96 2.3 p1443 issues

[Tlaurin3]

Hey guys. I know this one has been beat to death everywhere but I just want to make sure I'm on the right track.

Bavkstory: bought the truck a year ago and let it sit since I got butthurt when I changed the clutch kit ( harness fell between motor and trans while bolting up and snapped the ears off the sides with the alignment dowels.) It still runs fine until I get the new block so I decided to go with getting it all smogged.

I've so far done the autolite app104.

I'm in California trying to get smogged and my only CEL code is p1443.

I did clean the purge valve and thermister which were pretty dirty. I supplied voltage and confirmed the valve will cycle on and off and can blow through it. I did a resistance check of the thermistor off the vehicle and all 3 checks were within tolerance.

I've d3cided to replace the valve and thermistor. They will be in today.

Only thing I'm curious about is I've noticed that there is never any pressure in the fuel tank when I remove the cap. Could this be an issue.

My LTFT is also around +20% at idle and evens out when i give it gas.

Can any of this be a contributing factor??

Sorry for the long story!

 

[tomw]

The thermistor may be used to check CHANGE in temperature. If your valve is open all the time, it may be flowing all the time, and when the computer decides to purge the canister, it may command an open, and 'listen' for the change in temperature that has already happened. It sounded good as I thought of it. I'd check that the purge valve actuall goes closed when power is removed( I think ..).
tom

 

[Tlaurin3]

I have confirmed that it closes. The only thing I don't have is a mighty-vac or similar pump to pull a vacuum and check to make sure there aren't any tiny leaks.

My interpretation of the thermistor is that it is similar to the MAF, in that a wire heats up and when the purge valve opens, air passing through the thermistor cools it down, sending the signal to the COM.

I've replaced the valve and thermistor and will test drive it after work or tomorrow on my day off.

The only thing I am not sure of is if the filler neck is rotten or the line from the tank to the canister. If they are messed up, it won't build pressure in the tank. But that doesn't matter for the thermistor right? B3cause as long as the vacuum pulls the air through the thermistor, it should be happy right?

 

[tomw]

T:B3cause as long as the vacuum pulls the air through the thermistor, it should be happy right?

No, if the thermistor is being cooled by a leaky vacuum line, then opening the valve will allow flow that is already occurring... so there will be no change in thermistor value.
If the vacuum leak was small, the flow might change enough when the valve opens/closes to make a difference the thermistor could sense and report. If large, there would be no change in flow, thus no change in temperature.
tom

 

[Tlaurin3]

Well the p1443 is that low/no flow. So maybe there isn't a leak between the valve and intake.. I'll find out soon.

So I'm still wondering about the no pressure in the gas tank. Is it a pain changing the line from tank to canister?

 

[Tlaurin3]

So I went to put gas in the truck today and lo and behold, the filler neck is leaking. The lead time on getting this part will take a bit for me but would this be a potential cause of the p1443? I feel it shouldn't as long as when the purge valve opens, it sucks air, regardless of it being gas vapors or just air?

 

[Tlaurin3]

Well, I replaced the thermistor and the purge valve. I noticed the filler neck does leak.

I test drove it today and the code came back.

Can anyone give me any direction in where I should troubleshoot?

Thanks so much!

 

[Tlaurin3]

There is no fu&#,@;$&$ vacuum.... I feel stupid

 

[tomw]

If you have access, you can read the 'theory of operation', and explanation of how the engineers decided to operate and test the vapor control system. If you watch youtubes, you may hear some words explaining that the tank has to be more than 1/4 but less than 3/4 full, at rest for so long, temperature so hi or low, etc. The system will close a valve and allow the pressure to build in the tank(temp & evaportion/vapor pressure of the fuel), and check that it does, or watch a thermistor cool as the valve opens and lets the pressurized vapor stream past. Lots of tactics & strategy to get things tested without extra parts.
Dunno about your codes, but a failing test in the vapor recovery can come from a leak, bad valve, sketchy tubing, etc., which you undoubtedly know.
I think the 1443, lo/no flow, can come because, with the damaged filler neck, you can't get pressure in the tank, and thus, even without vacuum there'll be no 'flow' from the tank as the pressure bleeds down. No vacuum needed, and the flow should go to the canister, and get absorbed... awaiting the vacuum when the system has the engine running, temp of xx.x, and can feed it to the engine, applying vacuum at that time?
I think fix the filler neck and see what happens.
tom

 

[Tlaurin3]

Well yesterday, I decided to check for vacuum and I found that there was no vacuum at the tube bolted to the upper I/M. So I pulled the throttle body, cleaned it and the IACV and replaced that 3 in. Piece. I've got vacuum now. So I'm going to put it on the road today. Find out.

I really just need to it to pass. I need to complete my registration so I can park it outside my garage. I need a block. So I want to do it as cheap as possible and fix it all up after it's for sure in my name.

Also, I will be posting more questions because this thing has got GREMLINS. It's more funny than anything now but kind of a bummer.

 

[Tlaurin3]

Well it passed. I was just missing vacuum from the throttle body! Thanks all for the help! Stay tuned for more questions haha