hi All,

So I completed a complete valve job, Timing belt, H2o pump etc. Cleaned and tested all injectors, cleaned intake manifold thoroughly. I also replaced the passenger side 02 sensor above the Cat. Long story short, Fired it up and it ran, but not well. Drove it about 3 miles, had NO power. The Exhaust and Cat was glowing red like a meteor when I got back. The firing order was totally screwed up, so I rectified that by referring to manual. The previous owner had marked the coils incorrectly and I trusted it! I was so shocked that IT ACTUALLY STARTED AND RAN!!

Anyway, fixed the firing order and it started right up, idled perfectly and ran like it should. HOWEVER, drove it down to the the Smog Gods (Cal emission vehicle) said it was burning 10x the fuel it need and was dumping fuel, so it failed. My experience tells me the upstream O2 sensors are either bad or not working correctly. I threw it on my scanner and did an o2 sensor check. One was reading -3.1?? and the other didn't seem to vary much between .1 and .4 (B1S1, B2S1).

Is there anything else I should be checking?? I also looked for an EGR valve, but saw no tube from either exhaust manifold going to one anywhere on the engine.

For a Montero newbie, can I get a hand here???

Thanks in advance-

 

Change the idle air control sensor and check your throttle body for soot. If it's sooted up, replace both the throttle position sensor and the IAC sensor, and soak the throttle body in a gallon of throttle body cleaner. Remember to take the small O rings off the old sensors to put on the new ones! OEM O2 sensors are NGT (part of NGK). Running a NGK irdium plug will burn a bit hotter and reduce your overall unburned Hydrocarbon emissions. If your Carbon Monoxide levels are too high, the catalytic converter scrubs those from the exhaust gas... so you may need a new one, if it fails on CO. Black sooty sparkplugs are sure sign your fuel to air ratio mixture is off. If exhaust temperatures are too high from a clogged catalytic converter, Nitrogen Oxide emissions will rise!

 

Before you start replacing any sensors, take a reading of you Fuel Trims. It sounds like you have access to a scanner and may be able to do it without having a DTC set. From there you can proceed and find out why the fuel trims are out of whack. It is possible to have a vacuum leak, stuck fuel injector, MAF not reading correctly, etc. It is even possible to have a timing belt to be off by one tooth and that will give you wrong fuel trims and bad emissions.
As far as O2 sensors, does your scanner show you an O2 reading graph or just values? Does it give you average voltage only or can it show min/max values to?

My advice - do not replace anything until you confirmed that the said sensor is bad (not just guessing that it might be bad).

 

Thanks for the info everyone,

I failed to say I cleaned the throttle body and EGR. I also replaced plugs with Bosch Platinum II as recommended with new wires.

So I am 100% positive the timing belt is not one tooth off. I spent well over an hour making sure everything was aligned correctly, cranked it and checked it again, so we can eliminate that.

When I ran the scan yesterday, S1B1 was not fluctuating much at all and neither was S2B2. I ended up replacing both upstream O2 sensors and both are switching between .1 and .8 as they should now. I suspect S2B2 is bad as it hardly varies at all, unlike its brother S2B1.

As far as STFT and LTFT, I get percentages like "1.7", but am not exactly sure how to interpret. I read up on fuel trim but can't grasp the process. The MAF sensor is working well as I see it vary when the throttle is adjusted. Engine timing reads 18 +-1 degrees which I am assuming is BTC. Engine when warmed up smoothly idles around 850 rpm.

I would like to replace S2B2 just to know the PCM is getting all the info it needs for emissions management. Please chime in with anything else I should be looking at.

Thanks again for the hand holding :-).

 

You should have 4 different values for fuel trims. STFT=Short Term Fuel Trim, LTFT=Long Term Fuel Trim and both of them will have Bank 1 and Bank 2 values (on a V-type engine). If the values are all in the range of -5 to +5% - your engine is running perfectly. There is no way that with the values of 1.7 you will get "Extreme Rich Condition". Your trims have to be over 20% or 25% to set off the DTC and Check Engine Light. It is possible that one of your O2 sensors was not working and causing rich condition, but the CEL should have lit up in that case. It sounds like everything is in order. Have them check emissions once again.

I suppose first see if you can pull up the SFTF Bank 1 and Bank 2 as well as LTFT Bank 1 and Bank 2 just to be sure.

Just out of curiosity, what kind of scantool are you using?

 

Thanks HunterD,

The scan tool I am using is a U581 Super CAN OBDII. I did some homework last night and learned a bit more about fuel trim. So, FT is in closed loop, STFT for both banks 1 & 2 stayed between 1.3-1.7. Prior to my replacing the o2 sensors, they were higher. LTFT was at 6.4 but now is 3.1. From what I understand now from my research, these are excellent numbers and should be very efficient in achieving 14.7:1. My worry was that LTFT was 6.4 when they ran the first smog which should have been acceptable? I can't see how it would fail now with the numbers I am getting. Idle is at 850-880 not engaged in drive, and cant seem to get it to 700 as it says under the hood sticker. I sprayed the intake and vacuum areas with carb spray and there was no variance in idle whatsoever.

The engine runs like a fine Swiss watch. I can put a glass of water on the intake, and it barely moves. Unless the smog place is from Natzi Germany, I just can't see how it won't pass now!

 

Those fuel trim numbers are AWESOME. It is puzzling why you'd fail the smog test with those numbers unless they they were both higher before. The only possible explanation is an inefficient catalytic converter. Can you compare pre- and post- cat converter O2 sensor readings. The front (pre-cat) should oscilate while the post-cat should be stay almost steady at lean level (low voltage). Perhaps you have readings there that are just borderline and it is not setting off the P0421 code just yet, but heading in that direction.
As far as idle level - not familiar with your exact year model, so don't want to make stuff up.

 

So, to follow up, it failed smog, (even though I went to the Referee the last time) because of the IM Readiness monitors not clearing. All the emissions were WAY below threshold, but found where My model year was a bear to get cleared: http://www3.epa.gov/obd/regtech/420f08009.pdf. I downloaded the Drive Cycle procedures: http://www.obdclearinghouse.com/docu...DRIVECYCLE.pdf and spent all week trying to get them to clear. I got it down to two not ready (Evap and Cataylist) and was having hope. Well today the P0421 code came up after the drive cycle (Which I had to do 10 times). I'm screwed. I checked the post cat O2 sensors, bank 2 was semi steady, and bank 1 was varying between .0 and .7v. I know what that means. Cat time- Because i'm in California, I have to pay triple for one because it has the CARB stamp on it. At this point, I am thinking it's best to sell the car and find another like it where I dont have to worry about trying to get it smogged. Life's a b'tch sometimes and it just 'aint my week.

 

I think you are giving up too soon. Read the documents you posted the links to. The first document (EPA) states on page 5 that "All Model Mitsubishi vehicles from MY96-98 be scanned for MIL illumination without regard to readiness". What they are saying in the text before is that these vehicles are known to NOT correctly record "ALL Drive Cycles Completed" condition. Therefore it is not possible to get that condition set and the Pass/Fail for emissions should not be based on the "All Cycles Ready" conditions, but on whether the MIL light is on and if tail pipe emissions are actually good or bad. You need to clear your code, and go back to the testers and argue that point.

 

Thanks HunterD,

So what you are unaware of is that despite the Federal EPA officially stated in that document to "ignore the IM readiness monitors not being ready" the state of California does not recognize it. More bureaucratic BS. I printed out the document and took it down to the Referee station. His response was, "Oh ive seen that before, but Ca. doesn't follow Federal." "If its not in the computer, I can't do anything about it". "I just test the cars through their computer and it tells me whether it passes or not."

So, there you go. I don't have the time or money to fight it unfortunately. i'm sure there are lots of people that have been through this with the same result. Even if I did want to go through ALL the BS again by replacing the $600 cat converter (myself), there is a good chance the IM's wont clear and I've just wasted $600 more. There is a point where you have to cut your losses. That's unfortunately where I am.