Subject: 1994 Pickup – 2500 RPM Surging Issue (Fails CA Smog)

Hi,

I have a 1994 pickup with a 3VZ-E engine, 5 speed and 280K miles. I’ve owned it since new and rebuilt the engine at 220K after cooking an exhaust valve and head gasket. The rebuild included pistons, rings, rebuilt heads, all sensors, vacuum/emission hoses, TPS, O2 sensors, and injectors (12-hole Fireball type) rebuilt Mass Flow. I also installed headers and a free-flow exhaust, CA-exemp CAT, disabling the EGR and PAIR valve with a resistor and by not drilling the header for the EGR pipe.

The truck runs and idles perfectly as my daily driver except when in neutral and holding the throttle at 2500 RPM—it surges. I have a wide-band AFR that I put in the tailpipe and you can see it going rich lean during surging. Unfortunately, this is the same RPM required for the CA smog test (25 mph test), causing me to fail due to high NO emissions (693 ppm, max allowed 533). HC levels were close to the limit, but everything else passed. It has passed smog the last 5 years with no problems

Oddly, turning on the AC stops the surging. Recalibrating or disconnecting the TPS makes no difference. Pinching vacuum hoses while surging also has no effect.

I’m out of ideas and don’t want to blindly replace parts that are only 60K miles old. I love this truck and drive it daily, so I keep it well-maintained.

Any insights before I start spending money? Here’s a video of the issue: .

Thanks for your help!

 

Bump for any help please?

Thanks

 

I don’t have any real solutions but as far as the injectors go were these the same flow rate as stock?? Did you have this issue since the rebuild or did it just start recently?? Reason I’m asking is I bought into the whole injector thing when I first got my truck, I bought some that had all the hoopla of a better spray, better performance, etc. they were nothing more than a nightmare that would randomly dump so much fuel the exhaust made my eyes burn and was black from being too rich. I sent my originals out to be cleaned and flow tested and never looked back. My ECU wasn’t smart enough to compensate for any higher fuel flow and threw everything off.

As far as the AC idle up curing the issue sounds like it could lead to a key of what’s going on but that’s beyond my little brain

hopefully someone will chime in that may know why the AC being on fixes your issue…..

 

I've had the Fireball injectors for over 60k miles with no issues, I do remember them being slightly more cc's but they passed smog 3x in the past. so unless they are already worn out, I don't think they are a problem as the truck runs and pulls strong.

Got a few comments on the YouTube video. Someone said because I disabled the EGR, the computer thinks it's connected, but the additional air/exhaust is not entering the engine throwing off the mixture? Any thoughts on this, do others with the blocking plate have issues? I don't have the ability to custom tune the ECU

I also ordered a brand new Mass Airflow sensor. The one I installed 60k miles ago was a rebuilt unit from the auto parts store. When I tested it, I did see some possible dead spots on the meter, so this one is a new non OEM one from Amazon. I'll try it this weekend. I also replaced the TPS 60k miles ago, again and Auto parts store item, so I ordered an OEM one from Toyota.

 

Well as much as I don’t want the parts cannon getting thrown anything not OEM I question, I’ve gone down that road before due to Toyota is covered in gold as far as price……but for a reason hoping it’s as simple as one part is poo….

As far as the EGR I’m not sure, I still have mine intact and I have a 22re. There are tons of threads on EGR deletion you may comb over to get any ideas.

The injectors I was just curious, if they have worked for 60k then I would look elsewhere just making sure you had them in for a while, my experience with trying something new to make a slug a slug never works so I leave things alone

Report back any progress!!!!

 

Today I replaced mass air flow sensor, replaced spark plugs, re-enabled the EGR valve. No change, still surging, maybe a little worse even. It also has less pep now merging onto the freeway from 3k rpm up. Wasting time and money, thanks California 👎👎👎