High idle/Engine code trouble

[FrankyB7984]

Alright, so my 84 elco has been running at high RPMs when at idle. My timing light says it's running around 1600 RPMS! It's got a carbureted buick 3.8 in it. The choke light stays on constantly while running and even before I turn it over.After a while, the check engine light would come on, so I plugged in the code reader. The codes I got were...

Code 34: differential pressure sensor/ map sensor( I have no clue what a differental pressure is)

Code 44: lean exhaust

Code 45: rich exhaust

Code53: EGR valve stuck, bad EGR solenoid, or defective ECM

a few months ago I was having the same issue but I only got code 44. I replaced the O2 sensor and the problem was resolved. Now it's back and I can't fix it! I've changed the barometric/MAP sensor and nothing changed. I sprayed carb cleaner all around to check for vacuum leaks but couldn't find any.
What do you guys think? Could the ECM be bad? And if so where could I get another one?

 

[Clone TIE Pilot]

Got to be carefull with the vacuum senors, a MAP sensor and differential pressure sensor both read intake manifold vacumm, however they read vacuum inverse of each other so if you replace one with an incorrect model you will have problems. I think most CCC systems use a differential pressure sensor which reads inverse of the MAP sensors most EFI systems use.

Have you checked the M/C dwell? What is it reading?

Spary around with carb cleaner with the dwell meter connected to the M/C solenoid, don't forget to spay around the intake gaskets.

http://s299.photobucket.com/user/BrotherAl/media/CCCbook0049.jpg.html

 

[FrankyB7984]

Got to be carefull with the vacuum senors, a MAP sensor and differential pressure sensor both read intake manifold vacumm, however they read vacuum inverse of each other so if you replace one with an incorrect model you will have problems. I think most CCC systems use a differential pressure sensor which reads inverse of the MAP sensors most EFI systems use.

Have you checked the M/C dwell? What is it reading?

Spary around with carb cleaner with the dwell meter connected to the M/C solenoid, don't forget to spay around the intake gaskets.

http://s299.photobucket.com/user/BrotherAl/media/CCCbook0049.jpg.html

What is m/c dwell? Sorry, I'm kinda dull when it comes to emissions equipment and electronics on an engine. Also, what does a dwell meter look like and where could I get one? And I found that the vacuum line for that sensor is connected by the base of the carburetor. Is this a problem if it does feed directly into the intake manifold?

 

[Clone TIE Pilot]

The carburetor has a air fuel mixture control solenoid controlled by the ECM, the dwell is the measure of its on time to now how much it is cycling. When the solenoid is off the mixture is rich (and limp home default in case of a failure), when it is on the mixture is lean. Normally the dwell should hover around 30 degrees. Higher than 30 is a lean response to a rich condition, under 30 is a rich response to a lean condition. If there is a problem the ECM will try to offset it to keep the engine running, so a lean reading means a rich problem and a rich reading means a lean problem. A bad vacuum leak can cause nozzle dripping in a Qjet, which can trick the computer the engine is running rich when it is really running lean. Incorrect main body or airhorn gaskets can also cause nozzle drip as many cheap carb rebuild kits often have incorrect spec parts, it is why they are cheap.

Dwell meters are old school tools used for setting points on old mechanical ignitions since points have a dwell on time setting. CCC systems being early computer systems were designed so old school mechanics could work on them with mostly tools they already had. To see and adjust M/C Dwell you need a Analog dwell meter and use the 6 cylinder mode or scale regardless if your motor is a 6 or 8 cylinder. This is the only type they sell anymore. http://www.amazon.com/dp/B00062YUUS/?tag=gbody-20

The MAP being plugged to the base of the carb should be fine as those ports are usually manifold vacuum. Here is the vacuum diagram for the 3.8.

 

[FrankyB7984]

Hey so I feel I should have replied a lot earlier than I am now but I looked for the mixture control solenoid but I couldn't find it. I don't know if it is on the carburetor or off to the side. But I did replace the ECM. All the codes went away except for code 45 for rich exhaust and my choke light stays on.. I'm not sure on what to do from here. And for another route how would go about deleting the computer and emissions system?

 

[Clone TIE Pilot]

The fuel mixture solenoid is inside the carb, it has a blue plug on top of the airhorn. On the computer harness there is a green plug that normally isn't hooked up to anything, that is the diagnostic plug you hook your dwell meter too. CCC Qjets have various adjustments that are blocked by plugs from the factory, most CCC Qjets have had these plugs removed by now.

Here is the exploded diagram of a Qjet and list of its parts.

The solenoid is part 225 BTW.

Are you sure the choke is opening? Is the float set at the correct height? Is it the correct type of float for your car? Has it sunk? Is the float valve leaking? You can easily check the float needle valve with a Mityvac. Is your carb unrebuilt factory original, rebuilt, or a reman unit from a store or online? Remans are a real crap shoot.

Removing the computer system opens up a big can of worms. Don't know how many times I have seen newbies on forums complaining how they removed their computer system and winding up making their cars run worse than stock. It isn't an easy job and can snowball if you don't know what you are doing.

 

[FrankyB7984]

Ok I'll have to check everything on the carburetor on the next day off I get. Thanks for all the help so far. And thanks for telling me about deleting the computer. I was able to remove the whole smog system on my 79 elco so I thought I could do it on this one but I gu not because of the electronics operations. I'll keep it updated when I get back to working on the car.

 

[FrankyB7984]

Ok so after doing some further trouble shooting with a buddy of mine, I've found out that my choke relay was bad so it causes it to idle high. My problem now is that I tried to look for a replacement and cannot find one anywhere! Does anyone know what I should do from here? Should I wire up my own relay and If I need to, what kind of relay do I need? Here is the relay I took off...

This was screwed to the firewall.

This is the plug that plugs into it.

This is the back of the plug. There's 2 wires going into the left terminal, 2 wires going into the center terminal, and one wire going into the left terminal.

I don't have any diagrams to go off of especially on a relay with 3 terminals or contacts and 5 wires. If you have any ideas or know what relay and plug setup I need, let me know. I really appreciate all the help.

 

[Ribbedroof]

GM number for choke heater relay is 470374

Here are a few, hope you're sitting down

http://rover.ebay.com/rover/1/711-5...0001&campid=5335822911&icep_item=221858002159

http://www.rarenosparts.com/79-80-GM-HEAT-CONTROL-CHOKE-RELAY-NOS_p_634.html

 

[Ribbedroof]

Circuit 25 is feed, voltage regulator controlled

Circuit 250 is feed, ign switch on controlled, fused

Circuit 78 is electric choke feed

Circuit 931 is signal from oil pressure switch (allows choke coil to operate only with oil pressure present)