1990 Renix SMOG, CA problem with running Rich/Lean

[old_man]

The one sensor that can be causing this problem that you didn't list is the commonly overlooked Air Charge Temp sensor. It is located on the intake just to the rear of the TB. It can be easily checked with an ohmmeter. It commonly causes the ECU to stay open loop or to at least cause it to think it needs to dump too much gas.

 

[90XJ_Seth]

Interesting. Did not know that.

 

[90XJ_Seth]

The one sensor that can be causing this problem that you didn't list is the commonly overlooked Air Charge Temp sensor. It is located on the intake just to the rear of the TB. It can be easily checked with an ohmmeter. It commonly causes the ECU to stay open loop or to at least cause it to think it needs to dump too much gas.

1-What should the Ohms be?

2-Where do I get this part if it is failing? I've searched and nothing looks right.

 

[Ecomike]

It is no longer made. I think Cruiser posted the part number earlier here in this thread. Yep, Tomco 12134 IAT sensor. (Sometimes called an MAT sensor) Manifold or Intake Air Temp sensor

1-What should the Ohms be?

2-Where do I get this part if it is failing? I've searched and nothing looks right.

 

[90XJ_Seth]

It is no longer made. I think Cruiser posted the part number earlier here in this thread. Yep, Tomco 12134 IAT sensor. (Sometimes called an MAT sensor) Manifold or Intake Air Temp sensor

I am very grateful for all your help.
I checked Tomco's site and they call for part 12120 for air temp sensor.
I am not an expert but they had it in this catalog.
http://www.tomco-inc.com/Catalog/iat%20sensors.pdf

Should I look at 12134 or 12120?

 

[90XJ_Seth]

The one sensor that can be causing this problem that you didn't list is the commonly overlooked Air Charge Temp sensor. It is located on the intake just to the rear of the TB. It can be easily checked with an ohmmeter. It commonly causes the ECU to stay open loop or to at least cause it to think it needs to dump too much gas.

*The ohm readings are about 2,720 ohms at 79 degrees, printout says that is reading 20 degrees low and is registering close to 60 degrees.
*Printout says I should be closer to 1,200 ohms at 79 degrees.
Heat gun proves the IAT reacts quickly to introduced heat and drops ohms to 400 in seconds.

Any words of wisdom? Junk the IAT or is it reacting ok?
:helpme:

 

[90XJ_Seth]

*The ohm readings are about 2,720 ohms at 79 degrees, printout says that is reading 20 degrees low and is registering close to 60 degrees.
*Printout says I should be closer to 1,200 ohms at 79 degrees.
Heat gun proves the IAT reacts quickly to introduced heat and drops ohms to 400 in seconds.

Any words of wisdom? Junk the IAT or is it reacting ok?
:helpme:

So, poking through the forums, 3,400 ohms is 70 degrees so maybe the printout I located is wrong.

Did I tell you all I have no idea what I am doing...
:explosion:

 

[90XJ_Seth]

It arrived and it's the right part! Let's hope it works.

 

[cruiser54]

It arrived and it's the right part! Let's hope it works.

AC Delco?

Part number?

 

[90XJ_Seth]

Had to get new old stock Chrysler part number from eBay. It's a Mopar part. Originally shipped in May 2000. Put it in and everything sounded and felt a bit different. Emissions didn't stink anymore at temperature. Hoping to finally smog tomorrow. Mopar part 4713639

 

[90XJ_Seth]

Mechanic said he was having an issue getting O2 sensor voltage fluctuation on his digital SNAP-ON voltmeter, it looked like nearly vertical lines of up and down so he didn't run the test. I read somewhere the O2 sensor can only be checked with an analog voltmeter, anyone able to confirm this?

 

[cruiser54]

Every Renix owner should own one of these.

http://nickintimedesign.wordpress.com/

 

[Royal Nonesuch]

Every Renix owner should own one of these.

http://nickintimedesign.wordpress.com/

Definitely. That makes reading your 02 sensor pretty dang easy, I love mine.

Sounds like you're getting your sensor issues straightened out. As a side thought, check your fuel injector plugs to make sure they're going to the correct cylinders. It is possible to cross the pairs. One or two of those crossed over will definitely fail your CA smog and drive you nuts figuring out... don't ask me how I know :shhh:

If you gently peel back the little plastic boots the wire colors should be as follows:
#1 LT Blue
#2 LT Green
#3 Tan
#4 Yellow
#5 White
#6 Brown.

 

[90XJ_Seth]

Definitely. That makes reading your 02 sensor pretty dang easy, I love mine.

Sounds like you're getting your sensor issues straightened out. As a side thought, check your fuel injector plugs to make sure they're going to the correct cylinders. It is possible to cross the pairs. One or two of those crossed over will definitely fail your CA smog and drive you nuts figuring out... don't ask me how I know :shhh:

If you gently peel back the little plastic boots the wire colors should be as follows:
#1 LT Blue
#2 LT Green
#3 Tan
#4 Yellow
#5 White
#6 Brown.

I was just wondering that, thanks for the help.

 

[90XJ_Seth]

Last night I bought some of that CRC guaranteed to pass. I am not worried about the guarantee but more the concentrated fuel system cleaner. Since I think it is mostly a fuel delivery issue more than anything else they say it should help that. I ran it hard for about 100 miles. Even gassing it hard I saw my fuel gauge using less fuel than ever before (with my new 02 sensor). Normally I've used half a tank driving easy after 100 miles but now it looks close to 40%. after gassing it hard Checked the tail pipe and it smells like a bit of burnt carbon instead of any gas smell at all. The heavy gas smell was mostly already eliminated with the O2 sensor, so I think I'm nearly there but my registration is needing smog today. FINGERS CROSSED.

 

[90XJ_Seth]

Definitely. That makes reading your 02 sensor pretty dang easy, I love mine.

Sounds like you're getting your sensor issues straightened out. As a side thought, check your fuel injector plugs to make sure they're going to the correct cylinders. It is possible to cross the pairs. One or two of those crossed over will definitely fail your CA smog and drive you nuts figuring out... don't ask me how I know :shhh:

If you gently peel back the little plastic boots the wire colors should be as follows:
#1 LT Blue
#2 LT Green
#3 Tan
#4 Yellow
#5 White
#6 Brown.

Wires check out.

 

[90XJ_Seth]

Failed again.
Questions I now have for anyone who knows.
1 - Would the Bosch 746 Injectors cause a run rich condition by not working with ECU?
2 - Could all of this be from an EGR issue?
3 - Does the canister purge actually do anything with emissions?
4 - Is there any vacuum leak I can't think of?
5 - Could I have done poorly on the grounds at the dipstick? Could that be the issue?
6 - How should I properly test the O2 sensor until Nickintime finishes his next batch of REM's?

 

[Royal Nonesuch]

Failed again.
Questions I now have for anyone who knows.
1 - Would the Bosch 746 Injectors cause a run rich condition by not working with ECU?
2 - Could all of this be from an EGR issue?
3 - Does the canister purge actually do anything with emissions?
4 - Is there any vacuum leak I can't think of?
5 - Could I have done poorly on the grounds at the dipstick? Could that be the issue?
6 - How should I properly test the O2 sensor until Nickintime finishes his next batch of REM's?

1 - I also run 746 injectors that I rebuilt myself; they pass LA County dyno test w/flying colors. I have a 1988 with a 89-90 ECU.
4 - 4wd? Do you have a vac-disconnect Dana30? Those brittle axle vac lines could all be shattered causing some leak.
5 - As long as you gave it a good cleaning w/brakecleaner and a wirebrush I bet you're ok there.
6 - Like you mentioned earlier it can be done with an analogue voltmeter. I never had a lot of luck with it, but I suck with voltmeters. IIRC [this archived old thread had way more information on the process than you could ever want.

 

[90XJ_Seth]

Under the hood tonight, checking all my electrical connections with my shiny new analog multimeter... what do I finally find?... The O2 sensor harness on the vehicle side is falling apart (One of the wires doesn't even stay in place, it just slides in and out randomly, you know the one that is supposed to send the alternating voltage). The TPS sensor harness is literally disintegrating inside the weatherpak. The MAP sensor connector is also having a rough time. Time to get some decent connectors and rewire those little buggers. Ten 3-pin Weatherpacks arriving at my door tomorrow for the refresh. Maybe that's why I couldn't get a consistent voltage out of the O2 sensor... How did I refresh all the grounds and not even notice that the connectors were in such bad shape?!?!? I feel like an absolute fool right now. I hope that this refresh gives some solid results. Fingers Crossed.

 

[90XJ_Seth]

Grounding Question,
is it possible to ground the O2 sensor directly to the firewall instead of running it through the harness to achieve a more thorough ground?