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Discussion Starter #1 (Edited)
1999 Chrysler T&C Limited - Troubleshooting a "stumble" / "misfire"

I don't know if there is a direct causal effect resulting from my fix of the air conditioning or not. But this maddening "stumble" began to manifest itself right after the repair and is seemingly getting worse. The vehicle is a 1999 Chrysler Town and Country Limited. Approximately 100,000 miles on the body and the original engine was replaced by a previous owner with a low mileage 3.8L out of a 2000 Town and Country.

SYMPTOMS

  • I replaced the Compressor, Drier, Expansion Valve and Timing Belt one month ago. The next day, the van developed an intermittent “stumble/misfire” under load – only after vehicle was warmed up with air conditioning on while stopped at a light. It ran and and idled fine upon acceleration.
  • By the end of the first week, the “Stumble” began occurring when compressor was NOT engaged but still at idle with the brakes on.
  • A few days later, it began to occur intermittently during acceleration.
  • More recently, I have noticed that the dash lights and headlights flicker during these “stumbling” episodes.
  • The “Stumble” is less obvious in neutral or park, but it is there and may have been there all along and I am just now noticing it.
  • I have tried timing the frequency of the stumble, but it seems to be random. Sometimes 2 minutes between stumbles and sometimes just 10 seconds or so.
  • The "Stumble" seems to increase in frequency proportionately with the outside air temperature. More during the hot afternoon temps, less during the cooler evenings but it too random to definitively make that observation.
  • It has never triggered the "check engine" light and my fuel economy seems unaffected. The radiator remains full at all times, though the overflow tank loses maybe a quart every month. The van has never stalled.

I took it to an Autozone and used their Actron scanning tool. The tool was well-used and I have little confidence in the results, but it read the following codes (which could be old or in error):

2. Left Front Wheel Speed / Signal Malfunction
4. Right Front Wheel Speed / Signal Malfunction
10. Controller Antilock Brake Power Feed Circuit
13. Under Voltage
14. Chrysler Collision Detection Communication
15. Over Voltage


PARTS I HAVE REPLACED SO FAR:

Below are the troubleshooting measures I have taken so far and in the order I replaced them. None of them have curbed the stumble problem.

  • Plugs (all 6)(0.050 gap)
  • Plug wires
  • Coil
  • Sea Foam Injector Cleaner (2 tanks)
  • Throttle Body - thoroughly cleaned
  • EGR valve
  • Idle Control Valve
  • Throttle Position Sensor
  • Fuel Injector Wiring Harness inspected
  • PCV Valve


WHAT NEXT?

Based on what I have found in these and other forums, below are the steps (in order of likeliest cause) which I think I need to tackle next. I am traveling out west with my sons next month and want to get this annoyance resolved. Any guidance from others who have successfully troubleshot this problem would be most appreciated. I am flummoxed

  1. MAP sensor?
  2. Compression Test? Head gaskets?
  3. Secondary ignition waveform analysis?
  4. Reflash the PCM/ECM?
  5. Vacuum leak?
  6. Alternator?
  7. PCM power/ground circuits – corroded?
  8. Bad injector(s)?
  9. Cracked Flex Plate?
  10. Faulty Instrument cluster? (I had a bad cluster in a '98 T&C I owned previously, but the symptons were nothing like what I am experiencing now)
  11. Cracked Flex Plate?
  12. Crankshaft Position Sensor?
  13. Camshaft Position Sensor?
  14. O2 sensors?
  15. Low compressor oil
  16. Wrong timing belt? (When I installed the new timing belt, it seemed to be just a tad little shorter than it should have been. Can a slightly 'too tight' timing belt possibly cause problems like I am describing?)
Thanks in advance for any thoughts/recommendations.
 

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Hi!
You don't need to worry about the timing belt, this engine is an old school one with timing chain and push rods. If you refer to the drive belt, that one nothing to do with timing or ignition.
My bet is on the ground circuits. Or any wiring disturbed by your work on the air con.
 

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I would start by "disconnecting" the AC compressor clutch. Maybe your system is overcharged or you got a defective compressor.

Even with AC off, AC compressor still engages every now and then.

Let us know how your vehicle behaves with AC clytch disconnected.
 

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Discussion Starter #5
I unplugged the compressor and took it for a drive. Sadly, it did not solve the problem. But it was hot today and the stumble was significantly more pronounced.

Another possible clue is that while the dash lights and headlight definitely flicker with each stumble, the console radio, time, etc) lights do not.

And the stumble is much worse in drive and reverse than in neutral or park.
 

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I believe it is voltage related. That's why there were "under voltage" and "over voltage" codes. These vans are picky about voltage and electronics. Check and clean the grounds, clean the battery connections, check the battery cables (especially the ground cable) and check the fans for operation and weird smells. I once had a fan go bad (started seizing up) and it made a weird smell, like hot brakes do. It eventually caused the 40amp square green fuse to blow. I unplugged the bad fan at the motor and ran on one good fan until I got to the junkyard and got a replacement set of fans.

Also during a heat wave while trying to get my A/C working, it got hot enough under the hood to melt the solder holding the diodes inside the alternator! So I suspect your alternator may be having problems too, either with brushes or the diode bridge inside shorting or burning up. You can have a partially charging alternator with a diode burnt out. With a diode shorted, it will cause AC current to be mixed with the usual DC current and the computers don't like it.
 

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Discussion Starter #8
Lazy troubleshooter question: I have some braided ground straps but not much time to tear into the project tonight. Can I leave the existing grounds in place and just quickly run ground straps like wtz_ftw did here:

http://forum.chryslerminivan.net/showthread.php/155873-Critiquing-My-Upgraded-Two-Grounds?highlight=alternator

I have much more time to actually dig into the project (Plenum to firewall and under the battery tray) over the weekend to do it properly. But if the problem is under the battery tray, could my proposed quick fix clue me in as to whether or not I am barking up the correct tree?
 

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Discussion Starter #9
After testing my alternator, it is operating properly. I was wrong about the codes - they were old. After clearing the old ones and driving for the week, no new codes were generated. I cleaned all the grounds and battery connections. And the fans are running properly.

Thank you all though for the troubleshooting tips. I am zeroing in on the problem and have started a new thread. Something is going on with cylinder #4.
 

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Discussion Starter #10
Well, it took them 5 days, but after $586 in labor (+$240 for the rental vehicle), the dealer diagnosis was this: the #4 spark plug wire was missing the metal end cap.

I can't believe it. When I changed out the AC compressor and expansion valve in May, I figured it was a good time to change out the plugs and wires since I was taking the alternator out anyway and that is the only way to access them. I purchased new plugs and wires from Advanced auto. I didn't even buy the el cheapo's. Knowing that I had a lengthy road trip coming, I bought their high end offering. The job went itself went smoothly, but I was concerned when one of the plugs I pulled out of the box already had anti-seize on the threads. Someone had bought them and maybe didn't end up needing one? I don't know. But I inspected the plug and it looked fine. I gapped it to 0.50 and installed it anyway. (My car was all apart and it was night so I wasn't going to return it the next day). The plug wires showed no sign of prior use and they installed properly. I don't recall NOT hearing the "click" as they snapped onto the spark plug. But apparently, that was the problem. And it was the number 4 wire as I had speculated.

I am still miffed as to how the car could run absolutely flawlessly up until the point that it was up to temp and then develop all of these problems. And I don't know whether or not to go back to advanced auto and register a complaint. At a very minimum, I think I should get back my money for the wires and plugs.

What would you all do?

Total cost: $1,032 for a faulty plug wire!

[$206 (parts used in troubleshooting) + $586+tax (dealer diagnosis and fix) + $240 (rental car) = $1,032]...and this does not include the countless hours searching on here and under the hood. Nor does it include the generous time members took to respond with their thoughts.

  • Coil ($40)
  • Throttle body gasket ($7)
  • Sea Foams Injector Cleaner ($10)
  • EGR valve ($50)
  • Idle Control Valve ($15)
  • Throttle Position Sensor ($14)
  • Thermo Flex Wire Insultation ($15)
  • High Heat Harness tape ($9)
  • PCV Valve ($8)
  • MAP sensor ($38)
(P.S.- since I have two threads running about the same problem, I will cut and paste this into the other thread as well. But I don't want anyone to think "am I reading double"?)
 

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Hi, what you are experiencing sound similar to what I had, it turned out to be the spark wire to the right rear spark plug,the one behind the alternator had chaffed and caused a short.I hope this helps.
1999 T&C 3.8 engine. I still have the van. willing to part with, has new tiger paw tires, just want the price of the tires.
 

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Discussion Starter #12
I just realized that I never circled back on one additional problem that I discovered and solved last summer and for which the van has been running splendidly ever since.

When I remover and cleaned the throttle body, I ordered a replacement throttle body gasket from Amazon. In my haste, I reassembled everything but did not check the mating surface. After troubleshooting and troubleshooting, I eventually disassembled the throttle body again and discovered that I did not receive the correct gasket. It looked correct at quick glance, but the Venturi diameter of the gasket was about 1/2” less than the diameter of the actual Venturi. Thus, it was restricting air flow. I took a razor blade and trimmed it to the correct diameter and it has been running fine ever since.

So the moral of the story is to check the mating surfaces and make certain you have the right sized throttle body gasket!
 

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You had a throttle body gasket for a 3.3L engine. Glad to hear you got the van running well. You could probably argue to get your money back for the plug wires, but it ends there. You need an ASE certified mechanic to install the parts, or else the labor is on you. All the parts for "troubleshooting" weren't really needed, and diagnosis isn't covered. Inspecting the parts before installation (what they assume an ASE tech would do) would have prevented this problem. This is how the discount auto parts stores see it. Yeah, it's not fair and you paid a price for learning something, but that's life. I got a raw deal once with a new brake master cylinder that ruined my front brakes and cost me a couple of days of work, but I ate the cost and will avoid Dorman parts if I can.
 

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Discussion Starter #14
Gosh no, at this late date I am not looking to recoup anything. I am far from a master mechanic, but I know enough that I should have caught this. I was just rushing and learned an expensive lesson in my haste. Just putting it out there for others to check if they have similar symptoms.
 
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