Removed carb.
Pulled only the very top off.
A tiny tube (one of two), did not remain where it was pressed into. Put it back into top section.
Replaced TPS and spring/ very brittle Accelerator Diaphram and ring-shaped spring. Did not touch float/ needle/ seat, as the mixture solenoid rests on it.

Even this minor rebuild revealed lots of parts, including some tiny needles and springs. Hope these things are back in properly.

Re-assembled with new gasket.
***** were not quite large enough for a full rebuild.
Have not as yet adjusted TPS screw.

Car runs nice. Has more oomph. Perhaps TPS is adjusted for performance, not emissions.

When it gets fully warmed up, it seems to idle lean. No missing, but idle speed is not perfectly still.
I raised idle a bit, but best idle is still at 500 in gear (as before rebuild), not the 600 that I have it at right now.

Would not the computer tell me that things are too lean??????

Boy, do I miss the side-drafts on my Triumph.

Driving to girlfriends house soon; more car news tomorrow.

Goodnight.

Seth

 

I just fixed some bad emission hoses and 'Tees'. Then I brought idle down to 500 in gear.
Now, I get the impression that it is idling simply EPA lean But, exhaust doesn't smell quite right.

Last night, I drove it with some leaks in the crancase vent mess of hoses. It was so lean, thay idle was rough and slow enough to nearly stall. Even then, the catalized exhause smelled odd. Can temporary very-lean cook a cat? Cat is fairly new and name-brand, and has a hose to the air pump.

Just pulled one plug on each cylinder bank. PLUGS ARE PERFECT. LIGHT TAN/WHITE INSULATORS.

CAT???

Autozone does not have the 'D'screwdriver, so I have not as yet even checked to see how far off the TPS is.

Thank You

Seth

 

Ah, a full rebuild isnt as bad as it sounds. I've been there.

Uh, they didnt have the d screwdriver? Well you can use a 5 mil socket instead, if you are careful. That worked for me, and it sounds from what you said like that's what needs to be adjusted. How much vacuum is it pulling?

 

Thank you for the reply.
Last week, I was pulling 25 inches at idle.
Will dig up that same guage, and let you know.

Seth

 

Canadians are really sharp.
Vacuum is down to 20", and not as steady as before.
How a socket will fit in the hole, once I remove the tamper plug, is beyond me. No pun intended- the hole looks too small.

EDIT: For someone who fixes delicate electronics and turntables for a living, and a few days ago, fixed a blown tweeter on a $1250 speaker, I was all butterfingers this afternoon.
In an attempt to pull the tamper plug on the TPS, I was unsuccessful, and drilled at a bad angle. Can't get to the asjustment screw w/o removing the air horn and doing some fancy altering from below. The replacement plugs are a better design- brass, not aluminum like the carb is. There is now a spot of epoxy on the partially-exposed screw.
The setting is supposed to be 0.5 volt. It is close but no cigar at 0.65 to 0.67 volts.
Understandably, this gets a little lower [closer to 0.5 volts] as the car sits w/o actually running.

The smell- get a load of this- the air pump was not dumping into the cat. Had to power-down the computer, and now the pump is doing it's thing.

Plenty of bug bites, too. Wierd for October in N.Y.. What am I complaining about? Winter will be here soon enough.



Seth

 

Once the TPS is replaced, you should check the operation (duty cycle) of the mixture control solenoid. A conventional metod is to use an old ignition dwell meter (effectively a duty cycle meter). Lacking that, you can use a duty cycle scale on a DMM, or an oscilloscope. Sync on a 'scope can be difficult, but it can be done.

MC SOLENOID ADJUSTMENT

• Connect a dwell meter or oscilloscope probe to terminal ‘B' on the enrichment solenoid connector and reference it to ground;
  
• Start the engine and allow it to reach normal operating temperature. Set the base idle if necessary. The dwell meter reading should vary while this is occurring, or the oscilloscope square wave frequency (pulse length) should vary;
  
• Set the parking brake, block the drive wheels, and place the transmission in DRIVE for an automatic car, NEUTRAL for a manual car;
  
• The dwell meter reading should fluctuate between 10° and 50° on the 6 cylinder scale, the oscilloscope should indicate a 15-85% duty cycle. Adjust the idle air bleed valve screw (12) in 1/8th turn increments to obtain a dwell reading between 25°-35°. The optimum setting is 30° (50% duty cycle), so get as close to this as possible. Adjust the screw only a little at a time and allow the system to react between adjustments;
  
• If the desired reading is not attainable through this method, the idle mixture screws will have to be adjusted (87). This will require removal of the carburetor and cutting the throttle body away around the steel plugs. Then reinstall and adjust the idle mixture screws evenly , then adjusting the idle air bleed screw as described above to obtain the correct readings.

A "dwell" meter is basically a duty cycle meter that is graduated on degrees of distributor rotation for an engine. In Kettering (breaker point) ignition system terms, the duty cycle is the amount of time that the circuit is on (points closed) versus the amount of time the circuit is off (points open). The meter face is graduated in degrees of distributor rotation. A point dwell angle of 30° on a V-8 engine is basically a 66% duty cycle, or ON time versus OFF time. One cylinder fires every 45° of distributor rotation (90° of crank rotation), so if the points are closed for 30° of that time, they are open for 15° of that interval. 30° ÷ 45° = 2/3, or 66%.

A six cylinder engine is similar, but one cylinder fires every 60° of distributor rotation (120° of crank rotation). Typical specs for ignition point dwell on a six cylinder are 33°, and on a four cylinder engine 40° is common.

In terms of the mixture control solenoid on your carburetor, it is basically the same thing. The dwell meter is used to determine the amount of time the MC solenoid is ON versus OFF, or duty cycle. Since most automotive technicians have (or had) a dwell meter, the specification is presented in terms of dwell degrees. In reality, the measurement is the duty cycle percentage of the solenoid, but the common dwell meter is not graduated in those terms. Remember that 30° on the "V-8" setting on your dwell meter really means 66% duty cycle, and 45°would equal a 100% duty cycle.

Typical instructions for setting the solenoid are to set the meter on the six cylinder scale and adjust the "dwell" to an optimum of 30°, or in reality a 50% duty cycle. This means the solenoid is ON an equal amount of time that it is OFF. This is the optimum setting for fullest range of control by the MC solenoid.

If you don’t have a dwell meter, but do have an oscilloscope or better quality DMM with a duty cycle scale, just set the MC solenoid for 50% or as closely as you can get it. The typical instructions indicate that any reading between 10° and 50° and varying is acceptable (15-85% duty cycle), but “acceptable” isn’t good enough for most of us, or we wouldn’t be here.



Once you have it running correctly in stock form, you can begin the power tweaking and tuning.

 

Vader,

So this is why the plugs look right, but idle is not smooth?
Also, I really wonder if I cooked the cat, because even though the air-pump air is now once again going into it, the engine ran very lean [hose leaks] w/o air pump air to cool it, for about 20 miles. Exhaust smelled wierd then, and still smells wierd.

Thanks

Seth

 

careful Ryan, he's talking about a cc-carb, where everything is more complicated and weird. Also you're thinking of the mixture screws right? and he's talking about the tps adjustment screw. (right?)


Good luck with it.

 

Story as of this afternoon:

Dwell meter is spot-on for mixture solenoid. Very good.

Computer keeps shutting off the valve which permits air pump to go to cat. Don't know why, yet. So, I pulled off the solenoid valve from the diverter valve, and put the vacuum hose on the exposed nipple. Now the pump does the cat all the time, except when vacuum is low.

The TPS adjustment is a dead issue, as I cannot get to it and it is not too far off desired setting.

The car idles lean, and lean equals not as steady as slightly less lean. Perhaps everything is the way it should be, but for a possibly cooked Maremont brand cat.

Thank you for the input.

Seth

 

I would NOT directly connect the AIR pump. From what I remember reading, when you enter WOT the exhaust runs rich. That gas ends up in the CAT and all that air will heat the hell out of it cherry red.

 

I have had no time to tinker with car, as there are serious family problems to attend to.

Was thinking of putting back the air-injection tubes. BUT--when I attempted to remove the plugs that are in place of the tubes, I discovered that that at least two are seized in place.
They are in there for good, even though they were teflon-taped 1st.
So the choice is no injection into engine, but injection into cat; or no injection at all.

My Dodge van has air injection into a bellows-system upwind of the cat and into the engine full-time, [w/o a feedback-type computer]. The cat is from 1985, and still seems to work. Van has 65,000 miles.

WOT is a very temp condition, so I guess that as long as the exhaust is clean, it will have to do.

Thanks

Seth

 

Yeah, I was. Oops, should have mentioned that. I knew he meant a cc-carb though.

Also, how did I manage to miss that anyone had replied to this thread.

 

Non-Junction,

Take care of the home front first. The car will still be there, waiting patiently, and without complaint when you get back to it.

When you do find time for it, try not to lose too much sleep over the lack of AIR tubes on the exhaust. It really only helps complete combustion on startup, and should not affect the situation once the engine is warm and in closed loop. As long as the AIR tube to the cat is intact, the system will work just fine. If you are required to pass a visual inspection, however, the tester may balk at the lack of AIR tubes on the exhausts.

 

yea, me too, no email at all... WTF?

 

I finally had time to get back to the carburator.

Set the hot idle to 500 in gear. Set TPS voltage to .48 volts.

None of the factory adjustments have been been altered.

Hot idle is still sporatically smelly [rich]. Rich as in too rich for the cat to do its job. But, if the car is simply idling for some time, the exhaust does smell catalized.

Car runs very well, hot or cold. Idles smooth and very slow.

Rich condition began BEFORE the TPS required replacement.

Interestingly, when the temperature guage reached about 190, the 'check engine' light lit for a second.

I obviously need to do Vaders' idle air screw adjustment.

But, why did it go rich in the 1st place, several weeks ago? What is responsible for this change in the fuel delivery?

ONE GREAT THING: I HAVE BEEN COMPLAINING ABOUT AN INTERMITTANT RAT-A-TAT-A-TAT FOR 5 YEARS. THE NEW TPS SEEMS TO HAVE RESOLVED THIS ISSUE.

Thank You Again,

Seth

 

hey guys I also need help with setting the tps and the air mixture screw by no means do I want to hijack the thread but it's interesting on how much you guys know about carbs and just wanted to some info on to where all the screws are to adjust the idle screw, air misture and how to adjust the tps let me know thanks.

 

Welcome to 'Nightmare On Rochester Lane'.
[A joint Warner Bros./General Motors release.]
Opening in N.Y. & L.A. this Friday, nationwide the following Monday.



Seth

 

Good to hear from you.

You won't know it's "right" until you set the air bleed with the dwell meter. Right now at low idle your O2 sensor could be providing intermittent feedback if it's not staying hot enough. When the O2 fails to provide input the ecm will go back to 50% dwell at idle which could be off (rich or lean) if you haven't set the air bleed.

I wound up installing a heated O2 sensor in my camaro, but it has headers.

 

naf listen if you're talking to me I already switched the O2 sensor and nothing I did it because of tune up anyways but it didn't help any I also tried hooking up a dwell meter to my engine but the needle was not moving it wasn't doing anything I don't know if I was doing something wrong or what I was thinking it was faulty could that be why it wasn't woking? oh by the way where is the idle air bleed screw located do you know. thanks and hopefully [B]notransistors[B] won't mind if I use his thread.

 

10gunman: I wouldn't recommend making any adjustments to your carb until you verify that all the sensors and electronics are functioning correctly. There could be several reasons you're getting a constant dwell reading.

If you want to start a new thread and let us know what it reads we can give you some pointers. I'll be around through early this evening but will be away this weekend.

There's a lot of stuff on this site if you want to do a search and you may want to pick up a manual as it can walk you through some of the diagnostics with photos.

 

naf I have a thread started in the carb section under "emergency help" I have a couple of guys helping me out but the more the marrier if u want to check it out and we can go from there thanks naf greatly appreciated.