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Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 12592
Experience:  Dodge/Cummins and Chrysler Certified Master Tech
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I'm having some problems with my 2006 3.8 liter Dodge Grand

Customer Question

I'm having some problems with my 2006 3.8 liter Dodge Grand Caravan. I bought the van a month ago and the previous owner said he was simply driving down the road and the motor started backfiring sputtering and bogging down as if it were misfiring. the check engine light was on and had po403, po406, and po302. I replaced the plugs and wires change the oil and filter replace the battery and air filter also replace the EGR valve assembly. Now when I crank the van there is no check engine light and it idles smooth without any vibration for at least 20 seconds but then the motor starts to vibrate and shake horribly as it were misfiring. Also sounds like a pre ignition spark knock. Could the motor be starving for fuel? Fuel issue? what are the proper diagnostic procedures I should take?
Submitted: 5 months ago.
Category: Dodge
Expert:  Chris replied 5 months ago.
Hello and welcome to just answer. If you clear the codes, do they come back?Chris
Customer: replied 5 months ago.
Before I replaced the egr valve the 2 codes po403 and po406 instantly reactivated at each startup. The po302 activated when i drove for about a mile or so. Now after the egr valve replacment and tune up no fault codes present even after multiple test drives. The engine at idle shakes very very bad and barely stays running, and but this afternoon i pulled the main vac hose off the booster and it cleared up and ran like a new motor but at an elevated idle rpm of course, but no shaking or knocking or vibration. One more thing I noticed is, the van idle and at n.o.t
Customer: replied 5 months ago.
Push the accelerator pedal to the floor rpms reach only around 1800 on the tach then the rev limiter starts kicking in
Customer: replied 5 months ago.
I have read quite a few threads from people with the same issues that arise when they fillup at the pump. The plastic vac lines running from the charcoal canister to the purge solenoid and then to the intake plentum just behind the throttle body around the IAC, has wet/fresh gas residue inside them. And inside the intake looks wet, black carbon oily residue mixture even on the tb butterfly
Expert:  Chris replied 5 months ago.
Ok, you may have a failing fuel tank vapor separator which is allowing raw fuel to be pulled through the purge solenoid and into the intake manifold. Try this next: disconnect the hoses at the purge solenoid and cap them off. Drive the van and see if it is better. Let me know. Chris
Expert:  Chris replied 5 months ago.
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Customer: replied 5 months ago.
Hey brother sorry I haven't written back. I am a diesel tech for freightliner here in shreveport and i dropped my phone in a customer truck, just got it back. Man im now havin all sorts of issues with the van, the engine just isnt gettin enough air, motor still shakes vibrates pretty bad then it will level out somewhat then gets even worse. It fluctuates bad idle, okay/decent, horrible, okay, bad and so on and so on. Crank sensor or cracked flex plate maybe?
Expert:  Chris replied 5 months ago.
Hey no worries my friend. This is a strange problem you are having and as far as a crank sensor or cracked flex plate, maybe, but I usually see cam and crank out of sync codes when that happens. Some things I have been thinking about are is fuel contamination? (water, diesel, ??) Take a fuel sample and let it sit in a clear container and see if it separates. Plugged exhaust? catalytic converter coming apart? maybe a bad case of carbon build up causing the valves to hang up and not always seat? I will keep thinking about this. Chris
Customer: replied 5 months ago.
I thought the same about the catalytic converter myself so sunday I separated the exhaust and rodded the converter, so it's free flowing now. It seems that only worsened the shaking and vibration. I remember when I changed the plugs when I first bought the van, they all were completely burnt up, white chaulky ash. The gap on every one was at least 1/8 inch or more and the electrodes were all almost completely burnt into. Also found the air filter hasn't been changed since 2007 according to the receipt records. it was solid black. After checking the motor thoroughly man its pouring oil from every crack it possibly can
Expert:  Chris replied 5 months ago.
Check for fuel contamination, and check fuel pressure next. Should be around 50 psi. Chris