'70 D-jet runs terrible cold, great when warm,, Please share your wisdom Options

[r_towle]

I will run down the issues that it could be.

The ECU has an idle circuit that only engages if the TPS is porperly adjusted. A poorly adjusted TPS will give you a more responsive upper end RPM range, but it will require you tap the gas pedal to keep it at idle.
So, it can be the TPS...I will add a pic to show you how the TPS MUST look at idle.

The Decel valve...mine is removed, no difference.
AAR, mine is removed, no difference.
I live in the northeast...it gets damn cold here, runs ok without either part.

Valve adjustment.
If your valves are too loose or to tight it changes the valve timing and it also creates vacuum leaks..makes it impossible to get the idle correct.

(For this section, unplug the multi spark unit and wire up the distributor correctly for single spark...)
Point gap.
The dwell needs to be set to perfection on these cars, a little bit smaller (a larger dwell period) will provide a bit better burn, but your mutli spark unit will do this also.

Timing.
This needs to be set third...dont be lazy..do the valves, the the point gap/dwell, then the timing.
The timing changes with both of the previous items, so it MUST be done last.
Get the right plugs in there...though the multi spark unit works well with the 4 pronged platinum series plugs...quite nicely actually.

Now, reconnect the multi spark unit.

Vacuum leaks affect Idle.
Remove the intake runners and reseal them at the head.
There should be head---thin gasket---phenolic spacer---thin gasket--intake runner.
I put a small amount of liquid gasket on all surfaces...it helps seal this often overlooked vacuum leak up tight.

Rubber boots between intake runners and plenum.
Clamp them tight..they leak after 35 years.

Clamp all other vacuum lines.

If its still acting up, remove every single vacuum line from the plenum except one..the MPS.
Get rubber vacuum line caps at the parts store and close up all the holes in the plenum..do a very good job and make sure they are tight.
this includes the one or two little hoses that go from the throttle body to the distributor, cap them.

Make sure when you cap them you have no hoses...dont be lazy...get the rubber caps and do it right.

It should run perfectly.
At this point, add one vacuum line at a time..drive it and then let it idle...you will find the faulty part.

So,
TPS is first, adjust as pic shows at idle, flap closed on throttle body.
Valve adjustment
point gap/dwell (Multi spark unit unplugged)
Timing (multi spark unplugged)
Reconnect multi spark.
Reseal all vacuum lines on motor, including intake runners.

Rich

[r_towle]

TPS pic at Idle with flapper closed on throttle body.
Take note of the middle finger/contact. This position activates the idle circuit.
This shows that the TPS cannot be adjusted...it only has one home.
The adjustment is due to different throttle bodies and physical differences from one system to the next....same part for volvo, Merc, porsche etc etc etc.

Rich

[r_towle]

One more thing

Fuel pressure and new fuel filter.
replace the filter.
Check the pressure at idle...its an old pump.
I clicked mine up a few pounds...that helped.

Rich

[Porsche Rescue]

It pains me to write this..........and Rich Towle, Brad Anders and others are allowed to say "I told you so!"
To refresh memories, car very hard to start, very hard to keep it running until fully warmed and then it ran very well. I tested and retested all fuel injection components as per Anders web site, replaced head temp sensor (even though the old one tested OK), replaced coil, points, condensor, rotor, cap, checked timing. Removed the old Heathkit CD ignition. Nothing changed.

Then I decided to attack other issues (install ss heat exchangers, new Bursch exhaust) and since the exchangers were off it was time to replace the leaking push rod seals on #2. Upon finishing that task it was necessary to adjust valves on #2 so naturally I did them all. A much easier job without heat exchangers in place. Three cylinders were set at .004 (the PO had an old manual with incorrect spec of .004). One valve was even tighter than .004. Set all at .006. Put it all back together, with new plugs (but the old ones looked pretty good), and fired it up to check for exhaust leaks (I got 'em but that's tomorrows' project). Car started immediately, quickly settled in at about 2000 rpm just like it should. Didn't drive it because of the exhaust leak, but clearly my problem is solved.

Rich Towle, B. Anders and others repeated the common advice: before attacking the fuel injection, make sure that engine is in good electrical tune, properly timed and VALVES ADJUSTED. I procrastinated checking the valves, thinking I would get to it when I did the exhaust/seals. And besides, I was sure the car would not run so well when hot if the problem was valve settings. WRONG!

So, problem solved. Now, can someone tell me why tight valves would cause hard starting and very poor cold running, yet the car would perform well once hot? I would think heat would close the gap even more. But, obviously, I don't know nearly as much as I thought I did!

Now, how do I seat the ss exchangers so they don't leak!

[Bleyseng]

I don't know, its just that if the valves are too tight or too loose it affects the valve timing. EFI esp Djet is sensitive to valve timing, manifold pressure etc...screw with it and it runs poorly.

I have run with .005 for AX but normally at .006.

Everything expands in a AirCooled car but at different rates. Cylinders are cast iron, head aluminum as the pushrods so there is a small gap for the expansion. You can run the chromemoly pushrods without any gap.