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?

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.

silly thing to check, did you try pushing the throtle barrel nut back with your hand. sometimes the return spring is not closing the throttle all the way. See if you can push it shut by hand and the rpm drops.

i had a similar problem that went away with a new accelerator cable and a new spring.

Did you check the distrib. plate? Mine stuck once. Make sure you remove the rotor and put some oil on the felt.

2 liter D jets also had a resistor off the CHT. I got mine at radio shack. I can look up the ohm if you need it.

Is the thermostat bellow hooked up? is it stuck?

Is the intake air temp sensor hooked up? You can pull the plug on it to richen up the mixture.

Distributor was taken apart and cleaned.

I don't see a resistor off the CHT. The wiring diagram in the Haynes manual doesn't show one. Am I missing something? My CHT plugged into the wiring harness.

I have the bellows open. Oil temps appear fine.

check the plugs....number 3 is key.

If you find it running lean, make sure all the parts are right.
ECU, MPS, and CHT all MATCH...
Check the Banders site.

OR
Get a variable POT from radio shack. Hook it inline on the CHT line and start at about 300 ohms...(get a 1000 ohm POT) and work up slowly.

You will find the sweet spot...check the plugs...
Then if and when you are happy, measure it out with an ohm meter and buy a resistor.

Rich

So there is supposed to be a resistor inline with the CHT sender? Where is it normally found? I will do as you suggest and get a pot. All of the components are correct for a '74 motor.

The only D-Jet setup with a resistor was the '73 2.0. A specific brain, mps and CHT required the 270 ohm resistor in line with the CHT.

Check PBanders site for the details. Google is your friend and links have been posted here numerous times.

I did check the site you suggested prior to putting this motor in. I have his troubleshooting info in a 3 ring binder. All the part numbers of the components (ECU, MPS, injectors, CHT) corresponded to a '74 2.0 motor.

I've searched here and elsewhere for info on why these motors can run hot. I've read all threads and at this point I'm stumped.

I cooled one down by simply having it on a rack. I sprayed carb/brake cleaner thru the oil cooler from the bottom and then hit it with compressed air. The gunk from the cleaner prolly wound up somewhere else in the engine, but it ran much cooler.

Don't say it Cap'n ... I already know.

I had this motor apart down to a long block. The oil cooler was cleaned as well as the fins on the jugs and heads.

Here's a couple pics of a spark plug. The plugs I'm using are NGK BP6ES. The ground electrode (curved part) is white-ish in color, not tan.

Click to view attachment

Click to view attachment

relax...
So, you have all the correct numbers so all the parts match, including the CHT? Did you put a new CHT in?

Test that part cold and then hot with an ohm meter.
Unplug it when you test it.

What is your fuel pressure? What is your fuel pressure when hot?
Are you using the L-jet Fuel pressure regulator, or the Djet one?
The Djet one has a bolt that you use to adjust the fuel pressure.
You can turn it up, run a test and see if you have a better setup for the injectors you are using. You cant use the Ljet fuel pressure regulator with Djet.

If all of that is ok...go get a POT.

Rich

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

A leaky decel valve could be your culprit. Block it off and see if your idle rpm drops.

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?




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.

Decel valve removed and cold start valve disconnected.

Well,
You still have a vacuum leak if it idles that high.
Strip all the hoses off the plenum except the MPS...cap the MPS.

I just did my valve adjustment again yesterday...just to get ready to go to hershey. Do that again....do it really slow...after you think you are done...rotate the engine a few times, then check them again...re-adjust.

Get them all at 006...the tighter the better from what I have seen...seem to reduce the issues.
I now have a much better idle..I have it well below 1k now when cold and it does not stall.
I actually need to turn the idle screw out a bit to get it up a little higher..I think I am idling around 4-500 which is to low..sounds like harley now.

I was shocked to see that one change...just a well done valve adjustment, makes that much difference at idle.

If you unplug the CHT, the car wont start...simple as that.
I would need to see the numbers from PBAnders charts, but you may have the wrond CHT...
It can be adjusted with a POT and then fixed resistors...take a look at the proper range for the ECU (I think he lists it as the range for the right CHT...so you need to cross reference)

I lost your phone number....or you took that PM away.
Send it to me again and I can tell you alot more than I can type..

Rich

Another source of a vacuum leak it the air plenum under the throttle body. These can crack.

Quick update: car still runs hot and no idle below 1400 rpms. No vacuum leaks were noted using the starting fluid method. This method did find vacuum leaks at the intake to head junction and at the cold start valve. I fixed these and now no changes to rpms are noted when I sprayed the starting fluid.

Timing was a bit off but once that was adjusted, no change in temps. I also drove it with the fuel pressure at 35 psi and no change. I also flipped the plug of the MPS around and no change.

I will re-confirm the accuracy of the gauge with an infared thermometer. I will also try a couple of other plugs for #3 just to see what happens. I have a Bosch W7CC. I will also try an NGK B7ES

Rich - I adjusted the valves before I put the motor in about 100 miles ago so I think that is taken care of. The CHT is the correct one and is within spec.

I will try and get a hold of a different MPS. Mine holds vacuum but I'm not sure if something else is going on with it that would cause the motor to run lean.

If all of this fails, I'll slap the L-Jet on it. Hell, isn't that what Porsche did with the 912E?

On a positive note, no oil leaks after replacing all the seals.

you are running lean and the idle is high.
You have a vacuum leak.

I just put new head breather hoses on..I used 7/16 rubber fuel line.
Its tighter than the metric stuff (the correct size is 12mm)
I also used clamps.
Made it idle lower and perfectly smooth.
I also adjusted the valves.

Do you have a dwell meter? is that set right?
Timing...its set different than Ljet...its set at 3500 rpm's.

Rich

Yes, I have a dwell meter. Dwell is at 48. Timing is good. The head breather hoses are connected to the airbox, not the plenum so those shouldn't impact idle, right? I unplugged the hose going from the airbox to the 3-way connector and there was no change in idle. All those hoses are new. I've verified the AAR functions correctly.

I guess I will check the valves again. Can't hurt, right?

well, its running lean.
I cant accept that there is not a leak due to the car idling to high.

Pull everything off the plenum...I know you havent done this yet.
Yes it sucks...Yes it a pain..but it does work.
All holes plugged except the MPS.

ALL OF THEM.
So that means pull the AAR and plug it.
Pull the hose for the PCV and plug it at the plenum.
Pull both (or one) hoses to the distributor (I still suspect the advance can on the dizzy...you have not verified that vacuum device yet)

Pull them all, cap them at the plenum and get it to idle correctly FIRST...

Then put one hose at a time back on the plenum..just one at a time.

RIch

You only need the resistor if your ruinning the 037 ecu and 037 mps this was the first djet 2.0 1973 which used the 1.7 version control unit with a head temp anmd resistor.. i have a 74 2.0 djet no resistor no problem check this link it will go through very sufficiently all the djet components.. trouble shooting guide..

http://members.rennlist.com/pbanders/djetparts.htm

when i converted my 73 1.7 d-jet f.i. system over to 2.0 d-jet for the 2056 i found cracks on the underside of the plenum the throttlebody sits on. we brazed them up but i'm sure they would've contributed to some hard to locate vacuum leaks

p.s. i had 2 plenums and both were cracked so my guess is this is typical after 30 years

worth a check see

mike

Vacuum leak found: PCV valve. I pulled the vacuum line and plugged it and then messed around with the idle screw and the ECU adjustment. I now have a nice idle at 800 rpms. If I hook it back up, the idle goes back up.

As I recall, my PCV valve doesn't have any spring or disk inside it. That explains alot. It's basically just a port.

So my next question is can I convert mine to the '75-'76 setup that eliminated the PCV valve? If so, do I just connect the vacuum hose from the PCV valve (now really just a port) to the airbox?

From PBanders site:

The D-Jetronic PCV valve has two flow rates: metered (when the disk is on the intake manifold side seat) or closed (disk on crankcase side seat). This design is not optimal:

The metering slots restrict the flow of blow-by gasses under full-load conditions, causing the excess blow-by to flow back through the crankcase ventilation system.

The flow/no-flow nature of the PCV valve requires that the metering slots be somewhat larger than needed for idle conditions, so that there is sufficient flow under most operating conditions. This increased flow at idle causes the intake manifold pressure to increase, leading to a richer idle mixture and increased emissions and lower fuel economy, as well as potential idle stability issues.

These limitations are likely in part what led Porsche to revert to a passive crankcase ventilation system on the 75-76' 2.0L models, where the PCV valve is eliminated, and the breather on the oil filler is connected to the air box instead of the intake manifold.

Glad you figured it out and did not give up and go Ljet.

Rich

So can I just hook the gutless PCV (now just a port) to the intake side? I couldn't find new PCV valves at Pelican or AA.

PCV hooks to plenum ... generally hi vacuum area

'75-'76 hooks to air cleaner ... very low vacuum area


Hook'r up ....................... (to the air cleaner)