Exhaust sputtering

[CriticalB]

I do have the installation guides that came with the turbos, so I'm going to comb through them tonight and see if I find anything that requires modification to this part of the vacuum system other than a port to the boost gauge.

Read the docs, apparently this is how it's supposed to be set up. So the vacuum advance is constantly getting vacuum from the intake manifold port. However with everything connected this way, the idle has changed since I changed the plug wires yesterday.

Engine cranks and idles around 775 RPM, as it always has, but now after throttling it returns to right around 1000 RPM and idles there until next time the car is restarted. Don't know what I could have done to cause that to start out of nowhere...

[FABombjoy]

Ok, that's a lot of mods

Distributor:
Sounds like it's set up for manifold vacuum instead of ported vacuum. Island has you make that mod but BAE didn't. I'm not sure that it's particularly valuable. Our cars cut off the vac advance with the solenoid to (I believe) help with idle emissions. You can run it connected to manifold but it may have a tendency to high idle. I'm honestly not sure what the other effects could be.

Volvo used the throttle tap instead of our goofy solenoid arrangement to accomplish vacuum cutoff to the vac advance canister at idle. DO NOT DO THAT ON AND ISLAND OR BAE TURBO CAR! Draw-through turbo setups will send the throttle edge back in to vacuum when under boost, which will cause the ignition to advance under boost.


Control Pressure Regulator

There's a 4 port connector in the back near the CPR. One port runs to the boost gauge, one to the firewall facing side of the CPR (the outlet on the other side of the CPR is plugged), one port goes to the intake manifold. So the connection between the CPR and delay valve doesn't exist on my car.

Sounds like an attempt to add fuel enrichment under boost. I'm not sure it's going to work very well, honestly. In my experience you need the factory 2 hose setup to operate correctly when cold. The setup you are describing would cause poor cold running and who knows what kinds of AFR under boost. I would think that the C/O adjustment has been thrown way off to compensate.

Lastly, i've checked when cold, warm, under throttle, etc. and there never seems to be vacuum to the 'lower' hoses in the diagram (connected to the throttle edge tapping and charcoal canister.) Does that make sense? Is it a miracle this car is even running?

That should only see vacuum when the throttle begins to open

If you want to return the CPR & distributor setups to stock I have the delay valve, solenoid, and many other leftover K-jet parts.

Are the hobbs switch(es) in place? Any other deviations from the Island manual?

[CriticalB]

Quick update, since I last posted I've been through a couple of tanks with Techron added and the sputter seems to have almost vanished. Not sure if there's a cause/effect relationship there, but thought it was worth noting. It could have been the new plug wires or rotor. In all that driving, I did note the idle seems to be getting progressively higher. On a cold start it would hunt, and after warming up it would settle anywhere between 1k - 2k. I began to suspect something was up with the pipe of agony, but since I just put all new stainless fuel lines I was hesitant to undo them all and check. I finally bit the bullet today and pulled the fuel manifold out and found that, sure enough, the O ring behind the bronze cap was rotted and must have broken up when I took it out previously. I put in a new ring, greased it and put everything back together and the idle is back to ~775.

Ok, that's a lot of mods

If you want to return the CPR & distributor setups to stock I have the delay valve, solenoid, and many other leftover K-jet parts.

Are the hobbs switch(es) in place? Any other deviations from the Island manual?

If there's a hobbs switch, I don't see it, but I'm not sure exactly what I'd be looking for. I appreciate the offer for the delay valve, etc., but since I think I found the idle problem, I think I'll try to keep it as close to original as possible. Well, original + turbo mods, anyway.

[David T]

If a can of Techron helped it means one or more injectors was not spraying well and is now better. You really should have either catalytic convertors or mufflers installed and the O2 sensor in and working. My advice would be to try to get the turbo install back to an original installation configuration. Many owners did mods to their cars and some of them worked and some didn't. Get the original paperwork for the turbo install and try to get it back to that as a start. Might be worth checking the fuel injectors and the valve adjustments. The Island Turbo install will run the idle higher than 775 because of the way the vacuum is hooked up to the distributor. Now that you have a timing light you should check the vacuum and mechanical advance. If your base timing is 13 it is too much. It should be between 8 to 12 depending on your gas and altitude and how much boost you are using. You really should not go above 5 psi. Use the highest octane gas yo can buy to prevent detonation. In a forced aspiration Delorean stock PRV you won't hear the detonation and it can quickly destroy your pistons.

[FABombjoy]

Island / BAE have a Hobbs pressure switch (or two) installed to force the system to go open loop and add fuel enrichment on boost. The "book" method of installing them is bad as it cut/splices the O2 sensor which adds resistance to an already low voltage signal. You can get the same effect by grounding terminal 11 on the lambda box.

At first I had two adjustable Hobbs switches, one for low boost (triggering the WOT switch) and one for high (triggering terminal 11). After datalogging I found that terminal 11 added far too much fuel - like 10-11 AFRs. I turned it up the activation pressure and left it as an overboost failsafe. Eventually I switched to the UTCIS programmable CPR and dialed in a more progressive and sensible enrichment curve.

If the previous owner set the car up to use the CPR to enrich under boost and you reinstall the O2 sensor, you really still want some way to force the system to go open loop. I did this on my own car by grounding the wide open throttle switch which prevents the lambda box from trying to lean things out under boost. The lambda box will fight for fuel control and can do a remarkable job of leaning things out.

It's difficult to recommend any course of action without any data logs or precise list of fueling mods. There are a lot of ways to accomplish the same task and the Island/BAE methods aren't necessarily any better than what you have running currently.

[David T]

Island / BAE have a Hobbs pressure switch (or two) installed to force the system to go open loop and add fuel enrichment on boost. The "book" method of installing them is bad as it cut/splices the O2 sensor which adds resistance to an already low voltage signal. You can get the same effect by grounding terminal 11 on the lambda box.

At first I had two adjustable Hobbs switches, one for low boost (triggering the WOT switch) and one for high (triggering terminal 11). After datalogging I found that terminal 11 added far too much fuel - like 10-11 AFRs. I turned it up the activation pressure and left it as an overboost failsafe. Eventually I switched to the UTCIS programmable CPR and dialed in a more progressive and sensible enrichment curve.

If the previous owner set the car up to use the CPR to enrich under boost and you reinstall the O2 sensor, you really still want some way to force the system to go open loop. I did this on my own car by grounding the wide open throttle switch which prevents the lambda box from trying to lean things out under boost. The lambda box will fight for fuel control and can do a remarkable job of leaning things out.

It's difficult to recommend any course of action without any data logs or precise list of fueling mods. There are a lot of ways to accomplish the same task and the Island/BAE methods aren't necessarily any better than what you have running currently.

Some owners even tried blasting the cold start valve to keep from running too lean. None of these worked well because none of them were calibrated for the desired result. There are also water/meth injection schemes. The basic problem is boost control. Very rudimentary using straight boost pressure to limit, you guessed it!---- boost pressure! Today, with systems like MSD, you can fine tune all of your control parameters and they don't have to be linear. You can program fail-safe features and if they fail you can have other back-up features to prevent detonation.