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Smog check help please!

Old 06-30-2012, 06:56 PM
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Default Smog check help please!


First of all, thanks for the help this forum has already given my 16 y.o. son and me. We picked up a 87 with the 4.0 from a "Honda mechanic" who obviously was tired of fixing cars at work, and didn't do much to this one at home! We have learned a lot from this forum so far, and plan on still learning and maybe helping others as we progress!

for now, we have the XJ road-worthy, but are having trouble passing smog. Suspected the cat was bad (rattling sound within it), but tried anyway and failed miserably. Replaced the cat and tried again today, these were the results:
idle speed CO 2.25% (need below 1.2%)
idle speed HC 227 (need below 220)

We have already changed cap, rotor, plugs, wires. The mechanic was going to "tune it" for us, but it started overheating. That's when we realized the fan shroud was missing (already ordered!).

Between us and the advice we get from the forum, we are mildly mechanical.
Any suggestions?
Thanks!!
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Old 06-30-2012, 09:07 PM
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Originally Posted by lvcherokee View Post

First of all, thanks for the help this forum has already given my 16 y.o. son and me. We picked up a 87 with the 4.0 from a "Honda mechanic" who obviously was tired of fixing cars at work, and didn't do much to this one at home! We have learned a lot from this forum so far, and plan on still learning and maybe helping others as we progress!
Awesome - good on y'all for jumpin' in with both feet
Originally Posted by lvcherokee View Post
for now, we have the XJ road-worthy, but are having trouble passing smog. Suspected the cat was bad (rattling sound within it), but tried anyway and failed miserably. Replaced the cat and tried again today, these were the results:
idle speed CO 2.25% (need below 1.2%)
idle speed HC 227 (need below 220)

We have already changed cap, rotor, plugs, wires.
Originally Posted by lvcherokee View Post
The mechanic was going to "tune it" for us,
Don't do this. This forum and others like it have all the knowledge and experience you need to knock it out of the park yourselves.


Originally Posted by lvcherokee View Post
but it started overheating. That's when we realized the fan shroud was missing (already ordered!).

Between us and the advice we get from the forum, we are mildly mechanical.
Any suggestions?
Thanks!!
High CO means you are getting incomplete combustion, due sometimes to restrictions in the "air" aspect of the equation. One simple thing you overlooked (if your list of fixes is complete) is the air filter. Cheap, easy, and may well fix your problem by itself. Several other sensors, if they are faulty, can cause this problem, as well: O2, MAP, TPS, and Coolant Temp Sensor.

HC (hydrocarbons i.e. raw fuel) can be a result of poor fuel ignition. Timing isn't an issue with our RENIX systems...the timing is pretty much fixed and the computer advances or retards it. Faulty ignition components can also cause it. The only ones you haven't included on your list are the coil and distributor itself. Vacuum leaks can also cause high hydrocarbons as they can produce a lean-misfire condition.

Does the Jeep run well? It's just popping hot in these categories?
If it's not running well, can you describe the symptoms?

In order, I would take these actions:
  • Air filter
  • Verify O2 functionality and replace if defective
  • TPS, MAP and CTS checks and adjustments
  • Check for vacuum leaks
Here is a good guide for checking the sensors in our RENIX systems:
http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Cruiser54 on this forum pretty much knows it all. Here's a collection of his write-ups:
https://www.cherokeeforum.com/f23/te...itings-136452/
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Old 07-02-2012, 11:54 PM
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High CO means you are getting incomplete combustion, due sometimes to restrictions in the "air" aspect of the equation. One simple thing you overlooked (if your list of fixes is complete) is the air filter. Cheap, easy, and may well fix your problem by itself. Several other sensors, if they are faulty, can cause this problem, as well: O2, MAP, TPS, and Coolant Temp Sensor.

HC (hydrocarbons i.e. raw fuel) can be a result of poor fuel ignition. Timing isn't an issue with our RENIX systems...the timing is pretty much fixed and the computer advances or retards it. Faulty ignition components can also cause it. The only ones you haven't included on your list are the coil and distributor itself. Vacuum leaks can also cause high hydrocarbons as they can produce a lean-misfire condition.

Does the Jeep run well? It's just popping hot in these categories?
If it's not running well, can you describe the symptoms?

In order, I would take these actions:
  • Air filter
  • Verify O2 functionality and replace if defective
  • TPS, MAP and CTS checks and adjustments
  • Check for vacuum leaks
Here is a good guide for checking the sensors in our RENIX systems:
http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Cruiser54 on this forum pretty much knows it all. Here's a collection of his write-ups:
https://www.cherokeeforum.com/f23/te...itings-136452/[/quote]

Thanks for the advice, looks like enough to keep us busy on the long weekend!
The Jeep runs great, only has 125k, no popping or hesitating, seems to have plenty of power, that's why I figured we should be o.k. at smog. That said, we dont have a lot of miles on it, due to the lack of registration...

The old plugs looked like they were running rich (dark and a little soot, but not oily) and were in even condition (no one cylinder worse than others). The plug wires were old, with one being different from the rest, so changing those was a given. The air filter looked good, but I will change anyway just to make sure. Do you think I should replace the coil too?

Don't know how much of a difference it would make, but the front rubber boot on the top of the valve cover has deteriorated away (crankcase vent, I think, the back one goes to the PCV valve), am trying to order one, the local parts stores don't have it (Autozone, OReilly).

Will run the links and check the sensors and vacuum leaks, thanks a bunch for the advice!!!
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Old 07-02-2012, 11:58 PM
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Oh, I also bought a set of rebuilt 702 injectors, but did not install yet. I didn't want to add another variable into the mix. It should pass without them, I figure, but if it would help, I could put them in.

Thanks Again!
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Old 07-03-2012, 12:03 AM
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make sure the cat is good and hot when they test it try and go when there less likely to be a line maybe hi idle right up till the time they test it
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Old 07-03-2012, 12:05 AM
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[QUOTE=lvcherokee;1867609]

We have already changed cap, rotor, plugs, wires. The mechanic was going to "tune it" for us, but it started overheating. That's when we realized the fan shroud was missing (already ordered!).



i had a serious overheating problem i went and bought a 70 dollar raditor from rockauto.com and i also boght a new electric fan but i also ran a wire with a switch to the electric fan and i usto run at 210 quickly jumping to 230 in the heat and i run at 209 all the time now
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Old 07-03-2012, 12:14 AM
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HC and CO along with black sooty plugs = mixture too rich.

In addition to what's been mentioned, I'd pay particular attention to:
MAP Sensor- make sure it has vacuum to it and the lines are not leaking/rotted.
Exhaust manifold- check for leaks upstream from the O2 sensor,
O2 sensor itself including wiring and connector, and
Grounds...battery, chassis, engine, particularly those that run to the sensors. Probably best to just clean them all up.

eta: how old is the engine oil? If it dates back to dinosaur days, change it. Fuel dilution can mess with your emissions too.

Last edited by Radi; 07-03-2012 at 12:17 AM.
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Old 07-03-2012, 12:16 AM
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Originally Posted by lvcherokee
Oh, I also bought a set of rebuilt 702 injectors, but did not install yet. I didn't want to add another variable into the mix. It should pass without them, I figure, but if it would help, I could put them in.

Thanks Again!
Right on. Check out the build thread in my signature. I've got an '87 (RENIX) just like y'alls. A page or two in, I've got the NAPA part numbers for that hose coming out of your valve cover. Good luck!
You're right, it should pass smog w/out the new injectors, but i'd never turn down the help it could give you better atomization, better burn, lower smog.
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Old 07-03-2012, 12:58 AM
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Originally Posted by lvcherokee View Post
Any suggestions?
Howdy! For that 87, there is a deal here https://www.cherokeeforum.com/f23/tes...itings-136452/ On cleaning it up a bit. That C-101 connector...may well not be your issue today, but I really nice one to rule out!

That, and a bunch more if Cruiser54's writings are in my signature, (below) for the time being.
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Old 07-03-2012, 04:31 AM
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sea foam or any good quality cleaner in gas tank, good luck
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Old 07-03-2012, 07:38 AM
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Do the C101 connector cleaning and ground refreshing first. If there are issues there, and we know there are, the sensors give false signals to the ECU and the ECU doesn't do it's job well.

Along with that, be sure your intake manifold bolts are snugged up and check the vacuum line from the throttle body to the MAP sensor as already mentioned.

Last edited by cruiser54; 07-03-2012 at 08:40 AM.
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Old 07-03-2012, 08:39 AM
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Originally Posted by lvcherokee View Post
Oh, I also bought a set of rebuilt 702 injectors, but did not install yet. I didn't want to add another variable into the mix. It should pass without them, I figure, but if it would help, I could put them in.

Thanks Again!
fwiw iirc, the 703 injectors flow more fuel than stock, which may exacerbate your smog problem. I've heard of people not passing because of them or the neon injectors.
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Old 07-03-2012, 09:08 AM
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Originally Posted by lvcherokee View Post
but it started overheating. That's when we realized the fan shroud was missing (already ordered!).
X3, That little tube from the inside of the Throttle Body back, to the MAP sensor up on the firewall needs to be flawless! The MAP getting good manifold vacuum from there is a main deal for your mixture. On mine, that tube disintegrated.

The 703's are indeed capable of giving more fuel. Guys have passed with them though. The idea is that they are within parameters for your 02 sensor to adjust the mix correctly. With any miss whatsoever your HC will skyrocket, the stock injectors are worse than crap, they are a dangerous fire hazard!

Is your electric AUX fan coming on? It comes on about 217*, also when defrost is selected, and also when the AC is on. These things have week cooling systems....maybe Djb, (or someone) want's to expand on that, but yes, When you are not on the freeway, that shroud really helps. Good luck!
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Old 07-07-2012, 07:18 PM
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Originally Posted by letinsh View Post
Right on. Check out the build thread in my signature. I've got an '87 (RENIX) just like y'alls. A page or two in, I've got the NAPA part numbers for that hose coming out of your valve cover. Good luck!
You're right, it should pass smog w/out the new injectors, but i'd never turn down the help it could give you better atomization, better burn, lower smog.
thanks for the part numbers, ordered today!
funny, I called the store before and asked for that part before, they said it was not a stocked item, and I couldn't even special order!!! Glad you guys know what they have!

Fan shroud arrived today too... not a very impressive unit, but I'm sure it will help. Ironically, it is just too hot to work outside today, will have to hit it in the morning.

And Lentish, noticed the temp switch on the same thread, perfect timing. Our XJ just had the idiot lights, so bought a new instrument cluster from the JY. Got the oil pressure switch from donor, but didn't know where the water temp switch was. Thanks again for the advice and documenting your process! But first things first, got to pass smog and get 'er on the road!
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Old 07-07-2012, 10:33 PM
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Originally Posted by RenixHeep View Post
fwiw iirc, the 703 injectors flow more fuel than stock, which may exacerbate your smog problem. I've heard of people not passing because of them or the neon injectors.
They don't flow any more fuel than the stock injectors, they just have a better pattern for improved atomization.
Check the EGR valve and make sure it's not hung open causing a lean misfire.
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