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View Full Version : car runs ruff at idle but stil has good boost and runs fine while driveing.



my 1.8t
03-09-2011, 12:42 PM
ok the other day i was driving my car and it started runing ruff in idle. i have changed all spark plugs,checked all coil packs,had two vaccume leaks that are fixed now. everything that ive changed or looked at is good at this point but still is runing ruff at idle. could this be my MAF sensore and if so can someone post a pic of where thats at please or what else should i try or change to see if it works. i have a 2000 audi a4 quattro.atw engine code[headbang][headbang]

my 1.8t
03-09-2011, 12:44 PM
also forgot to say i did take it to a shop the other day and they ran my car and had some codes. 2 misfires and runing lean due to the vaccume leaks that are now fixed. so a little mind baggled rite now.

Seerlah
03-09-2011, 12:48 PM
I thought you said compression in cylinders 3 and 4 were 100psi, while 1 and 2 were 150psi?

my 1.8t
03-09-2011, 12:57 PM
well thats what he said not to sure how true that was... i mean anyone can say that just to make some money. a
everyone ive talked to says that they dont think its rings there is no smoke or anything like that. they say if rings were bad or were going bad that there would be some type of smoke.

Seerlah
03-09-2011, 01:03 PM
Why not do your own compression test? It isn't difficult at all.

1. Rent the compression tester from Autozone for FREE (you place a deposit, and get it fully back when you return the tool)
2. Take out the fuse for the fuel pump
3. Take out ignition coil
4 Take out spark plug
5. Place compression tool onto threaded spark plug bung
6. Crank car. Be sure not to crank for more than 5 seconds at a time, or else you will burn out your starter.
7. Read gauge on tool to get your compression for that cylinder
8. Release pressure from gauge and move onto the next cylinder

MikeD7
03-09-2011, 01:08 PM
Your MAF is inside the top of the airbox.

http://i930.photobucket.com/albums/ad149/MikeD7/Technical-MAF_Snorkel_07.jpg

my 1.8t
03-09-2011, 01:10 PM
i will just dont have time to do it rite this minute but i will try that. if anyone else has any ideas on what this issue may please help.
Why not do your own compression test? It isn't difficult at all.

1. Rent the compression tester from Autozone for FREE (you place a deposit, and get it fully back when you return the tool)
2. Take out the fuse for the fuel pump
3. Take out ignition coil
4 Take out spark plug
5. Place compression tool onto threaded spark plug bung
6. Crank car. Be sure not to crank for more than 5 seconds at a time, or else you will burn out your starter.
7. Read gauge on tool to get your compression for that cylinder
8. Release pressure from gauge and move onto the next cylinder

Seerlah
03-09-2011, 01:51 PM
ok the other day i was driving my car and it started runing ruff in idle. i have changed all spark plugs,checked all coil packs,had two vaccume leaks that are fixed now. everything that ive changed or looked at is good at this point but still is runing ruff at idle. could this be my MAF sensore and if so can someone post a pic of where thats at please or what else should i try or change to see if it works. i have a 2000 audi a4 quattro.atw engine code[headbang][headbang]

How does it ride while in motion?

You can run lean for a couple of reasons. The most common are from vacuum leaks. Then the MAF sensor and primary 02 sensor take second place. These are the reasons that most people run lean. But you can have "misfires" for other reasons.

And you really need to find out iwhat your compression is. I am sure others would want to know this also, to help you diagnose your vehicle better.

my 1.8t
03-09-2011, 09:53 PM
can you post a pic of where the ignition coil is at so i can do this test tomorrow. thanks
Why not do your own compression test? It isn't difficult at all.

1. Rent the compression tester from Autozone for FREE (you place a deposit, and get it fully back when you return the tool)
2. Take out the fuse for the fuel pump
3. Take out ignition coil
4 Take out spark plug
5. Place compression tool onto threaded spark plug bung
6. Crank car. Be sure not to crank for more than 5 seconds at a time, or else you will burn out your starter.
7. Read gauge on tool to get your compression for that cylinder
8. Release pressure from gauge and move onto the next cylinder

my 1.8t
03-10-2011, 01:20 AM
in motion it seems to run ok in 1st and 2nd gear it seems to shake a little and make a little noise but when im in 3rd and 4th doing about 40-50 it runs good.
How does it ride while in motion?

You can run lean for a couple of reasons. The most common are from vacuum leaks. Then the MAF sensor and primary 02 sensor take second place. These are the reasons that most people run lean. But you can have "misfires" for other reasons.

And you really need to find out iwhat your compression is. I am sure others would want to know this also, to help you diagnose your vehicle better.

Seerlah
03-10-2011, 01:54 AM
Take off the engine cover. Underneath it you will see 4 ignition coils sittin on top of the valve cover. There are 2 little bolts that I beleive use a 5mm allen head. You need to remove those to take out the ignition coil. Unclip the ignition coil from the harness and pull it out. With a spark plug socket (you will need this, along with extension), remove the spark plug down in the ignition chamber. You place the compresion tester into there to conduct the test.

BE SURE TO REMOVE THE FUEL PUMP FUSE BEFORE YOU CRANK THE ENGINE.

And don't crank the car more than 5 seconds at a time. If you do that, and don't give it a couple of seconds before each crank, you can burn out your starter. But a couple of cranks is all it akes to complete the test. Also, you think it's possible your new plugs are gapped improperly? That is why I like to use 3 prong pregapped (or no gapping required) plugs. Cancles that variable altogether.

If your compression is good, is would seem that you just have a simply "slight" misfire. That's no biggie and can be fixed very easy and cost less to nothing to fix.

my 1.8t
03-10-2011, 02:36 AM
ok cool sounds good. what else can cause misfires? and if it was my rings wouldnt i be seeing smoke at all? because like i said im not seeing any and my car runs fine and boost fully when i drive it.also when i got my new plugs i gaped them at 32-33 as i was told by some other guys on this forum last time i did plugs.
Take off the engine cover. Underneath it you will see 4 ignition coils sittin on top of the valve cover. There are 2 little bolts that I beleive use a 5mm allen head. You need to remove those to take out the ignition coil. Unclip the ignition coil from the harness and pull it out. With a spark plug socket (you will need this, along with extension), remove the spark plug down in the ignition chamber. You place the compresion tester into there to conduct the test.

BE SURE TO REMOVE THE FUEL PUMP FUSE BEFORE YOU CRANK THE ENGINE.

And don't crank the car more than 5 seconds at a time. If you do that, and don't give it a couple of seconds before each crank, you can burn out your starter. But a couple of cranks is all it akes to complete the test. Also, you think it's possible your new plugs are gapped improperly? That is why I like to use 3 prong pregapped (or no gapping required) plugs. Cancles that variable altogether.

If your compression is good, is would seem that you just have a simply "slight" misfire. That's no biggie and can be fixed very easy and cost less to nothing to fix.

ricekikr
03-10-2011, 02:43 AM
I thought you said compression in cylinders 3 and 4 were 100psi, while 1 and 2 were 150psi?

I'd bet this is your problem. Is there any power loss? It'd still probably boost fine, but there should be some power loss. And your gas mileage probably got worse. It could possibly not smoke @idle, but @WOT you probably would see some. @idle does your muffler sound like a Subaru (ie. glug glug glug glug not brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr)?

my 1.8t
03-10-2011, 02:52 AM
no not really it sounds fine to me... im so frustrated with this car rite now.and no it doesnt feel like there is an power loss at all seems to run fine other them what was stated ^^^^^
I'd bet this is your problem. Is there any power loss? It'd still probably boost fine, but there should be some power loss. And your gas mileage probably got worse. It could possibly not smoke @idle, but @WOT you probably would see some. @idle does your muffler sound like a Subaru (ie. glug glug glug glug not brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr)?

my 1.8t
03-10-2011, 02:47 PM
ok got the comperssion tester today ill be doing that in a little. about the exhaust sounds normal. so any other thought

my 1.8t
03-10-2011, 03:27 PM
ok did the test if i did this correct and the gauge was correct cylinder 123 were at 100 and cylinder 4 was at 95..so they all seem to be runing at the same not to sure what else to check.

Seerlah
03-10-2011, 03:44 PM
I have a feeling that you didn't have the gauge tightened down all the way. Or the tester was just old and needed replacement. Autozone has a reputation for doing crap like that. You can tell them to replace it because it's bent, broken, etc. Come back to rent the tool again later on, and it's the same damn defective bent unit. Ask me how I know?

I would def try to find out the "correct" compression of your cylinders. That is more than a stepping stone to figure out your issue.

ricekikr
03-10-2011, 03:51 PM
At those compression there should definitely be power loss. Try pouring some oil in the cylinder if the compression jumps up its the rings, if it doesn't its the valves. Or do a leak-down test (yup, another gauge).

Minimum I think is 140psi. 95psi is like a dead cylinder already.

my 1.8t
03-10-2011, 04:43 PM
yeah the part was missing something in the kit so i didnt do it rite. im going to take it to my mech asap and he said he will do all that over again for me. im thinking it may be a valve also but ill see what my mech says when i bring it to him. the thing is is that i dont have any power lose it runs fine and no lose of power and the exhaust sounds fine and boost fine .
At those compression there should definitely be power loss. Try pouring some oil in the cylinder if the compression jumps up its the rings, if it doesn't its the valves. Or do a leak-down test (yup, another gauge).

Minimum I think is 140psi. 95psi is like a dead cylinder already.

ricekikr
03-10-2011, 05:16 PM
The exhaust would only sound off if the compression of one or two cylinders is way off compared to the others (like your first comp test 150 vs 100). If the compression is still low after your mechanic tests it, do a leak-test. But if its up to spec, time to check the usual Idle issue causes (throttle/maf/vacuum/icm/coil etc etc etc).

And if your comp still comes up low, you probably just don't feel the power loss because compression gradually got lower thus power also gradually got lower and the power-loss can also be minimal, but still noticeable. Try driving another car with similar specs to yours, you might feel the difference. The thing that's should've been more noticeable though is, gas-mileage got worse (actual gallons per mile not using the OBC).

Compression test video:
http://www.youtube.com/watch?v=X_tbksFYhl4

my 1.8t
03-10-2011, 10:31 PM
does anyone think this may be a valve issue? and if i drive the car from phoenix to tucson do you think it will be an issue if i stay and a good 75-80 mph. its about an 1 1/2 hr drive. i need to get it home to my mech