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Discussion Starter #1
So I have a 03 1.8t sedan and when I let the car run in park or I’m sitting at a light (sometimes but getting more often) the check engine light starts to blink and the car starts to do like a little rumble/shake and it starts to rough idling and I have ran the codes multiple times and it says my idle control module rpm module or something like that along the lines can’t remember at the moment and misfires in cylinders 1, 2, 3 and sometimes 4 I have had the car in the shop and had a lot done and a lot not done that should have been done. All I have done is a touchscreen radio some after market speakers that the passenger side door won’t work now for some reason but that’s for a different day and time. But I really need help because I’m at a loss and I love this car so much and it’s been me and my wife’s car I’m just at a loss! I’ve looked and looked and looked for answers and something to maybe help or even some where to start because like I said I’m lost!!
 

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You need to start looking for vacuum leaks. They would affect the engine most at idle and can cause an uncontrolled idle. Usually they show up as a lean code. I would also check the MAF flow with VCDS. Clean and adapt the throttle body and double check the wiring.
 
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Also, please post the exact codes. You'll be all over the place trying to track stuff down without them. They provide valuable information on working towards a diagnosis. They tell you what the ECU sees from its sensors and then you interpret that to narrow down the cause.

Is the Idle control code P0507 by chance? If so, vac leak is the main thing to look for and it will cause misfires when not in boost (P0300, 301, 302, 303, 304).

Main areas to look for vac leaks:
  • N80 purge valve (electric) on top of the airbox (pinch or plug the hose end leading to the engine)
  • Suction Jet pump that connects to a hard vinyl pipe leading to the brake booster (separates at the seams)
  • L hose that connects the intake manifold to the suction jet pump
  • Bleeder valve under the intake (pinch the hose that leads down from the intake mani to the block breather hose "T"
  • myriad of vacuum lines (3.5mm id)
  • any check valves
 
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Discussion Starter #5
So I know by now y’all have seen like 3 posts about my 03 1.8t sedan yeah? Well here we are back to square one worked on my car checking testing ect.. Everything has been fine till 2 days later during them 2 day I have had no check engine light and no rough idle after removing my blow off and a few other things. Then today 2 days later with the things still off I’m getting my check engine light back on for misfires and system too lean. Let me tell you once that check engine light is on I sound like a damn tdi or even close to! I went back again after driving it checked for leaks clamps off anything that could cause this problem and still nothing have fixed it. Where do I go from here? Does anyone know what the causes could be I’ve checked and replaced all spark plugs new coil pack check hoses lines different valves clamps ect.. I’ve done a lot of research but everything I’ve found fixed replaced or even just tightened and nothing someone help me I’m desperately in need this is me and my wife’s only car for the time and she nor I can afford another at the moment..
 

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So I know by now y’all have seen like 3 posts about my 03 1.8t sedan yeah? Well here we are back to square one worked on my car checking testing ect.. Everything has been fine till 2 days later during them 2 day I have had no check engine light and no rough idle after removing my blow off and a few other things. Then today 2 days later with the things still off I’m getting my check engine light back on for misfires and system too lean. Let me tell you once that check engine light is on I sound like a damn tdi or even close to! I went back again after driving it checked for leaks clamps off anything that could cause this problem and still nothing have fixed it. Where do I go from here? Does anyone know what the causes could be I’ve checked and replaced all spark plugs new coil pack check hoses lines different valves clamps ect.. I’ve done a lot of research but everything I’ve found fixed replaced or even just tightened and nothing someone help me I’m desperately in need this is me and my wife’s only car for the time and she nor I can afford another at the moment..
WHAT ARE THE FAULT CODES ?
 

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So I know by now y’all have seen like 3 posts about my 03 1.8t sedan yeah? Well here we are back to square one worked on my car checking testing ect.. Everything has been fine till 2 days later during them 2 day I have had no check engine light and no rough idle after removing my blow off and a few other things. Then today 2 days later with the things still off I’m getting my check engine light back on for misfires and system too lean. Let me tell you once that check engine light is on I sound like a damn tdi or even close to! I went back again after driving it checked for leaks clamps off anything that could cause this problem and still nothing have fixed it. Where do I go from here? Does anyone know what the causes could be I’ve checked and replaced all spark plugs new coil pack check hoses lines different valves clamps ect.. I’ve done a lot of research but everything I’ve found fixed replaced or even just tightened and nothing someone help me I’m desperately in need this is me and my wife’s only car for the time and she nor I can afford another at the moment..
WHAT ARE THE FAULT CODES ?
WHAT ARE THE FAULT CODES ?
 
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Yes, but you have several more of them around the intake manifold. The one on the airbox is the 1st to go bad as the heat from the cat destroys them. Keep checking until every hose and plastic valves are checked.
 
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If those are all the codes, you have a vac leak.
I guess you never did anything that we suggested in the last 6 days, especially my post in #3. That's really it.

If you really did check for leaks, you either don't know how or didn't look too hard.

Touch EVERY check valve, manipulate them, turn them over. Listen for hissing while the engine is idling. It's not hard to find a leak that's bad enough to cause the running problems you have..
 

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If you suspect an air leak, often you can hear it better if holding a length of hose (say heater hose) to your ear, then moving the other end around the various check valves and hose fittings. Hoses can also be pinched to see if the engine runs better, which suggests that excessive air is flowing inside it. Basically, if you can hear a hissing sound, you have an air leak.

Other areas to check include any part of the intake tract, between the MAF sensor and throttle unit. Our '99 had numerous cracks in the rubber duct leading to the turbocharger's inlet, which I sealed with black Silicone adhesive/sealant after washing the thing thoroughly. Inspect the 'diverter valve' attachments, which is adjacent to the turbo.
 

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Just putting this out there again in case you don't scroll back through for where to check.

In that picture above, there is at least 4 check valves to look at, not counting the bleeder valve in the breather pipe.

Main areas to look for vac leaks:
  • N80 purge valve (electric) on top of the airbox (pinch or plug the hose end leading to the engine)
  • Suction Jet pump that connects to a hard vinyl pipe leading to the brake booster (separates at the seams)
  • L hose that connects the intake manifold to the suction jet pump
  • Bleeder valve under the intake (pinch the hose that leads down from the intake mani to the block breather hose "T"
  • Myriad of vacuum lines (3.5mm id)
  • Any check valves
 
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