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Engine Specific Info and Questions => IDI Engine => Topic started by: CarlosA on November 03, 2012, 01:47:53 am
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I've been working on my 1979 rabbit with a 1.6 NA engine for a while now. I got it on the road about a month ago and have worked out almost all of its issues. The final mechanical issue i`m dealing with is the vibration at idle. This one is literally driving me crazy, anytime i`m at a stoplight the vibration is so bad my fingers and toes start to go numb.
Obviously these engines shake and whatnot, but compared to my 1978 its night and day.
Here are some of the things i`ve tried, and obviously something is missing from this list that will be a solution... What has worked fro you guys?
- Rebuilt & balanced injectors (two sets tested)
- Changed all motor mounts
- Shimmed the front core mount til snug - no change
- Idle speed set with a digital tach at 894.5 rpm which is slightly high
- Vibration vanishes at 1000 rpm and above
- Checked and tightened every single bolt in the intake/exhaust/IP
- Engine was also rebuilt during the summer compression is flawless
- I`m sure i`m forgetting some little things
Now besides that stuff here are some other details:
Engine had a seized rod on #1, I replaced this and the crank - rebuilding everything else
Car runs and drives great, it has about as much power as I expect with the lower geared ACH 5 spd over the old GC 4 spd
Lately I blamed the entire issue on air in the lines, eventually tracking down and fixing that issue entirely - clear lines everywhere including return, and replaced the in tank pickup screen with new
Final detail ... I can't get the engine adjustment perfect according to bentley no matter what - it seems like it needs to slide back slightly more to be perfectly centered in the mounts, it just wont happen.
Last weekend I feel like the vibe was gone during a 250 mile trip, returning in the last 50 miles or so. This is immediately after changing the last motor mount on the passenger side. Tonight I re-adjusted engine and made sure all bolts were snugged up. No change, maybe slightly worse.
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What's the IP pump timing set at? Someone can correct me here cause I'm no expert but I want to say mine felt rough at idle but otherwise fine with slightly retarded timing.
Opening up a can of worms on myself I'd try a little more advance to see if it goes away. ::)
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Thanks for response. Running at .95 now after several trips from .87 to 1.05, 1.15 etc. Also no change with cold start advance. 107 AG IP is on my list to dig deeper if no other solution found.
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I am having an issue like this in my jetta right now. Everything is the same on this car except I took the turbo out and its injectors/pump.
That setup would idle smoothly even cold(just cackled more).
So I got the injectors, and I will actually try another set that were rebuilt in a couple weeks. But for me it seems to point at the pump? This pump used to do its job and was left with some fluid in it while on the shelf. But it makes me think I should yank it apart and clean it. That has helped various issues with more than on pump in my experience.
Mine isn't smoking badly or "missing" but I will come to a stop sometimes and the whole engine is out of balance it feels like. If I rev to slightly above 1000 rpm it seems to smooth out.
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Yeah same here. ^ I think the pump could use a tear down. I'm 100% sure it's not leaking or sucking air, but never drove this car before the rebuild.
I should add that my car also starts easily - less than a crank hot or cold down to ~ 40 degrees. No trouble there and little smoke, mostly after I retarded it a bit.
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I would start by thinking of the bits you changed -
Engine had a seized rod on #1, I replaced this and the crank - rebuilding everything else
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You sound like you know what you're doing but I thought I'd ask - did you weigh the new rod against the other three? Is there any possibility the new crank is not balanced?
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As a relative neophyte, I would imagine an imbalanced bottom would have pronounced harmonic vibration throughout the rpm range, not just at idle.
My Caddy had a lot of vibration in the chassis even after new motor mounts. It was later revealed to have been improperly straightened after a collision.
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I would start by thinking of the bits you changed - Engine had a seized rod on #1, I replaced this and the crank - rebuilding everything else
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You sound like you know what you're doing but I thought I'd ask - did you weigh the new rod against the other three? Is there any possibility the new crank is not balanced?
Yes, but have also found that the balance is pretty far out on stock engines I have disassembled.
My Caddy had a lot of vibration in the chassis even after new motor mounts. It was later revealed to have been improperly straightened after a collision.
I got the title in the mail yesterday and opened it last night to see these big words:
TITLE BRANDS:
TOTALED
RECONSTRUCTED
lol ... maybe that explains the impossible engine alignment!
I`ll measure everything according to the Bentley and see if its something I can deal with.
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I just drove this car hard for a while, at one point climbing a hill I got some white smoke for a bit, cleared up and got some power back but everything still acts the same. Seriously thinking about pulling the pump and seeing what it looks like inside.
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What kind of rpms when the smoke got white?
Have you checked IP internal pressure? AIUI, if it's on the low-end, dynamic timing may not advance as much.
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I haven`t checked the pressure on this one. The flow is decent, I filled a quart container the other day before bottle feeding it to try and troubleshoot. Didn't take too long, about like my other car/pump.
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I was just out there feeling around while the engine is idling and really driving myself crazy over this. Here are some findings on a scale of 1-10.
- The engine is a 10/10 for reference
- The front end & bumper vibrates on a 8/10
- The firewall is perhaps a 6/10
- The drivers side inner fender near the mount is probably a 6/10
- Passenger side near the mount slightly less than above
- The steering wheel & pedals are a 8/10
- The shifter knob, doors, windshield, roof (outside), seats, etc are a 3/10 (fairly normal)
The front core support mount has been shimmed 3/4" to make it 100% tight - I don`t know if this is correct, I see that BFI has a thin maybe 3/16" shim available. I will probably unshim this because its not doing anything.
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If I rev to slightly above 1000 rpm it seems to smooth out.
If i set my idle at 1000 rpm totally smooths out for me 850 not smooth vibrates like crazy.
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If i set my idle at 1000 rpm totally smooths out for me 850 not smooth vibrates like crazy.
Yeah that would totally solve my problem too.
One strange thing I noticed that may point to the pump is... if I rev it manually, slowly moving up to there 1000 rpm should be, it doesnt change at all then spikes to 1000 then drops off even if i`m still holding the lever, anyone know what that is?
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I went through a special process of adjusting the steering column as well, it actually reduced the vibes a bit. Only odd thing was prying on the steering column to get it within spec also caused the linkage to rub on the clutch pedal, and the shifter linkage to be bound up. Very strange.
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If i set my idle at 1000 rpm totally smooths out for me 850 not smooth vibrates like crazy.
Yeah that would totally solve my problem too.
One strange thing I noticed that may point to the pump is... if I rev it manually, slowly moving up to there 1000 rpm should be, it doesnt change at all then spikes to 1000 then drops off even if i`m still holding the lever, anyone know what that is?
Do you know if anyone messed with the governor on this pump? Isnt that kinda what happens when you shim the intermediate spring... part throttle surging?
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If I rev to slightly above 1000 rpm it seems to smooth out.
If i set my idle at 1000 rpm totally smooths out for me 850 not smooth vibrates like crazy.
if i have my idle set to 800 rpms like the book says, stuff will jump out of the door pockets on my mk2 when the doors are open...
with a 1000rpm idle, its quite smooth..
my car is a mk2, totally different engine mounts (hydraulic) and it still vibrates like a paint shaker at low idle...
its the nature of these engines..
having a bent front end will really make it hard, if not impossible to align the engine..
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My car shook so hard at idle it felt like the front wheels were hopping off the ground. I set the idle to 850, pulled the stupid urethane inserts out of the new rubber mounts he put on, replaced the front an rear mounts with rubber ones, and aligned the mounts as best I could. Now it just tries to rattle the dashboard in half.
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My car shook so hard at idle it felt like the front wheels were hopping off the ground. I set the idle to 850, pulled the stupid urethane inserts out of the new rubber mounts he put on, replaced the front an rear mounts with rubber ones, and aligned the mounts as best I could. Now it just tries to rattle the dashboard in half.
why not turn up your idle 150 rpm?
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Yea i see no reason not to set the idle to 1000. I turned mine down to do it by the book and i see no benefit of it aside from an annoying massage.
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Because I'm the kind of hipster prick who likes to remind everyone around him that he's driving a diesel. Either that or it just doesn't bother me that much.
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Yet, another reason I hated the earlier bodies.
Set your idle up to at least 1,000. Make sure your exhaust has good rubber donuts (with closed centers) and get on with your life.
Better yet, move up to a Mk. II body.
Better yet, buy me out of all of my cars and mountain of parts and let me get on with MY life.........
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Yet, another reason I hated the earlier bodies.
Set your idle up to at least 1,000. Make sure your exhaust has good rubber donuts (with closed centers) and get on with your life.
Better yet, move up to a Mk. II body.
Better yet, buy me out of all of my cars and mountain of parts and let me get on with MY life.........
Alright so the consensus is that these things are not fixable. WTF. My 1978 is silky smooth with no vibes in the mirrors, steering wheel, or pedals. I did reduce the vibes on this car by about 40% by using an obscure steering column adjustment - but the dash still shakes like crazy.
I guess i`ll just live with it and stop throwing money at it. This has made me hate a vw diesel for the first time though.
BTW... what is in your mountain of parts/cars? :D
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Yet, another reason I hated the earlier bodies.
Set your idle up to at least 1,000. Make sure your exhaust has good rubber donuts (with closed centers) and get on with your life.
Better yet, move up to a Mk. II body.
Better yet, buy me out of all of my cars and mountain of parts and let me get on with MY life.........
next time I go west ill get a hold of you about parts.
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This car is excellent in some ways. After not driving for 5 whole days it just started right up in half a crank.
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Ok,
I'm going to chime in one more time about balanced parts. You said you changed a few rotating things and I never heard if you checked the weight of the new parts VS the old ones.
While it may be somewhat true that "out of balance" gets worse as RPM's increase (as was mentioned), there's a lot more to it than that - namely harmonics.
All the rotating parts in every motor affect balance. If the motor vibrates at a given RPM that's because something is "out" of balance at that RPM. There are bits rotating and stuff moving up, down, sideways and what-not. It's all a symphony of various parts and while some may be "in tune" at a given RPM, they go "out of tune" at others.
IMHO - If the motor vibrates at the Bently spec RPM, something is out of balance. "edit" You've done a lot of things to this car but of all the things you did, changing the crank and one rod are the things that could affect balance the most (unless you weighed the new rod against the other three and knew the replacement crank was balanced).
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Yeah the crank came from another engine that I ran. The rods & pistons are all balanced. I also mentioned that several engines i`ve pulled apart have had fairly wild stock piston & rod weights, these engines were by no means balanced and blueprinted in 1979. Further, just what shade tree mechanics like us are doing now, 30 years later is far more balanced than back then. Anyway, I did take care to grind a bit off the rods so they were all within half a gram, the pistons are a new name brand set. The final weights of pistons, rings, rods was within a gram of each other.
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Gotcha.
But it's still a balancing thing and no amount of jigging mounts and twisting frames will make it balanced at 850 - it may even make it worse. As you stated, several engines i`ve pulled apart have had fairly wild stock piston & rod weights.
That could mean that the engine (with various weighted parts) was balanced as a rotating mass and would explain why that engine didn't vibrate at spec idle (assuming it didn't).
If the engine was smooth before at 850 and the parts you replaced weighed exactly the same as the parts you took out then I would look elsewhere (Ip, injectors, mounts, etc).
Balancing reciprocal mass is tricky stuff. I really appreciate your post because I am doing a rebuild (possibly the slowest on record) and will need to deal with the same issues.
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Cranks are balanced individually to spin smoothly with no components attached. This is why the average person can balance their rods & pistons to be identical weights and avoid having to have the entire rotating assembly balanced.
This is basically why cranks often have balancing holes from the factory - not only to remove weight but also to be filled with Mallory metal (an alloy of Tungsten) to add weight to the crank.
Anyways, i`m sure I could have the entire engine balanced at a race shop and be light years ahead of what VW was able to do in a production environment 30 years ago. And I agree with you that balancing the engine could solve this problem, but i`m also not convinced - both because of the single RPM problem, and because factory engines are notoriously "out of balance" when compared to what a race shop will attempt to achieve. I have about a dozen rods sitting here and every single one of them is 1-2 grams different than any other rod, in other words no set was ever fully balanced at the factory
I guess i`m just trying to figure out why the car vibrates more now than it did 30 years ago, and hopefully find out for the community that a poorly functioning injection pump, bent frame, or something like that is causing the issue rather than just adding to the issue.
Edit to add that another engine I worked on (the silky smooth 1978) also had a rod, piston, and crank replaced without any other work done to the engine in 30 years. Totally forgot about that. The parts i`ve used to replace components are just good used parts from old engines - not a new Brazil crank or something like that.
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I agree with you 100% and to be honest, getting a motor balanced like a race engine (unless that's your use) doesn't make much sense.
Please keep us informed if you get it sorted.
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Will do. So far i`ve only made improvements on the *noise*. Not so much on the feel.
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I might start messing with delivery valves. I don't know how to "balance" them; but AIUI, they do subtly effect injection timing.
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I might start messing with delivery valves. I don't know how to "balance" them; but AIUI, they do subtly effect injection timing.
I have found shims for them, I am sure with an adapter made on a lathe you could test them. I think it would be more of a flow @ pressure test rather than a pop, since they don't open when hitting a certain pressure like a nozzle does.
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If I understand correctly, they are essentially check-valves to maintain static pressure in the lines between pump pulses.
Thinkin out loud...
Maybe a pop-test could be revealing if the delivery valves were placed inline - but the gauge would need to be between the Delivery Valve and the injector(same one is used to test all DVs):
Pump>Delivery Valves>Gauge>Line>injector
Pump until break/spray, read the gauge and watch for any leakdown. Compare readings between DVs.
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Good idea about the leak down - if they are worn that could be a big issue to the entire system. I have another set, i`ll swap them and see if it makes any difference - certainly can`t hurt to try.
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I've just been battling vibrations in my cabriolet with turbo'd 1Y engine too - but I've got it pretty nice and smooth now. The mounts I'm using are all OEM factory, all new except for the gearbox main mount, with the front radiator support mount being one of the larger diameter rubber ones that GAP sells.
Basically the process should be to remove the rear gearbox mount and the radiator support panel mount and let the engine settle on the two main mounts where it pleases. Then bolt up the rear gearbox mount using the slotted holes so that the engine is still sitting neutrally - then finally bolt up the radiator support mount with the 2 bolts on the chassis side loose, then tighten them after the mount has found the perfect neutral spot.
After I did all this its idling very smooth and right through the rev range.
FYI - i have a lightened machined but not balanced flywheel injectors that have not been balanced either.