Less power after new exhaust..? (1 Viewer)

[yellowhouse]

First off, this is my first post but ‘Mud has been a massive resource for me these last few months. In the last year I acquired a 92 FJ80 and since I’ve slowly been building him (“Lando”) up. So far: water pump, belts, hoses, power steering pump/pulley, PCV/grommet, tires/wheels (Duratrac 265/75r/16), spark plugs/wires, distributor cap/rotor… This is the first time I’ve ever spent much time under the hood of my vehicle and it feels pretty great to stand back and soak it in. So thanks!

Now, I had a custom exhaust installed last week by our local shop after my wife and I noticed the floorboard/center console got piping hot after a 100+ mile camping trip. I’m pretty sure everything was all original and extremely rusty/corroded/weak. When I picked up the Cruiser from the shop I noticed he bypassed the cats, which is technically fine since my county doesn’t require emissions testing. I also noticed he removed one of the oxygen sensors but left the outermost sensor directly under the driver side.

That evening my wife and I took Lando out for a test drive. I was expecting a little more pep without the cats and better airflow, but it actually felt like I had less power than before. We were driving on a paved country road, 50 mph with a slight incline and maintaining speed was a chore. Later on when the incline increased pretty substantially 35 was nearly impossible. (Sorry, I don’t remember the RPMs.)

My question is, could the issue be the missing oxygen sensor? Before the new exhaust I was pulling 25/26 CEL codes, and since they’ve cleared and now I’m pulling 28. Also, the engine sounds like it desperately needs a valve adjustment (it’s on my list, along with the rest of jonheld’s 3FE baseline post), so perhaps that would be the problem? I spoke with the mechanic the next day and he thinks it’s because the valves need adjusting. In his defense he told me to bring it back if I’m still having issues after the tuneup and he’d make it right, but I wanted to get your opinions in the meantime.

Sorry if this topic has been beaten to death. I tried searching and couldn't really find anything.

 

[mikedamageinc]

You're pulling 28 different codes?? Something ain't right in that, not the exhaust or the second o2 sensor, that only checks reading from the first sensor thru the cat. The better flowing exhaust may have worsened another problem, clogged air filter, dirty MAF, leaky intake tube/manifold, or valves like you said. Could be many things, attack what you know-valves, tune up and existing codes, just don't worry about the second o2 code.

 

[LS1FJ40]

No. He's not pulling 28 different codes. He's pulling a Code 28. He has a 1992 OBDI rig.

Code 28 is the second O2 sensor. Both O2 sensors are pre-cat on the 1991-92. This can affect air-fuel ratio. My guess is that he damaged the wiring or messed it up somehow. I would take it back to the exhaust guy and have him take a look at it.

 

[jonheld]

The O2 sensors along with the TPS and AFM are the primary feedback signals to the ECU for proper A/F mix and injector timing. Without the second O2 sensor, your ECU is running in open loop (limp home) mode. You need both O2 sensors and they really need to be in good shape along with the wiring.
There are ways of "fooling" the ECU with fixed resistors, but that doesn't account for changing driving conditions. Not a good option IMO.

 

[yellowhouse]

I crawled back under there to make sure I wasn't just missing the second oxygen sensor. Nope, nothing. Pretty sure I can see the wire dangling from where he disconnected it. When he removed the cats he replaced the gap with a single pipe instead of duals. Not sure why he wouldn't weld both bungs back in. Maybe the wiring wasn't long enough to reach the RH sensor...?

Since the Cruiser isn't my daily driver (I live in a town where nearly everything is walking distance) I'll finish the valve adjustment before I take it back in to the shop. And I think I'll order a new pair of Denso sensors/gaskets from Rock Auto to have him install in case he decides to go cheap on me. Photos below.

 

[Tools R Us]

The OBD1 motors are somewhat controlled, run like two 3 cylinder motors, one O2 sensor is for the first 3 cylinders, the other the rear ones. To work correctly they both need to be there, and they need to be in the exhaust stream from the cylinders they control, so need to be upstream of the Y.

 

[ajax1]

You need both o2s as stated, you also might have exhaust leak going on too

 

[flintknapper]

I'd have him do the whole darn thing over (correctly) AND find someone who actually weld while he's at it, because what I see on there now is shameful.

 

[mikedamageinc]

I recant my post, didn't realize the early 80 engines/obd1 were so different. And those welds suck, probably pinholes all over the place and will develop to bigger leaks.

 

[Qball]

I would suggest a new shop

 

[LFD2037]

Like others have said, that's a botched attempt @ best. Took it upon himself to leave out an O2 sensor AND welds like that? I'd get my money back & go elsewhere.