Some Bucking at Low-end...then pulls like a mule, Trying to get all the bugs out--I need your help Options

[computers4kids]

I need your help...I've got my transplanted djet 2ltr (76 de-smogged motor) in and running...and driving. I'm trying to get the motor running good but I'm having a problem with low rpms.

If I try to slowly accelerate the motor seems to "buck," hestitate until the motor reaches about 3,000 rpm then it's smooth sailing. However, if I put my foot into the pedal harder and run through the gears it pulls hard and strong like a mule....awesome.
Below are some things I've done:

• valves adjusted while engine was cold .006 and .008(exhaust)
• Installed new petronix ignition
• Set timing at 27 degrees at 3500 rpm
• Completly removed and cleaned throttle body and blew out all the ports with carb cleaner
• Cleaned throttle position contacts (excellent condition) and adjusted idle and full throttle contacts using an ohm meter
• all injectors were serviced
• fuel pressure set and steady via gauge at 28lbs
• New plugs, rotor, cap...wires appear to be in good condition
• installed a rebuilt 043 MPS (Bleyseng)
• Checked for vaccum leaks
• Engine runs at 325-350 on CHT gauge
• New cylinder head temperature sensor
• New air cleaner

Things I haven't done

• adjusted the ECU....as I understand it...this is only an idle adjustment mixture....although the motor smells maybe a tad rich at idle
• Have not played with the trigger points (stock bosch dizzy)

At this point I don't want to just start throwing money at parts. From what I've read, the trigger points can cause bucking and too rich running. When I saw Pelican wanted $175 for them...I didn't want to roll the dice????

The only other symptom worth mentioning, is when I first start the motor when it is cold, the idle hunts quite a bit....like 1000 rpm...not to sure what that is all about. I did install a oem thermostat and the air flaps are working correctly. After it warms up the idle is fairly steady but a bit rough.

Sorry for the long story....I need some ideas

[computers4kids]

do you have your original temp sensor? measure its resistance (while cold) and compare with the new one. there is apparently more than 1 part # with different specs. when I replaced mine the resistance of the new was alot less and this caused bucking on accel especially when cold. I compensated with a 500 ohm resistor, but this is not really the proper solution if the right part can still be obtained.

My '76 2.0 did the same- almost 20 years ago. I called George at AA, and he asked if I had a ballast resistor in series with the TS2. I originally had one, which I had removed since I couldn't find any reference for it. He told me to put it back in. I did, and it ran great and with no problems through '02 when I pulled it for its rebuild.

Yes, I KNOW the ballast resistor isn't supposed to be in on a '76, but it worked.

Good luck!

Latest update...
I threw in a 270 ohm resistor in series with my head temp sensor and it made a world of difference on cold startup....no hunting idle...fast idle then settled right down as it warmed up (aux valve closing).

The resistor also improved my low end bucking quite a bit even after the car warmed-up...I guess this is telling me I was running my FI too lean??

Next, I want to get a air/fuel ration gauge and connect a variable pot to the head sensor and adjust for smoothest running at 2500 rpm (as suggested by Kjell Nelin article) or until CO is between 1.5-2.0%.

Checked the throttle position switch and I'm getting exactly 20 clicks...and tried unplugging it and running without it...amazing how well the car still will run...just a bit more sluggish....anyway, it appears to be OK so I plugged it back in.

I also advanced the timing a few more degrees which smoothed things out as well.

Overall, I think I'm on the right track. I don't want to play with the ECU idle knob until I know by CO levels are correct via the head sensor.

I'm getting closer and closer... (IMG:style_emoticons/default/mueba.gif)