Failed Smog in CA... Help :(

[ozzyleven]

Here's a picture of the 2nd smog test in case it makes more sense to some of you to pin-point the problem:

Sorry to hear you are still having trouble. My bets would be on the oxygen sensor since its a code 25. Im pretty sure the other issues for that code would produce more obvious driveability problems. Hows your mpg? Poor mileage but no other real drivability issues would be a pretty good indicator of a bad o2 in my opinion. If the vehicle has that. Many miles I wouldn't be surprised if its bad. Like I said buy a denso brand O2 sensor and install it yourself. It's really easy two bolts and a wiring harness. Your vehicle may have an upstream and downstream one since its in Cali. Check rock auto I know they have them for reasonable price/shipping. I would leave the timing alone until you replace these as thats just a bandaid. The o2 gives feedback to the computer and helps it determine the air/fuel mixture. I can't tell you for sure if that's the problem but in my experience a new one got rid of fuel mixture problem and improved mpg drastically. I can't remember if you can test the old one. If you can it would be in the fsm.
Was also thinking that if you haven't done a tune up lately, that can't hurt. Seafoam through the brake booster line can be a miracle cure in some cases.

 

[Lankan]

Wanted to update you guys on my progress so far. Didn't want to replace anything without being sure that it was the problem (as many others had done this and still failed), so read many many threads to figure out what the possibilities might be.

Since a couple of guys, including ozzyleven were suspecting the O2 sensor, there was a procedure in the FSM to check this. The main issue was finding a road where I could go at 30-60mph with the RPM @2000 for 90 seconds. I did this last Saturday, but used a lower gear (the one below "D") as the road I went to wasn't long enough (without having to stop). No error code showed up. Then yesterday I took off the EGR and it was clean as ever. Was a bit skeptical about the gear I used to test the O2 sensor, so afterwards drove a bit further from my house to find a road where I could keep in in "D" for 90 seconds. I had been frustrated all this time as my 4Runner ran fine,with no issues at idle or other sypmtoms associated with a bad O2 sensor. Only issue was that it's mpg was bad... about 200-220 per tank on the highway and about 160-170 in town. Towards the end of the 90 second test (at about 80 seconds) the check engine light lit up! I know it sounds funny, but I was overjoyed, as I had finally confirmed that it was the O2!!

A big thanks to all of you that helped me with this, and hope that this thread will help someone else in the future.

ozzyleven... you were right on the money!! About replacing the sensor. I've read that only the upstream needs to be replaced. Is there any way that the downstream sensor can be bad? Has anyone had to replace their downstream sensor?

 

[OCMike]

Awesome HC levels. Mine were just below Max. Hope the O2 sensors fix your problem.

 

[Lankan]

Received my Denso O2 sensor, spark plugs, and oil filter. All installed. Funny thing is, the O2 sensor that was in there had a slightly larger diameter electrode/sensor than the one I received (I did order the correct part number for mine: 234-4052), but the lengths are the same.

Should I go in for the smog right away? I have a weekend trip where I'll be driving about 600-800 miles... would it be any better to do the test sometime next week?

What timing should it be set at? I have read many threads with regard to timing set to maximize the possibility of passing the smog (for guys like me who have "NO" issues. People say to re**** the timing. The state allows +/-3 from what's specified (which is 10*BTDC). Should I keep it at 10* or re**** it to 13*BTDC?

 

[ozzyleven]

Its my understanding that on the Cali vehicles, all the downstream O2 does is confirm that the upstream and cat are working. I think its definitely the less important of the two. If you can drive with the new O2 for a little bit to make sure your code is definitely gone and doesn't reappear after 50 miles. I don't know about the timing. Montana doesn't have emissions so I never have to deal with that stuff. I know a lot of people on these forums seem to run at 12 degrees all the time and claim better performance, etc. I think stock timing though was set the way it is for emissions compliance though. Wanted to add that you should see your mpg issues resolve with a new O2. Running plus fuel instead of regular really seems to help also. My truck went from about 17 highway to 21-23 mpg after the new O2. Really its the best 50 bucks I've spent for my runner.

 

[Lankan]

Sounds good. Guess it makes sense to drive it a bit to make sure that the new O2 is doing it's job. Hopefully I will see an increase in gas mileage, as you say the best I've been getting is @16.5mpg on the freeway, and it's embarrassing to even state what it's getting in the city!

Hopefully someone else can give their advice on the optimum timing to pass smog!

 

[Lankan]

Bad news, I thought I would follow the FSM and duplicate the test that made me certain that it was the oxygen sensor that was bad (just to make sure that the new O2 sensor was working properly). To my disbelief... the check engine light came on!! This is the procedure I followed:

DTC 25 Air Fuel Ratio Lean Malfunction
DTC 26 Air Fuel Ratio Rich Malfunction
Malfunction: Open or Short in Heated Oxygen Sensor

(1) Disconnect the fuse EFI (15 A) for 10 sec. or more, with IG switched OFF
(2) Initiate test mode (Connect terminal TE2 and E1 of DLC1) with IG switched OFF
(3) Start the engine and warn n it up with all accessories switched OFF
(4) Idle the engine for 3 min.
(5) Quickly race the engine to 4,000 rpm 3 times.
(6) Drive at 50 – 96 km/h (30 – 60 mph) (Engine speed 2,000 rpm) for 90 sec.
HINT: If a malfunction is detected the Malfunction Indicator Lamp will light up during step (6)

When I connect terminals TE1 & E1 to read the code, it's giving me the 25 code again! What do you guys think it could be?? Along with changing the O2 sensor I also installed new Denso plugs and an oil change, but I'm quite sure these two items would not effect the test.

 

[ozzyleven]

This might sound dumb, but did you make sure the O2 is plugged in? Did you make sure to put the new gasket on and take the old one off? I overlook simple stuff sometimes like that. Same thing goes for all the engine grounds. I can't remember where I've seen it (maybe search Yotatech) but some guy had a nice picture with all the ground points circled. Next, do you have any air leaks on the intake? I would also consider checking for proper fuel delivery. I'm sure the FSM has plenty of tests for it, but I've never had to do any. A new fuel filter would be a good idea if you haven't done it. Maybe run some injector cleaner (or Seafoam) through it too. Can't hurt. Test the AFM too. You could probably run through all this in an afternoon.

Bummer that the O2 wasn't the culprit, but at least its new now and ruled out. These trucks can be a pain, but keep testing and working on it and you will figure it out.

 

[Lankan]

Yeah, before I posted I made sure that the new O2 was plugged in, and yeah I took out the old gasket. No air leaks on the intake as far as I know, as I tested all the vacuum lines by spraying some carbuerator cleaner during idle. A new fuel filter was also installed about 150 miles back. I suppose the next thing I should do is check for proper fuel delivery and to check if the AFM is working. Definitely frustrating, but I feel that I'm close to finding out what's wrong, so hopefully I will.

 

[Lankan]

Got a multimeter today, and here's what I've checked so far, and have been to spec:

1) EGR gas temperature sensor
2) Volume air flow meter (air intake)
3) Engine coolant temperature sensor
4) Heated oxygen sensors (both upstream and downstream, and the one I just replaced).
5) The 3 engine ground bolts and wires are all there/not damaged.

There seem to be no blockages or an open/short in the injector circuit, as I have followed the DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN two times, and both times the check engine light has not come on.

What I have not checked, and cannot find in the FSM how to check:

6) Open in E1 circuit
7) Open/short in heated oxgen sensor circuit (not the sensors themselves, but the wiring that carries the signals to the ECM).
8) Ignition system (not sure what to check here). If it's to make sure that the spark is occuring, it's fine.
9) ECM. Suppose the only way to check this is to replace it or use someone else's right?

I did another driving pattern test today to double check the new O2 sensor. The check engine light came on again. But what I did realize is that the instructions in the test procedure say:


(1) Disconnect the fuse EFI (15 A) for 10 sec. or more, with IG switched OFF
(2) Initiate test mode (Connect terminal TE2 and E1 of DLC1) with IG switched OFF
(3) Start the engine and warn n it up with all accessories switched OFF
(4) Idle the engine for 3 min.
(5) Quickly race the engine to 4,000 rpm 3 times.
(6) Drive at 50 – 96 km/h (30 – 60 mph) (Engine speed 2,000 rpm) for 90 sec.
HINT: If a malfunction is detected the Malfunction Indicator Lamp will light up during step (6)

NOTICE: If this procedure is not strictly followed, you cannot detect the malfunctio

What hit me is that both tests I have conducted AFTER installing the new O2 sensor, the check engine light came on after 90 seconds (usually at about 105-110 seconds). See item #6 and the HINT afterwards. Both times I thought I was trouble free and kept going as I needed to drive down the road that I was doing the test on to get home. The very first time I did this test (with the O2 sensor that was in the truck when I bought it) the check engine light came on at about 80 seconds into the test (as described in step 6 of the procedure). Maybe I should do the test again tomorrow and pull over after the 90-second test! Am I onto something, or its' just wishfull thinking??

 

[SDsurfx]

Hey y’all, I’ve got a slightly less complicated problem. I picked up a new to me 99 T4R with 298k on the clock. Failed CA SMOG today for high HC PPM. It’s BARELY too high, they measured 38 PPM (max is 35). There is no CEL or codes tripped, despite the test saying the OBD failed. It did get a new battery 2 days ago. I’ve already begun some extensive tune up maintenance, which will include new plugs, wires, fuel and air filters. Pic attached. Any ideas?

https://imgur.com/a/J221H42

 

[cap10]

I used to use the good ol paper clip method until a friend of mine loaned me his scanner that had several adapters that allowed the obd2 scanner to plug right into where the paper clip is used. It worked great.

 

[rgkharrison]

Reviving thread from the past since I'm new and can't create a thread yet.

Anyone have some input on this for me? Just picked up this 93 3.0 despite some of the issues it's having. It appears to have a couple faulty injectors that I'm hoping is causing most of the issues. Timing is also off by 6 degrees (per the person I got it from).

Anything else I should be doing while swapping the injectors? I'll at least do the PCV valve.