4.7 Stroker running hot under load

[mixedupjeeps]

We just put a 4.7 stroker into my son's Comanche. It runs well and makes good power but when pushing the motor hard to go uphill it will overheat. He has a Novak V8 conversion radiator and a high flow water pump. I hooked up my wide band AFR to it and can see that the open/closed loop behavior is as expected except at full throttle. As I understand it the ECM is supposed to go open loop at throttle positions greater than 75%. I also read that the ECM knows to switch to open loop when it sees a throttle position voltage greater than 3.9V. I checked the values on my son's Jeep and the voltage never goes over 3.8 V. The ECM keeps the fuel ratio around 14.7-15.0 at WOT running it a bit too lean. I have a bunch of spare TPS modules so I tested 5 other ones and none of them would go over 3.7-3.8V unless I clock the sensor slightly. When this motor was in my Jeep it never overheated and one of the things that is different is that I used a 4.7 throttle body and adapter. I checked the angle of the TPS blade and it is 3 degrees greater than the stock 4.0 TPS. I noticed in my Jeep that the MAP adjuster had a much bigger effect than it is having on my son's Jeep and I believe the difference is the angle of the 4.7 TPS shaft. Have any of you filed out the TPS holes so you can clock it CCW to get a higher voltage out of it ?

[Cheromaniac]

Which injectors are you using?

[mixedupjeeps]

I'm using 24 lb Ford injectors running at 48 PSI (with vacuum line off the adjustable regulator)

[mixedupjeeps]

I also clocked the TPS slightly so that I get 3.98V at WOT. My son did a quick run on the freeway and he said the heat still started to creep up. I'll have to put the wide band back on and see what is up.

[Cheromaniac]

If the engine's still fresh, it's normal for it to run hotter than usual until it's properly broken in.

[TJryder]

I would not dare to run newley built engine with lots of unknowns without wideband AFR gauge. To lean and you will kill the engine... Do you have a reading of that?

[mixedupjeeps]

Yes I have had the wide band on the motor. It reads very reasonable numbers 12.5-13.0 on cold start up, 14.7-15.0 after the O2 sensor is warm. The only issue is that it keeps running at 14.7 even at wide open throttle where I thought it should drop out of closed loop. I see it dropping out of closed loop on deceleration as it should just not at full throttle. I just took it for a ride and going slow or idling it never gets hot. Took it on a short loop on the freeway and the temp started to get too high but as soon as I got off the freeway it dropped back down to 210.

[Cummins90]

Is it still the renix ECU?

[Cheromaniac]

How many miles are there on the engine?

[mixedupjeeps]

The engine probably has around 600 miles on it. It was originally in my CJ8 where it had no heating issues that I was aware of. When we swapped the engine I transplanted the OBD1 wiring with it. His Renix was unreliable and would stop starting at times until you wiggled the wiring by the coil.

[SkylinesSuck]

Could something switching between the two systems have changed the base timing? They would easily affect the operating temps under load.

[mixedupjeeps]

I'll have to check the timing but I transferred everything from one Jeep to the other so it should have been the same as what it was in my Jeep.

[Cummins90]

Check the ohms on the TPS sensor ground/5v input and sensor output to the ECU. Ensure that the 5v is supplying 5v. Do a full sweep with a known good TPS if you have one.

Also test the map sensor with a mini hand vac. Do the same testing as you did for the TPS wires. Then use the hand vac to observe the voltage decrease with increased vacuum. My obd2 96 5 speed XJ seems to value MAP above all other inputs for WOT fueling. It would not allow WOT in any condition when I clamped the signal at 4.6v. I increased the clamp to 4.9v and can trigger open loop on demand.

My 95 auto seems to value MAP above 80% and
greater than 3200rpm to achieve open loop fueling. I can't confirm any of these things yet. These two tests should help rule out electrical issues.

Thinking away from electrical, maybe the thermostat is partially opening.

[mixedupjeeps]

I have done the full voltage sweep with six different TPS sensors. I am getting a good 5 volts to the sensor. With the sensor I have in now I get 3.98 V at WOT. I'll have to try the sweep of the MAP sensor. I know it gives reasonable values when the key is on but the engine isn't running. One thing that is different on my son's Jeep is where the MAP vacuum is being pulled from. He has one of the newer throttle bodies that has the map sensor port on the side of the throttle body, I had mine more on the manifold. One thing that I haven't figured out yet is his Jeep doesn't seem to react as much to the adjustable MAP voltage. On mine if the voltage was a bit high it ran way too rich when cold and his doesn't seem to react the same way. I'll have to try some different MAP sensors and change where the vacuum is pulled from.

[mixedupjeeps]

Also I'm curious when you say that you clamped the signal at 4.9V, is that something you do on your OBD2 settings or by a MAP adjuster voltage ?