Dreaded CEL

If you don't prime the pumps and the car takes a while to start when hot, that indicates that it might not be holding fuel pressure, which points toward one or more bad FPRs or injectors. But that doesn't necessarily mean that either are bad-- it's just another clue in the diagnostic process.

 

After I bought my 348 and while checking everything, I found the crossvalve butterfly partially open and frozen in position. I managed to remove the air box without removing the manifolds (undid in situ the nut at the bottom of the crossvalve shaft) and found that the shaft had just seized in its dried-out and gummed-up bushes. It just required cleaning and re-greasing.

 

Very interesting, Miroljub. Did you notice any symptoms while driving? My assumption is that it might impact overall power output, but it would not cause the rich condition that David seems to be experiencing. But I've never experienced that problem firsthand, so I don't know for sure.

 

Still cheaper than dating.

 

So very true!

 

Simple solution - just wait for the next November.

 

Prior to the discovery, the engine idled nicely and drove quite well (didn't notice any hesitation, flat spots etc.). However, I did have a bit of a sudden surge of pick-up at the start of opening of the main throttles but I attributed this to the stiff throttle cable which prevented gentle gradual movement of the pedal from the idle position. Perhaps the partially open crossvalve also contributed to the surge as the main throttles came off the idle position. After the fix, there was no noticeable difference. Probably just the top end power was somewhat affected by the not fully open crossvalve. It's effect is, I think, when the main throttles are 100% open, that it makes them like 110% (or something) open as each bank can "borrow" some additional air flow through the throttle of the other side.

 

I heard some dudes just put black electrical tape over the yellow CEL's and determine the extent of issues by how the car performs. Not me.

 

And others just pull the bulbs out.

It is always saddening to have "new owners" telephone us at Ricambi and admit the car is missing a CEL bulb on their brand-new toy.

 

Which is telling in & of itself as a burnt or pulled CEL immediately throws a code. P1447 if memory serves. Lack of homework on purchase / PPI.

 

OBDII is a fantastic tool. Not using it is just foolish

 

Dahveedam,

1. Did you experiment with the output of the TCU board to see if code 4121 goes away?
2. Did you leave your car in the rain somewhere before all this?
3. Did you check the analog signal at the ECU connector related to the code 4112?

 

The resistance of the CTS is measured between the two pins in the sensor socket, not towards the ground.

 

No OBD II in a 348, but I agree that even OBD I is a nice diagnostic tool that should be utilized and not ignored. The OP's car clearly has a problem, and hopefully the CTS code revealed its source. As you well know, there aren't all that many things that can cause a 2.7 car to run rich, and CTSs are about as cheap & easy as solutions get. So fingers crossed for David.

 

Well I'm aware of that but that's what I get for not reading the entire thread

 

Damn. Forgot it was a 348.

In my best Gilda Radner voice: "Never mind"

 

As posted by Miroljub earlier: "The coolant temperature sensors should measure about 2 K.Ohm at about 25C, more at lower and less at higher temps." I have not confirmed that spec but he is usually spot-on. The variation in temp between the two could account for at least some of the difference. As I said earlier though, what really matters is the resistance that the ECUs see. The best way to test them is at the ECU connectors since that takes into account any resistance in the connections. And you need to test them at various temps to ensure that they're actually changing resistance, and at the appropriate rate.

I still wonder if the root cause isn't a resistive connection between the CTS and the ECU on the bank in question. Hopefully you've been soaking the terminals in D100 while you were waiting for the CTSs to arrive. If it were mine I'd go ahead and install the new CTSs and hope that fixes it, but if it doesn't I'd apply D100 to all of the engine bay connectors every day or two and give it plenty of time to work. It probably took a couple of weeks for D100 to resolve the issues in my car and yet the pins looked great when I began the process. For me that really did highlight just how bad the OE terminals are, but hopefully DeOxit Gold will keep them working now that they're clean.

Good luck and please let us know how you make out.