Gargoyle_Runner

The black "filter" looking thing on my fuel regulator VSV broke off awhile ago and I haven't thought about it sense. Till today. I spent sometime searching for a replacement with no luck nor did I find any data on how to really test it. I've read about people bypassing it with no notice. So what is its reason for being?

scope103

The Vacuum Switching Valve (VSV) plumbed into the Fuel Pressure Regulator (FPR) vacuum circuit is the Fuel Pressure Up (FPU) vacuum valve. http://personal.utulsa.edu/~nathan-b...82operatio.pdf When the ECU senses that the engine is "hot," it opens the FPU valve, which reduces the vacuum to the FPR, which increases the pressure in the fuel rail, which reduces the likelihood of vapor lock (and other things).

The filter is just to keep the engine vacuum from sucking in dust, bugs, dried leaves, etc.

Can you bypass it? Sure, you can bypass anything on this truck, if you think you're smarter than the engineers who designed it. In this case, it will probably just make your truck hard to start on warm days.

Gargoyle_Runner

Thank you for the link. So I should assume it's working because I have no problems starting?

scope103

Probably not. If it never opens, it could be you haven't tried to start it on a hot, sultry day yet. (How hot DOES it get in Northern Washington? Maybe you don't care.)

If it's stuck open, you may just be running rich all the time (though that should throw a code.)

Ultimately, particularly since you're driving around in a 20+ year old truck, if it ain't broke, don't fix it.

Gargoyle_Runner

Oh it gets hot here. Last summer at my house it almost hit 80. Thought I was going to have to put the belt on my AC pump.

I don't have any codes, which I check often. I installed a toggle switch to run the diagnostic. What code would show for running rich anyway? I ask because I had an issue with running rich earlier this year and I didn't have any codes for that. Plus running rich would be bad for gas mileage isn't it? So if I am running rich wouldn't I want to fix it?

I'm with you on the "if it ain't broken, don't fix it" which my wallet is a fan of also. But my OCD makes me want to fix things. Ever since my rebuild last November I've had little eradict issues with the idle. I test and sample/swap things which just seems to alter or relocate the eradict issue. Knowing the little filter thing broke off the valve I've just always wondered if it was inhibited in any way.

Terrys87

iTrader: (1)

I have seen the filter broke off before and it makes a whistling noise. I just considered it a filter/muffler. I get them at the boneyard.

As far as idling, burp the system, clean and check all sensors, clean the intake. Codes will not always get thrown.

scope103

VERY generally, 26. http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf

Remember that your truck is smarter than you think; if your FPU was stuck open (and added more fuel as a result of the higher pressure), the ECM would detect that at the O2 sensor, and would correct the "learned fuel trim." Only if it was so far off that changing the fuel trim wasn't enough, would you get the code.

If you really wanted to check it, you could apply 12v to the VSV to see if the idle changed.

grumpin

You can also ground the wire for the FPU switch.

Gargoyle_Runner

Thanks Scope for the link bit I believe those codes were for the later 22RE motor. My motor is an early RE and I don't believe the codes run that high nor pause for a double digit.

My idle has a stumble to it. The truck drives really nice but the idle could be better. Rebuilt a few months ago with Engine Builder parts including a new super stock head and 268 cam. Had the intake scrubbed clean. New OEM TPS set proper. Fuel pressure is good, denso fuel pump less than a year old. FPR checks out. Injectors are just over a year old, swapped the old ones back in and no change. Injector relay checks out. Coil checks out good. Thermal switch is new. All vacuum lines are new. AFM is out of one of its resistance values but not by much. The AFM has been adjusted which helped. Timing is good, @8°, it stumbles worse the lower it goes. I've checked the chain and even bumped the cam back and forth a link to make sure. Denso O2 sensor new. The wiring harness has been somewhat rebuilt, had to pull out all the speaker wire and what I think was part of an extension cord the PO installed. I have a spare ECU that I've swapped with no change. I know the IACV is bad but I wouldn't think that would cause a stumble so much as a high idle. I have a new OEM IACV arriving Mon/Tue. Yep I found a new one. Haven't been so excited since I saw a midget in a Mexican wrestling match.

I haven't tested my ignitor, but the thread I read on that involved some tools I don't have. I would hope that one would throw a code which it hasn't.

So it could be the AFM but I'm not having any luck finding one in any better shape. I did just get a lead on an 82 Supra unit but it's not in the budget for a week or two.

The VSV is working. I put a light on the plug and it's getting voltage. I don't know how much because I ran out of time before I could break out the meter. I did jump 12v to it and it made a noticeable difference. So it's not getting 12v through the harness but I don't know what it should be getting. Unplugging the harness did make a difference just not a big change. Stumble still there.

Gargoyle_Runner

To better explain the stumble. It's just eradict with a bit of a miss that doesn't seem to be patterned. The lower the RPM's the worse it gets. The RPM's are currently at @1100 thanks to the recent collapse of the IACV. The idle screw is all the way down to get the idle as low as it is. Just before the IACV crapped I had the idle around 900 any lower and the motor would shake to much. Curious to see what happens when I swap the IACV this week.