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View Full Version : 2.8 Starts but idles rough/ won't stay up on its own...



gtsingh91
08-05-2013, 10:39 AM
I have a 2.8 B5 with just under 170k on the clock. It starts but idles rough and will cut off if it's not given gas. But when the throttle is pressed, it runs fine. It can be driven, but as you slow down for a stop, it will cut off and need to be restarted. Timing belt was done about 40k miles ago, MAF, Coolant temp. sensor, coilpacks, and plugs are the only things I can think of at the moment that were recently changed. What are some possible problems here? I'm a noob to the 2.8's, but I know the 1.8's fairly well. Any insight is greatly appreciated.

JaysA4
08-05-2013, 11:31 AM
IIRC I believe there are two Coolant Temp Sensors on the 2.8, not positive but have read it a few times, were they both replaced? Was having similar problems until mine was changed out. Recheck Plugs and coils?

bryans12v
08-06-2013, 04:55 AM
12v or 30v? There's an idle control valve that stabilizes the idle that can be cleaned. I do mine once every two years.

Artiemas
08-06-2013, 06:09 AM
12v has an ICV, 30v has an ECM on the throttle body.

OP, do you have any CELs? If you could, VAG it, insteadof just using a basic OBd-II reader. Report back with said findings.

gtsingh91
08-08-2013, 11:26 AM
The car is a 30v. There is a CEL and I'll report back what the codes are.

ATCOs4
08-11-2013, 06:51 AM
i have a parts car i was hoping to drive or sell before i ran the codes doing something similar VAG spit out that P1338/P1392 both camshaft position sensors.. but wont drive due to a bad TCU. maybe check those out.

gtsingh91
08-12-2013, 05:55 PM
Just picked the car up today. I'll start looking into it tomorrow but the codes that I pulled with a standard OBDII scanner before I cleared them were: P1545 (Throttle Valve Controller malfunction), p0411 (SAI system), and P0160 (o2 sensor). I'm worried about the throttle body code so I'm going to start with doing a TB realignment and if that doesn't work, I'll tear it apart and clean it then move on from there.

gtsingh91
08-13-2013, 08:56 AM
Easiest way to get the throttle body off to clean it?? I've read so many different DIY's but all for the a6 or passat I haven't seen any for the b5.

gtsingh91
08-13-2013, 10:17 PM
Quick update: cleaned the throttle body which had a lot of gunk built up and the car idled Fine and by itself without using the gas pedal. Took it for a spin around the block and the car seems underpowered. No misfiring or anything just really really slow. Im thinking MAF or o2 sensor(s).

gtsingh91
08-14-2013, 07:48 AM
Just wanted to add that after cleaning the Throttle body out, I did a TBA and cleared the p1545 code that I had. However, the code returned but the car is still idling and running on its own but it just feels sluggish/slow even if I'm flooring it.

gtsingh91
08-14-2013, 05:58 PM
Does anybody have a spare throttle body that they'd like to get rid of? That P1545 code is still coming back up.

ATCOs4
08-14-2013, 06:11 PM
i dont but i do have o2's for sale :)

gtsingh91
08-14-2013, 06:34 PM
I was just reading your FS earlier I really wish you didn't sell the car today or else I wouldve bought many parts off of it :( O2 sensors are next on my list if the throttle body doesn't solve it. I'm pretty sure it is the TB because that's teh only code I'm getting and the Previous owner said all 4 o2 sensors were changed within the last 2 years.

I'm still looking for a 30V Throttle Body though!

ATCOs4
08-14-2013, 06:56 PM
nope i just sold the motor lol sorry i updated some stuff

gtsingh91
08-26-2013, 12:17 PM
UPDATE: changed the throttle body with a used throttle body. The car idles great now and does not flutter whatsoever. However, while driving, it still seems as if the throttle is not opening all the way when you floor it. It takes forever to reach up to speed. I cleaned the MAF and reinstalled. No misfires, no codes, and nothing wrong with the idling. It drives but is just really, really sluggish. What should I check next???

Raacerx
08-26-2013, 04:06 PM
Did you do a TB alignment with the new TB?

My 30v 2.8L takes forever to properly align and will be slow and idle badly for 10-15 miles.

MadAudi
08-26-2013, 04:18 PM
As stated before, I would do a throttle body alignment. Make sure that after you set the alignment with VAG and it says OK, you let it sit for at least 90 seconds before you touch it.

Primary O2 sensors would be your next point to inspect, there is a way to check them with VAG for aging and flow, but that is another process that needs a lengthy explanation. I would also check the "mixer" tube and its actuator/vacuum feed. The mixer tube sits inside of the intake manifold. Make sure it is not caught up and still moving. I have seen these kill performance because they are restricting top end air flow.

gtsingh91
08-26-2013, 08:17 PM
Thanks for the responses guys, ill look into the TBA through VAG even though I did it with the key in the ignition, hold down gas pedal.....ill also check the o2 sensors and research more about the mixer tube.

gtsingh91
08-27-2013, 06:28 AM
Where exactly is the mixer tube, aside from under the intake manifold, and what does it look like? Is there a DIY or something? I tried searching but came up with no luck.

MadAudi
08-27-2013, 04:19 PM
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash3/1236616_10152146634493272_779011318_n.jpg

Part 2A is the tube.

Likely point of failure would be Part 1 assembly. I would take the actuator off and see if the tube turns freely. It should take VERY little effort to move. If there is a lot, take it out, clean it, lube it up. Also, check that the actuator holds vacuum and moves as vacuum is applied.

Goodluck!!

gtsingh91
08-29-2013, 10:04 AM
Is there a DIY on removing the intake manifold on the 2.8?

Artiemas
08-29-2013, 01:55 PM
Yeah. Do it yourself. Start disconnecting things in the way. It isn't a very "DIY" needed topic.

A4 Effort
08-29-2013, 03:53 PM
Have you done the TBA yet? I'm pretty sure that'll solve it

gtsingh91
08-29-2013, 04:42 PM
Have you done the TBA yet? I'm pretty sure that'll solve it

I've done the TBA using the key in the ignition and pressing the gas pedal but not through VAGCOM. I'm trying to find someone local to me to lend me their VAGCOM so I can do a TBA through that.

gtsingh91
09-03-2013, 01:54 PM
Haven't had a chance to find someone local with VAGCOM to do a throttle body alignment, but that p1545 code popped back up. Could bad injectors or a bad fuel filter/pump cause the car to be extremely underpowered? It idles perfectly without a miss at all. Plugs, wires, and coilpack were all changed and a throttle body alignment using the key/gas pedal method was performed.

A4 Effort
09-03-2013, 04:53 PM
Haven't had a chance to find someone local with VAGCOM to do a throttle body alignment, but that p1545 code popped back up. Could bad injectors or a bad fuel filter/pump cause the car to be extremely underpowered? It idles perfectly without a miss at all. Plugs, wires, and coilpack were all changed and a throttle body alignment using the key/gas pedal method was performed.

Get a vag-com and do it that way. That should do it.

I had the same code:

17953 - Throttle Valve Controller
P1545 - 35-00 - Malfunction

gtsingh91
09-04-2013, 07:59 AM
Get a vag-com and do it that way. That should do it.

I had the same code:

17953 - Throttle Valve Controller
P1545 - 35-00 - Malfunction
Yup that's it. I'm going to see if I can get a member from the regional area to come to me since the car doesn't have plates or anything. Do you guys think a tune could also be a problem? Because I believe the previous owner had a SpeedTuning chip installed. Is there a way to reset the ECU or do I have to purchase a used one?

A4 Effort
09-04-2013, 02:22 PM
Do you guys think a tune could also be a problem? Because I believe the previous owner had a SpeedTuning chip installed. Is there a way to reset the ECU or do I have to purchase a used one?

It's not the tune, i have the same speedtuning chip in mine. But to answer your question, you would need a new ECU since the ST chip is soldered on.

Expplucky
09-04-2013, 04:20 PM
removing the intake mani is a bitch! better lable hoses! if you want a new ecu hit up ebay you can get one for like 40 bucks!

gtsingh91
09-04-2013, 08:34 PM
I did the intake manifold today and cleaned out that vacuum "mixer" tube, wasn't too bad. It definitely needed to be lubricated it. However, I didn't install the fuel rail to the injectors back well enough so fuel is spraying out of that. I'll take care of that tomorrow and report my findings. If that's not the problem I'm leaning more towards a bad ECU or something. Idk what else could make the car not have enough power.

MadAudi
09-04-2013, 08:47 PM
Make sure the actuator has good vacuum and goes through the entire motion when vacuum is applied.

you MUST reset your throttle body with vag-com like I described in earlier posts. Make sure you get new 0-rings for your fuel injectors.

A4 Effort
09-05-2013, 06:17 AM
you MUST reset your throttle body with vag-com like I described in earlier posts.

It's like talking to a brick wall.

Throttle. Body. Alignment.

/advice

gtsingh91
09-05-2013, 07:10 PM
It's like talking to a brick wall.

Throttle. Body. Alignment.

/advice

I know about the TBA, I'm just trying to find someone local to me to help me out since I can't actually drive the car without plates/insurance. But I did check the actuator and everything there is now fine after cleaning it out. It moves smoothly. I'll update as soon as I get the TBA done but thanks everyone for the responses.

Expplucky
09-06-2013, 12:12 PM
you dont use a vag-com to do this in the 30v cars!

you turn the key to on for 5 mins and leave it before starting

gtsingh91
09-06-2013, 08:06 PM
^^ I've heard mixed reviews about that working but I'm going to get a VAGCOM this week to find out if anything else is wrong

A4 Effort
09-07-2013, 07:13 AM
you dont use a vag-com to do this in the 30v cars!

you turn the key to on for 5 mins and leave it before starting

Not everything you read on the interwebz is true, and it's obvious that your 'advice' is completely wrong.

To do the TBA correctly, you need a vag-com

Kronic Budz
09-10-2013, 11:46 PM
I tried doing a TBA today with full version of Vagcom and couldn't reach any of the groups correctly to go through the process... Guy helping me had s4 and couldn't figure it out.

I have afc 97 2.8 if that matters (cable throttle)

Same symptoms and hard start.

gtsingh91
09-11-2013, 06:40 AM
I'm actually having another member from AZ come over to VAG mine for me a little later today. I'll report what happens.

gtsingh91
09-11-2013, 08:56 AM
Update: Doing a throttle body alignment through VAGCOM under Measuring blocks and group 098 fixed the car. It is running stronger than ever. Thanks to all for the responses I'm just glad I was able to find someone local with VAGCOM to help me out [up]

A4 Effort
09-11-2013, 03:04 PM
Update: Doing a throttle body alignment through VAGCOM under Measuring blocks and group 098 fixed the car. It is running stronger than ever. Thanks to all for the responses I'm just glad I was able to find someone local with VAGCOM to help me out [up]

Bingo. Glad you got it sorted