Excess fuel in cat converter

That pretty much narrows it down to un-burnt fuel in the cats. I don't think the intake leak at the resonator would cause the problem. That would likely cause more of an idle problem. I'd test the spark before changing wires. If you're getting a red hot cat it's more that an occasional misfire. Pulling plugs should tell you something.

No misfire codes?

 

Just to confirm, this car does not have dual Motronics, right?

 

correct, 5.2 Ecu has only one ECU.

 

Check the fuel pressure regulator on that side. I usually associate heat with lean, not rich mixtures.
Also, did downstream O2 on that side check out?

 

Agree with Bruce that the FPR is easily the most likely candidate.

 

See post 11 or am I missing something? Also, if it were that lean I would think it would probable also knock.

 

Already checked with fuel pressure gauge. It is holding at 55 psi, not a problem in this case.

 

How are your coolant temps? Is the engine temp getting high enough (above 176ºF iirc) to the get mapping out of secondary enrichment? And on that note, how is the coolant temp sensor/s? If you have a bad coolant temp sensor it will give the ecu a false signal and can cause a rich condition, because the computer thinks the engine isn't at the correct operating temp.

 

I have not checked that but I can by using a real time OBD2 scanner that shows what the computer thinks the temperature is...

 

FYI, my 95 had a bad coolant temp sensor on 1-4 when I got it. The only symptom was failing emissions inspection. It did run rich. You could smell it, even with new high flow cats, but no red cats. I did have an SDL problem a few years later when one side of the 1-4 ignition coil failed. Cat over heated very quickly with engine running on 6 cylinders, but you couldn't miss it. Way down on power and obvious change in exhaust sound.

I know the cats look good from the pictures but can you see light through the cores? will they pass air?

 

Make sure Cat is good. Look from both ends. If you shine pen light on the bend side in front of cat honeycomb you can see light cleanly on the other side. It will look just like if you moved a light behind your radiator. When you do that you will see bugs stuck in your radiator core. a bad cat will see no light at spots when you move the light or full on burnt out sections. In advanced stages you get pieces broken off and wedged sideways for full obstruction.

I do not think this is a lean condition. It is a rich condition. You can verify that by an EGT high temp means lean. Red hot cat is fuel burning in the cat making it red. The excess fuel will cool the cylinders. Lean in the cylinders will be hot. If the cats pass and you are double damn sure the injectors are clean and flow well then it is electronic. If secondary is good then it is wiring. GOLD KIT baby! LOL. Lets start some trouble...

Hey when Ketel's car is at your house why not swap injectors? All you need is a little junk past the fuel filters to plug an injector up. Some injector service co's are better than others. But even the mighty RC engineering is not infallible. OBD2 should tell you about injector misfire but don't forget you have the easeliest OBD protocol and reliability is one reason OBD2 gets updates to the point where in cali later OBD2 cars get a computer read and no dyno or sniff test. I don't buy the temp sensor. Car should run fine in open loop map as the worst possible map. any other mapping profile in closed loop is ment for better smog. I can't see a closed loop failure where you dump extra fuel or we would be exploiting it to get extra fuel to mix with more air and go faster!

 

Well at least we agree on further checking the cats, not temp sensor, and that it's a rich condition. This really should take more than an after noon to find the cause.

Of course, it could be a burn exhaust valve or two, too.

But still, no codes?

 

So I only get to work on this sparingly .... there are other projects in the way. A mini Cooper engine transplant for example.

To sum it up,

Fuel regulator checked out
Fuel injectors cleaned recently (less than 6 months) by Mr. Injectors
No exhaust leaks
No huge intake leaks
O2 sensor, less than 1 year old (the pre cat one)
Cat is GOOD, from both ends

and Ketelmobile has come and GONE. Besides, FBB, removing an injector on a 355 is not a 15 minute job...

There will be more updates when I get around to doing more.

 

My money is still on coolant temp.

 

Fixed it for you. LOL!

 

Easy enough to check with an ohm meter: around 2k ohms when cold, 200 when hot, but even on a 2.7 car a bad CTS sets a code. Mitch has not been gracious enough to bless us with whether any codes or CEL are present. Don't know why. Maybe he is testing us.

 

I found some time this morning and reset the computer, let it relearn, and warmed up.

Emac, pulled codes this morning, none found. Some pending code with 1448 and 1449.
Ernie, you lost. The OBD2 scanner reads the real time coolant temp and it is very close to the indicated temp on the guage as well as the laser thermometer. At 198F the fan comes on and cools off.

Fuel trim
B1, ST: -0.8
B1, LT: 7.8
B2, ST: 0.6
B2, LT: 0.8

Be it that the computer was just reset, I am not sure these mean much. And I admit to not knowing what the 7.8 LT fuel trim means on bank 1

That is all for now.

 

oh, yes FBB. My car already has the pins redone.

 

Just throwing this out.....P1448 is bypass valve circuit. Possible vacuum leak in the bypass system that is causing the ecu to up fuel?

Fuel trim article:

https://www.autoserviceprofessional.com/article/94982/Fuel-trim-How-it-works-and-how-to-make-it-work-for-you?Page=1

 

Well, you obviously are getting un-burnt fuel in the bank 1 cat while the ECU thinks bank one is way lean. That's kind of a smoking gun.

 

Maybe swap precat o2 sensors or check them while they are running, maybe you got a bad one. Might be easier to just replace it with a new one

 

Well considering everything else that has been tried "lost" I don't feel so bad.

B1 = Bank 1
B2 = Bank 2
ST = Short Term fuel term (used during closed loop)
LT = Long Term fuel trim (used during open loop)

I'm guessing bank 1 = cylinders 1-4, which would make sense because your long term fuel trim is way off on B1, and you've been having problems with 1-4. Now if I understand this properly a positive number means the ecu is detecting a lean condition so it richness up the fuel (add+fuel). A negative number means rich condition so it leans out the fuel (subtract-fuel). The number represents the percentage the exhaust is rich or lean.
So B1, LT: 7.8 = would be 7.8% lean, or, it needs +7.8% more fuel.
Likewise B1, ST: -0.8 = would be rich 0.8%, or, it needs -0.8% less fuel.

Someone please correct me if I'm wrong.

 

I think I will throw on an O2 sensor....

 

Sure but...why don't you have a 02 sensor code? Maybe swap it from b1 to b2 and that will be more diagnostic because if sensor, which I doubt, is a problem it should move. Increase ltft happens for among other reasons a messed up injector. You can have an occlusion or partial that will read lean. Ltft is evidence of on going problem and adds fuel +x% and that allows stft to work in its operational range. You see the extra fuel burning in the cat. So are you sure the injectors are good? Me of little faith...

 

Perhaps it's still in range? (albeit the wrong end of the scale)