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Idle drops when braking near a complete stop

  #1  
Old 11-17-2016, 09:17 PM
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Question Idle drops when braking near a complete stop

Greetings, everyone!
I have 113K on my Jetta VR6 (see signature). I just replaced the fuel injectors last weekend. Bought them on eBay for $76 for all 6. I was worried my car wouldn't run after the replacement. The nozzle pattern is different, and I just didn't think a 1000% price drop (comparing to the dealer) would still yield a quality part. They work just fine, and run great above 2000rpm. The fuel efficiency increased again. Yay!

I have a new problem. When I brake, about 3' before a complete stop, my idle drops dramatically and idles rough near a stall, while waiting at a stop sign. Sometimes, after a short drive, the idle fluctuates in park. There is another problem with lights dimming at about the same time as I press the brakes hard for a stop. The dimming lights issue was there before I replaced the injectors. What could be causing this?

During the injector replacement, I put in a brand new 120 amp alternator, new spark plug wires, cleaned the throttle body, changed the valve cover gasket. Used recommended torques on the intake manifold and replaced its seals, as well as the seal on the throttle body. Replaced the fuel pump and changed front brakes 2 weeks ago. About a month ago, I installed a new air exchange rod with new bushings from ECS Tuning. 4 months ago I replaced the coil pack, and 6 months ago had new spark plugs installed.

Assumption 1:
I ordered a $35 cold air intake kit that came with a step-down hose, approximately from 3" to 2.5" diameter. The smaller end of the step-down wouldn't fit around the MAF sensor. I got a straight one at Advance Auto.

This replacement was before the fuel injectors, and it did add some power, but the engine was running like crap due to injector 1 not working. The car definitely runs louder and has extra power now, but only at higher RPM. My guess is that the mixture is jacked up now and the computer can't compensate. Although, I don't think I am in "limp" mode, because the car runs great at 3 and 4K rpm. There is a bit of a funny exhaust smell present immediately after the drive.

Assumption 2:

The plastic fitting the hose in red circle connects to (not the actual image) broke off flush with the wide part of the plastic 'Y'. I had to buy a connector and drill out a bit of the plastic 'Y' from which the original connector broke off. Used a very thin layer of super glue to tightly fit the new connector. I am wondering whether the shavings from drilling could have plugged the vacuum lines somewhere. I scooped it out though, I thought.

Could either of my assumptions be correct? I am hoping that I should just reinstall the old air filter housing, forget about the cold air intake and the problem will be fixed. I was afraid that I had a bad brake booster. Tested using some basic steps I found on the web, and the symptoms didn't seem to point to the booster failure. The vacuum line for the booster is expensive. I hope it didn't get clogged somehow.

Any help will be greatly appreciated!
 

Last edited by Sergei Chaparin; 12-15-2016 at 10:21 AM.
  #2  
Old 11-18-2016, 06:18 AM
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You should have fitted the correct part number not fleabay injectors.

You need access to VAG-COM\VCDS to check the system out.
 
  #3  
Old 11-18-2016, 11:36 AM
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I can't believe that I didn't save the paper from a pre-injector-replacement scan. However, I definitely had a P0262 (Cyl. 1 injector circuit high input/short to B+) on injector 1 before doing the work, and a couple of P0305 or P0306. Here is what Autozone gave me just now:

P0201 — cylinder 1 injector circuit malfunction
P0300 — random misfire detected
P0301 — cylinder 1 misfire detected
P0305 — cylinder number 5 misfire detected
P0306 — cylinder number 6 misfire detected
P0302 — cylinder 2 misfire detected
P0304 — cylinder 4 misfire detected

The wiring harness looked good, and VW wants $750 for a new one.
 
  #4  
Old 11-19-2016, 06:35 AM
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P0201 cylinder 1 injector circuit malfunction
P0300 random misfire detected
P0301 cylinder 1 misfire detected
P0305 cylinder number 5 misfire detected
P0306 cylinder number 6 misfire detected
P0302 cylinder 2 misfire detected
P0304 cylinder 4 misfire detected


VAG Error Code: 16684/000768
EOBD II Error Code: P0300

Fault Location:
Random/Multiple Cylinder(s) - Misfire Detected/Upper Limit Exceeded/Implausible Signal

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.
Lack/loss of power.
Hard start.
Engine hesitation.

Wiring/Connector(s).
Air Intake System leaking.
Fuel Supply faulty.
Injector(s) faulty.
Ignition Cable(s) and/or Spark Plug(s) faulty.
Ignition coil(s) faulty.
Exhaust Gas Recirculation (EGR) Valve (N18) stuck/open.
Camshaft Position (Hall) Sensor (G40) faulty.
Low compression.

Possible Solutions:
Check/Replace all faulty Wiring/Connector(s).
Check Misfire Recognition.
Check Air Intake System.
Check Fuel Supply.
Check Injector(s) and Injector Sealing.
Check Ignition Cable(s) and Spark Plug(s).
Check Ignition Coil(s).
Check Exhaust Gas Recirculation (EGR) Valve (N18).
Check Camshaft Position (Hall) Sensor (G40).
Check cylinder compressions.

Special Notes:
This Diagnostic Trouble Code (DTC) indicates that one or multiple cylinders are misfiring, but the Electronic Control Unit (ECU) fails to identify the cylinder.

Tech Notes:
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem.

When is the code detected?:
The control module monitors the crankshaft speed and has detected a misfire condition.

Description:
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position Sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.


VAG Error Code: 16685/000769
EOBD II Error Code: P0301

Fault Location:
Cylinder 1 - Misfire Detected

Possible Cause:

Malfunction Indicator Lamp (MIL)(K83) active.

Lack/loss of power.

Hard start.
Engine hesitation.


Wiring/Connector(s).
Ignition system.

Fuel injectors.

Fuel pressure.
Running out of fuel.
EVAP canister purge valve.
Evaporative emission system.
Low compression.
Base engine problems.
Engine Control Module (ECM) damaged.


Special Notes:
This feature search for engine misfire in a specific cylinder. Most of the time the cause for a misfire is a lack of combustion in a cylinder due to absence of spark, poor fuel metering, or poor compression.

Tech Notes:
The P0301 code means that the cylinder 1 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 1. If the problem persist more tests needs to be done to diagnose problem.

Description:
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position Sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.


VAG Error Code: 16685/000769
EOBD II Error Code: P0301

Fault Location:
Cylinder 1 - Misfire Detected

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.
Lack/loss of power.
Hard start.
Engine hesitation.

Wiring/Connector(s).
Ignition system.
Fuel injectors.
Fuel pressure.
Running out of fuel.
EVAP canister purge valve.
Evaporative emission system.
Low compression.
Base engine problems.
Engine Control Module (ECM) damaged.

Special Notes:
This feature search for engine misfire in a specific cylinder. Most of the time the cause for a misfire is a lack of combustion in a cylinder due to absence of spark, poor fuel metering, or poor compression.

Tech Notes:
The P0301 code means that the cylinder 1 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 1. If the problem persist more tests needs to be done to diagnose problem.

Description:
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position Sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.


Its the same for the other cylinders with a misfire


As taken from my new https://volkswagenforum.com/forum/ge...oftware-34973/
 
  #5  
Old 11-19-2016, 10:18 AM
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I would say this is one of my more frustrating experiences with cars. Since the essential pattern of the issues before and after the injector replacement seems to be the same, what is the likelihood that it's the wiring harness? I replaced the intake manifold gaskets ($60), and I torqued the manifold to spec. The new wiring harness from Volkswagen costs $700+. And could a stuck EGR valve cause a consistent fault with injector 1? Could a fuel pump truly cause misfires? The pump appears to be the last easy/cheap part that I could replace.
 
  #6  
Old 11-19-2016, 12:37 PM
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I have to add that I haven't had a chance to clear the codes. It's possible that those codes no longer exist. I will have to go for a full diagnostic at VW after my next payday.

The car tends to start great in the mornings, and the starter has to work a bit with every consecutive start that day, especially if the car sat a bit.

I was also trying to listen to the fluctuating idle in part. I think I am hearing the gears of the throttle body when this happens. The cycle of the fluctuation takes approximately 10-15 seconds, and at one of the stages has about 3-4 seconds when the idle is very smooth.

I can't imagine the wiring harness being bad. Can an EGR valve be cleaned?
 
  #7  
Old 11-19-2016, 12:45 PM
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I don't have a check engine light now.

https://axleaddict.com/auto-repair/B...-Do-About-Them

I am so confused! :-(
 
  #8  
Old 11-19-2016, 01:21 PM
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Has anyone aligned their TB?

Throttle Body Alignment (TBA) - Ross-Tech Wiki)

It might be more beneficial for me to buy the $250 Ross-Tech cable, than to pay for the diagnostics?
 
  #9  
Old 11-19-2016, 01:42 PM
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And how do I tell if I have an ISV or not?

Thank you for the attention and the replies so far!
 
  #10  
Old 11-20-2016, 08:27 AM
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I would think you have a Idle Stabilization Valve (ISV).

Throttle Body Alignment (TBA)


 

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