Idle issue

[TalBug]

I'm experiencing rough idle with an accompanying brake problem. It is intermittent and I have not gotten a CEL or an error code. All of the posts I've read direct me to a vacuum leak. I've inspected the hoses and changed many. The problem has disappeared a couple times, only to return.
Is a vacuum leak/bad hose the most likely problem or is it possible the low, rough idle causes the poor vacuum resulting in the brake issue. The car and brakes are OK with increase engine RPM.
I've been focused on the vacuum but cant find a smoking gun.
Any ideas would be appreciated.

[D2Beetle]

Some problems will not cause the CEL to come on; if it were me I would scan it for codes anyway. Might help to find that smoking gun.

[TalBug]

I have scanned for codes...none registered.

[IndyTom]

Originally Posted by TalBug

I'm experiencing rough idle with an accompanying brake problem. It is intermittent and I have not gotten a CEL or an error code. All of the posts I've read direct me to a vacuum leak. I've inspected the hoses and changed many. The problem has disappeared a couple times, only to return.
Is a vacuum leak/bad hose the most likely problem or is it possible the low, rough idle causes the poor vacuum resulting in the brake issue. The car and brakes are OK with increase engine RPM.
I've been focused on the vacuum but cant find a smoking gun.
Any ideas would be appreciated.

What type of brake problem are you experiencing? Brake pedal going to the floor? Pedal feeling mushy? Car crashes through wall and doesn't want to stop?
Could be just some air in the lines and could be unrelated to your idle issue. Bleed the brakes and see if that solves your brake problem.

Rough idle could be caused by many things. Faulty temp sensor, was it changed to the new Green type?
Spark Plugs, when is the last time you checked the plugs and the gap?
Coils, one or more of them could be on the way out. They usually throw a misfire code but not necessarily a Check engine light. Also check the plastic connectors to the coils. One of mine was cracked underneath and was given me all sorts of grief when I first got the car. I replaced the plastic connector housing and it solved my problem.
When's the last time you cleaned your throttlebody? Those things do get dirty and can easily cause a rough idle.
Clean your MAF Sensor, dirt or oil (especially if you have a K&N filter) can hinder the ability of the MAF to function properly. Take it out and gently clean it with some MAF sensor cleaner, then replace.
Failing diverter valve, N75 valve, crack or tear in the TIP (Turbo inlet Pipe), the list goes on and on.
If you could get it scanned with a VAG com that would be most helpful since it will show faults even if the regular OBDII scanner doesn't.
Good Luck and keep us posted on your findings.

[TalBug]

Back at it this morning. Started it up and had a very rough idle with CEL and misfire codes. (first time I got the misfire codes) I cleared them, started again and it purrs like a kitten.
I've owned this 2002 NB for only a couple weeks so I'm still trying to figure out what and where everything is. Not exactly easy getting to everything especially around the air intake and turbo areas.
I did go to a dealer to have them run the Vin to see if the recalls have been cleared. The ignition coils were just done in august. I assume the plugs were done too although I dont have access to service records.
Seeming the problem comes and goes so quickly, I'm leaning to a failing component that affects fuel/air. I guess I'll start with cleaning the MAF sensor and throttle body. The air temp sensor is black and may be changed as well as the secondary air solenoid. I just dont want to blindly through money at parts with my fingers crossed. Its just hard to T/S when the problem comes and goes.

[IndyTom]

Originally Posted by TalBug

Seeming the problem comes and goes so quickly, I'm leaning to a failing component that affects fuel/air. The air temp sensor is black and may be changed as well as the secondary air solenoid.

There is your problem! Those black sensors haven't been made in decades and were the problem with sending false readings to the ECM which adjusted the air/fuel mix according to the readings it received from the sensor. Change that sensor, then reset the ECM and my guess is that your troubles will be over.
It takes about 2 minutes to swap out and is the cheapest part to fix. Don't just stand there man, run and change it already

Volkswagen New Beetle 1.8T > Search > Temps Sensor > ES#1484 Coolant Temperature Sensor With O-Ring & Clip - 078919501CKIT

Your dealer most likely will have this in stock. But you will pay a premium of about $49 plus tax. If you get it from the dealer make sure you get a new O-Ring and a new Clip which they charge extra for. It is included in the ECS Meyle kit.

Also since you had this "BLACK" sensor in there a while your engine probably ran pretty rich especially at start up. You may want to check your plugs. They may be pretty dark or even fouled by now.

I use these NGK plugs. They work GREAT and only cost about $6.99 at Pep Boys http://www.amazon.com/NGK-BKR6EIX-Ir.../dp/B000BYDA8E

[Smileybug]

Air temp sensor and coolant temp sensor are two different things. The CTS is what should be replaced with the green top, which is what you have linked. Not sure if the air temp sensor really had any sort of issues commonly like the CTS did.

[IndyTom]

Originally Posted by Smileybug

Air temp sensor and coolant temp sensor are two different things. The CTS is what should be replaced with the green top, which is what you have linked. Not sure if the air temp sensor really had any sort of issues commonly like the CTS did.

I thought he meant to say Coolant Temp Sensor and just misstyped. The ambient air sensor doesn't have anything to do with anything except shows you the outside air temp displayed above your mirror.

[D2Beetle]

Originally Posted by TalBug

I have scanned for codes...none registered.

What scan tool did you use?

If it were me I would change out all those little cloth braided vacuum hoses on top of the valve cover. Clean the following sensors and their wire harness connectors, MAF, CAP, CAM and the Throttle Body.

[Smileybug]

Originally Posted by IndyTom

I thought he meant to say Coolant Temp Sensor and just misstyped. The ambient air sensor doesn't have anything to do with anything except shows you the outside air temp displayed above your mirror.

There is an intake air temp sensor as well.

[IndyTom]

Originally Posted by Smileybug

There is an intake air temp sensor as well.

True, but it's right behind the throttle blades of the throttlebody so if he cleans the throttlebody he will probably also clean the IAT.

[TalBug]

I did think you were first talking about the IAT, which I pulled and cleaned. The ECT appears to be black but I do see some green on it.
I also cleaned the MAF sensor. I've been driving it all day trying to get it to %#@k up again but its been running fine. I'll tackle the throttle body tomorrow. I'm not so good with all the acronyms yet...CAP and CAM??
Shouldn't the secondary air injection pump typically run at start up and idle? I've only heard mine run twice since I've driven it.

[IndyTom]

Originally Posted by TalBug

I did think you were first talking about the IAT, which I pulled and cleaned. The ECT appears to be black but I do see some green on it.
I also cleaned the MAF sensor. I've been driving it all day trying to get it to %#@k up again but its been running fine. I'll tackle the throttle body tomorrow. I'm not so good with all the acronyms yet...CAP and CAM??
Shouldn't the secondary air injection pump typically run at start up and idle? I've only heard mine run twice since I've driven it.

With the connector on top of the CTS (Coolant Temp Sensor) it is hard to see what color it is. Kinda looks like this when it is connected:


I never heard my Secondary Air Injection system ever. If it is suppose to make a noise I guess I must have ignored it or never paid attention to it. I think it is just a start assist and only makes noise when it's on it's way out?

To be honest, I have no clue what CAP and CAM means either
Maybe one is the crank positioning sensor? But I don't know for sure.