Chrysler Repair: 91 grand caravan 3.3L:wont idle, exhaust gas recirculation valve, exhaust gas recirculation

Question
QUESTION: the engine stalls when warm, wont restart for a few mins. only happens when idling in gear. i ran snap-on modis on it... returns nothing. all functional tests are fine. no dash codes (only 12 and 55) i've tried running the scanner during a failure but i dont have a flight record option. all sensors and voltage look fine. it has good fuel pressure at all times, even after the stall (i mean the asd hasn't been tripped). heres the kicker.. i can quickly recreate the problem by powerbraking in drive at about 1500rpm. it'll start cutting out and over about 30secs it'll get worse and worse until a stall. however if it starts cutting out and i throw it into park and rev it to 2000 it'll hold in until i let off the pedal, then stall. my best guess so far is the coil pack (being located above the thermostat) i figure it gets hot enough to quit.

btw the van sat for 6 years.

Thanks
-chris

ANSWER: Hi Chris,
I have a different theory related to mixture rather than spark. It would appear that your problem is manifested primarily when the throttle is closed, either slowing down or at idle. The two sorts of malfunctions under those conditions are a cruddy throttle body throat and the exhaust gas recirculation valve. Neither are likely to set a code under these conditions.
You could start by checking the mechanical function of the egr valve stem to be sure it is free to move back and forth and that the internal spring action closes it tightly to a dead stop.
My immediate suspicion is that your egr valve is sticking slightly ajar which will cause the engine to falter/stop at idle speed after slowing down. The valve is located near the throttle body air intake at the end of the engine, mounted in pipe that recirculates exhaust gas from the rear cylider bank exhaust pipe back around to the intake manifold. The exhaust gases have some fumes that can plate out a crud on the valve stem and thus keep it from closing tight when you are at idle. That makes for a too lean mixture so the engine stalls. The valve proper is mounted horizontally with the stem visible in a space between the body of the valve mounted on the pipe and the round top of the valve which is flanged and so if you look carefully you will see a metal rod (stem of the valve) with a slot around its circumference. You can take the tip of flat blade screwdriver and insert it in the slot and then lever the valve back and forth to check if it is moving freely (against spring action in one direction) or not. If it doesn't seem to close easily with the help of the built-in spring, then I would spray the base of the stem with solvent from a pressure can (such as WD-40 or carb cleaner) while moving the stem back and forth.  Then see if that solves the issue.
On the throttle body, remove the air intake that conceals it and clean the throat, both sides of the butterfly valve, and the idle air sidepassageway with solvent. That too can hang up slightly ajar mechanically but not precisely allowing the air to inter in the expected amounts.
Let's see if those fix the problem before looking into the spark coil, which is by the way better monitored for a fault code. Please let me know if these don't correct the situation.
Roland
PS: May I ask a favor of you? I am competing to be the 'volunteer of the month' at Allexperts which I will achieve by getting the most nominations from questioners. If you will click on the "Thank/rate the expert" button below you will arrive at a page which asks whether to nominate me for that recognition. If you would then click on the "yes" I would be most appreciative


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QUESTION: that all makes sense to me too except one thing, after getting warm enough it happens even during accell. its not a misfire or signs of lean mix. its got strong fire when its not cutting out. like i mentioned before i can powerbrake and it has plenty of power. its as if the cam/crank sensor was failing except it doesn't trip the ASD relay, and modis reads cam and crank both "on" the whole time, even during cranking after a failure.

i probably should have mentioned i'm a diesel mechanic for a transit company. i've got a few other mechanics (co-workers) helpin me out but we all come up with something different. one thing we can all agree on is the ignition system. we figured at first the cam/crank but like i said it should kill the ASD relay immediately and set off codes 11 or 54.

it'll drive all day on the freeway, one day after city driving all day and it failing a dozen times (each time more frequent) we finally got it on the freeway and at about 65 it sputtered for a second then lived to see our exit.

tomorrow morning i'm going to recreate the problem and test all the driver wires and power wires to the coil pack, i'll also try cleaning the throttle body and test the egr valve.

thanks again
-chris

Answer
Hi Chris,
Thanks for the further info. Please let me know if egr or throttle body remediation help. I'll try to think of something else in the meantime.
Again, please consider using the 'Thank/rate the expert' button to go to a page where you might offer me a nomination for volunteer of the month. Thanks very much
Roland