Home Forums Hunting & Shooting Hunter's Campfire Mechanic advice - Mopar - Driving me nuts

2007 Chrysler Town and Country Minivan.

3.8l Engine is great at 187k... trans, rack etc. all solid.

Old beater, but works as hunting/fishing camper (Stow and Go seats), haul stuff machine... so I want to fix.

PROBLEM: She won't hold low idle. Hold 700 for a second or two... then falls on her face.

What I know so far (my efforts as well as a really good mechanic):

1) No codes

2) Low Idle sensor/control has been changed 2 times (parts are cheap).

3) TPS also cheap and changed

4) Entire throttle body removed and cleaned

5) EGR is good.

6) New plugs and wires

7) New Cat and O2s (both). Old Cat/muffler were sad anyway... Runs better with new Cat, but still not right.

8) Manual throttle set screw advanced but no help... ECM compensates.

9) While running manually and holding 1k on RPM... sprayed the intake and about everything I can think of (vacuum related) with carb cleaner (looking for a leak)... no reaction. Did this twice.

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Up next...

1) Change/inspect vacuum lines to low idle sensor...

2) Check wires ohms on low idle (no codes, but maybe?)...

3) Check fuel pressure (clogged fuel strainer???). This is an in-tank MFer... so not an easy part to swap/inspect.

100% open to any suggestions... Gun, cash or ammo compensation paid for an accurate diagnosis/solution.

As for throwing a match on her... been considered OFTEN.

Got an '86 IROC Camaro ith a TPI engine that's doing basically the same thing...new fuel pump, lines, filters, injectors, throttle body / butterfly's, EGR, TPS, O2 sensors, re-ran all new vacuum lines, new 'Painless' (my a*#) wiring harness, spark plugs, wires, rebuilt the distributor. Only thing not replaced is the ECU/ E-PROM.....found a deal on a new 350 crate long block over the weekend..it's going in with an Edlebrock intake, 600 cfm carb, and dual point distributor..tired of messing with fuel injection and computer crap. I know I'll lose the efficiency of fuel injection and mileage, but this thing only sees about 4k miles a year...

Does it have a mass air flow sensor?
Leaking intake manifold gasket?

How about an internal vacuum leak in the brake booster ?
Had a BMW 540 eat my lunch over that a few years back.
Either clamp the line going to it shut with a pair of vice grips or remove the line and plug it with something.
May not be your problem but it will eliminate one more possibility.

Is (#2) on your list the same as an Air Idle Control Valve?

And if yes, did you replace it with Genuine Mopar part?

Or some big A oreillys vatozone chinese version?

After all the dinking around with replacing parts, is the Air Cleaner intake filter box snapped back together nice and tight?

Did the same with our old '06 Caravan. Manifold Absolute Pressure sensor was one part of it. An easy $15 fix right on top of engine. The Idle Air Control was another as some have mentioned. Throttle body has to come off for that. Reseal with correct gaskets and clean with TBI cleaner and a soft toothbrush, because of the Caravan's EGR routing the throttle tends to gum up and stick. Former Dodge service advisor from that era speaking to you now.

Also IIRC these did have an external fuel filter. Check your PCV valve, it is in the rear valve cover and likely plotzed by 187k and never been replaced. Careful taking it out, it gets stuck and can/will break.

Still thinking, after the fixes I mentioned might consider injectors, have they ever been done? At very least, resealing them.

Any difference whether in gear or neutral? Cold engine or warm engine? Does it restart easily?

Mass airflow sensors can get really flaky. You could try unplugging it. That would throw a code, but if it runs better you have a good indication of a problem. With a good scan tool, you can look at the readings and see if something is erratic.


Jerry

Did you replace the battery? If so or you had to jump a totally dead battery try driving it for a few miles. Sometimes the computer has to "relearn".

Changed the battery a few months ago... 850 CCA... so overkilled there.



Just ordered a MAP... cheap enough.

The OEM Idle Air Control was cleaned and retried... then a new one... then a third one... cheap parts... so I kinda am ruling that out... but maybe the vacuum line to it??? Next test (rotten internally... clogged artery?)

Cleaned the TB a few months back... NASTY... (FYI, Hopps #9 is +1)

EGR tube was nasty also, but no blockage... it seems.

My mechanic has the Snap-On Solus... he has been trying to troubleshoot and NO LUCK.



We held the throttle at 1k RPMs and sprayed carb cleaner all over the intake (i.e. trying to get a sign of intake leak... idle variation)... no luck.



Had not thought of that... probably original



Cold and hot... same.

Gear or Park... same.

It does get better after 15 minutes... won't stall (as much), but still studders on the RPMs about 200-300 RPM

Restarts easy.

Had a dodge pickup that acted very much like a bad vacuum leak except it was intermittent when it first started acting up. It would spudder at traffic lights and try to stall when I accelerated until the rpms were up to about 1200. After 5 or 6 months of it happening more frequently, no codes and changing parts out with my other Dodge, it wouldn't start one morning. Changed the crank sensor and it started and all the other symptoms were gone, never to act up again. Just another possibility. Good luck


Lee

Best answer...

Was the replacement catalytic convertor factory? Also the 02 sensors? Saw a wide range of weird problems with aftermarket parts in those two areas espc. cats not containing proper quantities of precious metals which screws up 02 sensor readings but not always enough to throw a code...

Second the Crankshaft Sensor or another timing part...

Swore I'd never work on a cars again, you can dump large sums of money into parts and an endless amount of time and never find the problem, or if you do it'll turn out to be nothing more than a frayed wire, cracked resister, blown fuse, or scratched/broken circuit board.

Not worth the head-aches...


Phil

I'd add gas first - to make sure it doesn't survive... Just sayin'......

Have you disconnected the battery since installing all those new parts?
Doing so would reset the computer.

Dump a half can of Seafoam into the brake booster vacuum hose and see how she fares.