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Old 01-28-2014, 08:36 AM
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PO455 DCP valve

So....I recently started getting this code, among others, on the Jeep. Also recently started having a problem with the jeep not starting right. If it sits all day, over night or for a couple of hours it starts just fine. BUT, if I turn it off for say 15 min to half hour and go back to start it, it's having trouble starting..randomly, not always...it turns over and tries to start..sometimes will putter and then die, sometimes just won't kick in. to me it seems like it's not getting gas. The other codes are for an oxygen sensor, which i know isn't the issue here, and I have P206 for the #6 injector circuit. Pretty sure one injector issue would not be causing the starting problem so I wonder if it would have to due with that purge valve? Could it be a plugged fuel filter? The fuel pump is just 2 years old. Jeep is 2001 JCG Limited with 4.7 V8 I can replace the purge valve in a few days...piece of cake to do that, but just wonder if I should be looking at other things that aren't giving me a code which is causing the start problem. THANKS.
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Old 01-28-2014, 09:53 AM
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It could be possibly dirty injectors. I would start with a good injector cleaner some cars need a few treatments, run some 93 octane fuel with it. It helps clean things up a bit.
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Old 01-28-2014, 08:31 PM
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Re: PO455 DCP valve

Won't expect the fuel filter, because then it would have the problem hot and cold. Would also not expect the purge solenoid, eventhough it could create false air when it would stay open. Normal start when cold and difficult start when hot is in many cases caused by a sensor. Next time when it has a difficult start let someone smell the exhaust fumes at the moment that it starts. What feels as no fuel, could easily be too much fuel. A faulty inlet temp sensor could be your problem. Do you have a scanner which shows live data( or an android phone with free Torque app, only dongle required), then you could check the inlet temp.
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Old 02-07-2014, 09:07 AM
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Re: PO455 DCP valve

The starting problem continues. It's so strange that you can try and try to start it and it cranks but just won't fire up. Then all of the sudden it fires up like normal. I cleaned the throttle body last weekend...the IAC?? was very nasty...sprayed and carefully wiped it down w/o getting any cleaner in the insides of it. ran a couple bottles of gumout cleaner through less than quarter tanks of gas so it'd be more concentrated. for 4 days or so it seemed to start ok....but I think that was just luck. not sure. Should also mention that one day my son had it and couldn't get it to start...put jumper cables on it and it fired right up. it's going to the shop next week to have cv joint replaced so i'll have mechanic check it over then. QUESTION. do relays misbehave intermittently or are they either good or bad?? I'm going to swap the #30 and #37 relays when my son gets home with it and see if that matters. they are the starter and horn relay...same part number and see if anything comes of it. but i swear...if it turns out to be the starter again I am going to be really PO'd. In ten years i've had this jeep, it's on it's third starter now!!(the original and two replacements)
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Old 02-07-2014, 09:10 AM
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Re: PO455 DCP valve

PS..when looking at starters on Rockauto.com...just in case, I see some that say 1.1kw and some 1.6 kw. i'm sure i could give them my VIN and they'd hook me up with the right one.....but why is there a difference in the KW and is this important to know?
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Old 02-07-2014, 10:38 AM
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Re: PO455 DCP valve

The kW is an indication for the torque the starter can produce. The bigger the engine, the more force it will take to turn it over and consequently the starter should produce more torque to do the job.
The 1.1 kW is probably for the 4.0 and the 1.6 kW for the 4.7.
Did you check for the smell of unburnt fuel at the moment the engine starts?
A relay normally works ok, or it doesn't, but there are always rare cases that they sometimes fail. Swapping a relay is always a good first step to rule this possebility out. But if the starter relay fails, then the engine will not crank at all. A non crank condition could also be the Park/Neutral switch in the transmission or even a bad ground.
Does the engine crank with normal speed, or is it slow?
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Old 02-07-2014, 10:55 AM
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Re: PO455 DCP valve

good info to know on the starter kw. :-) talked to my mechanic again to schedule appt for the cv joint and oxygen sensor. he went over a bunch of issues relating to the non start problem...probably not my starter since the jeep cranks....thank god. could be a sensor,he is going to check it when he has the jeep, but for now says I could try the auto choke/shut down relay. says they sometimes will act up. i'll pick one up tonight. It's $5 so not a big loss if that's not the problem. he also said to listen for the fuel pump to kick in when i turn the key over. and again...it had better NOT be the fuel pump which was replaced 2 years ago to the tune of $500!!! If it turns out to be a sensor...TPS, Crankcase, IAC, AIT, blah, blah, blah...I'm skilled enough to change those myself. :-) I'll let you know what it turns up next week! thanks
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Old 02-07-2014, 06:37 PM
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Re: PO455 DCP valve

When you want to listen to the fuel pump, be aware that it will only run for 3 secs. when you don't start the engine. But since your problem seems to be temperature related (at least it doesn't start when hot), i would be surprised if it turns out to be the pump.
The auto shutdown relay could eventually be the problem, since it switches the power to the coils and the injectors. For that reason it would be good to know if you smell unburnt fuel as soon as it starts, or not.
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Old 02-08-2014, 11:02 AM
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Re: PO455 DCP valve

I'll do the sniff test when i go to start it next time. lol. no luck with the shut down relay....had to order it. supposed to be at the store monday.
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Old 02-08-2014, 11:05 AM
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Re: PO455 DCP valve

Need to get some parts ordered for the jeep from Rockauto. Wasn't exactly sure which cv half shaft I needed so sent them an email with my VIN number. Their reply was my first bad experience with their customer service. They emailed back saying "all you have to do is put in your vehicle year, make, model, engine and search for the part you need and pay attention to any additional notes included with the part information". Geeze really??

@Frango100....this is the part I believe I need. How do I know for sure? My Jeep is 2001 GC limited 4.7v8 with quadra drive. and yes, its the front right CV joint that needs done. I'm doing the whole half shaft as this will save my mechanic some time and frustration versus just doing the cv joint.


CARDONE SELECT Part # 663301 More Info {#5012748AB} with Variable Lock Progressive Axle; Compressed Length = 41 1/8" One of our most popular parts
Front Right; w/Quadra-Drive (Only 5 Remaining)
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Old 02-08-2014, 11:14 AM
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Re: PO455 DCP valve

If you just want to do a test, you could swap the auto shutdown relay with the transmission control relay, which sits in the same box.
I dont think that they work with VIN numbers on Rockauto, but i ordered several items via them and it always worked out well.
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Old 02-08-2014, 11:15 PM
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Re: PO455 DCP valve

The injector code is not an injector problem, its a Throttle Position Sensor problem. Aftermarket replacement sensors for a Chrysler are HIGHLY NOT suggested... you have been warned!

I would not rule out any codes, the no start, these newer vehicles are pretty good about pointing out a sensor problem when they fail. I would consider getting your O2 sensor code fixed, who knows what it could be, they do control fuel and if you have one shorted to ground or shorted to voltage it could really cause some starting and running concerns.

What type of pump was put in it? Do you regularly run your tank very low on fuel before filling up? 2 yrs on a crappy aftermarket pump is actually pretty good, so if that is what was put in, be happy you made it that far. As far as letting it run low on fuel, the fuel pump uses gasoline to lubricate itself, when you run low on fuel and allow it to run dry a little bit here-and-there its a death sentence for fuel pumps.
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