Ok, you might remember I posted a thread not long ago about poor performance when the engine was warm. (UZZ31 V8).
Well, coming back from Newcastle tonight, coolant temperature was way low. Stop for 30 seconds and temp is back up to operating temp.
I just thought I would give it a test... On the main road back into town when the coolant temp was low, I stopped then floored it to test what the power would be like. To my amazement, the wheels started spinning and it started crabbing up the road, then when it regained traction it just took off. Tried a few times with similar results.
Stopped a little longer and got the coolant temp back up to operating temp, tried the same thing and couldn't even get wheelspin while holding the brake....huge loss of power.
First of all, should the thermostat allow the coolant temp to drop like that (very cold night)? Second, why the hell would it drop SO much power by being at correct operating temp? The few other V8 Soarers I have been in do not exhibit this symptom.
It's driving me nuts trying to get my head around WHY it would be doing it.
I know the basis of why when the ambient temp is cold the car goes much better, but I'm talking coolant temp/engine temp.
I felt the intake pipes while I was stopped when the engine warmed up, and they were still cold. So when the coolant temp is raising, it's not having any effect on the intake air temp as there is little to no heatsoak of the intake area. It's just a magical point when the car decides it doesn't want to pull like it should.
The ECU also adds more fuel when it thinks the engine is colder.
Ebay often has people touting power increase kits that are nothing more than a simple resistor to fool the ECU into thinking the engine is cooler and adding more fuel. $15 for a 10 cent resistor, not a bad profit.
Whether that is enough to account for your apparent power increase though... I have my doubts.
The temp sensor directly affects fuel and timing. If cold enough it puts the old fashioned choke affect on - more fuel and timing. Great for down low rpm power. I had a variable resistor pot on the temperature gauge. By varying the resistance I cold vary idle speed and even make the engine stall. 1UZ-FE's have more power when cold - it's factory tuned that way. I had a Blitz ECU that completely altered fuel - I could get wheel spin off the line, well not smoke 'em type wheel spin, just a few little spins, whereas with stock ecu I just got Mr Plod. My '32, like all '32s, is a dog off the line stock. My Unichip at last gave me power off the line, now at T-junctions I don't have to leave tons of space - I can just go! You guys without stock 32s don't know how bad it is!
When I had my top tank split replaced I installed a new thermostat and cover. My temperature gauge never budges from the half mark whether it's 2 degrees outside or circuit sprinting on a 35 degree day. Temp gauge that falls when cold usually means a thermostat getting stuck open a bit. My old thermostat did have a few rub marks on the moving part - the radiator guy said it was a sure sign of age and time to replace.
Peter, it's a good thought... It's a MASSIVE power difference though, not just a few Kilowatts from a little more fuel and timing...and it seems to affect the auto shift points quite dramatically also.(which I believe it would if the ECU thinks the car is cold anyway).
I've checked fault codes - none.
Temp sensor wouldn't be worth much would it?
Is there a fault code for when the knock sensors sense too much knocking? I can only see one 52 & 55 for "no knock signal" for each sensor, and 53 which says "Engine control computer (for knock control) malfunction for engine speeds yadda yadda". I don't know if that is meaning that it's sensing knock and can't do anything about it or what???
The only think I can think of is the heat getting to the knock sensors and fooling them or something, and winding the timing right back, but that is a majorly wild guess.
O2 sensors have been replaced, but I think it's open loop at WOT anyway?
I've been thinking about it Don , but I wanna get the few problems fixed first.
It's definately not just the way it's designed, as a mates V8, stock, is much quicker than mine off the line, can spin the wheels easily while holding brake etc... He drove my car and mentioned how sluggish it is compared to his also, so it's not just me.
hmmmm. I have also mucked around with the knock sensors and a variable pot. No difference on my car - but once the pot fell off mid acceleration and the car lost heaps of power as it thought the knock sensor wasn't there anymore.
On my car open loop wouldn't come on until 2800 rpm from memory. I had one of those autospeed air/fuel LED thingos on each sensor and it stayed in open loop for ages and just wouldn't go. Once it hit closed loop it was obvious and away the car went.
Your car should leap from the line being a UZZ31 with headers. I can't think what would be at fault making your car do what it does. Very frustrating. Your car shouldn't change temp like that so soon though. It might not be related - but perhaps that should be sorted first of all. Perhaps an investigation of the cooling system is in order first of all. I haven't heard of the temp sensor stuffing up. I have measured the resistance of the temp sensor with temp and it was the same as the one in the 21st century book - I don't have the figures any more. Basic stuff like plugs, wires, filters - are they all ok?
Neil Griffiths Moderator 1 x JZZ30,2 x UZZ31,1 x UZZ32,1 x UZZ Track Car,1 x AeroCabin,1 x Crown V8,1 x Celsior
I would replace the Thermostat first..Then see how it goes.. GENUINE ONLY..They are cheaper than After Market. About $30 from memory & $6 for the sealing ring. (Lets face it..most are as old as the car)
ECU Coolant Temp sensor sits in the Xover water pipe that the Thermostat lives in.
The prices I got were: Soarer thermostat 90916-03125 $24.60 Rubber sealing ring $9.85. I forget the part number for the latter but if you are buying it with the thermostat they will just about manage to work it out for you.
My car exhibits similar symptoms. Coolant temp drops wbhen it's really cold; time for a thermostat I think. I'll get it done and report back. Mine definately has more grunt when cold but it's not a dog when warmed up either. I have no trouble spinning wheels without holding the brake on and stalling it up. I do have a higher stall torque converter though which does help.
I think perhaps the ECU is adding advance when coolant is cold as the extra fuel alone doesn't account for account for it...it's already rich so more fuel shouldn't make it go better.
I changed my thermostat yesterday, then we had a warm night so not a fair comparison with recent evenings. It does appear to be heating up faster though, and was sitting at the centre instead of 1 block down where it usually sat during normal town driving.
Looking at the old thermostat, it looks as if it might have not been sitting in squarely as I can see a ring imprint on the valve face that is off centre and possibly goes off the edge a bit. The housing also had a bit of crud just around the shoulder where the thermostat sits which could have caused it to sit at a slight angle, hence not closing properly.
Parts from Salisbury Toyota.
Email email@example.com Mark it "Attention Gary" and ask for SC price. Prices include GST and there are equivalent replacement numbers (such as the number that David quoted).