1998 Dodge Caravan Running out of things the replace. (Two

Tiny
MOPARORNOCAR
  • MEMBER
  • 1998 DODGE CARAVAN
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 162,000 MILES
The radiator cooling fans on my 1998 Dodge Caravan began having issues sometime ago. The fans will not engage even at an engine temp of 220. The fan do engage when the A/C is running, so the fan motors are still fine. I have replaced the Fan Relay that is located under the air box, as well as the coolant tempature sensor near the thermostat. I am reading no codes involving the cooling fan circuit. I am however reading a random misfire and misfire counter at limit/maximum. These midfires began happening as soon as I had the transmission rebuilt. Upon taking it back to the tranny shop they said "We didn't do any work to the engine". I figure the problem begining just after the rebuild was no coincidence and researched a cause. I'm thinking they either damaged the camshaft position sensor or didn't re-install it correctly. Any help tracking down a way to fix these two issues is greatly appreciated. Thank you.
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Tuesday, June 29th, 2010 AT 12:44 PM

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Tiny
CARADIODOC
  • EXPERT
Hi MoparOrNoCar. Welcome to the forum. (Dandy username!). A fast test of the fan circuit is to unplug the two-wire coolant temperature sensor while the engine is running. That will set a fault code and the fan should turn on as a precaution because the Engine Computer doesn't know if the engine is overheating. If that works, suspect the other coolant temperature sensor for the gauge is inaccurate. If the fan doesn't turn on, suspect the computer. If your scanner has actuator test capabilities, you can use it to command the fan to run also.

If you suspect the crankshaft position sensor for your misfire, remove and reinstall it with the paper spacer that you can get from the dealer's parts department. New sensors come with that spacer already installed or a thin rib molded in the plastic. Either of those shear off as soon as the engine is cranked but those are what set the proper air gap. If yours has the plastic rib, the remaining part is to be cut off, then the paper spacer is used for reinstallation. Usually if the gap is set wrong it will cause intermittent stalling, mostly when warm. A simple single-cylinder misfire is more often caused by a spark plug or wire.

Caradiodoc
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Tuesday, June 29th, 2010 AT 2:05 PM
Tiny
MOPARORNOCAR
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I have installed a jump wire at the coolant temp sensor, it was the only way I could get the fans to run. I'll have to go hunting for this second temp sensor. I thought there was only one, when I skip the sensor the dash doesnt read temp, but my scan tool reads 260 degrees.

In regards to the misfire, wonderful info on that sensor. I had no clue. I did however think of the spark plug idea and had already replaced spark plugs, wires, distributor cap and rotor, as well as both O2 sensors. All this with no change. Also, the exhaust seems to be a bit rich using the "it burns my eyes and nose" method. I'm hoping greatly that it is not the PCM. That's gonna be a costly fix. Worth it to save the only cherry bombed out-the-side exhaust mini van in my town, but hopefully it's something simple.
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Tuesday, June 29th, 2010 AT 4:10 PM
Tiny
CARADIODOC
  • EXPERT
Your scanner should show when the system is in closed loop and switching between rich and lean. If you find it is staying mostly lean, check for a small exhaust leak ahead of the front oxygen sensors. Between the pulses of exhaust gas, the momentum develops little pulses of vacuum that can draw in outside air through that leak. The unburned oxygen will be detected by the O2 sensor which will tell the Engine Computer to hold the injectors open longer to enrichen the mixture. No matter how much fuel it adds, there will always be that unburned oxygen from the leak. The O2 sensor doesn't respond to fuel, only to oxygen.

You can also look at the fuel trim numbers. If they are high positive, the computer is adding fuel in response to something, possibly related to your coolant temp. Sensor. If the numbers are high negative, the computer knows there is too much fuel entering the engine and it is trying to reduce the amount but apparently not having much luck. Fuel pressure too high is one possibility. Fuel leaking through the spring-loaded diaphragm in the pressure regulator is real common on GM products but I've never heard of that on a Chrysler vehicle. A leak in the vacuum hose going to the pressure regulator will cause fuel pressure to go up just as it would under acceleration when manifold vacuum is low.

The MAP sensor has the biggest say in how much fuel enters the engine. Check its hose for leaks that would make it read low vacuum. That is a sign of acceleration which results in a richer mixture. The MAP sensor on newer engines is bolted right to the intake plenum and there is no rubber hose. These sensors don't really cause too much trouble like they did in the late '80s.

Caradiodoc
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Wednesday, June 30th, 2010 AT 2:39 AM
Tiny
MOPARORNOCAR
  • MEMBER
Replaced the Crank-shaft Position Sensor yesterday for good measure. $40 for a shot at fixing it is a good deal. My bet paid off. After removing the battery for a half hour to reset the computer, Hooked everything back up and drove around town for 15 mins. No engine light and I could feel the differance. Accidently chirped the tires around a corner. Then a 2 hour drive back home averaging 70ish MPH. Still nothing. Running top notch, now on to the driver window regulator to get everything working right. Thanks for all the input.
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Monday, July 5th, 2010 AT 10:37 AM
Tiny
CARADIODOC
  • EXPERT
Dandy. Happy to hear one problem is solved. One word of warning on the window regulator. Being a suspension and alignment and electrical specialist at the dealership, I never worked on a window on a '96 or newer minivan, but I watched the frustration of a few of my coworkers. It was common to see them squatting down while running across the floor chasing the wound-up spring in the motor or gear assembly. Be careful if you have to pop the cover off of the motor. I don't think an unraveling spring causes a permanent problem, just a frustrating one.

Caradiodoc
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Monday, July 5th, 2010 AT 1:26 PM
Tiny
MOPARORNOCAR
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I figure as much. Luckly I hate electric do-dads in cars. So, I keep as much of it manual as I can. Roll up windows are way easier to deal with. Thanks for the concern.
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Tuesday, July 6th, 2010 AT 2:50 PM

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