Beggin' your help w/ misfire plz!
#1
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
Beggin' your help w/ misfire plz!
hello, ive been having a problem with my car misfiring at times.. this is the best way i can describe it. When i turn on the car the car is fine, nearly idleing perfect, but then i step on the brake and hold it there, shifting to drive (A4) still holding the brake not going anywhere, the engine starts shaking!
i notice at when coming up to a red light or stop ,its misfiring..
okay i already paid 400 bucks tryin to find out/fix the problem,
we checked plugs&wires
checked for vaccum leaks
checkd MAF sensor
checked coil packs
checked Injectors
switched out knock sensors
changed fuel rail system or whatever
sent the heads out to check if they were warped
when they do that compression test it reads out low compression, cylinder 5 &cylinder7..
Do you guys think the piston rings need to be replaced??? cus thats what thier recommendin for me to do next!! What do yall think??
Thanks -Rey
i notice at when coming up to a red light or stop ,its misfiring..
okay i already paid 400 bucks tryin to find out/fix the problem,
we checked plugs&wires
checked for vaccum leaks
checkd MAF sensor
checked coil packs
checked Injectors
switched out knock sensors
changed fuel rail system or whatever
sent the heads out to check if they were warped
when they do that compression test it reads out low compression, cylinder 5 &cylinder7..
Do you guys think the piston rings need to be replaced??? cus thats what thier recommendin for me to do next!! What do yall think??
Thanks -Rey
#2
TECH Regular
Join Date: Feb 2009
Location: Geneva, IL
Posts: 426
Likes: 0
Received 0 Likes
on
0 Posts
iv always been told that when somethings wrong and you need to troubleshoot to do the cheap things first, rings....expensive if your not doing your own work, real expensive...so ME personally, i cannot think of anything else it could be, but you should see if anyone else does.....if worst comes to worst.....low compression would either be from a head gasket/warped heads, or rings......so if your heads arent warped, and your car doesnt puff some white smoke(head gasket)....that would leave the rings.
#3
TECH Addict
iTrader: (41)
Join Date: Jun 2005
Location: Jefferson City, MO
Posts: 2,329
Likes: 0
Received 0 Likes
on
0 Posts
Are you certain that its an engine misfire, and not a vibration of some kind? You saying it happens in gear holding the brake but not at idle in P, tells me that something may be hitting or something that's giving you a perceived miss do to the harmonics. Just a thought......
#4
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
Are you certain that its an engine misfire, and not a vibration of some kind? You saying it happens in gear holding the brake but not at idle in P, tells me that something may be hitting or something that's giving you a perceived miss do to the harmonics. Just a thought......
#5
LS1Tech Administrator
iTrader: (3)
Join Date: Nov 2001
Location: Schiller Park, IL Member: #317
Posts: 32,033
Likes: 0
Received 1,483 Likes
on
1,067 Posts
So compression is low on #5 and #7. First, how low is low? And second, have you done a leak down test? You can't just assume it's rings unless you're sure that both the intake and exhaust valves are fully closing on those cylinders. You could have bent valves or carbon build-up not allowing a valve to fully close when it's supposed to.
Also, are you burning large amounts of oil? If it was the rings, I would suspect this to be the case.
Also, are you burning large amounts of oil? If it was the rings, I would suspect this to be the case.
#7
TECH Addict
iTrader: (41)
Join Date: Jun 2005
Location: Jefferson City, MO
Posts: 2,329
Likes: 0
Received 0 Likes
on
0 Posts
Ever verify the coolant temp sensor connection is nice and tight. My 01 SS had a random situation where it would die idling and we thought it was a tuning issue, but turned out if you unplugged the coolant temp sensor it would kill the car and I had a loose connector... Just something quick to check...
Trending Topics
#8
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
So compression is low on #5 and #7. First, how low is low? And second, have you done a leak down test? You can't just assume it's rings unless you're sure that both the intake and exhaust valves are fully closing on those cylinders. You could have bent valves or carbon build-up not allowing a valve to fully close when it's supposed to.
Also, are you burning large amounts of oil? If it was the rings, I would suspect this to be the case.
Also, are you burning large amounts of oil? If it was the rings, I would suspect this to be the case.
Last edited by RoWDyWS6; 11-11-2009 at 11:06 PM. Reason: spelling
#9
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
they were also saying possibly with the way i describing the problem, that it could just be an o2 sensor! WTF! sorry i sound unintellegent.. im a newbie with this whole mechanics shiit... i just want this car fixed already! havnt drove it around in over 4 months.. just been turning it on, on the driveway..
#10
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
#11
Banned
iTrader: (2)
Do yourself a favor and get a scan using a real OBDII scanner, the ones the dealerships use.
See if the 02 sensors are switching properly after you're warmed up. When 02 sensors are "failing" but have not yet failed....you won't usually get a code or an SES light. Our PCM's are like the old style idiot lights for some issues. And a bad 02 sensor will cause the problems you're having.
.
See if the 02 sensors are switching properly after you're warmed up. When 02 sensors are "failing" but have not yet failed....you won't usually get a code or an SES light. Our PCM's are like the old style idiot lights for some issues. And a bad 02 sensor will cause the problems you're having.
.
#12
TECH Fanatic
iTrader: (6)
Join Date: Sep 2007
Location: Charlotte, NC / Ansonia,CT
Posts: 1,275
Likes: 0
Received 0 Likes
on
0 Posts
i was having serious issues with mine when the 02's were going. replaced both and havent had a problem since... with a situation like yours and 02's only bein like 10$ each and u can do it your self easily that would have been my first step
#13
Launching!
Thread Starter
Join Date: Dec 2006
Location: Mission,Tx
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
Do yourself a favor and get a scan using a real OBDII scanner, the ones the dealerships use.
See if the 02 sensors are switching properly after you're warmed up. When 02 sensors are "failing" but have not yet failed....you won't usually get a code or an SES light. Our PCM's are like the old style idiot lights for some issues. And a bad 02 sensor will cause the problems you're having.
.
See if the 02 sensors are switching properly after you're warmed up. When 02 sensors are "failing" but have not yet failed....you won't usually get a code or an SES light. Our PCM's are like the old style idiot lights for some issues. And a bad 02 sensor will cause the problems you're having.
.
#14
Banned
iTrader: (2)
i've always had that SES light, for about 2-3 years but car ran smooth.. SES started flashing every now and then. (that started a less than a yr ago) thats when i noticed small misfiring! Noticed the small misfiring at a fast food drive thru..i know the flashing SES means multiple misfire but im not sure what the problems is.. I hope it is a o2 sensor, that would save me a shiit load of money rather than payin 800 to get the piston rings!
Go out to your car, see if any of the spark plug wires are touching your exhaust manifold pipes...AT ALL. That causes misfires.
I know you said you checked your injectors...don't know what/how you checked them........but fuel injector(s) leaking will cause misfires at low rpm's and at idle. Only way to really make sure they're not leaking is to have them installed in the rails...then turn your key to "on" and let the fuel pump prime the system. Then see if any start to drip.
Get it on a scanner................
.
#15
Banned
iTrader: (2)
Cheapest place I've ever seen is www.rockauto.com
$40.00 for Denso sensors with the wiring harnesses and plugs built in.
.
#16
Launching!
iTrader: (3)
Join Date: Apr 2008
Location: Lancaster, PA
Posts: 215
Likes: 0
Received 0 Likes
on
0 Posts
I had the rings go on cylinders 5 and 7 and it would misfire in the higher gears if I lugged the engine too much. Shifter would shake also but yours may not since it's a A4. I ended up going with a used bottom end.
#17
TECH Addict
Join Date: Jun 2009
Location: Tulsa, OK
Posts: 2,012
Likes: 0
Received 0 Likes
on
0 Posts
Another thing you can try since you say this happens when you step on the brakes. Disconnect the vacuum line from the master cylinder and plug it so you don't have a massive vacuum leak. Then, start the car, step on the brakes and put it in gear and see what it does. If it doesn't start missing, replace the power brake booster.