simkard

Hi all,

This is my first post on this forum.
I actually own a Chrysler Crossfire 3.2 V6 powered by a MB engine.
It develops 218hp and is pretty fine to drive.
It is actually totaling 115000 Km.

I'm running into some kind of shaky idle problems and i don't know where it comes from.

-> Please excuse me if i don't describe very well the symptoms of my problem, i'm french and my english has troubles when speaking of mechanical words.

So let's get to the facts :
When the engine is cold or hot, the idle shakes.
It doesn't shakes a lot, but at least for me to worry about it.
For me a V6 engine should be stable enough (more than a 4 cylinder, at least ...).
I just replaced sparks (12x BOSCH FR8DPP33+), cleaned the sparks coils and the sparks wires : nothing changed.
I changed the fuel filter : nothing best.
I put some injector cleaner in my fuel : for now, nothing changed but i'm running on the tank on which i put the injector cleaner (so if it is injector related, the cleaner is actually doing its best ).

But ... as i'm sceptical, i would like to do further investigations on this idle.
For me, it is clearly "ignition" related problem.

I'm asking myself about replacing the sparks wires and/or coils ... but as it costs a lot, could the problem be coming from the crankshaft sensor and/or the camshaft sensor ?

Perhaps something else, like the MAF sensor and/or O2 sensor ... i don't know. (I heard about some spray to clear them // or does alcool is ok to clear them ?)

I have an ELM327 and can report values i'm getting if that can help.



Thanks for having read my post until there.
Hope you can help me ! ... and hope my english is clear enough to be read

itsky

Describe "shakes" a bit more. What is your idle RPM? Do you have issues starting? Do you have the stock air box? Is the check engine light on? The MAF sensors can accumulate debris which can skew information to the ECU.

Hopefully Google Translate makes sense here:

Décrire "secoue" un peu plus. Quel est votre régime de ralenti? Avez-vous des questions de départ? Avez-vous la boîte à air stock? Est la lumière de moteur de contrôle sur les? Les capteurs du CRG peuvent s'accumuler des débris qui peuvent biaiser l'information à l'ECU.

simkard

Hi,

Basically, i dont have problems starting the engine.
It starts really easily, no pb on this side.
Idle RPM is normal, based on what others owners reports (about 550-600 RPM, i CAN confirm through OBD)

I have the stock air filter box.
The "Check engine" light is not ON at all.
... No permanent/temporary defaults recorded in it too.

When i say shaky, it is not shaking as it would stall/die.
I can feel some little bumps constantly at idle, and, the RPMs is not stable (i can see the RPM sensor moving a little bit (like about 50/70 RPMs).
These bumps are not cycling, they are random.
Giving some RPMs, and running the engine stable on 1000/1500 RPMs, seems to render the problem less perceptible.
But at least, it seems to be still present.

I ordered camshaft sensor and crankshaft sensor, which are not expensives.
As soon as they arrives, i will install them and test again.

Of course, i will not install them at the same time.

PS : Does the MAF sensor can be cleaned using some alcohol ?

itsky

I was going to suggest the crank and camshaft sensors next as they can seem to go at anytime on these engines.

You may also want to look at this thread on CrossfireForum.org:
http://www.crossfireforum.org/forum/...tml#post585345

Could also be a loose vacuum line:
http://www.crossfireforum.org/forum/...ne-shakes.html

simkard

Thanks for these answers !

Based on the link about vacuum circuit being disconnected, it seems my shaking problems are very close to what the guy is describing !

Now, as it is my first gasoline engine, i just don't know where do i have to check for leaks.

Can you please help me with the locations ?


Thanks !

itsky

The MAF will be at the back of the engine. Take off the engine cover and you will see a 3" (~7.5cm) hole. This leads to the MAF and throttle body. From there you should be able to see smaller rubber hoses.

Service manuals for all model years of the Crossfire can be found here:
http://www.crossfireforum.org/forum/...ollection.html

simkard

Ok, so basically, i looked around the MAF sensor and i found a hose that had its end cut :


I could listen to the air flowing inside it (it is clearly a vacuum hose) and when i put my finger on the hole, i was stopping the leak.

... I cut the 1,5cm end of the hose and plugged it on the connector.
My idle is still shaky, nothing changed.

I noticed that when i swaped the plugs, i did forgot to plug one firmly (i plugged it while the engine was running but nothing changed ... still shaky ... ).

So now, i will wait for the crank/cam-shaft sensors to come and will replace them one by one.

Is it necessary for someone here to have all the OBD values at idle ?

I will go and get the values later and post them here.


NB : I read somewhere that there is a gasket on the O-ring that could leak. I didn't opened the thing because i did not had the time to do it right now, but, if after swaping the sensors, the engine is still shaky ... i will clearly do it.

By the way, when i listen to the engine, it seems that there are some weird sounds ... like banging but not too much ! just like something that makes me doubt about the ignition coils and/or spark wires.


I hope these informations will pop out an idea from you MB tech guys !

alx

you need to clean your throttle body if you have not done that. at 100k km it is due.

you might have another vacuum leak. buy a pair of stethoscopes and listen - if you have a vacuum leak you will hear it eventually.

btw, the v6 will shake- they are not good idlers like the v8 and v12s. so maybe your issue is not an issue at all. +-50 rpms variance is within acceptable limits.

also, i dont know about the crossfire ecu, but if your car is identical to the slk you might have "learned" some bad engine adaptations and resetting them might make a difference. also, while at it an "engine idle optimization" can be performed to smooth the idle. you will need a c3 or a c4 for those procedures though. also ofcourse- pull all codes. a no "check engine" light does not mean that the car has not logged problems.

simkard

Hi,

Thanks for your reply !

You are talking about "stethoscopes" for listening to vacuum leaks.
I'm okay to do it, but i just don't know how to do this.
Can you please explain it to me ?

What do you mean : "i might have "learned" some bad engine adaptations and resetting them might make a difference" ?
(I'm sorry, i'm french, i just don't understand every technicals words you say/write ...)

How can i do this : "an "engine idle optimization" can be performed to smooth the idle" ?
As the ECU is performing every tasks, i can't modify anything at all.

What is a C3/C4 ?

By the way, there is no DTC (no permanent / no temporary) recorded in the ECU.

alx

yes, mechanic's (not doctor's) stethoscope. very cheap tool to listen for vacuum leaks in engine compartment.

no problem. your english is decent what i refer to is engine ecu learning dynamic values that are less then optimal for idling. the ecu learns all the time and some times it might learn "bad" things. resetting the "adaptations" (dynamic modifiers to ecu settings for ignition and fuel mixtures) will force the ecu to go back to factory defaults. this is done only via das (see below)

assuming your car is like an slk you will need it connected to mercedes "das" (dealer diagnostic tool) which can be a c3 or a c4 model. find somebody that has it and knows how to use it. via das you can perform engine idle optimization which can smooth idle operation.

this is good.

simkard

So,

I replaced the camshaft position sensor, but it actually didn't helped the rough idle problem.

I couldn't replace the crankshaft position sensor because my tool is too big to go to the screw.
In fact, there is a thermal deflector close to the sensor and my tool is blocking on it.

Is there a way to remove it easily ?


Thanks !

simkard

I'm just wondering if, above all, it couldn't be some kind of compression problem on a cylinder ?!
Is there a way to know it ? (using the famous diag tool which costs a lot ...)
By the way, if it was some compression problem, the shaking should be perfectly cyclic, which is clearly not.
Moreover, since i repaired the soldering points on the RCM relay box, i found something curious.
- before repairing it : the engine could stall at a red light
- after repair : the engine gets its rough idle, but, i can hear the famous secondary air system starting (like the 1st minute at cold start) just before the engine would stall.


I would like to replace this damn crankshaft position sensor (which seem to be frequently causing these troubles) but for me to do it, i need to remove the thermal deflector which is next to the CPS.

After this, if it still doesn't change anything, i think i will be going for the MAF & O'Ring cleaning.
As it doesn't seems to be any vacuum leaks close to the top of the engine now...

simkard

Well well well ... so i replaced the crankshaft position sensor and ... nothing changed

I just don't know what to do next now ...
It must be some kind of misfiring problem so i must head up to the coils and/or the spark cables.

If i test the spark cables with an ohm-meter, what is the value i should get ?


Thanks !

simkard

So i tried to unplug de MAF sensor while the engine was idling and ...

The shaky behavior remains the same but the engine fan went ON and on full power + OBD error codes registered (3 error codes) :

P0112 - Intake Air Temperature Circuit Low Input
P0102 - Mass or Volume Air Flow Circuit Low Input
P0102 - Mass or Volume Air Flow Circuit Low Input (Pending)


So basically, i reconnected everything, the fan went back to its normal state, but, the engine light was still ON so i cleared the OBD codes and everything went back to normal.


... Except, that i still have the shaky issues ...

driveability

I am spent 20 years doing drive-ability and emission in several General Motors dealerships. HST, you could be looking at this problem incorrectly. From a keyboard talking about an engine is difficult. Since theres no misfire codes along with the idle speed being as ya said in the normal range you may not have a misfire. Without tools one could move to the tail pipe and listen for a misfire, pop burr pop etc. Could you be feeling a vibration ? I've found this to be true often.
You need to look at a few other cars and compare how they behave.

simkard

This is fine, i have a friend which has the same car, so it will be easy to know if it is acting same as mine.

By the way, his car has quite the same mileage, so it will be good to compare.

I will repost later ...