Take a look at the following components and measure. Find better mechanic that does actual testing and measurements. Without actually measuring things, you have no idea if they are good or bad. You end up spending A LOT of time and money swapping out perfectly good parts with brand-new perfectly good parts and results doesn't change because you haven't actually found problem... through testing and measuring...

1. Intake-manifold VACUUM - supplied to FPR should be around 20-22 in.Hg at idle with warmed-up engine. Measure vacuum in intake-manifold and at ends of hoses going to FPR and MAP sensor.

2. TPS - is used by ECU to determine load placed on engine (how heavy your right-foot is). With larger throttle-opening, more fuel ECU sends to engine. Measure angle of throttle-plate and TPS and verify correct setting as dictated in FSM. Measure output-voltage of TPS at idle and check with values in FSM

3. TPS idle-switch tells ECU you've let off throttle. ECU uses a completely different fuel & ignition map when idling. Test that idle-switch is electronically closed when throttle is let off.

4. MAP sensor - tells ECU how much load is on engine (throttle opening). Measure MAP-sensor output voltage with key ON and engine NOT running. Then measure MAP-sensor voltage again at idle with warmed-up engine.

5. FPR - it reduces fuel-pressure when operating correctly. Pressure in fuel-rail should be around ~35-38psi @ idle with vacuum-hose connected. And around ~45psi with hose disconnected



By measuring all these components, you can determine if they need to be adjusted or replaced to restore to proper operation. You can even replace ALL of the above components at great expense and still have same smog-fail because it might be as simple as a leaking intake-manifold gasket. This would reduce vacuum in intake and trick MAP-sensor & ECU into thinking you've got more load on engine than actual. And it would also cause the FPR to generate too-high of fuel-pressure. Very first thing good mechanics would do is measure intake-manifold vacuum. Been doing this for 100-yrs as standard practice.

 

Thanks Danno excellent advice. Of the items you mentioned I know the manifold vacuum is book perfect and stable. The map sensor was replaced 1 year ago due to a bug eating into the back of it causing the engine to stall. Car has run great since. And the fuel pressure tested at the outlet side of the fuel filter was exactly 38 psi engine running with an instant increase of 10 psi when the vacuum was removed from the fpr and instant decrease of the same when the vacuum hose replaced. Ill look at the tips and tips idle switch ( didn't know I had one) when I pick the car up from the shop. Also just as an FYI a scan of the engine showed no misfires at any time. And I agree, this shop is throwing parts at the car instead of testing individual components. Ill post the results of these other component test after I'm done. Another FYI I've read a lot on this forum of these engines burning oil. I change mine every 2.5k with fram filters ( they have a check valve to prevent oil drain back when the engine is shut down) and either Castro gtx or Quaker state 10 w 40. I've never had to add anything between changes and it's never down. Of course it's only got 69k on it..

 

Was replacement MAP sensor a Denso unit? Or 3rd-party aftermarket? Many parts from FLAPS can be bad right out of the box, or out of spec. Make two MAP-sensor measurements and let's see how close it is. All that's required for smog to fail is MAP or TPS signal being off by just 10%. A slightly rich mixture makes the car run great!

 

Thanks danno...the map sensor is genuine Toyota..quick update as of an hour ago. Found the downstream o2 sensor would intermittently stop switching Rich/lean for several seconds then start again. Both up and down stream sensors are new denso. Replaced the downstream and the car passsed smog. HOWEVER the h c levels are still higher than average at 43 ppm. The max is 61 ppm with an average of 9 ppm. Obviously there is still something wrong. The car is out of the independent shop now. I have an appointment with the local toyo dealer to diagnose the high h c levels. The independent shop feels the cat would clean that up to bring it into line with the average. FYI the co is .05 ppm (great)which is average max is .54 and the nox is 4 ppm which is great max is 467 average is 67. Ill keep the forum posted as to the results from the dealer.

 

Downstream O2-sensor isn't used to adjust fuel. It's only used to monitor catalytic efficiency and throw a code if cat's not working.

Probably something is tricking ECU into injecting too much fuel. The IAT and ECT sensors can also affect that as well.

 

Is the intake air temperature sensor connected? It's a common miss when an air filter is replaced that the step to re-connect the intake air temp sensor harness is forgotten...

 

here,s a real kick, went to check the oil and coolant level while thinking about the i a t sensor. saw a hole in the air box i dont remember seeing before. started looking around and found the i a t sensor laying under the air box. plugged it back in and the car starts and idles great almost as usual but better. ill get the h c level checked this week and post the results. my guess is thats the problem.

 

Timing advanced much? Advanced timing will raise one of the substances they test for, and if I remember correctly, that substance it HCs.

Those '66-'67 Chevy II/Novas are good-looking cars!

 

97 is OBD2 and has a fixed distributor. No advancement of timing. I guess you could still measure timing with a timing light to confirm it's spot on.

 

thanks guys, timing is spot on. engine temp is dead center on the gauge [when fully warmed up]where its been since new. injector pulse width is 2.9ms at hot idle.just for kicks im going to check my 2014 camry for pulse width just to see the difference. and yes pete i agree about the 66 67 shoe box nova,s. mine has a documented 17 k on it. sat from 1973-2000. its a vin 118 original v-8 auto bucket seat 2 dr hdtp coupe..

 

Gauge uses different temp-sensor than ECU. In the '80s, it was common practice to insert resistor or pot in-line with ECT to trick ECU into thinking engine was cold. Thus it would inject extra fuel as part of cold-start cycle.

What is impedance of ECT with cold engine?
What is impedance of ECT with warmed up engine?

 

Haha, I meant the hard top, but left that out in case yours was a sedan. There was a bluish-green color available on those which was just killer!

Back on topic, another possibility is your oil. If the oil has lots of miles and blow-by gasoline in it, and the engine burns some oil, it could be 'falsely' contaminating your exhaust. But re-reading the thread, it sounds like that might be a long-shot just like my timing idea...

 

ya, the oil is so clean it looks like vegetable oil. the car doesnt use a drop of anything. i add nothing between oil changes at 2,500 mi.. the car has 0 blow by. i cant do any more checking until next week, but ill check some of the other items mentioned by other members, but im also going to check compression and ALSO cylinder leakage. i know the car is a 97 but it only has 69 k on it and has been serviced 3 times as often as the factory recommendation so i dont think lack of maintenance has anything to do with the high h c readings. ill keep everyone posted. thanks again

 

2500 miles is WAY too early for an oil change!

 

Maybe he's actually changing it based on time, not mileage. Shouldn't oil be changed after a year regardless of mileage?

 

here,s a real kick, went to check the oil and coolant level while thinking about the i a t sensor. saw a hole in the air box i dont remember seeing before. started looking around and found the i a t sensor laying under the air box. plugged it back in and the car starts and idles great almost as usual but better. ill get the h c level checked this week and post the results. my guess is thats the problem.

 

my first thought is why didnt the independent shop find or look for this.....ill keep the forum posted

 

Yes it should. Good point.

 

ill have the car sniffed for emissions output next weekend to see the difference with the i a t sensor back in where it belongs and post the results. and yes, since the car doesnt get used a lot, the oil is changed based on time and not just miles.it usually ends up at 6 months or 2.5k or close to that.

 

You should probably aim for 12 months or 5000 miles. Oil lasts a long time these days, even 5000 is conservative.

 

thanks 94 rolla dad. you hit the nail on the head. ill post the results of the emissions output and other stats [inj pulse width etc] later this week. as to the oil change interval, driving in so. cal. can be hard on any car especially in extreme heat conditions, but when you add mostly short trip stop and go driving the oil can get contaminated and break down sooner than on long trips [maybe its just me ]. ive just retired from the r.r. been maintaining all my cars this way since i was a kid [ a million years ago] and ive never had a major breakdown especially one related to lack of maintenance. had a head gasket leak on a 740 volvo with 220k on the b23ft engine [4 cyl turbo]. the fire ring rotted at the rear next to a water jacket. when i pulled the head to replace it, the top end was immaculate inside. i like keeping my cars and truck that way..oil and filters are cheap when compared to an engine.

 

94RollaDad didn't exactly hit the nail on the head. He suggested that the IAC was disconnected which would cause the CEL to immediated come on. Actually, the IAT popped out of the air box probably because someone didn't even notice it and unplug it when changing the air filter.

So, I only give 94RollaDad credit for being in the ballpark.

And the reason the independent shop didn't notice is they only charge $100/hour. You probably have to go to a shop that charges $200-300/hour for them to find something as complicated as a misplaced IAT sensor, lol.

 

94RollaDad didn't exactly hit the nail on the head. He suggested that the IAC was disconnected which would cause the CEL to immediated come on. Actually, the IAT popped out of the air box probably because someone didn't even notice it and unplug it when changing the air filter.

Guilty :spanking:

 

That's close. For $200/hr they tell you, you have an iat sensor. For $300/hr they tell you the iat sensor is working. For $400/hr they look at it to see if its still there!

 

Hair splitting, eh?

Technically we also haven't yet proven this was the cause as it needs to be retested. Good luck!

 

Here you go...

I think we have makings of classic EGR code thread again...
Almost as amusing as Altima brakes thread..

 

Any news on this?

Did plugging the IAT sensor back into airbox fix running rich problem?

I suspect it should make it worse. ECU will be measuring cooler denser air coming from outside rather than hotter engine-compartment air. Then it would inject more fuel to match extra air mass it thinks is being ingested.

 

dont have the FINAL results yet, but danno is right. the initial pre test results were: fail. everything was slightly higher than the test with the i.a.t. sensor hanging out of the air box, but the hc was past the max. about 20 ppm higher than before inserting the sensor back in. i didnt have time to test anything else at home due to some health issues, but the local toyota dealer now has the car. i gave them a complete history print out since this problem started 4 years ago. i also told them i dont need the car so please keep it as long as they need. they are confident their long time smog tech will find the answer. i hope so. again, as i go, ill post the results. and thanks to you guys for all the ideas and support. [ just a side note about the sensor hanging out] it is possible the shop that issued the smog for the car 2 years ago were the ones that pulled the sensor out as they told me they were having problems getting it passed. finally did by replacing the upstream o2 sensor. that being said the car has just barely passed the last 2 smogs and while nox and co were higher than the average it was always the hc that was off the scale. but in any event, if rolla dad hadnt mentioned the iat sensor it would still be hanging out which im sure would cause issues somewhere down the road.

 

Awesome, thanks for the info. Would really be interested to see what fixes problem. As there's been some cases similar to this but they never came back for a final report (or if the problem was ever fixed).

Also , can you post your smog-test results? Nice to see before & after numbers.

Thanks!