P0442 and P0303 troubleshooting

|V3nom| · Mar 28, 2012

P0442-EVAP system medium leak

P0303-Cylinder no. 3 misfire

already cleaned the pcv valve and replaced the purge control solenoid to no avail for the p0442. been having that one for a while but the p0303 is new and the motor makes a funny noise around 2k rpms when accelerating which might be the misfire but i always figured a misfire would make the engine run rough or out of balance or feel a lack of power and ive felt none of those.

anybody else throw these codes and know how to fix them? just looking for a good place to start instead of going through everything if it isnt needed.

04 limited 3.7 auto 2wd. thanks guys.

rockymountain · Mar 28, 2012

swap the #3 coil with another and see if the code follows the coil to the next cylinder to see if its a coil.

|V3nom| · Mar 28, 2012

well it shouldnt be the coil or spark plug because i just recently changed them out a few thousand miles ago but i can try that.

was reading in my haynes manual and it said that a evap leak can cause a misfire so maybe if i can fix the leak i can fix the misfire.

|V3nom| · Apr 2, 2012

brought it to firestone today to get it fixed. apparently the computer is showing them false readings. it said the misfire happened at 38000rpms lol i dont think theres a motor on the planet that can run that fast. they also said it was giving them false injector readings, cant remember if they said it was way too high or low.

the jeep isnt running bad or stumbling or anything so im not sure whats going on. maybe the computer is going out but i figured that would make the engine run bad if it was that.

how much is a new computer and can i buy one already set up for my jeep or would i need to bring it to the dealership?

rockymountain · Apr 2, 2012

Just a suggestion. Get a computer from the junkyard and send it in to get it programmed.

Welcome to B&G Performance "A World Leader in DCX & EURO Tuning Solutions" - Dodge/Jeep/Mini/Bentley Motors/AMG/Mercedes/Ferrari/Porsche PCM/TCM(Computer)Flashes

|V3nom| · Apr 2, 2012

man screw bandg. literally no email support. i got a engine tune from them thats "supposed" to give you more power and mpgs and i got neither lol. felt exactly the same as before and i still average 18-19. plus i had to mail them my ecm so i was out of the jeep for a week or more. yeah that was a waste of $350.

im thinking more along the lines of a junkyard ecm and send it to the dealership. that is unless bandg will put the stock tune on for free.

thanks for the suggestion though.

speaking of junkyards do you have any with kj libertys near you? i dont have any junkyards within a reasonable distance is why i ask.

|V3nom| · Apr 2, 2012

giving bandg another chance. just sent them a email about programming a ecm from another jeep to work in mine. lets see if they email me back...

cuatroXcuatro · Apr 3, 2012

I was having the same problem, would move the coil to a different cylinder to see if it would follow it and it didn't, then I started getting misfire codes for other cylinders. Took vehicle to the dealer to have the ECU programmed with the latest firmware version (this was in 2010), one of the bug fixes was incorrect misfire messages. Fixed the problem.
From the list of bug fixes:
18-008-05 FEB 05 Engine Controls - Erroneous Ignition Coil DTC's/MIL ON

|V3nom| · Apr 3, 2012

well ive already put a couple hundred miles since resetting the codes and no cel yet but that might just be a matter of time. ill give it a couple of weeks and see what happens.

|V3nom| · Apr 5, 2012

no cel yet but i havent driven it since posting last. gonna go to the dealership tomorrow and get a tire sensor, the 5th one, replaced and finally get rid of that tire sensor bad/missing message every time i start the jeep!

also gonna see if they can flash the stock tune back on for me.

|V3nom| · Apr 7, 2012

well it was good friday so they werent open long enough to get the tire sensor fixed so ill do that another day.

just gonna hold off on the computer for now unless it acts up again. got that new hypertech 52501 on the way so ill give a review once it arrives.

hope ill be able to feel the power and get better mpgs like it promotes...

|V3nom| · Apr 9, 2012

the hypertech doesnt work lol. well it uploaded on the jeep and it drives like normal but i cant go wot or it cuts ingition or something to that effect. emailed hypertech about it and gonna try putting the stock tune back on and reflashing it to see if that fixes it.

|V3nom| · Apr 10, 2012

tried the hypertech again to no avail. it wont let me go wot as in the transmission doesnt downshift properly and when it finally does it stays at whatever rpm its at. sent the information to them via the programmer so they have their engineers looking at it right now to see if they can fix whatever is wrong. such a hassle lol.

rockymountain · Apr 10, 2012

Thanks for being a giunnea pig. For $350, staying far away!

snsheil96 · Apr 10, 2012

Anyone one have problems with 3.7 Idle. Seems to be a little ruff like a misfire but throws no codes.

rockymountain · Apr 10, 2012

snsheil96 said:
Anyone one have problems with 3.7 Idle. Seems to be a little ruff like a misfire but throws no codes.

Stop highjacking and start a new thread.

|V3nom| · Apr 12, 2012

snsheil96 said:
Anyone one have problems with 3.7 Idle. Seems to be a little ruff like a misfire but throws no codes.

yup and according to firestone its normal for jeeps to idle rough.

|V3nom| · Apr 12, 2012

bad news. got the jeep back from the dealership after taking it in to get checked out...and apparently i need a new motor. they didnt get the emissions leak code but got a misfire code for all the cylinders.

they did a compression test and found out that all but one cylinder is bad at 120psi vs 170psi which is where its supposed to be. they quoted me ridiculous prices on a used motor with 60k and a 1 year warranty at $5100 installed and a new motor at a little over $7k installed with a 3 year warranty. no thank you lol.

i emailed a local shop and he i briefly told him about my situation and that i need a motor rebuild but he said that i wont need it if it still runs fine even being at 120psi. he wanted more background so i told him everything from when i first got the originally P0442 and P0303.

so now i have a programmer i cant use, because it wont work with the b&g tune still on so i have to get the dealership to reflash it or b&g to do it, and a motor that might be going out. im not doing any ecm reflashing until the motor issue is resolved, unless b&g actually email me back saying theyll do it for free.

at least the dealership replaced the last bad tire sensor so no more tire sensor bad/missing alarm every time i start the jeep. thats something to look forward to!

|V3nom| · Apr 12, 2012

oh and i got two more codes once i left the dealership.

P0129-Barometric pressure out of range

P0688-ASD relay sense circuit low

anybody know what that actually means?

|V3nom| · May 3, 2012

good news. the libby isnt dead or dieing. the shop i brought it too found a bad coil and the libby didnt like the spark plugs i had in it which were iridium autolite. they also did and induction flush to clean out the carbon which apparently the 3.7 is bad about.

been a week since getting it back and no codes and it feels a little smoother now.

P0442 and P0303 troubleshooting

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