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[FIXED-ish] 2001 Chrysler Town and Country 3.3 Rough running at partial throttle
Hi there,
2001 Chrysler Town and Country 3.3. Symptoms are rough running at partial throttle, both in and out of gear.
Fuel trim readings are in range at idle, but when RPM's are raised, there's like a switch at 2500RPM and all of a sudden the fuel trims drop super negative (-25 LTFT and between -17 and -25 STFT). Engine starts chugging.
Same thing happens on the road...fine accelerating, fine at WOT, but at that mid-range cruising, very negative fuel trims and rough running.
I have a code for a Large EVAP leak...though I can't imagine why something like that would effect the running of the engine at such a particular RPM alone.
Again, it's as if something switches on or off or opens or closes very suddenly at 2500 and the performance and fuel trims nose dive.
Any ideas? I was suspicious of the 02 giving me a faulty reading....pulling the brake booster line from the intake, for instance, never made the front 02 go full lean. Additionally, I was watching fuel trims when the car was started cold. Things were running okay until the front 02 started switching and then it started running horribly. So I swapped the O2...but that hasn't made any difference (and makes me feel stupid for jumping at the wrong thing).
With the limited information I would be a little suspicious of the maf. I'm really only replying to add my 2¥ on that vintage 3.3. I have had multiple 3.3 with lower intake leaks as well as injector harness melting on rear or firewall side. It runs next to leaky valve covers gets oil soaked melts injector wires together and takes out the ecm. If it's your van I recommend at least looking inside that harness. I've saved a couple(not that saving a dodge/chryslr caravan ranks high ) that were stuck together but hadn't shorted to each other yet. Good luck with your van
Andy,
Thanks for the feedback. I've given the entire EVAP system as thorough a visual inspection as I can. I've also verified the operation of the purge solenoid and the canister vent valve. If there's a leak (which the codes indicate) it's certainly not obvious. I don't have a smoke machine so I'm at the end of my ability here.
Other than that, it seems to me there's very little likelihood that the evap code is related to my symptoms. Any other thoughts?
Rockyroad,
Thanks for your input. This particular model doesn't have a MAF sensor...just a MAP.
The very negative fuel trims I'm seeing certainly would correlate with some sort of injector fault. I suppose that's my next step...remove the upper intake and check out the state of the injectors with a visual inspection and an injector balance test. Thanks for the tips!
Be very careful moving that injector harness. Split it apart first where it drapes over the back of the motor to see if it's hard brittle or melted by pulling on the wires individually. If you just swing it up out of the way cracking and splitting the insulation and then put it back on and attempt to start it you'll take out the engine computer. Also, did you check all those little rubber hose connections under the air filter box? You have to pull the box to see them. I just use some vac or fuel line never had a comeback for either. Although I don't think it would cause a rich condition.
One last thing, you can get a new harness and remand ecm package on eBay flashed for you, send the old one back. It was less than $200. Hope you find your problem, good luck
After re reading this post, have you ever just checked the coil and wires or plugs. I guess I assumed ('cause I'm good at it) that they were already checked. If anybody changed the power steering res., for their common "whining" there's a good chance the coil is bathing in oil. I d spray the wires when you pork the throttle. I think the evap code put you in the wrong frame of mind for this stumbl issue. I want to know what the problem is now, my curiosity, it can be a bitch.
Hey Rob,
ck o2 with dvom voltage while looking at scanner data....I had the same vehicle short to power inside pcm causing scanner to see 4-5 volts from o2 on scanner and pull all fuel making run like sh*t. and the o2 looked normal on dvom, new pcm fixed it. btw there is a bias voltage on cold start up that is around 5 volts but drops fairly rapid(1 minute) Also stft and ltft go to 0 as a limp mode to save cat
I 'm guessing. good luck!
Goodluck
unplug the egr valve. try driving it again. also check the purge valve for a leak. to do it
1 unplug purge valve electrical connector
2 unhook vapor line (not the one that goes to the intake)
3 use vaccum gauge see if its leaking if it is replace.
Cheryl for the win! After doing an injector balance test yesterday and finding all good there, I moved to the EGR.
Earlier in the diagnosis, I'd applied vacuum to the EGR at idle to see if it was stuck open...the motor died right away...so I figured things were good.
HOWEVER, on this second pass, I figured I'd just disable the EGR entirely, wondering if maybe it was performing a faulty apply at those mid-range RPMs. Unplugged the vacuum hose from the EGR, pinched the hose off and test drove with scanner...negative fuel trims gone...stumbling and rough running gone!
Clearly this is the culprit. HOWEVER...what's going on here? Is the computer screwing up the timing of the EGR? Or is there something inside the valve/solenoid/DPFE diaphram thing that's malfunctioning? Anyone have access to Mitchell that could provide me with a operation description for this particular style of EGR? Don't just want to replace it if it's not the true culprit.
In the mean time, the driver is simply happy to have a well-running vehicle again:-)
Thanks for all your help, all!!
Rob
Bump. Anyone have info on the EGR operation description? Want to be sure whether or not this is an issue with the device itself or if there's some bad input to the PCM that's causing it to apply the EGR at the wrong time.
Just doing some Googling, this system looks goofy...