Rough Idle, Engine hesitation..?
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From: Nor Cal
A Car
Rough Idle, Engine hesitation..?
Car now has 94k miles. Done tons of mods and maintainance on her this past couple months.
Engine is idling rough, it shakes at stop lights and coming to a stop. When taking off from a stop, engine hesitates to go. It doesnt happen all the time and but when it does, the roughness varies from crazy to moderate. No codes stored.
Things i have done so far:
NGK Iridium IX plugs
MAF
CPS
Air Filter
New Valve Cover Gaskets
Techron Concentrate in tank
Oil/ Oil Filter
Reset ECU/TCU and Erased all stored codes
-I checked fuel pressure in the system, its good, engine is getting enough fuel.
-Injectors, plugs, wires for each cylinder is all working at optimum level.
-Air filter, MAF is getting enough induction
Whats up with this?! Ive literally tried everything and yet the engine refuses to act normal. Already searched around but couldnt get a definate answer to the problem around the forums. Ive been in n out of garages and mechanics, money is flying out like water the past few weeks, what should i do?
Vacuum leak??
Engine Mounts?? (but it doesnt happen all the time, remember)
... those are my only thoughts for now.
How do i check to see if theyre bad?
Performace has remained the similar, MPG went down due to the NGK plugs, but i notice a lil loss in low end torque but in the higher end, it pulls hard.
HELP, thank you!
Engine is idling rough, it shakes at stop lights and coming to a stop. When taking off from a stop, engine hesitates to go. It doesnt happen all the time and but when it does, the roughness varies from crazy to moderate. No codes stored.
Things i have done so far:
NGK Iridium IX plugs
MAF
CPS
Air Filter
New Valve Cover Gaskets
Techron Concentrate in tank
Oil/ Oil Filter
Reset ECU/TCU and Erased all stored codes
-I checked fuel pressure in the system, its good, engine is getting enough fuel.
-Injectors, plugs, wires for each cylinder is all working at optimum level.
-Air filter, MAF is getting enough induction
Whats up with this?! Ive literally tried everything and yet the engine refuses to act normal. Already searched around but couldnt get a definate answer to the problem around the forums. Ive been in n out of garages and mechanics, money is flying out like water the past few weeks, what should i do?
Vacuum leak??
Engine Mounts?? (but it doesnt happen all the time, remember)
... those are my only thoughts for now.
How do i check to see if theyre bad?
Performace has remained the similar, MPG went down due to the NGK plugs, but i notice a lil loss in low end torque but in the higher end, it pulls hard.
HELP, thank you!
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C240
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Change that fuel filter!!!! - You are pressure testing the system with no fuel demand I imagine? This can be misleading. I see you have done the CPS. The other thing that can cause engine stumble is O2 sensors cycling too slowly & reaching the end of their useful life. This could answer why it is storing no misfire codes. It could also be a vacuum leak - this should throw a fuel trim code though.
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Thread Starter
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From: Nor Cal
A Car
Yea, im beginning to think its the O2 sensors and the fuel filter is causing the rough idle and hesitation.
I just want to make sure still though cause the parts alone for this is already gonna be expensive. Ive already spent more on repairs/maintainance on my car than whats its worth already.
I just want to make sure still though cause the parts alone for this is already gonna be expensive. Ive already spent more on repairs/maintainance on my car than whats its worth already.
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Yeah! - the early cars could be a nightmare. You should have a really good car now!
Do the filter first & if you do O2 sensors only do the upstream ones. The downstream sensors only tell you if the Cats are good & I would not do them until you have a a persistent CEL.
Do the filter first & if you do O2 sensors only do the upstream ones. The downstream sensors only tell you if the Cats are good & I would not do them until you have a a persistent CEL.
Thread Starter
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From: Nor Cal
A Car
Yeah! - the early cars could be a nightmare. You should have a really good car now!
Do the filter first & if you do O2 sensors only do the upstream ones. The downstream sensors only tell you if the Cats are good & I would not do them until you have a a persistent CEL.
Do the filter first & if you do O2 sensors only do the upstream ones. The downstream sensors only tell you if the Cats are good & I would not do them until you have a a persistent CEL.
Ive changed nearly everything on her, everything from regular/preventative engine maintainance to suspsension components, to all the fluids/filters, sensors... the list goes on...
BUT, i still love it.
Drove the car again today and its definately getting worse and worse. Im getting it diagnosed tmrw, lets see if the fuel filter could be the curlpit. Thanks Glyn
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From: Nor Cal
A Car
...oh another thing i noticed, it idles fine in drive or in neutral. But idles rough when in gear.
I really wish the CEL was on so i dont have to keep guessing what the problem is.
I really wish the CEL was on so i dont have to keep guessing what the problem is.
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From: Camas, WA
2007 C230SS; 2014 ML350 BT
Thread Starter
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From: Nor Cal
A Car
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From: Camas, WA
2007 C230SS; 2014 ML350 BT
I hope that is our issue too, as that is a cheap easy fix. Probably won't get to mine until this weekend. I look forward to your results.
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From: Nor Cal
A Car
Yea, soo after much diagnosing and such... rough idle and hesitation is still present. Damn.
Got CEL now, codes read: misfire in cylinder 2,3,5.
My next guess would be wires? coils?
Why would there be multiple misfires all at once?
I lost half my cylinders when driving, and my exhaust made a deep muscle car grumble. It went away obviously after restart.
Got CEL now, codes read: misfire in cylinder 2,3,5.
My next guess would be wires? coils?
Why would there be multiple misfires all at once?
I lost half my cylinders when driving, and my exhaust made a deep muscle car grumble. It went away obviously after restart.
Last edited by holycaoAMG; Aug 14, 2010 at 06:05 PM.
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
She shut down on one bank - are misfire codes the only codes? Yes - wires & coils are next check & maybe an O2 sensor. Sounds like lane's car all over again.
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Codes were ONLY misfire codes, nothing else.
How can i tell if i have a clogged cat? Would i know i need to replace o2 sensors via a code? Like i said, there were only misfire codes, meaning i might just have to replace wires/coils next.
Any last calls? Thanks
How can i tell if i have a clogged cat? Would i know i need to replace o2 sensors via a code? Like i said, there were only misfire codes, meaning i might just have to replace wires/coils next.
Any last calls? Thanks
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C240
If all of your cylinders started to misfire on one bank all of a sudden, I would suggest a clogged cat. It's rare three coil packs/sets of plug wires go out all together like so. If it's random, then I would start with wires and coil packs. Just my $0.02.
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
If you have a cat problem the Cat should either rattle or the car should wheeze as though one exhaust is blocked on one bank.
O2 sensor should throw a code but we seem to have many problems that should throw or store codes & don't - who know's why.
Rough idle can be caused by a dirty or damaged throttle body. This does not cause misfires though.
Wires & coils are the logical next step but might not cure the problem. Swap around & see if code changes cylinder. This is still the best DIY.
EDIT - the damn misfire codes are not all on one bank!
O2 sensor should throw a code but we seem to have many problems that should throw or store codes & don't - who know's why.
Rough idle can be caused by a dirty or damaged throttle body. This does not cause misfires though.
Wires & coils are the logical next step but might not cure the problem. Swap around & see if code changes cylinder. This is still the best DIY.
EDIT - the damn misfire codes are not all on one bank!
Thread Starter
Senior Member
Joined: Jul 2008
Posts: 420
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From: Nor Cal
A Car
If you have a cat problem the Cat should either rattle or the car should wheeze as though one exhaust is blocked on one bank.
O2 sensor should throw a code but we seem to have many problems that should throw or store codes & don't - who know's why.
Rough idle can be caused by a dirty or damaged throttle body. This does not cause misfires though.
Wires & coils are the logical next step but might not cure the problem. Swap around & see if code changes cylinder. This is still the best DIY.
EDIT - the damn misfire codes are not all on one bank!
O2 sensor should throw a code but we seem to have many problems that should throw or store codes & don't - who know's why.
Rough idle can be caused by a dirty or damaged throttle body. This does not cause misfires though.
Wires & coils are the logical next step but might not cure the problem. Swap around & see if code changes cylinder. This is still the best DIY.
EDIT - the damn misfire codes are not all on one bank!
-Cant be dirty throttle body
-What are symptoms of a bad o2 sensor???
-Could it be a vaccum leak somewhere? how can i tell?
-Coils/wires are my next, probably my last resort, as they are VERY pricey to do.
