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Volkswagen Jetta, Golf, GTI: 1993-1999, Cabrio 1995-2002 (A3) 98 jetta rough idle after repairs


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Last Post: Jul 16, 2012 6:29 PM Last Post By: FKH161
tmw

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Registered: 04/18/19
98 jetta rough idle after repairs
Posted: Jul 13, 2012 7:54 PM
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I have 2.0 gas engine. I replaced the valve cover gasket, which involved removing the upper intake manifold and trottle body. I also replaced the PCV valve and breather hose. Now it runs very rough. It ran fine before these repairs. Is there something that needs to be re-learned by the computer?
Thanks for any help
tmw
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 13, 2012 8:33 PM   in response to: tmw in response to: tmw
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Did you re-attach the brake booster hose at the back?

Did you disconnect any injector plugs?
tmw

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Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 8:04 AM   in response to: FKH161 in response to: FKH161
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I did not touch any of the injectors.

I believe the brake boster hose comes off the right(drivers) side of the upper intake manifold, and I did re-connect it. does that sound right?

Help is very appreciated.
thanks
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 9:16 AM   in response to: tmw in response to: tmw
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Sorry, the A4 booster feeds off of the back... brain f a r t.

Did you disconnect the battery?

Does she drive fine once going? Could be it lost its throttle adaptation value. In that case you need to clean the dirt from inside the throttle bore and then do a throttle adaptation via scan tool.

The dirt is not allowing enough air to get through... the ECM lost its "adapted" idle position values due to battery disconnect.

If that is not it, I might think of something else... hmmmm.

Edited by: FKH161 on Jul 14, 2012 10:03 AM
tmw

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Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 9:45 AM   in response to: FKH161 in response to: FKH161
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I did not disconnect the battery.

It continues to run extremely poorly when you drive the vehicle, not just at idle. It has very little power, and very rough.

What do you use to clean the thottle bore? Do I turn the spring to open the valve and just reach in as far as possible?

Is the scan tool the same one that reads the codes? I am not familiar with the process of doing the throttle adaptation with the scan tool. Do you have any reference for this?

Before I replaced the PCV and breather hose, the upper breather hose had a large hole in it, yet the car was running fine. I do not know if that sheds any light or not. Why would it run OK with a large hole in the hose, then run very poorly, with new hose and PCV? To me it does not seem to make sense, unless alterations were done to make it run OK with a hole in the hose. I do not know if such alterations are even possible. I have had the car for 5 or 6 years. Got it with 82K miles and now has 117K.

I was also wondering if it is possible that I got a bad PCV valve? I got my parts from German Auto Parts.
Thanks again for your time and expertise.
tmw
FKH161

Posts: 7,661
Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 9:59 AM   in response to: tmw in response to: tmw
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Not a throttle body issue if it does it while driving as well, so don't worry about cleaning or adaptation.

But FYI, a simple code reader will not be able to do adaptation. The first procedure in the below link is how to do the adaptation on your tab.

http://www.ross-tech.com/vag-com/cars/throttlebody.html

Could be that the intake manifold is not sitting correctly (not sealing the intake) causing a lean issues?

I've seen pcv hoses that were not attached and also running fine... so I don't think that its because you sealed the system.

Just gonna walk through some steps that I recall when doing a VC gasket.... ignore or let me know if I missed something.

  • disconnect booster hose
  • disconnect intake hose
  • disconnect tab & temp sensor wiring at intake manifold
  • disconnect vacuum hose form fuel pressure regulator
  • disconnect vacuum hose for heat riser & egr if equipped (nipple next to fuel pressure regulator vacuum nipple)
  • disconnect egr (if equipped)... this might be the issue if you somehow have constant vacuum to the egr diaphragm
  • disconnect the mounting bolts front & back of intake
  • lift intake

If the engine has an egr, remove the vacuum hose going to the diaphragm / pod at the back of intake... any better?

Edit:

Auto spell check turned TB (throttle body) into tab twice above.

Edited by: FKH161 on Jul 14, 2012 10:00 AM
tmw

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Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 11:44 AM   in response to: FKH161 in response to: FKH161
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Thanks for the link on TB adaptation. For my info, where would I get the tool that allows me to do a TB adaptation?

From reading the literature in the link, I think it is saying to do the adaptation if you have done one of the 4 mentioned actions. One of those actions is removal of the TB or removal of the cable?

Regarding the seating of the upper intake manifold. It appears to be evenly seated. I tightened the 5 front bolts evenly and torqued them to 15FLB. I used a new gasket. Maybe I should take it off and examine the gasket?

Steps to remove Intake manifold - The only items I see that you did not mentioned are:
Unplug electrical plug from TB.
Remove 2 hoses from the top of the TB, one is a normal size vacuum line that goes to the gizmo at the intersection of main intake pipe and the short hose from the PCV. the second hose is bigger at about 5/8" diam. and I am not sure where it ends up.

What is the gizmo I mentioned above at intersection of intake pipe and short hose from PCV? It has an electrical connector attached to it.

I am thinking I do not have an EGR. Where would it be? I see nothing shown for my year jetta on GAP.com

Back to the 2 small nipples on the passenger side of IT manifold. one goes to Fuel reg, the other goes to the air filter box. I replaced this vacuum hose since it did not look good. Does this line operate the baffle in the air box? Does it matter which nipple these two hoses are connected to?

With regard to the two hoses that come off the top of the TB, I disconnected the small hose and nothing happened. When I disconnected the larger hose the engine almost stalled, so I was quick to replace it.

thanks
tmw
FKH161

Posts: 7,661
Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 12:00 PM   in response to: tmw in response to: tmw
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tmw wrote:
Thanks for the link on TB adaptation. For my info, where would I get the tool that allows me to do a TB adaptation?

http://store.ross-tech.com/shop/cat/VCDS.html

From reading the literature in the link, I think it is saying to do the adaptation if you have done one of the 4 mentioned actions. One of those actions is removal of the TB or removal of the cable?

Again, don't think it's an adaptation issue since throttle adaptation on this model only affects idle.

Regarding the seating of the upper intake manifold. It appears to be evenly seated. I tightened the 5 front bolts evenly and torqued them to 15FLB. I used a new gasket. Maybe I should take it off and examine the gasket?

If it looks flush... should be ok. No need to take off again. If you have an air leak, you should be able to track it down by listening for air being sucked in... hissing sounds.

Steps to remove Intake manifold - The only items I see that you did not mentioned are:
Unplug electrical plug from TB.

Spell check turned my TB remark into "tab"

Remove 2 hoses from the top of the TB, one is a normal size vacuum line that goes to the gizmo at the intersection of main intake pipe and the short hose from the PCV. the second hose is bigger at about 5/8" diam. and I am not sure where it ends up.

The bigger hose is for EVAP purge... fumes from charcoal canister.

What is the gizmo I mentioned above at intersection of intake pipe and short hose from PCV? It has an electrical connector attached to it.

The gizmo is the PCV heater element... the small vacuum hose sucks oil/fumes out of the valve.

I am thinking I do not have an EGR. Where would it be? I see nothing shown for my year jetta on GAP.com

Yes, my mistake. I don't recall the obdii engines having egr.

Back to the 2 small nipples on the passenger side of IT manifold. one goes to Fuel reg, the other goes to the air filter box. I replaced this vacuum hose since it did not look good. Does this line operate the baffle in the air box? Does it matter which nipple these two hoses are connected to?

Yes, baffle in air box... doesn't matter which nipple. They both have the same / provide the same vacuum to the two components.

With regard to the two hoses that come off the top of the TB, I disconnected the small hose and nothing happened. When I disconnected the larger hose the engine almost stalled, so I was quick to replace it.

Bigger hose = more vacuum (air leak),that's why the engine almost stalled.

thanks
tmw

Can you post a cellphone video so I can see & hear how she runs?
tmw

Posts: 24
Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 12:25 PM   in response to: FKH161 in response to: FKH161
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Right now it is raining here in Delaware. As soon as it stops I will get a video.
Thanks
tmw
tmw

Posts: 24
Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 2:30 PM   in response to: tmw in response to: tmw
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I am new to doing these phone videos. My droid would not let me send a longer video. I tried to attach a short 16 sec video with this text but it said it was too large. Do you have any wisdom here? should I make it even shorter?
tmw
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 2:32 PM   in response to: tmw in response to: tmw
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Send to: fkh161@

Edited by: FKH161 on Jul 14, 2012 2:44 PM
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 2:46 PM   in response to: tmw in response to: tmw
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It seems to sound & run OK to me... can you do more of a PAN shot of the running engine.

Record around the whole intake (not too close, so I can see everything around the manifold as well).

Also, while recording... move the throttle body with one hand to accelerate the engine so that I can hear how it picks-up rpm.
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 5:32 PM   in response to: FKH161 in response to: FKH161
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Throttle Cable Adjustment ... did you happen to move the adjustment? Forget to install the retaining clip?

Engine off, have someone press the gas pedal all the way to the floor... then, move the throttle by hand to see if it will open further.
tmw

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Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 6:37 PM   in response to: FKH161 in response to: FKH161
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I unbolted the throttle cable bracket from the back of the intake manifold, then just re-bolted it back in the same hole.

The throttle can not be moved any further by hand. With engine off and the pedal pushed to the floor the throttle bottoms out on the high-end stop, when let off, it bottoms out on the low-end stop, so that seems to look fine.

I checked the tension on the timing belt and that seems to be proper. Just thinking that somehow the timing got off, but belt is tight.

When sitting in the car at idle you can really feel how rough it is running.

Is it possible that I hit one of the injectors during the process?

On the trottle body, what do all the wires do that are connected to it? It appears to be purely a mechanical device operated only by the cable, which opens and closes the valve.
tmw
FKH161

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Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 6:45 PM   in response to: tmw in response to: tmw
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To rule-out injector or ignition... disconnect one of the spark plug wires and set it aside so that the spark can not reach the spark plug.

Start the engine and observe the roughness of the engine.

Re-attach the spark plug wire and test #2 cylinder the same way... do this for all.

The cylinder that is causing the LEAST amount of change in "roughness" is the cylinder that is contributing the least to the engine... in terms of power.

Focus on THAT cylinder then for further diagnosis (injector plug, spark plug itself, compression etc.).

The throttle body has a motor attached to it that controls idle speed... if you carefully look at the throttle lever, you can see the "movement / adjustment" that the ECM makes in order to maintain an idle.

I have a good video of it here: (first video of the bunch)

http://fkh161.ca/Video/

Let me know "how much rougher the engine is with one cylinder (at a time) disconnected.
FKH161

Posts: 7,661
Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 6:51 PM   in response to: FKH161 in response to: FKH161
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When you took the manifold off... did you happen to plug any of the openings with a rag?

I've seen rags in MAF sensors and one that was partially stuck in the throttle body (not an A3 vehicle though).

I'm running out of ideas.... this is usually a straight forward repair that should not cause any adverse performance issues.
tmw

Posts: 24
Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 7:52 PM   in response to: FKH161 in response to: FKH161
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I did put one rag in each of the lower intake holes, so nothing would drop in there. I was careful to remove them prior to re-assembly.

I will check the spark plugs in early AM. Must be at work by 10am, so might not be back to you until later in the day.

I agree with you that the repairs I made should not have caused a problem like this.

Could a broken rotor cause a problem like this? Maybe something else just happened to go bad at the same time that I was making these repairs. Not usually one for strange coincidences, but they do happen some time.
thanks again for hangin with me on this
tim
FKH161

Posts: 7,661
Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 14, 2012 8:14 PM   in response to: tmw in response to: tmw
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Broken rotor would cause it not to run... scratch that, a burnt rotor could cause high spark demand, allowing it to run but seem sluggish.

Pop the cap off and have a look. While you are at it, remove all the leads from the cap (one at a time and check the end pins & the resistance of all the wires).

Timing is easy to check at that time as well... rotate the engine by hand until the rotor lines-up with #1 slot and then check the camshaft notch & the flywheel notch.

It could very well be that something else failed at the same time frame that you did the repairs at... but I still find it strange.

A noticeable misfire should set a code... I forgot if I asked you if codes were stored.
tmw

Posts: 24
Registered: 04/18/19
Re: 98 jetta rough idle after repairs
Posted: Jul 15, 2012 7:37 AM   in response to: FKH161 in response to: FKH161
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per your previous post about checking each cylinder buy removing the spark plug wires one at a time while running, is it acceptable just to remove the wire at the cap instead? Just that it is easier to do that. When removing the wires from the spark plugs, is there a preferred tool for that, since the 2 internal ones look hard to get to with the intake manifold directly above. Long n nose pliers?

Looks like if you are getting new spark plug wires that you need to remove the IM, right? There is a wire guide or harness that the wires go in which is under the IM, and is bolted the the valve cover bolts to secure it.

How do you check the resistance of the wire?

I Have a friend who has the gizmo to read the codes so I will get him over to check that.
thanks
FKH161

Posts: 7,661
Registered: 12/29/05
Re: 98 jetta rough idle after repairs
Posted: Jul 15, 2012 12:04 PM   in response to: tmw in response to: tmw
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Sorry about the late reply...

tmw wrote:
per your previous post about checking each cylinder buy removing the spark plug wires one at a time while running, is it acceptable just to remove the wire at the cap instead? Just that it is easier to do that. When removing the wires from the spark plugs, is there a preferred tool for that, since the 2 internal ones look hard to get to with the intake manifold directly above. Long n nose pliers?

Yes, you can do so at the cap.... if you feel lucky, place all the wires loosely in their place, start engine and then move one wire at a time away from its post. Don't get zapped!

Looks like if you are getting new spark plug wires that you need to remove the IM, right? There is a wire guide or harness that the wires go in which is under the IM, and is bolted the the valve cover bolts to secure it.

No, the plastic rail sits in clips... the whole thing can be maneuvered out from under the intake, but yes, its easier with intake off.

How do you check the resistance of the wire?

You need a volt/ohm meter to measure resistance. 1000 to 6000 ohms (need to double check spec), if wire set is older than 8 years, well worth to put a new set.

I Have a friend who has the gizmo to read the codes so I will get him over to check that.
thanks

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