Engine vibration at idle

[pogo]

The Golf starts and runs fine, except at idle, and then there's a lot of vibration. Replaced the engine mounts as they were getting tired, and it got a little worse.

Dug out my ISO-COM and VCDS and set the IQ to 4. I'd set it to 2.4 10 years ago for reasons forgotten. No help.

The thing that struck me as odd is that under Adaptation Ignition Timing, the IDLE timing being called for by the ECU is > 5deg BTDC at 903 rpm. The IP is providing that, and I suspect that's the cause of the engine vibration.

As soon as the rpms go up a couple hundred, the timing advance drops down below 4, and the engine smooths out. At higher rpms its around 2 deg BTDC, and then starts to advance again at much high rpms, which is what my intuition tells me it should look like.

Why could be the ECU call for such advanced timing at idle? The temperature shown on the IQ seems accurate. 79C after 15 minutes drive. Any suggestions for sensors to check?

 

[pogo]

Meh, I think I misdiagnosed the link between advanced idle start of injection and engine vibration. I manually tested settings down to 2 deg BTDC and there was no change in vibration. Yet the engine is smooth at just a couple hundred rpm more, and if its in gear engine braking at just above idle, it seems to be smooth, but its hard to tell.

I'll need to find a VCDS guide for the engine to determine whether any of the available data points to a problem. If anyone knows of such a resource, pointers would be appreciated.

Thanks

 

[sisyphus]

I don't know. Is 5 deg BTDC that advanced? Makes me wonder what mine is.

 

[Razorthirty]

Bad DMFW can cause strange vibrations. If your flywheel old?

 

[JETaah]

^^^.

If the Group 13 injector balance looks good I would suspect the flywheel, too.

 

[golffriend]

I want to share my experience about PD engine cut off after partly warming up (and not starting after), because it has a simple

cure. Sorry for bad english. I am not mechanic, but have some experience.

After long time spent testing fuel lines, connections, after drilling output valve from fuel tank I found air collecting in fuel

lines (inserted clear lines temporarily) when engine is warming up. Air (blow-by gasses) are pushed to fuel near injectors through

bad injector seals and possibly injectors itself. Strange that disconnecting good MAF sensor solves it frequently or I am thinking

so... Possibly only in some circumstances in function of air in fuel quantity, air pressure, engine temperature, how long tried

cranking before. Worth to try if nothing helps, it is faster than 1 minute on starter but with (good) MAF...

When gasses are collected in fuel and fuel with gasses is compressed by tandem pump, nothing bad happens. But when fuel

temperature reaches thermostatic T on fuel filter setpoint and engine temperature needle comes about 1 sector before vertical

position "90 C" (it corresponds real engine temperature higher than 75C - not real 90C) - be carefull! If you let RPM sudden drop

lower 2000, and at that moment T opens, compressed air would expand to tank but before it would be pushing fuel from fuel lines and

filter, so warm engine would die and not start. Needs priming fuel lines.
If you dont let RPM drop, pressure would be maintained, fuel effectively sucked from tank by pump and engine not dies, only short

unstability in T opening moment. So, engine dies only at that temperature!
When you started warm engine, T opens faster (so gasses are not at critical level collected because of shorter time before T

opening) and engine runs fine without T modification. Until it cools to negative temperature (actual only in winter season).
Tip: if problem persist and you can not drill T at the time, please dont push on gas pedal when engine cold - that forces blow-by

gasses to fuel at higher rates! And so with MAF connected (I think). And long cold engine idling helps for air in fuel collecting

(low heat, longer time T closed). Problem more actual in lower temperatures because of longer T closed time ant more advanced (and

longer) fuel (and gasses) injection.

Real simple cure is to drill 1mm hole in thermostatic T in/out ports through, letting to pass blow-by gasses to tank in all

temperatures (through hole, when engine is cool; through open T when engine hot). It is all. No problems after that. Bigger hole

would be bad because of fuel temperature drop in warming up stage. 1mm is sufficient, letting about 1 l fuel in 1 minute through

(if on higher pressure side, tandem output with T closed - tested). That cure I have read, but here are my explanations of process.
--------------------------------------------------------------------------------

And about hard cold starting because of air in fuel (not blow-by at this time): air sucked to fuel lines past the same injector

seals (?) or other weak points - only when fuel in tank cools down to negative temperatures (some negative pressure in tank air?) -

when engine is long time shut off. Hard starting after long trip with near empty tank (in winter)- because of that suction to

tank, when air in tank heats and cools in cycles.
Cure - mounting cut off electric valve in return to tank fuel line. This not passes fuel to tank (when engine shut off only), so

no air in lines after cold night. When ignition turning on, valve must open. Be careful - valve must pass fuel when engine is

running and hot. Fuel temperature must not exceed max limits. Valve must be operational. Good choise is brass valve with emergency

manual open function (from gas equipment).
Possibly- new, not used fuel filter thermostatic T closes (slowly, when engine shut off and cools) - so good that build some

vacuum in tank (cools more quickly than T) stays closed from return fuel line and fuel stays in lines. But old, used T has more

free play inside it and with slow vacuum build up does not close fully (there isn't any tandem pump pressure). So air could be

sucked to fuel lines. That is suggestion, needs testing.
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My 2000 1.9 TDI PD has no fuel lift pump in tank. Lift pump would be usefull for light cold starting (no need in electric valve in

this case). But trapped air in fuel system stays there all time till engine and fuel heats up to the moment when T opens. Fuel with

air will circulate through fuel filter with or without in tank pump (if blow-by gasses accumulates). Only new tandem pump possibly

could deliver normal fuel flow at the T opening moment (worst scenario), but not in all cases. Air still is there. Small hole in T

could be made from factory.

Possibly you have air in fuel.

 

[UhOh]

When you're getting that vibration disconnect your MAF and see if that changes anything.

 

[Rembrant]

Meh, I think I misdiagnosed the link between advanced idle start of injection and engine vibration. I manually tested settings down to 2 deg BTDC and there was no change in vibration.

Yeah, I wouldn't be too concerned with the timing you're seeing with regards to engine vibration. I have my timing advanced a couple degrees in adaptation, and this time of year (when the fuel is colder) the timing advances another couple degrees, so I see 5*BTDC at idle all the time. In the summer it's more like 3*BTDC, and with the adaptation removed it's more like 0-1.5*BTDC.

I can't tell you why your engine is vibrating, but I can tell you that it's not likely the timing.

Rem

 

[UhOh]

I'm going to toss this one out there because it's something that one normally wouldn't look for...

Check your fans. Look to see if either of them have broken outer rings. You'd only notice an issue when the fan(s) ran. I had this with my wife's car and it drove me nuts; even was starting to suspect the DMF. It's amazing how one of these fans can transfer that unbalanced vibration to the entire car. I'd have never imagined it possible.

 

[pogo]

If it's the dmfw (original) the car gets the heave-go cause it's too much work to replace. But it might not be as there's no of noise or difficulty engaging the clutch, just vibes between 900 and 1000 rpm. Injectors seem balanced. That is, the adjustment for all 4 is different, but an order of magnitude less than the total IQ. I'll get the exact numbers, and try the other suggestions, this weekend.

Thanks.

 

[pogo]

Well, its 3 weeks, and $1700 later, and there's still a vibration at idle. And I get to eat my words from my last update.

- its not the MAF sensor
- its not the Dual Mass Flywheel (the 02J transmission failed, and my mechanic put in a used tranny with a new LUK DMF kit, and rear main seal.)

The only headway I've made on this is that it appears to be directly linked to cold intake air temperature. It the air temp is > 50F, the rough idle is gone. The colder the air is below that, the greater the idle vibration.

Whether or not the engine or turbo are warm doesn't make a difference.

Is there an air intake temperature sensor? I thought that was built into the MAF sensor, but I put a new one in, and it made no difference.

 

[Ill Named]

I just changed out all the motor mounts in my wifes 03. The dogbone mount was a Lemforder and stiff. That car now vibrates pretty good at idle too. It is worse when it's cold outside for sure. I'd be willing to wager that that is your issue...

 

[JETaah]

Well, its 3 weeks, and $1700 later, and there's still a vibration at idle. And I get to eat my words from my last update.

- its not the MAF sensor
- its not the Dual Mass Flywheel (the 02J transmission failed, and my mechanic put in a used tranny with a new LUK DMF kit, and rear main seal.)

The only headway I've made on this is that it appears to be directly linked to cold intake air temperature. It the air temp is > 50F, the rough idle is gone. The colder the air is below that, the greater the idle vibration.

Whether or not the engine or turbo are warm doesn't make a difference.

Is there an air intake temperature sensor? I thought that was built into the MAF sensor, but I put a new one in, and it made no difference.

Intake air temperature sensor is combined with the manifold air pressure sensor. It is mounted on the top of the intercooler on your car.

 

[joep1234]

Have you checked the alternator pulley and idler? Mine went bad and had my car acting up. Replaced both and then was able to tell my DMF was bad as well.

 

[eddieleephd]

Just because I saw the post recently I want to throw the thought of the Fuel Temp Sensor out there. Sounds like a possibility and its $20 -$40 World Impex - dealer.
http://forums.tdiclub.com/showthread.php?t=75308