bergertraian

hello ..

can anyone help me?

i have a boxster 2.5 from 98 ..

my problems :

when i bought the car i was getting missfire on cyl. 1.2.3 or 4.5.6 at 2-3 days
turned up the AC. problem went away..(no other error on the duramatic only missfire ) after i erase the errors the car runned ok .

after 3-4 months


i'm getting foult end check engein light again only this time its on cylinder 3 the car is not running ok .... if i erase the errors p0300 end p0303 still the car is not ok ... end after 1-2-3 min check comes back again ..

what i did :

changed spark end coil
changed injector 3 with injector 2
i verified the wires to the computer (they are ok )
i forgot to say that at cold start the car turns of ... it has to warm up to run whit out accelerating it ...

what can i do ?

TY end sry for writing mistakes!

Macster

The engine is certainly acting up isn't it?

Let me see if I can offer some help.

Long shot: How's the gas? Have you added fresh fuel to the tank since you bought the car? Often a car for sale sits for a while and the gas can go stale. Also, the *right* gas may not have been used before the car was put on the market. Sometimes a buyer just wants to be rid of a car he has decided to sell and the result is he opts for the cheap off brand stuff probably not even the right octane grade.

So, there's stale gas, but it would have to be pretty stale.

I take it the CEL is not flashing? This is a sign of rich misfires.

So the misfires are lean misfires, or mechanical misfires. But with no other error codes/pending codes (like something related to the VarioCam system) I'm guessing the misfires are lean misfires.

Probably not plugs or coils though these may need to be replaced at some point. (Often bad coils/plugs create rich misfires. I assume the engine has the right plugs installed?)

Doesn't act like an intake air leak.

Doesn't like to be started cold and needs throttle to get the engine running? Runs better when warm?

Reads then like the engine is not being fueled correctly for a cold start. This points to possibly the MAF (mass air flow sensor) -- it is not able to report the correct intake air temperature or can't come up with the right amount of air the engine is using -- or it could be a bad coolant temperature sensor. If this is bad it can read too warm and the fueling will be off if the DME is led to believe the engine is warmer than it really is.

(The '98 engine has an ICV (idle control valve) which can affect idling. Being a used car and something of an unknown to you this could be part of the problem, but probably not responsible for the misfires. Similarily, the '98 has a serviceable fuel filter. Unless you have documented proof this was done recently I'd seriously consider replacing the fuel filter, but like the ICV I don't think this is causing the misfires.)

Unless you are prepared to throw parts the symptom, and I'm not recommending that you do this, you need a tool to view some engine telemetry. I'd look at the intake and coolant temps at cold start. These want to be pretty close to ambient and each other. Continue to monitor these after the engine cranks/fires. They may be ok initially but go bad very shortly after engine start or even before, during engine start.

Might add another possibility is sticking injectors. If the engine runs fine but just misfires a bit upon cold start -- which is what one of my Porsches currently does -- something to try is to run a bottle or two of Techron through the fuel tank. If the engine perks up run a 2nd bottle. Best if afterwards the oil/filter service is done to remove the additional contamination using Techron can cause.

(I've run the 2nd bottle of Techron through the engine but the jury is still out on whether this helped or not.)

But with the engine running so poorly I'm not sure I'd want to try to continue to run the engine just to run Techron through the engine. If you can find no other explanation for the misfires then perhaps having the injectors cleaned is something you want to consider. Well, cleaned or just replaced. But I'd be sure I've eliminated other possible explanations first.

bergertraian

ty for the replay

the engien now is not running wel ...the exhaust gas smels like fuel .. the check engien binks 2-3 times end then stays on ...

i bot the car end changed filters , oil ... end all the front suspension ... (i work at a service )

i dont think its the injector ... becose i changed them 3 with 2 end no change .. I HAVE MISS ONLY ON CYLINDER 3

but i remember that in the day the car boked .. i put gass in it ... like half of reservoir at 13:00 at 20:00 the care started running bad ...

i dont understand whay only cyilinder 3 missfires ... end not the hole bank ....


SRY FOR MY BAD writing

Macster

Ok with the blinking/flashing CEL that's a rich misfire.

You have replaced the #3 cylinder spark plug and coil I take it?

You have swapped the #3 injector with the #2 injector? As an aside the #2 cylinder injector is suspect, as are the others this arising from fact all cylinders were misfiring at one time. You might try swapping yet another cylinder's injector with the #3's injector, though granted this is a bit of a long shot.

And still the *rich* misifres persist with the #3 cylinder?

What about the plug? If the cylinder's injector is bad it could have fouled the new plug and you might need to clean the plug so it sparks right.

My 2nd hand (fortunately) experience with persistent single cylinder misfires is often this is a mechanical problem as in (one case) a burned exhaust valve.

But a lifter might be bad or possibly a camshaft lobe of one of the valves of the #3 cylinder.

Thus this might be the time to do a compression test of say at least the 1, 2, and 3 cylinders to verify the integrity of the cylinders on the bank with the troublesome cylinder.

Pull the fuel pump fuse so the fuel pump isn't running when you crank the engine for the compression test.

BTW, in your 1st post you said something about turning up the A/C and the misfires went away? Can add more detail as to what you did exactly?

bergertraian

hello ... sry for the long time replay ...

the car runs the same ... vv bad ... now wen i start it up it dose not stay in idle until the engie warms up ...
it smels very bad (petrol not burned) i have changed plugs , coil , gas in tank , swaped injectors , 02 sen , fuel filter ... i notice wen i take the spark out of the bank (its connected to the coil ) end put it on ground (metal) the spark is very very little .. on cil 3 on cil 2 its mutch more bright end faster ... (i tested the ecu end its ok ) ... im thinking of taking the engien off end change the solenoid on back 1-3 but ... i dont have cam tools end they are 200 euro

the compresion test shows that i have 10 in 10,5 in all cylinder

bergertraian

its like the power to the spark is not sufficient ... i have new coils ...

Macster

With a weak spark the coil is certainly suspect but also the coil's connection to the wiring harness and the engine.

The coil receives electrical power and then when a signal is sent by the DME this power is cut and the collapsing electrical field is what generates the spark.

When you replace the coils be sure you connect the coil to the plug properly, but check the electrical connector of the harness and make sure you get this connection right.

Last but not least be sure the coil is properly bolted down.

johnsjmc

Nowhere do I see that you have done a compression test. A leakdown would be better. Have you confirmed the general mechanical condition of the engine ? Compression should be about 180 psi on all cylinders +/- 5% . I would at least check all 3 cyl on one bank before swapping parts around.

bergertraian

on monday i have e guy that wil come end he wil check the electrics ... if the coil /spark hase the correct amount of electricity... i have 145 / 152 psi tomorw il make a video of the car ... so u can here it ...


10 bar on cyl 3 end 10/ 10.5 on others ... my problem is that i have to buy a camshat tool to take the engien apart ...

bergertraian

i dont have a problem to take apart the engien ... i can hover cylinder heads , change all the seals ... i can change the solenoid ( i have one ) but i need a way to copy the cam tools ...

Macster

Not clear to me the compression test results warrant engine disassembly.

You measured 10 bar on #3 and 10 to 10.5 bar on all the rest. I'm not sure where the"180psi" number came from that johnnysmjc offered. AFAIK Porsche doesn't publish compression test numbers for these engines.

What one wants to see is no cylinder down on compression compared to each other cylinder and 10.0 bar to 10.5 bar I think is pretty good.

You have to be sure there is no electrical or DME problem that can account for the misfire.

You have to be sure there is no injector problem, a sticky or leaking injector.

There are a number of explanations possible for the misfire that don't require an engine tear down.

johnsjmc

I got the number 180 from my own 3.2 2001 S . I expected similar and I also wouldn,t dismantle an engine with 10 bar in a cyl. The key in a compression test is high and equal (within 5 % is typical). Your engine appears to be in good enough mechanical condition to continue looking for another cause of the misfire.

bergertraian

ty for the replay

at sec 17 in the first video u can here the missfire
https://www.youtube.com/watch?v=1ELy...ature=youtu.be
from the back (dont mind the starter )
end the check engien
error code :
p0300
Factory fault code 75 -Misfire damaging to catalytic converter
p0303
Factory fault code 65 - Misfire , cylinder 3 , damaging to catalytic converter

Macster

No doubt about it the engine's not running right.

To recap you have replaced plugs and coils and you are sure the coils are connected securely to their respective plug and engine wiring harness connector.

You swapped injectors between 2 and 3 with the misfires staying put with cylinder #3. A long shot and I'm always reluctant to mess with these any more than necessary but swapping bank #1 injectors with bank #2 injectors might be provide some enlightment.

A compression test found all cylinders with about the same compression.

Sorry, but I don't have much else to offer. A persistent misfire can be a burned exhaust valve. But I would think the compression would be down on the cylinder with the burned valve. Perhaps a leak down test of say the #3 and #2 cylinders would be of some value? Since the misfites occur during a cold start of course the leak down test wants to be done with engine cold.

It is not clear from my rereading the posts but does the engine ever run ok say when it is warm?

What else? I have in the past come upon at least one Boxster with misfires on one bank that were traced to a bad MAF. A new MAF is a rather expensive item and in some early model Boxsters the new MAF requires the DME be updated with new code to support the new MAF, so just throwing a new MAF at the behavior is not a slam dunk decision.

One rather crude way to possibily eliminate the MAF is to disconnect the MAF at the engine wiring harness and clear the codes -- to primarily reset all the fuel trims to their default values -- and see if running sans the MAF makes a difference.

If you have the abilty, an OBD2 code reader/data monitoring tool, and checking the intake air temperature and coolant temperature at cold start. What you want to see is these two readings are close to ambient temperature and remain reasonable as the engine runs.

Another thing to check is fuel pressure at both cylinder bank rails. There are test ports available to test fuel pressure. Be aware the cap that seals this port is not reusable and must be replaced.

Before you do this you can observe the short term fuel trims using the aforementioned OBD2 code reader/data viewer. What you are looking for is both banks should have about the same fuel trim numbers. These can vary/swing some as the engine starts and runs but both bank fuel trims should be about the same.

What you find or don't find helps determine what you do next.

bergertraian

hello ty for the quick reply ...

i had a friend come ... he is a very good electician .. he sed to me that : there is no electical problem .. i have piwis clone ... the car is little beter wen the engine is warm up ( but u canot drive the car ... )
i trust him .. we tested injecotrs , end the spark from the coil ... its very good ..
i worck in a service ... il buy cam tools tomorow morning ... end take the engien down ... clean it , change solenoid bank 1-3 ,4-6 verify the valves ... mby the one from cyl 3 is broken end its remains opened or closed ... ty for your reply ... il take pictures end whrie about the procedure ...

sory for my bad english ... hope u can understand it