Hello Yotatech, this is my first post, thanks for having me.

My truck, 1988 4Runner 22-re, failed CO emissions around a month ago, this is the result:

CO GPM Reading: 33.5770 Limit: 25.0000

I went back about a week ago after replacing my air filter and following the emissions tech guy's advice of fuel injector cleaner. Here are the results:

CO GPM Reading: 80.5069 Limit: 25.0000

They offered to diagnose for free so I set up an appointment. Here is the information they gave me:




The guy who did the diagnoses was less than friendly and he seemed eager to tell me it would cost $2000 to fix. I tried probing him a bit to see if fixing the VSV for the fuel pressure regulator, or the VSV for the air injector would help. Each time he just repeating that I needed a major engine repair and "these trucks weren't made to go this long" and "You'll have to decide if you wanna keep it".

I also know that my spark plugs could use replaced, just as additional info.

I was so close the first time what went wrong? Any advice would be very much appreciated. I just need to know where to start. My plates are 4 months expired and I need to get on this.

[Edit: the bit about my tires not being the same size is due to the spare tire, I got a flat yesterday]

 

First don't ever go back to that guy ever! He was trying to scan you out of your truck. These trucks can last a life time. You need to do a general time up. Plugs, wires, distributor cap, rotor. These need to be oem, or denso brand. No exceptions. Second before you have the truck tested take it for a good long run. Keep the engine hot do not turn it off. Check and adjust the timing according to the factory service manual. How does the truck run? Smooth? Rough? Does it feel good on power?

 

Running too rich will really run up the CO. http://www.cygnusx1.net/Media/Supra/...taTech/h56.pdf A broken FPU VSV alone won't do that, but if your Fuel Pressure Regulator vacuum line is allowing atmospheric air to reach the FPR, that will definitely make it run rich. Just play it safe and replace the vacuum line to bypass the VSV (you might end up with a vapor lock issue on hot days, but the goal is to pass smog).

A non-operative PAIR valve isn't going to help, but there is only one vacuum line to the valve from the VSV. Trace through the vacuum diagram yourself and figure that out.

Code 51 could be a TPS problem, or just not setting up the test correctly. Pull the EFI fuse to reset store codes, and check them yourself. (Is the CEL on? In California, that's an immediate fail, so I doubt it.)

Poor compression can easily raise CO; it's not a difficult test so you might want to pick up a compression gauge to do it. Checking leak-down is more useful, but much more involved. I'd wait on that.

You can replace the plug wires, etc., if you want. Those are easy to do. But it probably won't affect your CO issue. And don't spend much time on "old wives tales" like getting the engine "hot."

 

It may be frustrating having to deal with emissions checks and glad I don't have to deal with emissions but in some ways like your high CO limits, it does tell you roughly where you have a problem that needs fixed and better off when you eventually do pass. I don't know what causes CO fails but I would

1.start with an great tune up with factory tune up parts,
2.replace all the vacuum hoses if not already done, and correctly routed
3.clean the Intake System of carbon build up
4.most of your sensors can be cleaned with a brass tooth brush
5.run a compression test
6.EGR operating,cleaned
7.timing according to factory manual

I have taken worn out TPS and cleaned them and got them to pass test according to test procedures. If it is a high mileage truck and original TPS, I have seen the pass test but still just cause issues. A TPS sensor I no longer clean and just replace it if I know it is bad or worn.

As close as you almost passed the test, I cant see it being much and would take my business elsewhere instead of the guy that you are dealing with. He doesn't sound like much of guy that I want deal with.

 

Thanks for your responses.

The CEL is not on.

Is there a downside to bypassing the VSV for the FPR?

My plan is to verify my vacuum lines are good and replace if needed, bypass the VSV for FPR, check the TPS and replace if necessary, and do a tune up.

 

One more thing, they marked FAIL for the AIS column under emissions control equipment. What does AIS stand for?

 

based on the other text, I'd guess Air Injection System. Which would be the PAIR valve. http://web.archive.org/web/201311071...20pulsedse.pdf

The VSV to the FPR is the Fuel Pressure Up. http://web.archive.org/web/201501160...ne/41fuelp.pdf Under conditions likely to lead to vapor lock, it admits atmospheric air into the FPR vacuum line, which raises the fuel pressure in the rail. So if you bypass it, you might run into a vapor lock problem on hot days. Then you'll wish you had fixed the VSV. Or not.

 

Alrighty so I replaced spark plugs, cables, replaced the VSV for FPR, replaced vacuum lines.

My brother and I foolishly tinkered with the AFM thinking it was a MAF. We broke it and replaced it with one from his parts Runner.

The line going to the VSV for FPR was indeed open due to the broken VSV.

I cleaned inside the throttle body (did not remove it).

I noted that my dashpot is pretty beat up and sticks a bit but it looks brand new compared to the one on my brother's runner.

I took it back thru after all this and the emissions are half what they were.

CO LIMIT: 25 GPM

1st test: 33
Ran fuel injector cleaner thru
2nd test: 80
Did the above repairs
3rd test: 39

On the second test, the CO emissions spike and stay high while the truck is running at 55 mph.

On all the tests the CO emissions spike while accelerating.

The biggest spike, and the one I think is failing me, is while accelerating to 55mph. Here's what that looks like on the read out:





I've been reading up on the TPS and PAIR valve and those are the next things I'm going to check. I also dug around in the file I got from the previous owner and found that they were having similar trouble back in 2013 and they replaced the catalytic converter and then passed with flying colors. Is it possible the cat went bad over the past 3 years?

Thanks everyone.