Yotawitz

Hi all,

Looking for help on a recently purchased 1999 3.4L 4Runner with NOx problems. Cat, upstream O2, plugs & wires all were changed by previous owner's mechanic.

1st fill up with gas a 0171 code appeared, cleaned the MAF & it went away.
2nd fill up a P0120 code, checked the TPS resistance & it was okay. CEL went away when gas level went down.

1st emissions test HC & CO were fine but the NOx was 2.78 GPM with 2.0 limit.
2nd test: ran a can of BG44K through & made sure the engine was hot and the NOx was 2.08 , HC 0.19 & CO 5.7.
3rd test: ran another can of BG44K and put 91 octane in it NOx 4.13, CO 10, HC 1.1, CO2 413. The higher octane did not help NOx levels in this case.

Looking through posts this model doesn't have EGR, but uses a 3-way Cat, is there a way to tell if the Cat is the correct one? Downstream O2 is original, but from other posts it doesn't sound like this one helps emissions levels.

It runs great, the exhaust does smell a little. May try to check the fuel pressure and timing, but it runs so good, I don't anticipate that being the problem.


Any thoughts or suggestions would be appreciated. Thanks.

Yotawitz

after re-reading my post, I'm thinking it was too much detailed emissions info....even my eyes glazed over...LOL

Anyway, thought I'd update & follow through, in case anyone else has similar problems.

Replace the TPS, although I'm fairly certain it did need to be. Although, like someone else said in a post $50 to eliminate it

Decided to check the plug & lo and behold, they weren't gapped or torqued correctly...appear to be good plugs (NGK BKR5EGP) but they were gapped around 0.038...changed them to 0.044. They were screwed in, but not tight..torqued them to 15ft-lbs. Burning off the rest of the 91 octane, because the owners manual indicates 87. I'll get it retested tomorrow and update after that.

Any other 99 4Runner owners out there? I just ordered the FSM (ouch!)...probably do the timing belt/water pump next.

bikerjosh

Is there a way to check the cat? I had a similar problems and after replacingeliminating everything else I ended up putting in a new cat and it passed.

fish0281

I would think an emmissions test is about the best way to test a cc and I also would assume a high NOx reading would mean they're not performing up to snuff.

If you can return that FSM, you can find it online for free...

Yotawitz

bikerjosh & fish0281

Thanks for the input...it didn't pass with the TPS & plug changes...so I'm going to take it to a muffler shop and have them check the Cat....I'll keep you posted

fish thx for the heads up on the FSM...I should have figured that.....oh well, planning on keeping the runner til the end...

Take it easy