1983 "flathood" questions

[2-3 heaven]

I didn't have the O2 disconnected but had it on 4cyl. I'll give that a try. Thanks. How do you adjust the idle speed on these?

[2-3 heaven]

I disconnected the O2 and went to set the dwell. At the red wire connector, under the ignition box, I was reading 75. Didn't matter which way I adjusted it, it wouldn't move. I ended up going a little counter-clockwise and it did seem to help for 10 minutes or so then back to black smoke. I checked the fuel pressure and it is sitting at 74psi running. It dips down to about 70psi when I rev the motor, but it climbs back to 74 if I keep it at rpm. I'm going to try the O2 sensor next, I guess. It seems to run better when cold and I noticed when unhooking it that the wire was wrapped in electrical tape. Took the tape off and all the insulation was gone under it. I tried snipping off that part of wire and connecting a new piece, but the issue seemed to get worse. I'll have the new sensor in tomorrow. Anything else I could be missing? Why would my dwell not be moving? Wrong lead?

[jimmy57]

if it is stuck at 75 then the likely problem is the boost enrichment switch on firewall is stuck closed. It is a switch/sensor on firewall behind engine with a vacuum line(actually pressure or vacuum depending on what's going on) to intake manifold. The switch should close at 4-5 psi and provide enrichment by fixing control signal to Lambda control valve to a rich level. Un plug that and see if dwell decreases and the mixture can be adjusted
I see I made a mistake. Check for it to be 45 degrees with sensor discinnected and they want it to be 41-44 with sensor connected.
The idle is computer controlled. 750 a/c off, 900 a/c on. The microswitch on throttle must be clicking when trhottle closes to turn on the idle control system. There is another lead over behind battery, blue/white?--can't remember, that if you ground it on a warmed up engine it sends the lowest control signal to idle valve and the engine should be 500 rpm more or less. If it is lot lower or dies then throttle needs to be cleaned and the stop screw for throttle may need to be adjusted. The throttle stop screw can't be opened so much as to apply vacuum on the port that has hose to vapor canister or you'll start other problems. The canister port hose is the smaller of the two that are next to each other on throttle.

[Bigblue]

Dwell harks back to the days of ingniton points and is not an adjustable factor in a car with electronic ignition...Dwell refers to the lenght of time the ignition points are closed, or "dwell" on each other...It is a function of how many degrees of rotation of the distributer cam that the points are closed, the longer, the better due to better coil saturation...In some big V-8's 2 sets of points were used to extend dwell time...It still matters and is a factor in electronic systems and it will tell you if something is wrong with the black box, but it is not adjustable and will not change with mixture adjustment...A tachometer is needed for that...

[2-3 heaven]

Unplugged the boost enrichment and it dropped to 45 degrees. Took it for a drive and it was awful. Checked the dwell again and it was 88! Unhooked the O2 sensor and it dropped back down. Replaced the O2 and with it hooked up was able to adjust it to 41-44. Thank you so much for the help. It does idle at 1500 now. I'm going to check the microswitch and vacuum lines to the idle air motor. Also, there is what looks like a check valve in front of the boost enrichment switch. Guessing if it is supposed to read vacuum and boost this should not be there?

[jimmy57]

No it is a check valve with a backbleed orifice. It is to protect the diaphragm in switch and to prevent switch going on and off for driver's with a busy throttle foot.

[Bigblue]

From Bosch CI manual

[2-3 heaven]

Thanks for the info. Everything helps. Unhooked the rod from the cable pulley to the throttle body and the rpm dropped a bit. Backed off the screw a touch and it helped a little more and got the micro switch back in play. Think the previous owner had adjusted it up to counter the poor idle from it being so rich. Hooked the boost enrichment valve back up also. Seems to be working fine. The car wasn't building boost still, so I threw on a downpipe from a 740 and 90+ manifold. Boosted up to 6lbs easy. Found out the cat had disintegrated and chunks of it were in the muffler. Having a new one put on Thursday. Thinking about just doing a resonator, but I'm a little worried that would be too loud. That should be the last issue though. Then it is on to some mild upgrades. You guys have been invaluable. Thank you so much.

[9394volvo850s]

glad you guys figured it out. shouldnt be to loud if you do that. what do you want for that 850 manual swap?