My 2.0 D-Jet motor runs hot,, Edit - idle fixed, vacuum leak found Options

[Cevan]

I swapped out my 1.8 L-jet motor for a stock 2.0 D-Jet motor. I’ve put about 75 miles on the car since the engine swap. According to my CHT gauge, it seems to be running hot. I had a similar problem with the old motor. That engine was running lean and I adjusted the AFM and got it to run around 325-350 on the highway (70-75 mph).

The 2.0 motor runs around 350 in 3rd or 4th gear at 3000 rpms and goes up from there when it’s on the highway. The gauge is definitely reading hotter temps across the board compared to the 1.8 motor.

The only issues I have currently are a minor vacuum leak (idle is a bit high) and a TPS that is a bit worn. The car runs great otherwise. It accelerates nicely (noticeable improvement over the 1.8).

All the tin is in place, fan is intact, no blades missing. Dwell and timing are correct. Valves adjusted. Injectors cleaned and tested. MPS good and is the correct one for a ’74 2.0 motor. New points, cap, rotor, plugs, plug wires, vacuum lines.

I need to pull a plug and see if I see signs of it running lean. This is what I suspect. I will also check the fuel pressure. Could this be a timing issue? Could it run cooler at a different timing setting than the factory spec? Any thoughts? (IMG:style_emoticons/default/confused24.gif)

I also can't get the idle below 1300 rpms. I have the idle adjustment screw all the way in and when I go to turn the idle mixture screw on the ECU CCW to get it below 1300-1400 rpms, it does this up and down thing with the revs. I've sprayed of starter fluid at every place a vacuum leak might exist and the revs don't change. I'm this close to putting L-Jet on the damn thing.

[r_towle]

Let me try this so you can start hunting.

I will simplify this so Capn can yell at me. (he will whip out the factory manual on me...thats ok)

Lets say there are three air fuel maps, hard coded maps.
You pick which map to use based upon the CHT...there is a cold, part warm, and hot air fuel map. (I know that is wrong...but I dont care)

So, now we are done using the cht...at least once the motor it hot.
That is the point here...if that part works...move on.

Even the wrong CHT will still be at a high enough ohm reading to get you to the warm/hot fuel map...so when its hot you are fine.


So, now we are dealing with just fuel timing (injector pulse width/time)
and we are dealing with fuel pressure (volume that gets squirted)

We are using a fixed air/fuel map now...it wont change.
What changes is open time...that is the variable..
Fuel pressure is constant..injector size and flow rate is constant..
Time is the variable...
Fix and check the fuel pressure first and foremost..get that set right...about 3-5psi higher than stock is what I like. I run 40psi.
Yes it runs rich...I know (I still get 30 mpg)

Fuel timing is controlled by the TPS, and the distributor...its a combination of those...distributor tells the injector when to open..the TPS tells it how long to keep it open. (along with the MPS...our friend)

The amount of fuel is controlled by the size of the injector and the fuel pressure...

So, if I was running lean, I would first crank up the fuel pressure to about 45psi cold...then check it hot...I would suspect the fuel pump also..and filters etc etc.
Get a fuel pressure gauge hooked up live...


Rich

[Cevan]

Lets say there are three air fuel maps, hard coded maps.
You pick which map to use based upon the CHT...there is a cold, part warm, and hot air fuel map. (I know that is wrong...but I dont care)

So, now we are done using the cht...at least once the motor it hot.
That is the point here...if that part works...move on.

I checked when the engine was cold (2.7k ohms) and after idling for about 5 minutes (125 ohms). I'll check it again after I drive it and really warm it up. While it was idling, I unplugged the connector and the engine died. I assume this is supposed to happen?

Fix and check the fuel pressure first and foremost..get that set right...about 3-5psi higher than stock is what I like. I run 40psi.
Yes it runs rich...I know (I still get 30 mpg)

I would suspect the fuel pump also..and filters etc etc.
Get a fuel pressure gauge hooked up live...

I got 27-28 psi at idle. When I reved the engine, it pretty much stayed right there. I will crank up the pressure a bit and see what happens.

I also checked the air intake air sensor per PBanders site and that checked out.