'99 chrysler lhs engine shutdown @55 mph

QuestionEdit

QUESTION: what is suspect when 99 chrysler lhs engine shutdowns at 55 mph on last shift. it will not restart for 2-3 minutes, happens intermittently and does not show on chrysler tech computer. checked asd relay, showed slightly burnt prong ?

need to self repair as shops are having a field day with women and repair ( not repaired) bills

ANSWER: Hi Kimberly, You might try to exchange the asd relay with one of the other relays in the box with the same part number such as the high speed fan relay nearby. You might also check fuse N (30 amp) and fuse T (20 amp) to see whether either of those has a subtle crack in its wire which may be spontaneously opening as it warms up due to conducting current, and then restoring itself as it cools down. The other type of parts that begin to fail as you described are the engine rotational sensors, specifically camshaft and crankshaft sensors. Those should produce a code (0340 or 0320 respectively) but in early stages of failure the engine controller might not 'see' it. If you were carrying along a voltmeter and tools you might catch one of those "in the act" as it were, but you would have to move quickly before it cooled off. Those are the only ideas I have at the moment, except for one possibility if the shutdown consistently occurs when you take your foot off the gas. That would be a sign that the exhaust gas recirculation valve is not closing tightly and is rather hanging up slightly ajar which leans the mixture too much to sustain the idle situation when you have released the gas pedal. It can do that but not set a code. It can be cleaned out/valve stem lubricated to correct that situation. You will find it in a small pipe that branches off the right side exhaust manifold and flows exhaust gas back toward the rear where it feeds into the intake manifold near the throttle body. The procedure for removal is different for the 2.7L and 3.2/3.5L enginess and in the latter case may be more than you want to get into because it involves removing the fuel rail and intake manifold plenum. You might look at the valve to find the valve stem and spray it with WD-40 but I am not sure it is exposed or not for such remediation.

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QUESTION: this may be a silly question, but I am unsure what fuse N & T are exactly and where located as it is not obvious to me by looking at them?

ANSWER: T is the fuse right next to the high speed fan relay at the outboard end of the box N is a fuse in the front row of fuses that are smaller in size and it is immediately adjacent to the most inboard of the big fuses (or itself is the most outboard of the small fuses in the front row). PS: If the engine only dies at exactly the same shift point and at about 55 mph, and doesn't die at any other time, then I would believe that there is an electical short in the transmission's electrical control system, specifically the actuation of the torque converter lock-up function/torque converter clutch. You should experience four separate gears (3 shifts) when accelerating from 0 mph. Finally there is felt a slight decrease in rpm (and as shown on the rpm gauge) around 50 and that is in fact when the torque converter clutch locks the two turbines of the converter together as a means of improving fuel economy. See if that is the only time this happens, which would corroborate that theory of what is causing this.

PPS:On the other hand, it may be a solenoid inside the transmission which is an electrically operated device that controls the flow of hydraulic fluid inside the transmission, and the wire that actuates that solenoid could be short circuited. I think this makes more sense than the torque converter clutch which seems to be only operated by hydraulics and not by electrics. If the shift where this happens results in about a 30% drop in the rpm that would corroborate an 'overdrive solenoid' relationship. The change in rpm when the torque converter clutch happens is smaller, around 10%. If you can hold off taking this to a shop until the cutoff happens all the time, reliably, that would be a more diagnosable situation. Something that only happens sometimes can be very time consuming to deal with when a mechanic is being paid to wait until it does it. One idea might be to drive in the D position, but not the OD position, of the gear shift indicator and see if in that gear you still suffer the shut down. If not then that would be very relevant to the diagnosis. You will find that the rpm is going to be higher at a given speed, and the gas economy may suffer a little bit as the result. But if that simple change prevents the shut down of the engine I would believe that it would be a lot less costly to not get the very highest fuel economy compared to what could be a very expensive transmission repair. So give that a try. Roland

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QUESTION: The first time this happened, the transmission did jar noticeably. The following events have been as you described. The RPMs drop substantially, but then of course drop to zero. The vehicle only has Drive ( as it is Auto-Overdrive) do you mean 3rd gear? Will this cause further damage and will this situation leave me stranded on the Interstate, when it goes? I am usually in a suit for work, with my dog, so I know what to expect? ( like having tennis shoes to hike with her :) ) Thank you very much for your time with this!

P.S. It has happened 5 times in last three weeks. Only when I drive it of course, and not at all while the two shops had it, each for a week.

AnswerEdit

Hi Kimberly, Until we know exactly what is the cause it is hard to predict. I would believe that there should be a fault code stored in the transmission control module memory. A nationwide autoparts store, such as Autozone, will often give a free readout. So if there is one convenient to you give them a call and see if that is offered. Once a code appears we should have an idea. Yes, I meant to suggest you drive in the gear directly below the top gear, which would be 3 and see if that is reliable. When a significant issue develops with the transmission it will shift into 2nd gear and refuse to shift to others. That is a fall back strategy that allows you to 'limp-in' to a garage. So that will be the more likely scenario. The 2-3 minute refusal to restart though sounds to me like an engine issue, not a transmission issue so that is why I suggested looking at the fuses and switching the relay as that kind of flaky situation may well be something related to the power supply circuits that can shut off the engine/transmission or both momentarily. You might want to listen carefully when you first turn the key to the 'run' position (before the 'start' position). You should hear a hum from the fuel pump under the back seat. Then when it next stalls out on you, do the same listening test. If you don't hear the hum then tha would implicate the power supply such as the ASD relay that you menitoned showed some abnormality. Did you switch that out with the fan relay? So see how this strategy works until something definitive happens. Roland

PS As to the fuse identifications, I am speaking of the ones in the power box located in the engine comparment on the driver side of the vehicle. When it is opened, by inboard I mean toward the midline of the car, and outboard means toward the left fender. The relays are labelled no doubt on the box lid of the circuit board. Thanks for the kind remarks and nominations.