88 XJ 4.0 Wont Pass CA Emissions

[jcnoble]

Yes, thank you. I measured this and it was equivilant to the table in the FSM.

 

[bajacalal]

Definetly a good idea fourbanger to get that motor and cat hot hot hot. Go in there when its slow like 15 minutes before they close and ask if they can squeeze you in so youre the last car there. That way, its done right away not2 hours later. Also, before you pull into their bay, rev the engine and hold it at a fast idle, so its hot (this is if the cat is weak or you think the HC&CO are slightly high). If they tell you to not rev the engine, blow them off.

 

[jcnoble]

The smog guy ran it at a high RPM (over 2500 RPM) for at least 10 minutes before testing. The temp was 210. It failed. I think the cat would be hot enough. Anyway , they have it now to run diagnostics. Thanks everyone for your input!!!! At the very least I have learned much about my XJ and have killed many a beer. I will see you SW, CA guys sometime when I get this on the road (trail) eh? By the way , I am a dirt bike rider, anyone else out there in Ventura County ???

 

[dizzymac]

140 K miles.....thats not even boke in yet....those are "puppy" miles, shouldn't have to pull head to clean carbon.

 

[XJXJ]

Should never adjust throttle plate stop screw for idle unless you know the IAC is fully closed and disconnected from the ECU. If not, ECU/IAC will constantly try to compensate idle and throw many things out of whack. Further, the TPS MUST be properly adjusted with a meter anytime you mess with the throttle plate idle position. The ECU could simply be thinking your throttle is open more than it really is and trying to provide more fuel based on a mis-calibrated reference signal.

If the 02 is strongly switching (You said you checked.) it should be in closed-loop operation. Therefore, the "loop" isn't calibrated correctly. Figure out what/why and you'll solve the puzzle.

 

[jcnoble]

When I attemted smog the second time the TPS was set to full not open position. My thinking was that that would be the leanest since it would think throttle not open as much. Also the mech. told me that in order for the cat to work properly, it must cycle from lean to rich. Is that why the Ox sensor cycles from low voltage to around +5 volts? And...when I cleaned the throttle body the idle jumped up so I had to back the stop off to its original position.

 

[XJXJ]

Engine HOT, close the IAC and unplug the connector. Next adjust throttle plate to about 600RPM. Re-connect IAC and adjust TPS per FSM for your transmission. The "test" for you is to understand the IAC enough to solve a method of closing it with the ECU. The clue is that it has something to do with vacuum hoses.

 

[jcnoble]

The mechanic replaced the air temp sensor, it was reading 30 degrees hotter than it should have, it made a little difference but still failing Hydrocarbons at 170 and 1% CO. He is going to replace the cat with a larger hi flow unit which he thinks (and I hope) will make it pass. He also said the ECU was reporting a partial open throttle with the TPS set at .65 , he had to go to .4 volts to get it to report closed. I guess thats out of spec. but as long as it reports closed when closed and open when open I don't see any problem.

 

[JoBo]

Ok, Im thinking about pulling the head and cleaning off the carbon deposits and the intake/exhuast (140,000 miles) unless there is an easier way , has anyone done this?? What results did you see?

Try running a can of SeaFoam through the intake first.

JoBo

 

[jcnoble]

Never heard of it, does it really work. Ive tried lots of stuff that claims to do about everything. Even Viagra gave me a headache. ??

 

[bajacalal]

Yes I think its a good product as is the Redline injector cleaner (pep boys). Seafoam is sold at napa, it does a pretty good job, probably doesn't get everything but works. You pour it slowly into the intake and vaccuum ports on the manifold w/ a tube or straw. After adding it cut the motor if it starts to stumble or stalls. Leave it overnight, next start a huge cloud of smoke appears as the dissolved carbon burns off. If you have an air pump, disconnect it. Seafoam also claims to clean out the cat. Oh yeah its good that you have a helpful smog mechanic, heats up the motor... I've seen shops that test your car cold (heard theyre actually supposed to!) looking to sell you repairs.

 

[jcnoble]

OK, I had the new hi-flow efficient cat installed. This XJ still fails hydrocarbons at 170 PPM. It should be less than 124 at 15 MPH and less than 104 at 25MPH. The guy did a full diagnostic test and everything appears to be ok. That is , whatever you can look at on this thing. The only thing left I havent replaced are the fuel injectors and fuel pressure regulator. The pressure looks good on my guage, factory spec. The plugs look fine too. If this doesnt help I guess Ill have to replace the motor. Oh , I havent replaced the ECU (computer) either.