mzr310

while working on my truck today, running like crap, we noticed the engine was warming up but the radiator wasnt. we ran it for about 10 minutes when we noticed it. the temp gauge was showing it was warmn but radiator was ice cold until we took off the radiator cap then it started heating up. what would cause this and would it cause the truck to run bad. also the truck runs a hell of alot better with the tps sensor unplugged. what else would cause it to run lean?

Death Runner II

The cooling issue you describe may just be a fluke, or stroke of luck as it would seem. My '92 4Runner don't open till its hot, which could take up to 20 mins depending on outside temp. But I know my thermostat sticks, this could also be the issue for you as well, or you could have something else restricting coolant flow (i.e. weak water pump). If you get this continuously, look into it further. This would not cause a poor operation or lean out, however a bad coolant temp sensor could.The TPS being unplugged will throw the computer into a default mode and depending on how the computers are programmed, this can effect multiple control systems, forcing the system to run at a factory preset to prevent engine damage. If you are running lean and that system is effected by the default parameters this will richen the fuel mixture and therefor making it run better. Its also possible the TPS's resistance values are out of spec. I'd manually Ohm the TPS to verify its within spec. If this doesn't help or after inspection, all is good, then your problem may be somewhere else

goodyota

feel the radiator hoses and see how "tight" they are along the surface. possibly the head gasket is leaking, pressurizing the cooling system so when u pop the cap, pressure is released and coolant is able to flow. And if it runs better w/o the tps, check its resistance/replace it. just a thought.

Death Runner II

Excellent point goodyota, I thought about the head gasket possibility shortly after posting.

Another possible way to check this is a gas analyzer or even checking the oil to see if there is coolant in it or if its milky. This is a good indication of a head gasket failure, BUT not always will this help.

mzr310

not a head gasket i wish it was that simple. checked the resistance on both the tps and air flow meter and both showed to be good. will the coolant temp sensor cause it to run lean. also what is the other sensor by the coolant temp sensor. thanks

Seanpatrick

i just bought a 92 pickup for $3000. two days later now, the motor is making horrible knocking noises and is pretty much shot its sounding like, i dont know whats wrong yet. any suggestions for a good avenue to pursue towards getting a brand new 22re put in? i really like the truck and wanna get it running and keep it for a long time. Im from Oregon but im living in NorCal for another year now, thanks.

Death Runner II

Yes there should be 2 coolant sensors, one for the gauge (usually a 2 wire connection) the other for the engine control management (usually 3 or 4 wire connection) if the one for the ECM is faulty or out of range (say reading coolant temp at 210 degrees and its only 50-60 degrees outside) it could learn the fuel system out or the air intake temp sensor could be reading too low in temp. I had a '93 Blazer that did that. Read 20 degrees when it was 90 outside. This could be a long shot in your situation but it may be the cause. Also check the ignition system, if the spark timing is to far retarded or advanced it may richen or lean out the fuel system in attempt to avoid internal engine damage (also referred to as an ignition ping) I would also check the idle air control system (i.e. IAC etc.) for faults, making sure its not dumping too much air. Then again I would start with an oxygen sensor before all the other checks I suggested, These are known for failing often and will lean out the fuel system.
Good Luck!

lostinafog

if when you removed the cap it didn` have pressure on it the you do not have combustion gases interring. removing cap was just happenstance
PM change the thermostat--fresh coolant
& yes a bad ECM temp sensor will make it run bad you have two sensors one for gauge one for ECM.

TPS can effect operation as well

are you running rich or lean?

mzr310

what is the other sensor on the intake by the temp sensor?

mzr310

running lean