3 times all spark plugs with NO resistor version (Tried Bosch, Denso and Beru).
- New distibutor cap (Bremi one first time and now a brand new Bosch)
- all fuel injectors have been reppaced with original Bosch and also new seal.
- K jetronic refurbished and tested
- New OVP Relay
- Earthground checked
- Idle valve and related electronic module checked.
- Cilinder compression tested and are all ok
- New Bosch coil
- Tried to swap the TSZ module with a brand Hella one
Also the car has been checked by two mechanics but tit still has the same problem: when engine in idle it shacking a little bit and disappear when go up 1000 rpm.
I've tried to read forum all around the world but honestly I do not have any other idea on how to solve it.
Please do you have any suggestion or check to be done?
reading your list seems you checked everything but maybe:
how old is fuel and is it ethanol free?
you know full tank with good fuel?
Dear ygmn, that's a good question anyway: the car is driven everyday since 3 years ago when I bought it. In Italy we have only 98RON standard and I believe is ethanol free. Also I use to refule only on branded gas station such as: ENI, Q8 etc....
The only doubt is about the Hydraulic pin, part number A1160500480
As far as I know if worn could inpact on valve lifter. Some owners had this problems and when replaced they solve it.
you can remove valve covers and rockers to inspect those..
HEck should have been as part of rocker adjustment. ya feel the ball getting scored up.
But I can say back when these cars were newer and I Was a kid working on them we never changed this part.
We would remove heads replace head gasket and freshen head parts by dis-assembling and cleaning valves and inspecting and then having head machined and valve seats redone and then reinstal valves with the seating past and use that little vacuum cup on a stick to grind the valve back side to head seat to ensure a good seal.
Maybe need old school Shop Igntion checking machine
We had one on wheels, big a large tool box but would hook up exhaust sensor to measure for lean or rich.
Spark plug lead clamp type sensors to check spark timing of each cylinder and other things...
I dunno... maybe go back thru what you have done - and check for a bad part?
It happens where you get a broken new part.
No intake leak?
I would need to be there to suggest anymore with beer in hand
you can remove valve covers and rockers to inspect those..
HEck should have been as part of rocker adjustment. ya feel the ball getting scored up.
But I can say back when these cars were newer and I Was a kid working on them we never changed this part.
We would remove heads replace head gasket and freshen head parts by dis-assembling and cleaning valves and inspecting and then having head machined and valve seats redone and then reinstal valves with the seating past and use that little vacuum cup on a stick to grind the valve back side to head seat to ensure a good seal.
Maybe need old school Shop Igntion checking machine
We had one on wheels, big a large tool box but would hook up exhaust sensor to measure for lean or rich.
Spark plug lead clamp type sensors to check spark timing of each cylinder and other things...
I dunno... maybe go back thru what you have done - and check for a bad part?
It happens where you get a broken new part.
No intake leak?
I would need to be there to suggest anymore with beer in hand
WOW, I'm 100% agreed with you. Car has 190,000KM and is 41 years old so probably refresh heads, valves and all other parts is probably the best job to do.
Also yea, you're right. I have friends that after replace cables, spark plugs, thermostat etc.... found one of this not working properly!!! and them were brand new.
Anyway yes probably using and oscilloscope I could verify the signal on ignition cabling that were replaced with brand new Bosch but not 100% sure they were working.
Many thanks mate.....really appreciated your kindest help and sorry for my english not very good. Daniele
Check that the distributor does does not have excessive shaft wear such that you can grab the ignition rotor and move the shaft side to side. Will make odd things happen at low speeds in particular. Bushings for the distributor were readily available when I was fiddling with them 25 years ago. Monitor the signal made by the pulse generator and compare with what you see on an old school oscilloscope that is monitoring ignition primary and secondary. Coils get lazy, ignition boxes too. Lower the engine speed the more noticeable it is.
A flat cam lobe is not usually noticed at idle; but the tick-tick-tick of that rocker arm will be.
You didn’t mention fresh engine mounts. They help.
just an update: yesterday my mechanic swapped the injector holder with all 8 new one!!!
Unfortunately the previous mechanic ( As i mentioned in the car history) when replaced the injectors He has damaged the grommet.
The car was running as a tractor so I called a frined in MB and ordered all new injectors grommet.
Tomorrow will be the "day" and finger crossed, hope to solve this problem for ever!!!!
Very long story but I learned that injetors, holders and grommet are very critical and must be very careful when replacing.
Hello gentlemen,
here we go!!! The car is now perfect and you know what????
3 years ago, the mechanic installed the injector grommet wrongly and the seal was worn.
Anyway now ids runnign very smoothly, no more shaking in idle and i believe looks like to be brand new.
As sson as possible I will post the "coin test" putting it on the head while running in idle !
I would like to give my thanks to all and I really appreciated suggestion, indication and mainly how you're so expert!!
EGR reduces temperatures in the cylinder by adding inert gas to take up space when the mixture gets lit. This reduces formation of Oxides of Nitrogen.
In practice as things get old EGR passages and the valve itself get plugged up with carbon. This can make for zero flow or a leaking EGR valve which can make for low power and a rough idle. Apply vacuum to the EGR valve at idle. Idle drops or it stalls? EGR is able to flow. Checking for a small leak is best done with a temperature toy you point at the base of the EGR valve after starting from cold. Does it very quickly heat up at idle? If so it is leaking.
EGR reduces temperatures in the cylinder by adding inert gas to take up space when the mixture gets lit. This reduces formation of Oxides of Nitrogen.
In practice as things get old EGR passages and the valve itself get plugged up with carbon. This can make for zero flow or a leaking EGR valve which can make for low power and a rough idle. Apply vacuum to the EGR valve at idle. Idle drops or it stalls? EGR is able to flow. Checking for a small leak is best done with a temperature toy you point at the base of the EGR valve after starting from cold. Does it very quickly heat up at idle? If so it is leaking.
Dear John, sorry for my delay. No, teh temp raise normally. Anyway I've tested the EGR and after 41 years it'n not roking anymore but "VERY IMPORTANT" remain completely closed.
Anyway the car, after 150 miles, it's running very smooth and the shaking seems more ore less desappear.
Despite I've swapped all ignition parts, I'm still pretty sure that the problem could be not enough power on spark plugs and thus could affect the combustion on idle. What could be? I have no idea because evething has been swapped including:
- Bosch Coils
- Bosch Spark cables
- NGK Spark plugs (3 times) using the NOT resistor one.
- Bosch rotor
- Bosch ignitor cap
- Hella TSZ ECU
- New OVP Relay
- Check all earthground.
The only part that I didn't change is the green cable from TSZ ECU to the distibutor
But I0ve checked the impedence and seems ok.
The only check to be is to find a mechanic with the old hoscilloscope to check the power discarge in every cable but where I'm based (Rome/Italy), is veru inusual and difficolt.
07-17-2023, 08:03 AM
