Volvo 7.4 Gi PEFS rough & surging idle

[slow&steady]

Hello, I have a 1999 Regal 2850 with a Volvo 7.4 Gi PEFS thats runnning rough and surging at idle. Rev it over 1000rpms and it runs perfect. So I've been working on this for weeks now and I'm loosing my mind. I'll give you a run down of what I've done so far. New IAC, MAP, coolant sensor, Fuel Pump assy, Fuel pressure regulator, Fuel Filter, Intake gaskets are all new ( had the same problem with the old ones to) Checked push rods, Timing has been checked atleast 5x and set with Rhinda Shunt for base timing at 10 degress. Fuel injectors were professionally cleaned on machine all within 2%. Fuel lines were cleaned, fuel rail was cleaned, throttle body was cleaned, New Cap, Rotor, Wires, Plugs. So everything that was replaceable has been. The Engine is new and was replaced last year right before I bought it. Compression is 160psi all cylinders cold, throttle closed.

So what I have found and still have issues with. Old Fuel cell low side checked 20psi so I replaced it, The new one is still the same 20psi low side and 43 high side. Not sure whats causing the high pressure on the low side. I've ran fuel from the boat tank and a Aux tank with no change.
I've used a vacuum gauge and I get 8.5hg at idle. No vacuum leaks can be found anywhere.
I have a rich fuel smell and my plugs are black from running rich at idle.
So I have researched this problem as much as I can, I'm leaning toward replacing the Ignition control Module next and Trying to figure out why my low side fuel pressure is 20psi. However I don't see how having a High low side pressure will give me rough surging idle.

Any suggestions for Ideas would help. I'm sure there is more that I've tried and done by my brain hurts right now.

The Motor was already doing this when I bought it, I save a bunch buying it running like crap, the previous owner was tired of dumping money into it. I thought it was going to be a easy fix, I've been building engines for 20 yrs. This thing has me stumped. My last option is to take it to the local Regal dealer to have them hook it up to their computer.

Thanks

 

[DCinVA]

I see you have not had any help with your problem, as yet, so I will try to help, but I am no expert.
It sounds like you have multiport fuel injection. The low side does seem pretty high, and I don't have the spec in front of me but I recall 5-8 pounds as the spec.
I had some EFI issues with my 7.4 and I found an excellent engine manual on this site that had extensive test procedures for the EFI system. Although it seems a bit overwhelming, the systems are really fairly simple. I suggest , if you have not already, to print out the manual and follow all the testing procedures. If that does not work, perhaps someone with more experience than I can help.

Good luck.
Dave

 

[Bremner]

Slow and steady what was the final resolution thxd

 

[GA_Boater]

He never returned.

Closed.