90 V6 code 52, bad MPG and overheating

[phil2810]

"I have a new to me 90 V6 Camry with some issues that may be related but maybe not...

First, when I jumped Te1 and E1 it gave a code of 52 for the knock sensor. The engine idles and drives smoothly. The previous owner had done a top end rebuild and I think he may have not connected the sensor when he was putting it back together (I "fixed" the dash temp gauge by reconnecting the sending unit). I know the knock sensor is difficult to get to, but where exactly is it? I've looked down between the firewall and the engine, up from underneath near the o2 sensor, but I don't know exactly where or what to look for. Possibly I could follow the wiring back from the harness it runs through?
Next, she never overheats sitting at idle, but will get hot intermittently while driving. I drained and flushed the radiator and block (the radiator flowed garden hose amounts of water fine), replaced the T-stat and radiator cap, disconnected the fan temp switch so the fans ran full while driving (didn't help), tried to bleed any air out through th e bolt in the upper hose pipe, made sure the belt was tight etc. When she gets warm, I can decrease the temps by going wide open throttle for a second... then the temp gauge drops quickly to mid scale, but usually creeps back up (sometimes it stays mid-scale). I'm afraid it may be the water pump but it's not whining or weeping OR worse, the tranny is heating up and transferring the heat via the radiator. I may have overfilled the system, but wouldn't it just overflow from the expansion tank until it was normal?
Lastly, she's getting 16MPG mixed driving. I've had the windows down because I've been running the heater to help manage cooling system temps, but I can't imagine it affecting it that much. I've replaced the air and fuel filters, but no joy. I'm going to pull the plugs tomorrow, but the last owner replaced them and wires)less the 2K miles ago and the engine sounds good, no missing or knocking. I worry about the tranny and maybe I'm not getting all the power to the tires, but she seems to shift fine. The tranny fluid was BLACK when I got it, but I've drained the pan and replaced 3.5 quarts, drove a week and did it again. The fluid looks good now.
Could the knock sensor problem cause the other issues? Or maybe the code is actually single digit 5 and 2, and it's the O2 sensor so the ECU is dumping more fuel? Again, I don't know if these are related problems or I'm chasing seperate issues. Thanks!!"

[Doctor J]

The knock sensor is located in the valley, under the intake manifold; the intake needs to come out to get to the sensor.
Make sure that the thermostat is correct type for this engine [it MUST have 2 valves]
The air bleeder plug bolt is located near the upper radiator hose outlet, you may try to bleed air from there.
In theory the disconnected sensor can cause ping and overheating, but mainly during the acceleration, not during the cruising.
The radiaror is the suspect if the car runs hot on the highway or with a/c but cools down in stop and go, or slow driving.

[phil2810]

I spent my Saturday pulling the intake assembly off and found the knock sensor.... It ended up being loss of continuity from the sensor connector in the valley and the gray connector that's near the front drivers side injector harness. I replaced the wiring and put it all back together and no more code 52 (I'm GLAD, that would have been a lot of work for no gain!) The engine seems to run a little better, so we'll see if I gain any MPG.

....BUT the overheating issue remains. She idled fine for 2 hours, but once I started driving, the temps rose quickly. She doesn't get ALL the way to the red, but darn near it. Again, if I rev the engine, the temps go to below mid-scale but will start creeping up again. Tonight when I gave her a test run, I ended up splitting the upper hose near the clamp. Water was spraying out of it with pretty good pressure and increased flow when I increased RPM, so I think my water pump is OK..... I'm leaning toward the radiator being obstructed. I shut her down before I checked the lower radiator hose to see if it was collapsed, but I'm going to replace it tomorrow when I replace the upper....

Any other thoughts?

Phil

[Doctor J]

remove and check the thermostat before doing the radiator

[phil2810]

Originally Posted by Doctor J

remove and check the thermostat before doing the radiator

Hmmmm, I removed the thermostat and it looked fine, but I left it out so and put some zerex super-flush in the system and took her around town for several hours running errands. She never went more than halfway on the temp gauge the whole time. I could also tell my water pump was pumping well when I looked in the radiator and upped the RPM.... I wasn't getting very good flow before.

I've only had the car 2 weeks and it overheated on the highway from day one. I replaced the t-stat (along with the radiator cap and a system flush) last week, but no change in symptoms. I suppose it could have been a bad "new" thermostat, but more likely the wrong type. I got the other at NAPA.... I guess I may go to the dealer to make sure.

Thanks,
Phil