JonnyO78

Ok, so when I picked it up this beast was running. A little sluggish feeling, but running. After getting it home and starting it ever couple days to keep the battery conditioned, it stopped starting. I was waiting on caps for the ECU at the time, so I put it off until after the recapping, which went pretty well (there's a post). I plugged the ECU in and turned it over a couple times and it threw the engine light, code 12. I looked it up and it points to distributor caps. I pull the caps, rotors, and wires off my 91, get them installed, and she fires right up. I get it all buttoned up, and it's running rough now. I start by unplugging the MAF; problem clears up. I run it out about 200 miles to Portland and back without a hitch. Smooth sailing, if the gas consumption is a little high; that's to be expected as an unplugged MAF translates to a rich fuel mixture. I drive it to work the next day; 16 miles. After work I swing to the Toyota dealership for a quick oil change; 10 miles. The dealership points out that my intake where the MAF is isn't properly hooked up to the plenum, and that could be why my MAF is causing issues. Quick fix, plug in the MAF, engine code (I think 24) disappears. Drive it home about 10 miles, and have no real problems, but maybe a minor new belt squeak. Now, this is a project vehicle, so I'm mindful of noises and I watch the gauges. I go out the next morning, hop in, and take off to work. The squeak I'm not sure if I heard the day before is definitely here this morning, but nothing too serious, so I'm off to work. As I drive on, I notice the temp gauge riding hotter than usual, but it cools down during higher RPMs, so I think maybe it's the belt and possibly something wrong with the water pump, seeing as it had been recently changed (I was unaware these pumps aren't on the serpentine until later). I get closer to town and it's consistently creeping into the red mark and dropping quickly at higher RPM, so I stop for an inspection, check my coolant (which is green and a flush is getting done next week), it seems kinda low, so I top it off with a bit of the coolant I got for after the flush. That seems to quiet it down. I continue on and get about another mile up the road and I hear a snapping noise and my batter light comes on and the motor gets REAL quiet: obviously I snapped my serpentine. So I turn around and head back and stop at the O'Reily's in town. I buy a belt and start inspecting. Well, I found the idle pulley had frozen; looks like I found the squeak. I get a pulley as well, and replace both. Fires right up, and I continue on to work. As I'm headed in it starts running hot again and cooling fast at higher RPM. Otherwise smooth sailing for the 6 miles. I go to leave for lunch and it's running rough again. Stalls. Fails to start. I unplug the MAF. Starts. Runs strong. Turn off, plug in MAF. Starts, runs rough stalls. Unplug MAF, hard to start, but does. I get about a mile away and it starts running rough then loses power. Shift into neutral, won't start. I pull over and park. Engine light is on again. Check codes: 12, 13, 24, 31. Cleared codes. Try to turn over. Code 12. I'm getting a new set of caps and rotors in the morning. I also grabbed a coolant temp sensor. I guess I should pull and inspect my thermostat as well.

So I'm hoping new caps and rotors clear it up. I've been doing my research and the code 24 seems to be kinda elusive for a lot of folks. I talked to one person who says they've replaced almost all the sensors and are waiting on TPS in the hopes of getting their LS going. I'm about to go through and just start replacing any and all sensors I can afford since this is a 24 year old car with 284k miles.

Any suggestions are greatly appreciated.

RA40

iTrader: (6)

I feel you are on this pretty good. Keep us posted. The vacuum lines are likely due for replacement too.

Yamae

The code 12 is often generated when a crank position sensor or a cam position sensor is not working right.

JonnyO78

Are there physical sensors? Everything I'm coming up with says it's part of the distributor housing, but there are definitely leads running in behind the timing belt wheels. Are they back there?

Yamae

Yes, the early 1UZ-FE engine has a rotation sensor in the distributor housing. The distributor shaft rotates synchronizing with the crank/cam shaft and the ECU gets the timing signal from there. This link and this page might be useful to see what it is.

JonnyO78

Yamae always on time with the info! Oddly, that says for 95-97 LS400, and that it doesn't fit my 94? But it LOOKS like the housing from my 94, as best I can remember. And that sure looks like the same sensors! Based on the diagram, I should be able to swap just the sensors. Is it possible to remove the sensors without removing the housing? Because it looks to me like removing that housing means removing the timing belt, which I'd rather not do, seeing as it looks like it is new, and the water pump was just replaced, so those things line up. I'd really rather not risk throwing off the timing, since I haven't had to set it before. However, if I can replace just the sensors without having to remove the housings, I may go ahead and grab the sensors. Rock Auto has some for $67 and $71, so I'd totally add that to my list of sensors to replace.

In the latest news, I've installed new rotors and caps from NAPA (opinions?) and it fired right up the first time! I did this in the pouring rain, with the wind whipping the hood around so bad my wife had to hold it down to keep the prop from flying away. I drove it home about 16 miles and the temp gauge was all over the place. I got home and realized I left the little hose that goes from the reservoir to the thermostat body off at the body. Fixed that. I've left the tops of the covers off for now, since I'll be doing plugs and wires next. I'm going to run it my usual 16 mile commute and hopefully the error 12 doesn't come back again. If so, It looks like I'll be needing those sensors sooner than later. I really need a day after work in the shop so I can replace the passenger latch and door panel, as well as some much needed leather conditioning.

I wasn't able to replace the coolant temp sensor, as it's in a place where I can't seem to get a tool, and it's too deep for any of the sockets to fit. I'm going to check the 1/2" deep-well impact sockets tomorrow, as I think they are deeper than the standard sockets. I won't be using an impact tool however!

I have just a whole myriad of issues. I guess I should go ahead and start a build thread, but I'm just not sure what I'm going to do yet.

JonnyO78

WTF is this sensor without any apparent connection? It's under the right hand coil pack behind the thermostat housing.

JonnyO78

Now it's running hot. I think? The temp gauge is topping out, but appears functional. I'm not sure if it is actually overheating or not, because there doesn't seem to be a lot of pressure in the coolant tank. I can still touch the block and hoses; they're hot, but not that hot. I tried to find the nominal temperature range, but I'm having trouble finding anything. I don't have any leaks, and it's not acting any different. But I also don't have working heat. Can a failed heater valve cause this?

JonnyO78

Ok. So I grabbed my infrared thermometer and the highest reading I'm getting off the block is about 310F. Unless the temp sensor is in a magic spot where the coolant barely reaches boiling, I don't think I'm overheating.

I do however have disappearing coolant and A LOT of white exhaust. So it appears to be consuming coolant somewhere. The oil was just changed and I don't see any signs of water on the dipstick. I also plugged up hoses coming from the PS pump, so it's not that (though the PS pump is leaking and needs a rebuild). I'm getting a fairly consistent stream of bubbles in the coolant reservoir. I'm going to have to wait and hope it doesn't start pouring again today to see if I have a coolant leak somewhere. But that white smoke is disheartening.

JonnyO78

Well, I guess I flushed my radiator! I filled it with water and cleaner and I'll finish the flush in a few days. My fill plug is seized from rust, so filling through the reservoir is a time consuming pain. But I got it all fixed. Now to make a fresh post about my NEW issue.