About my carb problems.

Zac,

Please do not set your timing back 5 degrees. You are going to create MORE unburned fuel issues if you do.

The flame front needs time to work through the mixture in the cylinder. If you start the process late, less time is available for the burn to work efficiently.

That is why the timing is supposed to advance as the engine RPM increases. The burn time is pretty much a constant, but the higher engine speeds means that the spark has to occur sooner in the compression cycle.

The reason high mileage vehicles get timing retarded as a method of "fixing" emission problems has more to do with carbon build up in high mileage motors. They tend to detonate the mixture, or cause increases in NOX, neither of which you are experiencing in your fresh engine.

Some auto parts stores have a "loan-a-tool" program. You "buy" the tool, use it, and then take it back and get your money back.

Ok, I will just make sure it is timed right then. And I am very aware of the loan a tool program LOL... I do it all the time. You just need the money to pay for it and a goo timing light is a couple hundred.

Right now is pretty crazy, I am in my exam week which is why I have been on a lot less for the past few days. And I dont have a vehicle so I get tot ake the bus everyday and that means I don't get to make random trips to canadian tire to pick stuff up all the time like normal. I am gonna have to put this on hold until this coming tuesday... But then I have like a week off so lots of time to tinker.

Sorry about the delays...

Zac

. . . did I hear somebody mention "EXAM WEEK"?

. . .this got me cogitating. . .

17 year old school kid with no money to speak of, with a truck in dire need of repair.

here is an idea. . .

Go to your VO-TECH counselor (used to call them shop teachers) . . .

Explain what you are needing, with copies of your test paperwork (flunks) and printed off Mazdabscene dialogs.

School budget probably has money set aside for the high dollar testing equipment. And the equipment for the aspiring students.

You might hit paydirt and find out they have a three-gas analyzer available.

The multimeter you have to have to verify closed-loop operation requires a setting for dwell. Not volts, ohms, amperage. Dwell.

A normal multimeter will allow checking an O2 sensor and is useful for some of the tests you might need to do.

He might have a star student in the wings already. Or decide to use your truck with it's problematic emission system as a class project.

Something to think about. After EXAMS.

added information for problem isolation, once you are ready to pursue your emission issues:



easier than reposting . . .

Thanks man.

I am dropping my truck off at the shop tonight to get it timed. If the timing is way off then I will get it etested right then and there, if not, it comes home and I will put the carb on it when I get it and go thru all the other info you have given me.

Other then that I get my second exam tomorrow... Yay.

Oh and about my school shop, I would probably be able to con a few tools out of them and I will try but its pretty impossible to get your vehicle in the shop there. Our school has 2000 kids and the people that get their cars first in there are people in the class... And I'm not...

Zac

After reading this, I am kind of at a loss.

1. I assume youare going to be paying for the timing test. With money that you really don't have. To "EXPERTS" who will probably not entertain any of your requests, if any, that centrifical, vacuum, and total advance be verified.

Even if the timing advances "some" there is not really any way to ascertain a good vacuum advance without a vacuum pump. It might sort of work, even though it leaks. A problem of that sort can cause surging.

2. Without verification of operational essential subsystems, you are going to start swapping parts in the hopes that your problems will magically fly away. I had a bad ground wire to the ECU on a truck in my murky history, Swapping parts doesn't fix a problem like that. Have fun in the cold taking those kinds of chances.

3. You have an instructor for those classes. He decides what the students will be repairing, not the students. Because your truck has a rudimentary emission control system, he MIGHT think you have a good teaching tool for the students who plan on becoming professional technicians. Those are the ones who look for challenges, not play at fixing their own whopdidos.
Golly, you might even get his help personally, like after class, but that might take a little sacrifice on your part. After reading your post and your dismisal of the idea with your premature pessimism. I don't know why I offered it to you.

delete

Well after trying as much as we could in this post and narrowing things down as much as possible we ended up finding that the O2 sensor was actually bad even though my first mechanic said it was fine. I replaced it and it did not help the emissions.

We then ended up narrowing it down to the carb. And more specifically the fuel control solenoid. It seems that the solenoid is getting a constant voltage. So therefore at idle it is operating at the proper voltage and I am getting good emissions readings. However at 40km/h the solenoid is supposed to have different voltages applied to it to change I guess the amount of fuel. But it is not getting different voltages which is why at 40km/h it will not pass.

So we decided to help narrow down problems to just put the new carburetor from BJ on and see if it helps any.

It didn't.

So now we stopped working on it for today but at this point are assuming there is a problem with the computer which is what sends the different voltages to the solenoid. So we are guessing either maybe a bad connection or wire. If not then possibly a bad computer.

I did notice when repairing the rust in the passenger floor and footwell. The computer which mounts to the right hand side did have some surface rust on the case and what not because it was right over where the rust is.

I didn't think too much of it but do you think it is possible that the computer has had water damage?

Anyways I will let you know what happens after I check out the computer and the wiring and all for it on Monday.

I've got to admit I hate this f****** truck.

Zac

I would guess it is entirely possible that the programming in the computer could be comprimised. Or portions of the circuitry could have been damaged if the computer got wet while the truck was running. On the positive side, it is easy to change the computer. Many of the bsceners probably have a computer that they will give you. And, you might actually find that some of the other emission circuits start working properly. Good luck and keep us posted!!!!

. . .Why am I not suprised that you found out what you did, the way you did?

Before I dove into this thread, I asked you a couple of questions.

You told me you are pretty good at following directions.

So far I haven't really seen it.

If you are really interested in fixing your truck, instead of hating it, maybe you will start doing what I have been offering in the way of diagnostic proceedure.

One step at a time.

Instead of throwing money away.

I paid $25.00 for my state of the art, new, Craftsman timing light, which came with the inductive pick up and adjustment for variable timing.

The mixture control solenoid opearates on a 12 volt, computer grounded signal. It will always show 12 volts while the vehicle is running. It is tested with a DWELL METER. Either I am missing something here, or you are.

I am still not convinced that your expensive timing test was done with anything beyond verification of base timing.

I can walk you through this emissions nightmare, but you are going to have to do what I offer, in order to eliminate what is causing these issues.

I am about at the end of my patience with you.