Failed smog :(

[RonD]

The Calif. means it has the required EGR system, so it may have been installed when vehicle was moved to Calif, assuming it was from another state

 

[rang-a-stang]

I towed it down to CA from Oregon 2 months ago. It had EGR on it when I bought it but I have no idea what the history is (if this is the factory motor or if it was changed or if this truck ever spent time in CA). I did notice the EGR Transducer sensor connector was unhooked when I bought it, though. I am fairly confident this motor was either rebuilt or replaced. There are a few wire connectors with hand written labels that tell me either the wiring harness was swapped (not likely) or the engine was out and back in (more than likely). I would not be surprised if the original engine puked and someone went to a wrecking yard and grabbed an engine/computer that was close enough and threw them in.

Should I order a CA computer since I have EGR? Even then, there are 2 part numbers for 1986 Ranger, Manual, CA emissions. I have been scouring the interwebz for the last 2 hours trying to figure out the right part number.

 

[Eddo Rogue]

When I lived in CA, moved out in 2002 (Thank God!), vehicles 25 years and older didn't require smog. They do now? 82 is a 35 year old vehicle. Where I live, no smog checks.

I think now its pre '74 only

 

[rang-a-stang]

It's 76 and newer that have to be smogged. 75 and older are exempt.
DMV Website with reference

 

[rang-a-stang]

Ok so I have been thinking about this a lot. I cannot find any differences in the wiring diagrams between a CARB or an EPA configured vehicle. So if the pinouts and the wiring is the same, the only differences between CARB and EPA must be programming. The truck runs awesome with the computer it has, it just does not use it’s EGR. So I think I will just replace the computer with the same part number.

 

[rang-a-stang]

YASSSS! Ordered a CARB computer from RockAuto (a Bluestreack Electronics brand for 2.9l manual) and plugged it in. First test, KOEO, got an 11. Yess.

Next up measure ground to computer pin on connector. The readings were different than before but I don't remember what they were. Had 12V on the red line. Cycled the line and reading changed; again, I don;t remember what it was but it was different than before. YESSsss.

Plugged the EGR solenoid in, started the truck, let it warm up, and ran KOER. No code 83! YESSSSSSSSS! shut the truck down and put a vacuum gauge on the signal line to the EGR solenoid. Ran KOER again and watched 10" of mercury hit the vacuum gauge toward the end of KOER. YESSSSSSSSSSSSSSS! I got a code 33 (as expected because the EGR signal was on my gauge, not EGR valve). Put it all back together and cleaned up my tools. I am waiting for a suspension bracket before I can put the truck down and go smog it. I am feeling much better now! So close!!!

 

[RonD]

Good work

 

[rang-a-stang]

FAILED.

Exact same issues. Then my hood flopped open. GGgrreeee. I am about ready to torch this truck! It runs amazing, sounds brand new, runs great, fails smog. I need a brake from this thing.

 

[Roert42]

Have you tried installing more cats?

 

[Cees Klumper]

Last year I replaced the old single cat on my '90 2.9 with a dual cat system ordered thru Autozone, I believe it was around $500 at that time, 'CA Compliant'. It sailed through the smog (here in Long Beach) with very good values. Also replaced the injectors with rebuilts and new cylinder heads, otherwise 240K miles on the truck. Are you sure your vacuum hoses are all connected properly? There are before and after throttle body ports which makes a difference. On mine a PO had misconnected several. I have a spare CA computer you're welcome to try (for an automatic though) but that doesn't sound like it's your problem anymore. Good luck, I can imagine how frustrating this is.

 

[rang-a-stang]

I have been trying to get caught up on some old threads. This one was left hanging too.

So after my last failure I decided to pay someone to troubleshoot my truck. after a $120 diagnostic he said the cat was hollow, my EGR passeges were clogged, and my Throttle position sensor was out of spec (more on that in just a minute).

We ordered a new CA compliant cat from Rock Auto. It was some no-name generic CA compliant part and was $800. Ouch. but that was THE MOST affordable one out there. GGGGrrrr.... when it showed, it was in a box with that same name and part number I ordered but when I opened the box, there was a Magnaflow cat, Magnaflow paperwork, and a Magnaflow sticker! That same Magnaflow part number was $1250 at Rock auto! Super stoked to have a high quality cat under there. Woooo Hooo!

While the old cat was off, we removed the EGR valve and I blew crushed walnut shells through the EGR passage down toward the Y-pipe. I cleaned the EGR valve with brake cleaner and a wire brush and cleared out the EGR passage in the intake with a wire brush.

I threw this all together and it dawned on me, if my cat was gutted and the exhaust was fairly free flowing, my passages probably were not plugged, I just did not have enough back pressure to put exhaust up in the intake. We also swapped the TPS but I realized as I was doing it, he probably did not do the goose test with KOER and my TPS was just fine.

Smogged it the next day and it sailed through! It is running really well right now (other than when it is stone cold and that is another story).

Anyway:

Have you tried installing more cats?

Yes and no. In CA you cannot have more cats than what your vehicle left the factory with. So if it left with 1 cat, it is illegal to have 2 cats so I could not add an extra cat to continue scrubbing my exhaust. Which seems stupid but it's Smog law so it's stupid.
I did replace the hollowed out cat though.

Last year I replaced the old single cat on my '90 2.9 with a dual cat system ordered thru Autozone, I believe it was around $500 at that time, 'CA Compliant'. It sailed through the smog (here in Long Beach) with very good values. Also replaced the injectors with rebuilts and new cylinder heads, otherwise 240K miles on the truck. Are you sure your vacuum hoses are all connected properly? There are before and after throttle body ports which makes a difference. On mine a PO had misconnected several. I have a spare CA computer you're welcome to try (for an automatic though) but that doesn't sound like it's your problem anymore. Good luck, I can imagine how frustrating this is.

I super appreciate the offer! I am VERY sensitive to vacuum lines. One of the first things we did when we bought this truck was verify every single vacuum line. We made sure they were in the correct routing and they do hold vacuum. They all do!

I think we are good now! Fresh cat, fresh computer, fresh tune up, and it is almost completely dialed in now! Thanks everyone for helping out!

 

[RonD]

Good stuff

But just to correct your assumption on the way the exhaust works, there should NEVER EVER be any back pressure in a 4-stoke engines exhaust, ever, lol
EGR valve SUCKS in exhaust when it is opened, because of the lower air pressure(vacuum) in the intake manifold, there is no pushing

Factory exhaust manifolds actually lower the pressure in exhaust in the mid-RPM range, best torque RPM
Its called a scavenging exhaust, thats what 3rd party "headers" do to change power band, but usually at a lower or higher RPM

Most factory exhausts have used this since the 1960s
And that's where the MYTH of back pressure came from
People would put on "headers" with larger pipes(free flow) and then go for a drive
"WTF, I lost power!!!???"
"This engine must need back pressure", and the MYTH begins, lol

They lost power because they removed a scavenging exhaust manifolds so lost the extra mid-range power it provided

Stock size Cat converters and mufflers should never ever restrict exhaust flow, if they do then they are broken inside


How scavenging exhausts work
If you have a smaller pipe that runs into a larger pipe and you pump air(or a fluid) thru it, when the smaller pipe dumps into the larger pipe there will be a Pressure Drop
That's the science part it's based on

The art and science part is the velocity of the air flowing in the smaller pipe, and the size of the smaller pipe and then the size of the larger pipe(collector), these all decided the amount of the pressure drop and at what RPM it occurs, in the case of exhaust

With multiple smaller pipes like 4cyl exhaust manifold or V6 or V8, dumping into the same collector, this pressure drop in the larger pipe causes pressure drop in all the smaller pipes
So when an exhaust valve opens the exhausts it PULLED out of the cylinder, the piston doesn't need to PUSH it out, and that leaves more power on the crank for the rear wheels
Free power................by design

Most factory exhaust manifolds are tuned for mid-RPM
3rd party are almost always tuned for lower RPM, off the line power, but you lose the mid-range

Racing headers go for high RPM scavenged power, no low or mid range

Even engines with short stack exhaust, one open pipe per cylinder use it, the diameter and length of that one pipe can be tuned to give best power(lower pressure) at a specific RPM

 

[rang-a-stang]

Copy that! I have never thought "you need some back pressure" but assumed that EGR needed some pressure to flow enough volume to do it's job. I appreciate the correction! Sounds like my EGR passages probably were blocked.