CPU Nightmare

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A couple years ago I changed my 318 (97) to a 360 (98). I figured I should have a 97 CPU for a 360 to make it run properly and got one from a salvage yard. To make a long story short, I have one CPU that works in cold weather and one that works in warm weather. It is easy to switch CPUs but still a pain. Any suggestions?

 

[dapepper9]

What's the cold weather pcm do in warm weather?
What's the warm weather pcm do in cold weather?

 

[sbarron]

never heard of such a thing.

 

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The one that works in warm weather dies easily in the cold. Restarts are comparable to starting a flooded car with a carb.
The one that works in the cold dies easily and runs rough in the warm but restarts are ok. Both run better as the engine warms up.
Weird problem I know. Thought of switching to carb system but this is probably an easy fix if can find an answer.

 

[dudeman2009]

The one that works in warm weather dies easily in the cold. Restarts are comparable to starting a flooded car with a carb.
The one that works in the cold dies easily and runs rough in the warm but restarts are ok. Both run better as the engine warms up.
Weird problem I know. Thought of switching to carb system but this is probably an easy fix if can find an answer.

The 360 is injector based, if you replace it with a carb it is going to get all sorts of pissed. It will trow codes for every single injector, O2 sensor, potentially MAP sensor and IAT sensor unless you rig up the carb onto the existing TB.

The problem you are running into is whatever computer you replaced is not designed for that engine. What you will need to do is match the computer to engine year, not truck year.

Which computer did you replace, PCM or ECU? both run different things, and may not play nice unless they are a compatible pair, the CAN bus will take care of comms, but they might not like the values the other is sending. It may be worth the investment to get a tuner and tune your engine, that will rule out the ECU being programmed for a different engine.

 

[dapepper9]

Pcm (powertrain control module, engine and trans) and ecu (engine control unit, just engine) are the same thing. Only one computer on these trucks. Changing to carb just needs intake manifold change, distributor change, trans, and harness removal though is possible to make the pcm work with the carb and gauges

When changing pcm in these trucks you need to match year, engine, and trans.

One thing i just thought of: which engine harness did you use? 97 318 or 98 360? If you used tbe 98 360 with a 97 pcm that could very well cause you're problem as the 97 uses 2 temp sensors to the 98s single

 

[dudeman2009]

Pcm (powertrain control module, engine and trans) and ecu (engine control unit, just engine) are the same thing. Only one computer on these trucks.

Is it different between the 01 and 97/98? I've got an 01 and its got two on the pass. side firewall, as well as both being listed in the service manual as controlling different functions.

As for the carb, sure its possible, you are completely right, but is it more work than just getting the proper computers and tune.

 

[dapepper9]

2001 should also be a single computer. Dsl I'm not sure but v6/8/10 yeah. It's not letting me but I'd post a pic of my 01

 

[dudeman2009]

2001 should also be a single computer. Dsl I'm not sure but v6/8/10 yeah. It's not letting me but I'd post a pic of my 01

You're right, the ECU is only on the diesels. It bolts to the block right behind the fuel filter. Both my buddies Cummins have them, upon further reading it appears that the ECU on the diesels is solely responsible for running the fuel system.

None of the gassers have them, its combined into the PCM along with the injector controller. I guess I just transferred it over to mine as well. What I thought was the ecu was actually the ABS computer. I went out and checked because I havent worked on that engine since last summer

Also, pertaining to my previous post about ABS, I was looking up the parts and the front ABS setup is 4wd wheel assemblies only. My idiot former classmate is trying to sell his 97 4wd for $5500 even though it has an engine and tranny oil leak, the rear diff is burned out and the 4wd doesnt work due to a vacuum leak. Plus its only got the 318 in it. Not to mention the body rust.

The best part about that is, he tried to get me to sell mine for $800 saying that was all it was worth. I didnt know adding a slight body lift, non-functional 4wd, engine and tranny leaks, plus a bad diff added another 4K to the value.

 

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I used the 97 wiring and sensors. There are no scan codes. To make sure of which computer I am changing, it is on the firewall, passenger side and has three large wiring connectors.
I guess most of my problems are cold engine related.

 

[dapepper9]

Did you do an intake manifold swap?

 

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sensor

You are correct about the temp sensors. I used the 97 harness and was missing a temp sensor. I had forgotten about that. I plugged in a sensor at the time but it is just laying there. Maybe thats the whole problem.

 

[dapepper9]

If you still have the 97 engine swap the intake manifolds (perfect time for plenum if you haven't) otherwise you'll have to drill and tap a new hole. I would also recommend a replacement for the sensor that is just sitting there

 

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Thanks for the advice. I will get it done and hope that takes care of my problems.