The last week has been a busy one for project Joyce The 300M.
You may recall I bought the car for my son as a first car a few months ago. Cosmetically on the top side it is not in bad shape, but there are some minor rust holes in the floorboards, as I've come to discover. It needed the headlamps polished up, and, as it turned out, a host of minor-to-medium sized repairs.
I chased after an issue where the interior lights would not turn off for a couple of weeks. I traced every circuit, both signal and ground, from the door ajar switches in each door to the main ground stud under the front seats and also to the body controller tucked up under the dash.
After a LOT of disassembly, testing, and reassembly, I finally noticed that even when the doors were all shut and the switches were open, I would briefly see continuity between the body controller and ground on the sense wires. It was there and gone in a second as soon as I touched the meter probe to the backprobe pin I had in the connector. I was testing all of this with the vehicle's battery disconnected. Since the sense wires pull the pins on the BCM low when the doors open and the door ajar switches close, a brief, momentary ground at those pins apparently is all it takes to make the thing think a door is open. So I yanked another BCM out of the yard from a 300M, plugged it in, and voila! I've got properly working interior lights again. Oh, and my odometer mileage went from 167K to 98K!
Moving on...the car had a rough idle and it did not appear the battery was being charged by the alternator. The rough idle smoothed out when the car warmed up, however it was bad enough it would stall several times before it got warm enough. Spraying starting fluid at the mating surface between the upper intake plenum and the lower intake made the idle smooth out instantly, so I decided to replace the intake manifold gaskets. I also didn't know how long it had been since the timing belt had been changed, so I added a new timing belt/water pump/idler pulley/tensioner to the list of tasks.
Late last week I finally wrapped up the timing belt job. I have done timing belts now on three LH cars: an Intrepid ES 3.2L, a Concorde LXi 3.2L, and this 300M. For the Intrepid and the Concorde, I had no problem fitting my impact wrench in to get the crank pulley bolt loose with the fans and radiator removed. With the M I had to lift up on the condenser in order to get a mini
impact gun in. Methinks the nose of the M is just a tiny bit shorter than the other cars, although I was under the impression that it wasn't supposed to be. The timing belt job, although tedious, was relatively uneventful. It took me a couple of tries to get it timed right because I screwed up at first and put the tensioner in place (with the pin in) before attempting to put in the belt. My memory of how to do the job must be faulty. Once I figured out what I was doing wrong, and had the camshafts sproing! out of time a couple of times, I finally got the timing set dead on and buttoned up the front of the motor. A quick start-up confirmed that everything was good, and then I moved right on to the upper/lower intake cleanup and reseal.
My water pipe under the lower intake was crusty, but still solid. I wire brushed it on my grinder and got it more or less shiny again, and treated it to a fresh coat of high temp engine paint. I reinstalled it with a seal that came in the Felpro kit; the factory install was just a press fit with no seal!? Either that, or someone had been there before me and didn't install the seal.
After cleaning all of the carbon out of the lower intake ports, I reinstalled it early this week. I then made up a gizmo that let me pulse the injectors while I forced carburetor cleaner through them. Unfortunately I broke one of the retaining rings on the top of one injector removing the O-ring. I picked up three of them (in order to hopefully get one good one) at the pick-n-pull for $10 each. All three tested good and cleaned up well, so I have a couple extras. Maybe I'll megasquirt my lawn tractor, LOL!
Did you know the stealer wants $12 for two O-rings per injector? I walked out in disgust, and paid a buck and a half a pair at O'Reilly's. I'm all about using OEM parts wherever possible, but at those prices they'll have to come out of the junkyard!
Lower intake reassembled, resealed (found a torn gasket on the driver's side head, thus confirming part of my diagnosis), and properly torqued down, I moved on to cleaning the throttle body, IAC passage, draining as much oil as possible from the upper intake plenum, and then putting on a new gasket and reassembling all of it. I also removed all of the carbon from the EGR tubes and replaced the PCV valve.
When I got that all back together on Monday of this week, I reinstalled the radiator, put in the new hoses, reusing the cleaned up and freshly painted factory spring clamps, and refilled the engine with coolant...and got a leak from the vicinity of the water outlet. It was mildly rusty, and of course it's in an impossible spot to see clearly, much less remove easily, so I dropped the $35 on a new one and set about removing the alternator again to do the reinstall.
God I hate LH car thermostats! They're just awful to get to!
When I got it apart, I discovered that my problem was I had somehow bent the thermostat
during the installation the previous time!
I'd like to say I don't know how that happened, but I do: it's just such a clumsy place to work, and I must have gotten the thermostat in cockeyed and attempted to bolt it down like that. Of course, it wouldn't seal. The water outlet was probably fine, but seeing visible rust through the paint, and also seeing the mating surface not exactly looking smooth, I decided to replace it anyway along with a fresh gasket and new thermostat. It sealed and held water this time!
Did you know that when you fill your cooling system slowly over the space of several days (because you goofed up the thermostat install) that you benefit from a cooling system which has all of the trapped air at the top of the motor? As soon as I finished putting the second gallon of Zerex G-05 into the recovery tank, it started coming out of the bleeder screw perfectly. I closed the screw and called it good. This was Tuesday or so.
After finishing reassembling the engine compartment, I started it up. It lit off immediately, and then started idling roughly again. Dammit!
So reading around on the web I discovered that it's supposed to have to re-learn its idle strategy. I let it sit idling in the driveway while I puttered around on other things and sure enough, it smoothed out and ran OK. I drove it 15 miles that night and thought I had it in good shape for my son to start using the car. This was Wednesday.
On Thursday morning, I started the car, and went right back into a rough idle again. But...this time there was a Check Engine light, and thus a code. P0123: throttle position sensor circuit high.
I spent the rest of Thursday in between working and doing other stuff researching the code and watching YouTube videos on how to test a TPS. It got repetitive fast, but then I dug out my powertrain service manual and looked at the steps there too, which except for the fact that I don't have a DRB-III, were more or less the same: check the voltages at the sensor, check for continuity between the sensor and the PCM, use a scan tool to watch the sensor as you open and close it.
The sensor never got higher than 70% at WOT, and the minimum opening was about 9-10% throttle. I ohmed out all of the connections and did not come up with anything conclusive, but I had pretty solid evidence that the wiring was not the problem.
$7 at the pick and pull isn't too much to risk on a TPS sensor out of a 98 Concorde 3.2L with about 105K miles. I yanked it out, got the IAC motor while I was at it, grabbed a replacement coil for the one I had that was cracked near the connector, and nipped off all of the coil connection plugs from the donor car as mine were a collection of broken tabs and missing parts.
Tonight I swapped out the TPS for the junkyard unit, replaced 5 out of 6 of the ignition coil connectors, and started the car up.
Smoooooooth! Really high idle in park -- 12-1,300 RPM, but no hunting, stalling, bucking, etc. I took it for a ride tonight, and the car drove well. I stopped a few miles away from home to run into the grocery store, and when I came out and restarted the car the high idle was gone.
We shall see how it runs after a cold start in the morning. I may have the driveability issues cleared up. I cleared the codes tonight using Torque for Android, and they did not return, so we shall see.
Next up, if the idle problem is resolved: brakes.