QuestionThanks. I spent the afternoon checking all the hoses and conections and didn't find any leaks or loose fittings. My check engine light came on after fiddling with everything and the original problem persists. I went over to a buddy's who has a diagnostic computer and got a p-code which says the LPD sensor is failing. As far as I know that sensor is related to emmisions. I'm stumped!
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Followup To
Question -
I have a 96 Town & Country w/a 3.8L engine. The transmission was recently rebuilt and afterwards I started having this problem. The TPS AND Idle control sensors have been replaced. The engine stalls if the car is left to idle 15-20 minutes. It also stalls while driving after a longer period or occasionally when a bump or pothole is encountered. Usually it starts immediately after shutting the ignition and restarting. After this happens a few times(4-6) it then takes about 30 minutes, sometimes longer to restart, after it cools down. I get codes of 12, 31, 55 off the check engine light test. According to the website you listed in other articles the 31 code shows: Bad evaporator purge solenoid circuit or driver.
Plugs, wires, air filter are all new as well.
Thanks for any ideas you may have!
Answer -
Hi Johnny,
My first inclination was to think a solid state sensor was overheating and failing but the absence of a code for such a sensor belies that approach. I would suggest that you check all the vacuum lines of the evap system. I can imagine that if you have a disconnected or cracked hose in that system that when the engine warms up (at which point the purge solenoid should open the system vacuum line so that it sucks trapped vapor stored in the canister into the intake manifold) that if there were a leak in a vacuum line that might cause the engine to stall out (though an alternative response might be for the idle to speed up, but a very large leak might cause a stall). The fact that a bump can provoke a stall also supports the idea of a loose vacuum hose somewhere in the evap system. So look at all the vacuum hoses attached to the intake manifold, giving particular attention to the ones that derive from the fuel tank and the charcoal canister, and to the purge control valve and solenoid which appear from my Haynes manual to be located near the cooling system overflow bottle. I would try to trace the entire evap system elements because they are all connected by such vacuum lines. The charcoal canister and its hoses are under the vehicle (rectangular black container) but the picture in the Haynes doesn' give me enough clues to identify its exact location).
So lets go with the code and try to resolve that before trying to identify something without any clues which can often be a very frustrating and expensive approach.
Roland
AnswerHi Johnny,
Thanks for the feedback and information on the code.
The P1494 code troubleshoot says to do these things:
Check that there is vacuum on the vacuum hose that comes to the LDP with the engine running (should be at least 13 psi)
If not check the vacuum line for leak/pinch/obstruction.
If that doesn't fix the problem then you have to make sure the leak detection pump is running when it is asked to. Without the diagnostic reader, the best way is to see if the pump is activated when the ignition switch is turned on and the engine started (this may be hard to detect with the engine running which is why the diagnostic reader is needed but see if you can feel it run). If it runs then the pump is o.k. If not then test the pump motor.
If that is o.k., then you have to check the yellow/black wire of the harness to make sure it isn't shorted to ground or disconnected between the harness plug and the powertrain controller.
But I suspect the problem is in the vacuum line from the pump to the intake manifold, which is the first thing you should check.
Roland
Hi Johnny,
The LDP (leak detection pump) is part of the evap system which corroborates the 31 code. You might ask your friend if you he got a P1494 or P1495 so that you can troubleshoot specifically for the correct code. I have the troubleshooting guide for the 2001 model year that includes the 3.5L engine which should have virtually identical LDP system as your 3.8L. I could copy a couple of pages on the specific P code that he logged and send them to you by postal mail. So if you want to do that find out which P code and give me a postal mailing address in a follow-up question. Once you solve the LDP issue then see if the problem has resolved itself.
It all has to do with a the system that recycles fuel vapors into the intake manifold and it is saying there is something the matter with that. To me that would be the basis for a fuel mixture problem that would be a reasonable cause for a stall after warm up which is when the system is first called into play by the engine controller.
By the way, the LDP is located directly under the steering gear, sitting on the cross member called the engine cradle, on the drivers side of the cradle (pretty much in a direct line behind the trans, i.e., centered on the longitudinal member of the cradle that is inboard) It has several vacuum hoses and other connections to it.
Because you had trans removed, I would bet it is possible that the LDP electrical or vacuum lines were disturbed. So get under the van and look for LDP and check it out.
Roland
