failed inspection

[wildcat-xj]

1989 4.0 auto. the tech let the jeep idle for about 10 minutes before testing. it is cold and rainy today.

on high speed, HC was 207 (189 standard) and CO was 3.23 (2.36 standard)

on low speed, HC was 200 (194 standard) and CO was 3.71 (1.74 standard)

co2, o2, nox and dilution all passed.

doing some research it seems there is too much fuel in the exhaust.

i put on new plugs last week, but not wires, cap, rotor. i also put on new cat last month. slowly been checking/fixing any vacuum leaks. would the knock sensor cause ignition/timing issues? can the o2 sensor on these be checked?

any other ideas?

thanks!

 

[kastein]

Sounds like an O2 sensor to me, but could be a few other things - check for cracks in the exhaust manifold first. A leaky exhaust manifold/gasket can look like a bad O2 sensor because they suck in clean air, making the O2 sensors read lean, which makes the ECU enrich the mix.

 

[MoparManiac]

I'd do wires/cap/rotor if you haven't done them before.

Check for what kastein posted as well.

 

[Shorty]

copy-n-pasted from another post, but still applicable:

1. too much gas into the combustion chamber
--I'd check the MAP sensor vacuum source to see that it's getting correct
vacuum
--fuel pressure to make sure it's not too high
--fuel pressure after shutdown to make sure there's not an injector leaking
--coolant temp sensor to verify it's not reading too cold

2. unburned fuel exiting the combustion chamber
--verify all plugs are firing consistently
--air filter is allowing enough air to enter and atomize the fuel

 

[sjx40250]

Does it have the original injectors? Maybe time for replacement. My 90 gave them up at 175K and 18 years. They often leak between the plastic and metal housing junction. This would not cause emission failure but if they are original, they may not be working to spec while injecting.

 

[birchlakeXJ]

1. Finish the tuneup with new cap, rotor, wires. If you don't do that, you may be missing something simple and secondary igntion is important in keeping spec numbers in the areas you mention (HC and CO)

2. Keep looking for vacuum leaks

3. Test your MAP sensor and your COOLANT sensor and ensure map sensor vacuum lines are good. Both of those sensors are big contributors to determining your fuel air ratio which can hose up your emissions testing.

 

[orange]

I was told by a smog tester to:
-Be sure you have a fresh oil and filter (<200 mi.).
-Run at cruise on freeway 30 minutes (+) and then do the test immediately.
------------
This should clear out all the cold start rich mixture crud and fully warmup to real operating temperature.

Note: normal warm up is about 3-5 minutes for coolant, BUT a oil temp gauge shows it takes about 25-30 minutes for the whole engine to get up to operating temperature.

-Good Luck-

 

[orange]

Check that the coolant is at 195*. May be a weak thermostat letting it run cold.

 

[joe_peters]

Lots of good ideas posted here.

Follow the tests in this link for the sensors: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

 

[jth877]

You have smog testing in TX? Wow, I thought that was one of the last places of freedom in the US. We don't have that crap in NY.... YET.

 

[wildcat-xj]

You have smog testing in TX? Wow, I thought that was one of the last places of freedom in the US. We don't have that crap in NY.... YET.

with 4 of some of the largest cities in the country we have to play along with the eco-nuts.:bs: been going on for about 10 years now.

 

[wildcat-xj]

i did full tune up, o2 sensor ans knock sensor. it passed the emission test with flying colors. prolly runs cleaner than my corolla now. thanks for all the help!