Timing and fuel economy

I put in a new timing belt about a year ago. Since then the fuel economy doesn't seem to be where it was before. I am at about 38-40mpg now and was at 42 then. I have a 2002 beetle 1.9tdi. The belt broke on me and I had to rebuild the head. Everything seems to work fine except when I start the motor it has white smoke and idols rough. Once it warms up its fine. I timed it using a Vag-Com and it says its fine. I even advanced the timing a little and that just made the engine louder. That is another thing I believe the engine to be very loud now compared to before. I am wondering maybe the mechanical timing (i.e. crank and cam) are not right. I read somewhere I am supposed to use a dial indicator in the first glow plug whole to get this within .005 btdc but I am not sure. Any help would be great.

Toughguy19 said:

I put in a new timing belt about a year ago. Since then the fuel economy doesn't seem to be where it was before. I am at about 38-40mpg now and was at 42 then. I have a 2002 beetle 1.9tdi. The belt broke on me and I had to rebuild the head. Everything seems to work fine except when I start the motor it has white smoke and idols rough. Once it warms up its fine. I timed it using a Vag-Com and it says its fine. I even advanced the timing a little and that just made the engine louder. That is another thing I believe the engine to be very loud now compared to before. I am wondering maybe the mechanical timing (i.e. crank and cam) are not right. I read somewhere I am supposed to use a dial indicator in the first glow plug whole to get this within .005 btdc but I am not sure. Any help would be great.

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"Vag Com says it's fine". Could you be a bit more specific, as in exactly where in the graph you are currently plotting??
"Dial indicator in the GP hole"/"within .005 btdc"??? Did you do this TB job yourself, and if so did you have the proper cam lock tool, etc.?
If the cam is not locked into place EXACTLY right you can have VAG Com readings that show "timing within spec" but still have cam/valve timing off resulting in poor preformance, mileage, starts, etc. etc... In other words the IP might be injecting at the proper time, but if the valve train isn't in the correct time-well it won't be good.
Who rebuilt the head?? How extensive was the damage?
Lots of potential issues here, need more info.

finally getting back to this

I did have the proper tools but the belt was already broken so everything was misaligned. I believe you are correct with the valve timing being off. If this is the problem what is the procedure to fix this issue. Any help is greatly appreciated. I do know now the engine is very very loud. We have compared it to several other TDI's and it is alot louder than they are. It seems to be like the diesel knock sound that is very loud. I would love to quiet this thing down to a less noticable roar. Thanks for any help.

If everything was all mangled up and torn all apart what was replaced ?? Did you measure piston protrusion ?? Were the pistons & rods replaced ?? IF not how bad were they imprinted , were the rods checked for straight ??

All could figure into fuel consumption now . Loud means combustion is taking place late , ATDC . Lower peak compression can lead to this .

Toughguy19 said:

I did have the proper tools but the belt was already broken so everything was misaligned. (snip)

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__. If you had the proper tools, it wouldn't matter if the parts were misaligned. In fact, the proper tools will make all new parts align properly when the timing belt system is being installed. Did you use the cam lock and crank lock and also the injector pump pin -- and follow the process to loosen the cam sprocket? If so, your mechanical timing is correct (unless there was an error somewhere else). If not, the mechanical timing is almost sure to be off.

I did not have a crank lock. I did have a cam lock and injector pump pin. Also nothing was mangled. We assumed it would be and took it apart, but everything was good. No marks on the head or valves nothing. I brought it to a very good machine shop in town and they rebuilt the head. (since I had it out I figured I might as well have it rebuilt). I did do the timing myself and figure the odds are that I am the problem in the equation. To get the crank in the right position would I have just lined up the marks and locked in place or is there more to it? My guess is that the crank is off.

Toughguy19 said:

I did not have a crank lock. I did have a cam lock and injector pump pin. Also nothing was mangled. We assumed it would be and took it apart, but everything was good. No marks on the head or valves nothing. I brought it to a very good machine shop in town and they rebuilt the head. (since I had it out I figured I might as well have it rebuilt). I did do the timing myself and figure the odds are that I am the problem in the equation. To get the crank in the right position would I have just lined up the marks and locked in place or is there more to it? My guess is that the crank is off.

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Or the cam...
I don't know where to begin-but let's try this.
Under "Articles" scroll down to:
TDI How Tos....
A4 Timing Belt Change:
Print it and read it a couple of times.
It will cover ALL the steps in the order that they should have done and MUST be done. Much more detailed and concise than I ever could try to be.

Try not to ridicule and add to the problem but possibly put an idea out and maybe help in solving the problem.

He's asking for help not ridicule.

Cya

J.R. FEIK said:

Try not to ridicule and add to the problem but possibly put an idea out and maybe help in solving the problem.

He's asking for help not ridicule.

Cya

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Are you reading the same thread I am? No ridicule that I can detect and no-one has edited their posts. Seems like good serious advice posted so far.

Bill

Toughguy- When you lined up the crank marks, did you use the flywheel marks observed through that hole in the flywheel housing? Those are the ones to use but are a bit of bugger to see. -Eric

Ski in NC said:

Toughguy- When you lined up the crank marks, did you use the flywheel marks observed through that hole in the flywheel housing? Those are the ones to use but are a bit of bugger to see. -Eric

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__. Yes, it's *possible* to get proper timing without locking the crank but you must be extra careful. That crank just *luuuuvs* to slip and wiggle out of the best position. And if it moves and you lock the cam sprocket down, then you've "preserved" that mis-timing. You can do a good job without the crank lock, but a policy to use it is probably a good thing.

Just a comment and nothing more!

I have changed the TB on my Jetta twice. Now, read close!

Neither time did I loosen any sprockets. I just released the tensioner and slipped the old belt off and "wiggled" a new belt on. Of course, I used the crank lock, cam lock and pin for the IP. I have never checked the IP timing, etc.

I have been told that I was doing it all wrong. Maybe so, but my engine runs great, almost 51 mpg life-time average. And, at 237k miles, I believe it has performed very well.

A side note: I have changed my brother's TB once using the same procedure and his car performs equally well!

mrGutWrench said:

__. Yes, it's *possible* to get proper timing without locking the crank but you must be extra careful. That crank just *luuuuvs* to slip and wiggle out of the best position. And if it moves and you lock the cam sprocket down, then you've "preserved" that mis-timing. You can do a good job without the crank lock, but a policy to use it is probably a good thing.

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I do have the tool to do this but I never use it but I have close to 30 years of doing this without it . It does take experience to do it without locking the crank . But you must always use the cam & pump locking tool .

You must have the crank set a few degrees early before tightening the belt . As it tightens up the crank rotates into proper alignment . And you must rotate the engine at least 4 rpms BY HAND to check for no resistance to rotation . Then recheck the timing to see that the locking tools slip in without effort and that the flywheel mark is lined up properly .

If not properly aligned you must redo the entire timing procedure from the start . And in my experience with the current sprung tensioner it takes two tries to get it correct even if you do it right the first time . The tensioner marks misalign after the first rotation . I have not yet done one of these with a sprung tensioner without this happening the first try . There is a way around this happening but I wouldn't suggest it . You can slightly over tighten it to avoid this but if you over tighten it too much you will ruin the tensioner . I wouldn't recommend doing that as it can damage the tensioner beyond resetting the timing correctly if you aren't right the first .

Also you must always take the cam pulley loose while timing the engine up to get it correct . Failure to take the cam pulley loose will make the timing off when re-installing the T-belt , new of the old one .

Any error in timing , cam shaft , crank shaft or injection pump pulley can make the engine hard to crank and effect fuel consumption . Also injection pump timing error can lead to over boost leading head gasket failure and turbocharger damage . Also leading to crank case over pressure which can cause oil to be spewed into the intake leading to an overrun condition , a run away engine .

rotarykid said:

I do have the tool to do this but I never use it but I have close to 30 years of doing this without it . It does take experience to do it without locking the crank . But you must always use the cam & pump locking tool .(snip)

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__. Thanks, RK, you described what I was trying to say -- and did it much better than I did. I hope that we've adequately informed the prospecitve first-time installer about the critical nature of the timing and the importance of following the process.

mrGutWrench said:

__. Thanks, RK, you described what I was trying to say -- and did it much better than I did. I hope that we've adequately informed the prospecitve first-time installer about the critical nature of the timing and the importance of following the process.

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Yes, a good job-better than I could ever do. That is the reason for the suggestion to read/re-read the how-to. There was no ridicule in that suggestion or in my previous posts.
Hope he gets it resolved.

Hey jettawreck, I apologize for accusing you of any ridicule in any of the posts. I reread the posts and I misread before.

I'm sorry....Thanks 40X40 for pointing this out.

There is always excellent advice given out on this forum.

Cya

Thank you very much for all of the help. I dont take anything as ridicule. Firstly I did the timing before finding this website. I would never do anything now without one of the how to guides. I have read the timing one over and over actually (well after the fact) to see what I screwed up. This site has helped me realize I'm not working on a chevy 350 here I need to be precise and ask for help before I do something not after. But to answer my original question. Would the car run and get 38 mpg if the timing was off one tooth? Would it be loud but run ok after warming up?

J.R. FEIK said:

Hey jettawreck, I apologize for accusing you of any ridicule in any of the posts. I reread the posts and I misread before.

I'm sorry....Thanks 40X40 for pointing this out.

There is always excellent advice given out on this forum.

Cya

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I don't take that as an accusation-more like a misunderstanding.
No problem and no apology needed, I could have worded it different/better. Let's hope he gets it figured out and posts back when it's running right.

Toughguy19 said:

Thank you very much for all of the help. I dont take anything as ridicule. Firstly I did the timing before finding this website. I would never do anything now without one of the how to guides. I have read the timing one over and over actually (well after the fact) to see what I screwed up. This site has helped me realize I'm not working on a chevy 350 here I need to be precise and ask for help before I do something not after. But to answer my original question. Would the car run and get 38 mpg if the timing was off one tooth? Would it be loud but run ok after warming up?

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This is a great source of help isn't it? Wish I had found it before starting my project years back.
The engine will most likely run while off one tooth. I don't think one off will cause valve contact, but certainly cause poor preformance/mileage. The only way to really find out is go back and lock/pin everything down as the others have outlined and make sure. The most common error is getting the pin in the IP incorrectly, there is a spot very close to the right one that has swallowed many an errant locking pin.
After it's been rechecked make sure to run the VagCom timing graph. Has that been done as of yet?? Never did notice if that was confirmed.
All the best and keep us "posted".

I've had complaints of poor mileage after changing a couple people belts early on. I've always use the correct tools. That said, it is possible to have everything correct as far as the manual and how-to goes, and get reduced mileage.

You read on here over and over again that the timing is optimized at the top of the graph. This is true...for the most part. A few comments:

With the engine warmed up, correct engine selected, etc. and the timing set in the upper 25% of the graph, The timing will be off. What!??? Yeah really.

If you look at measuring block 4, actual timing vs requested, You'll see that the actual is somewhere in the 2-3 BTDC range, while requested is in the 0-1 BTDC range.

Everything is correct, but the IP is at the limit of how far it can retard. Yes, with the static timing all the way at the top, it can reach more advance, but realisically, you're going to be driving at light load on the freeway a lot more than you'll be at 4K+ RPM @ full load.

At idle, this has very little effect on the fuel economy. At light load on the highway - cruise on, 70 mph - the timing will be in the 1.5 BTDC range. If the car cannot retard below 3 BTDC, you'll knock a few MPGs off. The more time at light load, the more it will effect the economy.

So if you've dilligently followed the proceedure and you have the static timing at the top of the graph, - put it in the middle and see what you get.

Also, after changing many, many belts these cars, I think the best practice is to:
Warm the car up
Check the timing
Advance the IP as far possible without making the cold start/advance solenoid duty cycle (again, block 4) rest in it's full retarded position. If the cold start solenoid duty cycle value is 2.8%, it's completely retarded.
I shoot for the 15-25% duty cycle at warm idle.
This is usually slightly above the blue line in the timing graph; depending on ambient air temp, barometric pressure, and fuel quality.