Engine Shudder in cold

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CKemahli
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Hi all,

Has been a while since I've been here. Thanks to Arnie who very kindly gave my G a once over before I drove her to Turkey and pointed out the lack of transmission fluid!! Revs down - Power up after that mistake! She is now back in London but with a little issue:

Anyway onto my reasons for being back!

Car drove to turkey and back, no issue. Took all the rust out of her and repaired body panels, checked the mechanics and all was well.

Recent changes:

Took head off, checked pistons, new gaskets and new timing chain. Engine purring, pistons almost looked brand new.

Thermostat is now reading very low. Rev counter not working.

In the morning the engine shudders quite noticeably, even in Park, after about 20 minutes when engine warm (although needle not in middle) the car works fine and engine performance is normal, I think. Initially I thought gearbox as it happened when i set off and the moment it jumps up a gear it seemed to be less of a problem, its most of an issue at slightly higher revs, but without a working rev counter i cant say for certain what they are.

What do you think it could be? 

Injectors? Spark plugs (they are 6 months old)? I have a feeling it is something to do with this thermostat issue and that the engine isn't getting up to proper operating temperature but i'm afraid I am not mechanically minded enough to figure it out.

Thanks as always!

CKemahli
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Re: Engine Shudder in cold

Sorry, should say:

Car is a 280GE 1987

Pistonhead
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Re: Engine Shudder in cold

As a 'had been mechanic' I would like to know the Valve clearence are not too tight but that requires the rocker cover to come off and checking idealy on a stone cold engine. Bar that if the idle speed is low and irractic until the vehicle begins to warm up suggests to me that the fuel mixture is too lean and or the fuel enrichment is not happening which could be the fuel enrichment injector issue either electrical fault (at the injector or coolant temperature sender unit - sensor is not the same as for the coolant temperatur gauge reading) or the injector itself.

Associated with the same, the warm-up regulator could have issues or more likely false air leaking into the inlet tract. Likely false air breeches occur at the warm-up regulator with the vacuum pipe to it from the inlet manifold coming off at the regulotr itself or by the inlet manifold side. Then there are some pipe truncking under the inlet manifold itself that usualy is adrift or frail, these are not easy to see but the best way to identify this sort of leak is by carefully spraying some brake cleaner (perfreably an aerosol can) around and under the inlet manifold area and note for the engine to pick up speed or run better. Word of caution, brake cleaner is flamable so you DO NOT go spraying near or at ignition coils, sparkplugs or leads, even distributor caps. The spray fumes can easily ignite and flame up.

As you have mentioned your thermostat could be an issue but will not effect in irratic runing only give higher fuel consumtion, the engine shold start warming up in about 10 minutes or so and at normal operating temperature the needle should be sitting at the top part of the digit 8 of 80 degrees celius on the gauge which is about 85 degree to 90 degrees. 

CKemahli
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Re: Engine Shudder in cold

Thank you Pistonhead. I passed your words to my friendly mechanic and we decided to initially replace the thermostat.

As such - New thermostat, car warmed up in 5/10 minutes and I set off....the shudder returned, most noticeably as it tried to change gears. However it would also shudder in neutral after I pulled over. Fearing something needed to warm up more I waited for a little longer before setting off and as before the shudder passed after about 20 minutes of idling.

Having a proper heater does feel great though!!

Arnie
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Re: Engine Shudder in cold

When the engine is cold, the idle speed is increased through the cold-start enrichment device. The idle-speed will then drop when the engine is warm (about 20 minutes, as you say). 

It seems that at low-rpm, the engine vibration is not sufficiently damped by the engine mounts.

Check engine and gearbox mounts. If original, they are probably passed their useful life. You may also find that one or more have split.

Try to rock the engine when cold, it shhould move a little, but you should feel a good amount of resistance.

If you have even compression on the cylinders and all spark-plugs are all firing, it's likely to be an engine-mount issue. (unless you have not replaced the timing-chain with the correct alignment, which could lead to rough idling.)

 

 

CKemahli
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Re: Engine Shudder in cold

Hi Arnie,

Sorry for not responding sooner. We have given the mounts the rock test and the engine seems fine.

The shudder is still present with the new thermostat, we checked the hoses going to the cold start system and one was a little loose and has been fixed.

 

Alas this hasn't solved it, the car backfired today when it was at high rev still quite early into a run. It hadn't shuddered this morning so I had set off immediately only for it to backfire and then I saw and waited for it to warm properly once more.

My garage is keen to check the injectors, my uncle who is rather car savvy says perhaps it is a water temperature sensor failing and causing the choke to stay engaged. I have no idea whats the best course of action and dont want to throw good money after bad.

 

CKemahli
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Re: Engine Shudder in cold

Sorry - just a follow up - does anyone have experience with a malfunctioning Warm Up Regulator?

ErnestTBass
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Re: Engine Shudder in cold

I got my WUR rebuilt by http://www.kmipetrolinjection.co.uk/ and the fuel distrib checked ( was ok) (these guys are very good!!)

Also check the AUX AIr Valve is open at the right temp and all the vac pipes are sound (there are a lot under the inlet manifold and they rot!!)

injectors arent worth cleaning - just replace them. (they are expensive to clean and you still have old injectors)

The whole injection system is vaccum and fuel pressure, if any of these are off it wont run well (so fuel pump and filter must be ok as should the operation of the fuel distibutor.

gooch
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Re: Engine Shudder in cold

Hi, just reading your post etc.

Have you gone over your Ignition leads? Distributer cap? Rotor arm?

This stuff that can make the engine behave irraticaly.

Petrol model right?

prwales
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Re: Engine Shudder in cold

K-jet is a closed system, worth checking for an air leak too

CKemahli
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Re: Engine Shudder in cold

So a little follow up.

I had the WUR inspected - no problems.

I took the fuel injectors to KMI and they gave the whole system a once over and although expensive I’m happy with the quality of the work.

Problem is - shudder is back. I drove her around the day I collected her and no problems but today same issue. Low power, shuddering under acceleration, won’t change up, and then a back fire and bit of smoke. My next step is fuel pump and filters as I don’t know the last time they were changed. I’ve read the other suggestions but nothing quite yet fits with my problem. When she is warm it’s as if she’s a new car, smooth running - good acceleration and very calm drive. It’s this initial 20 minutes that’s the problem.

Jdring
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Re: Engine Shudder in cold

A bit strange.  I feel the frustration.

Asides from the previous comments - I had the timing on my 230 checked and it was 6 degrees out !!  But it had been running fine with it, just better after correcting it!

Given the backfire, I am wondering if timing is an issue (unburnt fuel in the exhaust cycle, igniting), or fueling/injection.

I am not a mechanic, but played with a few things over the years. 

Oil on the spakplugs - dripping in from the valve seals? Would cause problems and burn off once warmed up?  Valve seals are common to service.

-jd

 

michaelrozzell
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Re: Engine Shudder in cold

If it were me, i'd take it to someone who really knows their stuff. I mean someone with a Rolling Road dynomometer (dyno). Quite a number of years ago I had a 20v Audi 90 quattro which I was looking for more power from. I took it to Owen Developments Oxford. Whilst there I spotted a Mitsubishi GTO and chatting to the guy who ran the dyno he said it was a standard vehicle that had been in and out of a couple of garages where they had been diagnosing one problem after another, owner throwing more & more money at it but problem still remained. Eventually he'd brought it to OD and they'd resolved it pin-pointing the exact problem straight away.

Might be worth a try?

 

CKemahli
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Re: Engine Shudder in cold

Thanks for the ideas.

The care has had the valve stems replaced and she is now in Mercedes, they have noticed a leak on the injectors, it would explain the fuel consumption but not sure it would rectify the original shudder in the mornings.

What confuses me the most is that the problem is only for 20 minutes and then you can drive her for days. Any timing issue I feel would stay with her throughout the journey.

Hoping Merc can identify the issues as I am now at a loss as to what to do.

Jdring
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Re: Engine Shudder in cold

I am sticking with the Valve stems/seals being the issue. Once stood for a bit it will be sticky and lumpy running, and you would see blue smoke in the exhaust until burst off and clear.  Then if use regularly you might nt see it shudder again.  

See what the garage says.

Arnie
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Re: Engine Shudder in cold

read this

 https://www.zeepoort.nl/jetronic/K-Jetronic-troubleshooting.html

and then double-check the warm-up regulator. it's one of the few things that alters the fueling within the time period you mention.

your issue sound like a fuelling problem.

CKemahli
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Re: Engine Shudder in cold

Thanks all for your messages. I have now sold the car but worked with the new owner on fixing this issue. Turned out - tappets and timing was off, warm up regulator needed adjusting, leak on the injection system and worn injectors. All together they caused the issue and now shes running as sweet as anything and I regret selling her! But with ULEZ coming I had little choice...

Jdring
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Re: Engine Shudder in cold

Thanks for updating.  Good to know.

My old 230GE was about 6 degrees out with its timing and still ran, but lacked power!  Much better when corrected.  Tappets expand as they warm up, so maybe you had too big valve clearances which improved with expansion?  But probably that warmup regulator helped a lot too.