I have a 1972 P1800 es I rebuilt the engine and it runs fine but i have this strange problem that right off idle it acts as though it has a major Ign. brake down or a lean surge. i have a new fuel pump and i set the pressure at 30 lbs. It seems to like that pressure the best.
It does have a aftermarket electronic Ign. but it ran fine before the rebuild

I have checked the primary resistance in the coil and have 8.0 ohms new cap and tune up parts.

I checked the vacuum control unit by using a mini vac and it held at 15 pounds. the old one failed that test.

I set the throttle switch

I had a spare computer and replaced that, and i do get a better idle but that wasn't it either.

I must be missing something does anyone have any suggestions? HELP!!

Right off idle - as in you press down on the gas pedal and the engine initially hesitates or responds poorly? If so then I would first focus on the throttle switch.

You said that you set the switch. What was the procedure that you used for setting the switch and setting the idle speed (you can really screw up the D jet if you don't follow the exact procedure set out in the service manual). Also, have you checked the operation of the contacts in the throttle switch as set out in the service manual? If you don't have a copy of the service manual for the D jet, you can get a .pdf version from this web site:

http://volvo1800pictures.com/sweden/Volvo_1800_dokumentation_main_page_en.php

Have you checked the operation of the ignition advance? With the vacuum line clamped off, your advance should be around 10 deg BTDC at idle increasing to around 32 deg about 3000 RPM.

Thank you for the return email.
Yes i did set the switch and the Idle stop to the specifications. I also cleaned the contacts.
I thought that it may be electrical so i took out the pertronix ign. system and installed a original distributor No luck.
The problem was a lean surge off idle so i made sure that my pressure regulator was set correctly. The engine liked 32 Lbs.
After going round and round i checked intake manifold vacuum and sprayed around the injectors but there was no injector leaks but i only had seven to ten inches of vacuum the cam specks noted that it should be fifteen to eighteen so i removed the intake and exhulst and that is were i found the problem. I ran a flat file over each to check high and low spots and that is were i found my leak because of worpage. This is the only engine that i ever done that was warped and twisted. I did the machine work.
Turns out that the manifold to head surface was warped also seven tho. in places.
I got a new Felpro intake gasket and noted that the sealing rings weer larger. But beware if you use this gasket it does not have the aligement pin hole so i had to cut one into the gasket.
I went together with it last night and i will check the torque and run it today.

I am sure that will correct the problem.
Thank you for your response.

David

David;

I have to agree with 142G...those symptoms sound like you're not getting any enrichment pulses, and the TPS is responsible for those...take note if a stumble also occurs when increasing Throttle from a higher RPM (not just idle)...that would rather confirm no enrichment pulses...assure TPS is CORRECTLY adjusted... you can also check for enrichment pulse clicks when sweeping up Throttle range with Ign On but Engine not running.

Good Hunting!

Thank you for your response.
I found out that i had worped manifolds and had only seven to ten inches of manifold vacuum. Reinstall good used from performanceauto (Eric,) Great looking part. Put it back together last night and will re torque today and after running. I think that will correct my problem.

Thanks again

David

I'm also on board with this. The quick check is to unplug the TPS and see how it runs. If it stops stumbling, there's your problem.

Thank you for your response.
I finely found the problem. It was a intake manifold leak (seven to ten inches of vacuum) resurfaced manifolds and will try again today.
Thanks again
David