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TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

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Old March 13th, 2009, 06:58   #1
Dieselsmoke
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Unhappy 3000rpm rev at hot start

Ok I feel that my baby is dying!

98 jetta 225,000 miles way overdue on timing belt

One day I got in the car and it revved up when I started it (car was warm), I thought nothing of it but immediatly noticed she was down on power.

It like throttle from 25% to 100% makes no more power, it's really a dog now.

If the car is fully up to temp. and I shut it off for 5 min., when i restart it it revs up to like 3000rpm and blows a big cloud of black smoke.

She desperately needs a TB and I am getting ready to do it, i have all of the parts.

My concern is that I also now have other issues like a faulty injector or the IP is going bad.

Has anyone heard of a 98 TDI doing this rev at start?

could it be that an injector is like hanging open and filling a cylinder with fuel when its hot, making it rev when i first start it?
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Old March 13th, 2009, 10:45   #2
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no thoughts??
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Old March 13th, 2009, 15:23   #3
2004STARWARSTDI
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Default reving to 3000

Sounds like you are sucking oil into intake! Beware of a runaway! Check to see if turbo is leaking oil. Also clean the egr valve & remove intake & clean it while you are doing timing belt. Check your oil level.
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Old March 13th, 2009, 16:29   #4
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sound like a good tip. sound like we need to check the intercooler as well
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Old March 14th, 2009, 13:39   #5
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bump.........
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01 VW Golf TDI new south gauges 5spd RC5 EGR gone w/ ventectomy, Evo skid plate, south bend stage 3 with 17lb flywheel pp764 17/22 turbo.
2012 TDI SEL P.O.S.
120k miles timing belt replaced at 100K
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Old March 14th, 2009, 16:35   #6
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check the coolant temp reading with vag-com/vcds.. if the computer thinks the engine is VERY cold it'll flare up like that when it's hot and have no power..

Good idea to check the turbo as well.. I would suggest pulling off the hose that goes from the upper intercooler pipe to the intake before you start it and look for a bunch of oil to come out when you fire it up..
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Old March 14th, 2009, 21:08   #7
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Fuel shut-off selenoid!

Symptoms:
-Reduced power (Boost deviation code - Low)
-Revs up on start-up

You may only need a new selenoid o-ring, either way the selenoid needs to come out, replace the o-ring and this should fix your issue. If not you may have a bad valve/plunger, cost is around $113 for a new selenoid

O-Ring Part number: 068 130 139
Cost $1.92
http://www.worldimpex.com/parts/genu...eal_44154.html

Fuel shut-off selenoid part number: 028 130 135 F
Cost $113
http://www.worldimpex.com/parts/genu...di_177697.html


O-ring is under #3 in the diagram:




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Last edited by Drivbiwire; March 14th, 2009 at 21:17.
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Old March 16th, 2009, 05:29   #8
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Thanks for the input, sorry I was away from the scope for the weekend. I was suspecting something with the IP. I will look into the fuel shutoff solenoid and report back. I would like to fix this issue before tearing it down becasue it was running perfect. I will also be cleaning my intake and IC when I tear it down.
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Old March 17th, 2009, 19:13   #9
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First I have to thank Drivbiwire, not only for the explanation, but also the PN's and a fix!

I bought the new Cut-off solenoid and replaced it. The old one looked fine mechanically and the o-ring was not split.

As soon as I finished I started the car , it turned over for a few seconds as it primed. I checked for leaks and took her for a ride, immediately I noticed it was still down on power. So I drove it about 2-3 miles around the block and back to my garage.

I pulled out the generic scan tool I have (yeah I know Vag-com on the way), and checked for codes. None. I also tried to restart the car to see if it did the 3000 rpm rev at start, and it seemed like it started to but caught itself. I turned it off and restarted it about 3 times and hooked up my scan tool reading real time data (painfully slow sampling).

Before I even got out of the driveway I could tell the power was back!!!

So... I found it interesting that it did not immediately fix it until a few restarts. Is there some sort of calibration that occurs after a few start cycles?

Seems like it is just and electromagnetic solenoid, I didn't think it had any kind of feedback control.

Last edited by Dieselsmoke; March 17th, 2009 at 19:17.
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Old March 17th, 2009, 19:42   #10
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I am very confused on how a sticky shut-off solenoid can cause the engine to over rev. All the solenoid does is stop the flow of fuel from the case into the fill port of the pump plunger. If it sticks closed it doesn't start and if it sticks open, it doesn't shut off the fuel. So what happens when it sticks part way that causes the rev at start-up?
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Old March 17th, 2009, 19:51   #11
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My first thought is that if the fuel shutoff stays open, a little extra fuel can be injected during shutdown. It must be just the tiniest bit as the engine loses speed and can't inject in the ignition window.

Since there is a fuel shut-off valve it is reasonable to conjecture the control collar does not move (fast enough, or all the way to zero) during shut-down, relying on the cut-off to stop the flow.

Last edited by jcrews; March 17th, 2009 at 20:11.
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Old March 17th, 2009, 19:53   #12
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You beat me to it ^^ essentially it leaks some fuel into the cylinders that does not get burned until restart.

In fact if you let it sit long enough it wouldn't do it. The fuel eventually vaporizes
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Old March 17th, 2009, 19:57   #13
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That part I understood but... I assumed that the loss of power was due to it not completely opening.

This also confuses me, why then did it not work on the first test drive if it was fully open??

Maybe a fluke?

Also I just remembered my scan tool found "enhanced code" p1144, has anyone seen this (I will search it)
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Old March 17th, 2009, 20:04   #14
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Do a search

just kidding - MAF open/short to ground.

Here's a thread for your enjoyment.
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Old March 17th, 2009, 20:32   #15
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That's a reasonable explaination and I'll run with that for now.
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