Saxondale

iTrader: (2)

Mileage has been 12 mpg. But first noticed tonight that vacuum line was disconnected from the EGR diaphragm. Hopefully that helps.

However, upon further inspection I see the choke opens as shown on attached photos. Engine is at full operating temp, and at idle.

Should the choke plate be fully open? 1984 L69.

Thanks,
Rich

sofakingdom

iTrader: (1)

Not really significant; but, feel free to adjust it slightly. Especially if ti doesn't have any trouble with cold starts.

Give up one thing (ultimate cold starts?) to get another (pleasing appearance of the choke blades).

Try it and see. If you like it, it's good. If not, .... don't feel too bad about putting it back.

Saxondale

iTrader: (2)

Visited the garage about an hour after my post because noticed on this attached [flash] photo that he screw head on the plate was shiny. Apparently someone in past felt the need to crank on it with a screwdriver.

The plate was now full open. Started the car and it stayed full open.

Will not mess with it, whether either partially angled or full open. Suspecting other causes for poor mileage, if it turns out to not be the unplugged vac line to the EGR diaphragm (or the choke plate).

I trust what you say about it being OK. Thanks.

naf

iTrader: (7)

Recommend you take a minute and carefully inspect your cts and its connector. Looks to be the original type, and their connectors are prone to failure due to design and interference with the air hose. Open circuit here will cause the ecm to stay in warm up mode, with resulting low mileage.

There could certainly be many more causes, but this is one of the easy ones to check. A scanner is a big help in these type of diagnoses.

Saxondale

iTrader: (2)

Will be nice if it is that simple. Thank you.


The wires are bare at the plug, so black tape and physical separation at this point.


Have not had luck finding that style plug in two wire.


I understand can change the Coolant Temp Sensor to modern plug style, and upgrade the plug. Does that sound right?


Anyone have a part number for a replacement CTS?

naf

iTrader: (7)

The new style temp sensor should come as a replacement part at any parts store. Some will come with a new pigtail, some may not. Best to open the box and look. Replacement pigtails should be available hanging in the electrical stuff aisle at most parts stores.

A shorted pigtail will signal 'full hot' and cause cold start running issues. If a lead is broken, or open, it will never send a signal to the ECM that the motor is at running temp, keeping it in a rich, cold running state. Best to swap it out when in doubt.

May not be your (only) issue, but if it's a known possible fail point...

If you need any additional help, feel free to post. We can walk you through some troubleshooting.

Saxondale

iTrader: (2)

I picked up a new CTS with wire. Just need to finish by soldering.

I think the old connector was functioning based on continuity test. But I agree it needed to be done with the bare wires, even if not touching.

None-the-less I anticipate more work will be needed.

Already seeing vacuum connections that could be tighter. Hard vac line connectors in particular. 31 years of heat and use, even if only 65,000 miles.

Damon

When you turn the key to the Run position (but don't start it) do you hear the MC solenoid clicking in the carb? If so, just keep going down your current diagnostic path. If not, you got other issues like bad wiring, bad ECM, bad MC solenoid or something non-obvious. When MC solenoids aren't cycling like they should the default mixture position they stop in is full-up (full rich) and mileage goes right down the toilet.

Saxondale

iTrader: (2)

OK. Checked Mixture Control Solenoid and it is clicking.

Should be able to get some miles on it over next couple days and check mpg again.

Will also change the hard vac lines when time permits to get better seals at air management valve connections and EFE TVS, and at carb.

Did previously observe the air temp vacuum switch in the air cleaner is functioning, opening the snorkel flaps when warmed up.

I am wondering if the fuel tank pressure control valve might have a bad diaphragm. Noticed gas in the vac line on the carb side of that valve. Replaced the vac hose to carb and have not observed wet gas since, but does still get a gasoline odor when I check the hose.

Saxondale

iTrader: (2)

Basic tuneup completed.
Vac line connections look good.
New fuel filter (which was not presoaked or rinsed).
New Coolant Temp Sensor and Plug.
MCS is clicking at key on.
Choke plate operation appears OK
During warmup idle it idles better holding choke plate full open (running rich).
Cuts out at intersections after first or first several starts from full stop (not getting fuel, seems ECM is signalling MCS to reduce fuel).
After warmup and restart from those first engine stall(s) it appears to run better, but still poor MPG.
WOT operation is fine.

Have a multimeter available.
Anticipate will need a timing light and dwell meter for much more diagnostics.

It's a nice car with 65,000 miles. Minor restoration continues. Intent is to keep it as stock as practicable, down to the smallest bolt, hose, sensor (except shifter).

Any suggestions, additions, corrections to above are welcome. Thanks.

Edit Additions 09-27-2015:
Has a new O2 sensor.
Distributor shaft wobble not indicated, based on no damage to old dist cap.
New plugs, wires, cap, rotor.
Did gap the plugs to 0.045, but need to correct per attached smaller sticker I never read until yesterday! 0.035.
Check TPS voltage. Seemed smooth, but slightly high on idle. Range was 0.72 to 4.25ish.

-=Z28=-

iTrader: (3)

Hang in there. You are in good hands.

From the looks of the pics, you have a nice clean L69 and I'd keep it stock too.

There are a few members here who know everything about those computer controlled carb's and will walk ya through it like Naf said.

naf

iTrader: (7)

Looks as if the tamper proof plugs are still present and the carb is cleanish. I'd resist the temptation to make any changes to the carb before ruling out every other possibility.

Check your choke pull off by pressing in the plunger with your finger over the vac fitting. It should stay in until you release your finger.

You can 'rent' a mity vac from one of the parts chains to check each vac system. You can also remove them one at a time while the motor is at a smooth idle. One that causes less change to idle is likely leaking.

Dist cap, rotor, plugs and wires new? Inspect the dist itself for excessive play, rust and stuff? Cap wasn't gouged, indicating a wobbly shaft?

Check timing with a light and at 0-6 with four wire est disconnected. Then reconnect and verify timing at idle looks to be around 20ish and increases with rpm.

Brother Al

A couple thoughts I have.
Check your EFE Valve to see if its opening and closing properly. It is a flapper valve located between the Pass-side exhaust manifold and the Y-Pipe flange.

Not likely the issue but... Does she have a new fuel filter? And if so, check to see if it was installed backwards... be careful if you change it, use 2 wrenches and soak the fittings with PB Blaster and let it soak in before you attack it. This is to prevent twisting of the fuel line and damage to the carb threads... when re-threading it, it should go back easily... lots of people accidently cross-thread them because the aluminum can make it seem like its threading correctly when its not.

Another possibility is carbon buildup in the egr passageway. Seeing the lower mileage, it may be an issue where she was never fully warmed up all the time and the carbon never had a chance to burn off. Also, with today's gasolines, its not that common, but back when these cars were new, gasoline was still hit 'n miss in quality, and lower octane fuel made it worse. Checking if there is carbon buildup is a bit of a PITA, & requires you to remove the EGR Valve... the two bolts that hold it in are often locked tight into the aluminum intake, so be patient so you dont round them out, (differing metals, so PB Blaster is your friend). Once its off, look in the manifold egr port... some black crud is normal on the sides, but if there is big chunks, you will need to clean it... a wet/dry vac and a flathead screwdriver might be enough if its minor, but if its choked up, you will need to remove the intake and soak it with brake fluid or some other solvent (remove every last thing if you need to fully clean it as brake fluid will destroy everything not made of solid metal.)

Finally we come to the dreaded Ethanol problems... this stuff is nasty and causes a lot of problems if its not dealt by taking precautions. I wont dive into that one just yet, but Stabil Ethanol Treatment and some other products are great preventative measures to prevent Ethanol from damaging all vehicles made before 2005 and just about any small engine machine... snowblowers, lawn tractors, gasoline-op generators, snowmobiles, boat motors, etc.

gt4373

Is That The Factory Carb,What's That Second Cable Attached To The Throttle Linkage.

John in RI

iTrader: (167)

Cruise Control..............

gt4373

Thanks,Iv'e Never Had It On A Car, I'm Not Not Familiar With It.

-=Z28=-

iTrader: (3)

I agree, the carb looks nice and clean...... How about one pic of the car???

gearhead141

I haven't had this problem with my 1985 LG4 equipped car. However, I do own a shop manual. I checked under the "Poor Fuel Economy" section. Most of the things it points out, you have checked. It does say to check the TCC for proper operation. On my car, I notice that once the coolant temp reaches operating temperature, the transmission locks up and the revs drop about 200rpm. When the TCC is working properly, you will feel it go into overdrive around 35mph. If you have a 160 or 180 t-stat, it will take much longer for this to happen. I went through this and just ended up putting the 195 t-stat back in. The car runs much better with it.

You haven't mentioned anything about the oxygen sensor. Has it been replaced at any time? There are tests to check if it is still good.

And finally, what do the spark plugs look like. They are usually a pretty good indicator of what is going on.

-=Z28=-

iTrader: (3)

Did you get it running better? Please post results.

Someone else may have a similar issue and could use this thread to fix his/her car.

Thanks.

Saxondale

iTrader: (2)

Seems to run fine and is driveable after the first warmup of the day. That first warmup is ugly. Runs super rich. Sounds like it is missing. Stalls sometimes at first intersections. Then after warmup the check engine will come on on the highway, after about 5 minutes of operation. Always been a O2 sensor rich code. Then at next intersection the light will go out and stay out rest of day. The subsequent starts in the day are generally never from completely cold engine. Usually after car shows or such. But even then it is using to much fuel and providing poor mpg.

The above is description of operation today. Still have things to check off the recommendations lists. And still no timing light or dwell meter on hand. May have to order, which will take up to a week.

Started soaking EGR bolts in hope of breaking them loose this week.

3tas4me

Looks to me that the carb has never been apart. The cover is still on the idle air valve. You might have a sunk float that is causing the carb to be so rich. With the choke on, the rich condition will only be made worse.

Saxondale

iTrader: (2)

Is it difficult to change the carb float?

What parts would be necessary, beside float? Gasket(s). Just get rebuild kit and use only select parts?

Thanks

Edit > Additions 09-27-2015:
Has a new O2 sensor.
Distributor shaft wobble not indicated, based on no damage to old dist cap.
New plugs, wires, cap, rotor.
Gapped the new plugs to 0.045, but need to correct per smaller sticker in attached photo. 0.035.
Checked TPS voltage. Seemed smooth, but slightly high on idle. Range was 0.72 to 4.25ish.

3tas4me

Buy the factory service manual if you don't have one. You need a systematic plan to track this problem down. Start with the simple stuff and move on to the more complex. All these suggestions are good, but they are all just shots in the dark. If you want to check the float, do it with the carb on the car and full of gas. Remove just the top portion of the carb with it still mounted on the engine and see how much fuel is in the float bowl and what the float is doing. It is also possible that a piece of dirt/debris could be keeping the needle from seating properly and thus overfilling the carb with gas. Is your choke operating as it should? Do you set the choke before starting the car by pressing the gas pedal to the floor once and then releasing? Send me a PM on where you are located as I live in Wisconsin and if you are close, maybe I could help.

Brother Al

I would STRONGLY recommend having someone who has solid experience with E4ME carbs help you. Seeing that she runs ok after the initial warmup, I dunno if the float is to blame... but if it might be the float, you might as well have it rebuilt. This is not something a novice should attempt, especially if you care for a numbers-matching L69-spec'd E4ME... L69 carbs had a different hanger and metering rods, no AV tab, and each year carried its own part number, with the '84 having specific Automatic & Manual part numbers.

I will echo the ideas of:
A.) Getting a GM Shop Manual (Ebay)
B.) starting with the simplest first and then work your way back to the most complex...

A Qjet is simple, yet not... there is a lot of ways to ruin a perfectly good one if you dont know them well and they require a bunch of specialized Thexton calibration tools that are no longer made and difficult to obtain... Because Qjets are made of aluminum, you can easily strip threads and break things if you are not careful. When people put them back together, they often overtorque the bolts to the body of the carb, causing it to warp and leak. Another thing that people tend to do is pop open the idle mixture screws. I never recommend this unless the carb has a million miles. The last resort is a rebuild of the carb... "after all else has been tried"... have it sent out to a professional shop that is familiar with these...
S.M.I. "Sean Murphy Induction" is a great example, and there are others... A good shop knows what they are doing and will not only use quality parts, but they will identify any other issues and correct them if they can. They will also anodize the carb so it looks just like it did when it was new...

naf

iTrader: (7)

Probably not EGR. A stuck valve will cause rough idle but you can check by pulling the valve open with your fingers from underneath while at idle. Opening the valve should cause the motor to severely stumble. A valve that does not open will not cause rough idle, as the valve is only commanded open at part throttle conditions.

Probably not sunk float. A bad float would cause consistent running issues.

Your latest posted symptoms are consistent with a choke that is not opening correctly. Try opening the choke manually and maybe zip tying it open for a drive after a few minutes of warm-up. Your first pics of the choke plate show a choke that is open enough not to cause a problem, although 90 degrees straight up is nice. It could be opening too slowly or sticking shut. This would throw a rich code and could cause a stall. Rough idle, maybe. Easy to rule out though.

gt4373

Are You Using The Factory Air Cleaner Or An Aftermarket One,I See You Have The Port Going To The Factory Air Cleaner Capped Off.

sofakingdom

iTrader: (1)

This (the vac line to the MAP sensor) looks like.... if not a "problem", certainly at least "an opportunity for a solution".

Saxondale

iTrader: (2)

Had time to look at it again tonight. Started and watched choke for approx. 5 minutes. Never really opened enough for smooth operation. Ran better when I held it open. So took out the screw on the choke shaft and disconnected the electric choke. The vac pulloff is working so left it alone. But test drove it then with choke full open and it ran fine. Don't know mileage yet, but ran as it should.

Hence it is possible the electric choke is not opening adequately, if operating at all.

It has 14+ volts going to it. Then checked amps and it read zero. Maybe not any current flowing through the electric choke? Sound possible?

Damon

It's possible. They go bad every few decades or so.

A quick test you can do (which won't prove it's working properly but MAY prove it's NOT working properly). At full-cold, room-temp, check how many ohms of resistance between the coil terminal and the body of the carb (ground). A fresh one should be around 10 ohms. Used but servicable 10-20 ohms. If it's shot, it'll be over 25 ohms.

Saxondale

iTrader: (2)

Infinity ohms through the choke circuit, cold engine. Difficult to change electric choke? Seems it could be problematic. Remove rivets. Install screws? Any recommended testing before going to that "extreme"? Remove carb and take it to a pro? Thanks.

naf

iTrader: (7)

Drill rivets and install screws with the little tabbies that hold the cover on. Could probably even be done with it on the motor. If you need the screws and tabs, pm me your address. I don't think a new coil will come with them.

3tas4me

If you do replace the choke coil, do NOT install a gasket between the coil and choke housing. If you do that, you will create an open circuit in the choke and it won't work.

Saxondale

iTrader: (2)

Using the factory dual snorkel. Been capping the port when the cleaner is off. Thanks.

gearhead141

I think you may have found the smoking gun. From your photo, it appears that the choke coil is original. I say that because the cover is still riveted on. Replacing the unit isn't that hard. OK, now that I said it, let me say that it isn't very hard once the carb is removed from the intake. Trying to work on those rivets with the carburetor still on the engine is just a bear. Don't misunderstand me, anything is possible, it's just how difficult will it be. Good luck and let us know the outcome.