FJ62 no power/acceleration until engine warm (1 Viewer)

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T

tony stone

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I just finished a coolant rebuild on a 62 I bought from a guy who abandoned it after he blew the water pump while he was on a road trip (I wasn't able to test drive truck). I replaced pump, clutch, fan, radiator and replaced both power steering lines while i was in there. I also had the alternator rebuilt while the easy access was there. I also replaced all the sensors and switches in the thermostat housing.
My question is the truck fires up and idles beautifully (650-700 rpm) but once I take it out on road I have NO power. Acceleration is non existent. I tried 2 quick test drives of about 1 mile then got back in garage to look around for vacuum leaks etc. I then tried again - this time letting engine warm up and get to operating temperature. This time I had much better/more normal acceleration - although I did have some slight sputtering.

Since the truck seems to operate more normally once engine is warmed up could it be one of those sensors in thermostat housing? Or something else?

I did try the "paper clip" trick on diagnostic test and I got no errors (continuously blinking engine light)
 
Is your cold start injector working?
 
Try pulling up on a STEEP hill to burp the cooling system, should take at least 10 min, then run the rear heater on hot for a while...

That will get air bubbles out of thermostat housing, and rear heater hoses.
 
This seems to be my issue. Only thing is I removed the rear heat due to the lines completely rusting out. I did the bypass now the same exact synthoms you are experiencing I'm having. Absolutely no power when cold. After 45mins of warmup as if nothing happened. Did you rectify this?
 
To talk about this and the possible issues, you need to understand how things work. As 'confusing' as it seems (especially with 3 coolant sensors) it's all actually pretty simple.

Simplest first - the single wire (with a spade connector) coolant sensor goes straight to the gauges. Nothing else. All it does is report a resistance value to the cluster.

2nd - The cold start injector (CSI). There is a coolant sensor that ties directly to the CSI.... AND they are wired to the STA circuit (starter). CSI is supposed to turn on at cranking events under a certain temperature. The CSI is an additional injector that simply sprays (it does not pulse like a traditional injector). If you think this might be a problem, simply unplug the CSI and see how it reacts. During cold cranking if the CSI is disabled it WILL take longer to start.

3rd - The sensor for the ECU. The ECU uses coolant temperature as an added input to increase or decrease the pulse-width of the injector (essentially - more fuel if cold, less fuel if hot).

There is also a "waxistat" in the throttle body - essentially there is a coolant based mechanical system that will allow air to bypass the throttle body (kind of like a choke) until coolant warms up and the bypass closes.

Any of these could add/remove fuel or add/restrict air depending on engine coolant temperatures - which can affect fuel mileage and acceleration.
 
toyotaspeed90 said:
To talk about this and the possible issues, you need to understand how things work. As 'confusing' as it seems (especially with 3 coolant sensors) it's all actually pretty simple.

Simplest first - the single wire (with a spade connector) coolant sensor goes straight to the gauges. Nothing else. All it does is report a resistance value to the cluster.

2nd - The cold start injector (CSI). There is a coolant sensor that ties directly to the CSI.... AND they are wired to the STA circuit (starter). CSI is supposed to turn on at cranking events under a certain temperature. The CSI is an additional injector that simply sprays (it does not pulse like a traditional injector). If you think this might be a problem, simply unplug the CSI and see how it reacts. During cold cranking if the CSI is disabled it WILL take longer to start.

3rd - The sensor for the ECU. The ECU uses coolant temperature as an added input to increase or decrease the pulse-width of the injector (essentially - more fuel if cold, less fuel if hot).

There is also a "waxistat" in the throttle body - essentially there is a coolant based mechanical system that will allow air to bypass the throttle body (kind of like a choke) until coolant warms up and the bypass closes.

Any of these could add/remove fuel or add/restrict air depending on engine coolant temperatures - which can affect fuel mileage and acceleration.
Click to expand...
Thanks. I'll keep checking things out. I do have a new oe cold start injector. Have to figure it out
 
Maybe the PO ran it hot, blew the HG and it takes it a few minutes to get the coolant out of the cylinders. Water in oil? Let it sit overnight, and gently open the oil drain plug see what comes out first. Green coolant is bad.
 
Similar to same issue with my 62. Poor/bad acceleration at first. Let it idle for like 20 minutes, get in and drive and the problem is nearly gone but not completely. I would love to solve this issue as it has remained the same the whole time I have owned my rig. I have done a bunch of things to try to remedy this but to no avail. I'm beginning to think it could be an issue with the transmission and the way it communicate with the engine. The engine seems to have plenty of power when its in the right gear at the right RPM's. Seems like it shifts too early and then not downshifting when needed to say go up a hill. If I let off the gas when its is experiencing power loss then get on it again it does improve, but this is clearly not right. When it does run right, it feels like I'm driving an FJrocket in comparison to when its running badly.
Lets get this solved.
 
@toyotaspeed90
Can you elaborate on the "waxistat in the throttle body"?

Where is it and what does it look like?
 
emac said:
Maybe the PO ran it hot, blew the HG and it takes it a few minutes to get the coolant out of the cylinders. Water in oil? Let it sit overnight, and gently open the oil drain plug see what comes out first. Green coolant is bad.
Click to expand...
I owned for 8 years now and recently oil pan change out. Recent coolant change like said before was good. Hope it's just the sensor
 
Check your vacuum lines. If that’s fine then maybe adjust your idle a little it should idle a little higher than 650 to 700 when cold.

Had a similar problem mine ended up being an AFM that had the screws of death pulled by PO and then soldered back on like a mud dobber. It would idle fine but had problems getting into 4th gear. Replaced AFM and the vac lines on the air box and it is like a new truck.
 
So, vacuum lines issues (a leak) will actually cause a different issue, mainly that the vehicle won't start or it will REALLY bog down off idle.

That's because these vehicles use an AFM (air flow meter). The AFM has a 'door' that opens (it's linked to a potentiometer that sends a variable value- there is also the AIT housed in the front of the AFM) when vacuum is present. This "meters" the amount of air entering the engine (the door opens based on vacuum from the engine).

A vacuum leak will cause a path of lower resistance for air to enter the engine bypassing the AFM.

An additional function of the AFM is to keep the fuel pump running. If that 'door' isn't open, the fuel pump is off (with the exception of the priming when first starting). It's a safety feature - vehicle gets in accident engine stops, vacuum stops, fuel pump turns off (and a potentially severed fuel line stops spraying at 50psi).

Most likely if you have a vacuum leak, no manner of engine temp will affect the AFM more than when cold and at idle. This is why ensuring the tube between AFM and throttle body is tight and isn't cracked.

Only exception to this would be a coolant temp based VSV (vacuum switching valve) that closes when hot (no idea if that even exists on these vehicles) - which a simple test would be the brake cleaner spray test over your vacuum lines.
 
Well after waiting a few days to be sure I believe I fixed my issue. I read online of other people with different makes/ models having similar issues after coolant jobs? So I rebled my system and boy did it need it. Followed instructions from YouTube. Took about 20 mins. What a world of difference. Or could just be one hell of a coincidence which I dont believe in lol.
 
If you have an air compressor this type of tool is exceptional. No car, that I've had nor heard of, are as problematic with coolant air bubbles than first gen MR2s (that's what happens whe you have coolant lines the length of the car, then the engine nor the radiator are the highest point, instead there's an odd fill within one of the main radiator lines).

https://www.amazon.com/FJC-43610-Radiator-Coolant-Vacuum/dp/B00804HWOU

I have a snap on radkitplusa that I bought, used, for around $100 more than 10 years and works perfectly.


In short - compressor air is used to pull all air out of the coolant system and put the system into negative pressure. This can then tell you if there are leaks as the negative pressure won't hold. Then there's a hose that runs to a coolant bottle- flip the valve and the negative pressure fills with coolant.
 
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