Status update on GCK install

It should be pretty close to the same procedure. There will be some differences, but nothing that big of a deal. For example your expansion tank is in between the plenums, and the radiator feed pipes have a different connection compared to the 348. But it shouldn't be that big of a deal. I think it took me 2-ish hours to do the job on my 348. Matter of fact, you're in the bay area no? Hit up Mitch (yelcab) and see if he'll give you a hand. He's pretty handy with a wrench.

As for testing the thermostat, other than what you have already done, the only other test I know of for the t-stat requires it to be out of the car. You stick it in a pot of boiling water, with a thermometer in the water, then watch to see what temp t-stat pops open. But the thermostat has to be out of the car, so there's the rub.

The Motronic ECU relies on the coolant temps to adjust the fuel mixture. On the 348 it does full enrichment up to 140°F. Between 140°-176°f it goes to a secondary fuel enrichment, continuing to add extra fuel to get the cats up to temp faster. Based on the pic you took of your temp gauge, you car is running in the 155-160°f range = secondary fuel enrichment (at least on the 348 anyway, it could be the same, and it could be different for the 355, but not by much if anything). Based on the codes your car has been spitting out, pre and post cat O2 sensors, and the cat temp codes, plus the coolant temp you've posted up, to me, points to extra fuel in the exhaust. If it was just failed cats, then it would have been the second O2 sensors only, and you would not have gotten a cat temp code. But since you have the first and second O2 sensors, on both banks mind you, plus the cat temp codes, AND a car that is running cool, what else is there to conclude???? Bad coolant temp sensors? I don't think so, because the temp gauge is seeing the same thing the Motronic is seeing. They "could" be bad, but I doubt it. Cat temp codes mean the cats are too hot = extra fuel. That is what the OBD codes are for, to help you diagnose problems with the car, and to me the OBD codes are all pointing to extra fuel in the system. Where is that extra fuel coming from? My guess is a thermostat that is opening too soon.

The t-stat will cost you $20-$40 bucks, depending on where you buy it, and 2 hours or so of your time to change it. The worst that can happen is you have a new thermostat, and have spent as much money as it would cost you to take your wife to the movies, and as much time as to watch the movie. If I wasn't on the other side of the country I would come over and give you a hand changing it.

 

We have been trading PM and we are working on Ketel's car this weekend. Although I bet he is handier than I am judging from how he tackled the installation of hundreds of pins, twice.

 

Ernie,

I know you are trying to help, and there is a possibility that you are correct. However, as I stated in a previous post, my car had a bad coolant temp sensor which is what controls the ECU as far as mixture depends on engine temp. With a bad CTS the engine was running full rich. It did not cause any codes other then that for the CTS. No slow down light, no cat temp code. I have also read here about another 355 owner who had the same problem, CTS code, bad CTS. Again, no SD light, no cat temp code.

I really would not trust the gage to tell me what the ECU is getting for engine temp. Start the engine and monitor the CTS impedance while it warms up. Then watch the temp gage. When it hit the position shown in the picture note the impedance of the CTS and check the engine temp based on the temp impedance curve for the CTS shown in the 355 manual. This will tell you exactly what temp the ECU thinks the engine is running at.

I know, it's too much trouble to get an Ohm meter out and do this 10 minute check. Much easier to tear the engine appart.

If you just want to throw parts at the car, fine. Replace the T-stat, all the O2 sensors, the CTS, the cam position sensor, the thermocouples, MAFs, TPS, the cat ECU.... Not my style.

 

Easy there John John. Big breaths, big breaths.

I get what you are saying, and you know what, your right. Why not check the coolant temp sensors? 10 minutes and you can see what temp the t-stat opens, right on the ohm meter connected to the coolant temp sensors. Heck he can even watch the temperatue gauge at the same time to see if it's displaying the same thing the coolant temp sensors are reading.

The other thing is, ketel's car didn't put out any coolant temp sensor codes. Another reason I don't think it's a bad temp sensor. It still wouldn't hurt to check it, and like you said, it's only a 10 minute job to check the cts.

But I still have my money on the t-stat being kaput.

 

Right on Mitch!

Hey!

Why don't you guys take a bunch of pics and post up a DIY thread for the 355 owners. Haven't seen anyone do that yet.

 

I am confused.

I do believe it COULD be the t stat......HOWEVER....I am with JohnK....why not do really, really, really simple tests firsts?

Please pull out the multimeter! Check the O2 sensors...like we suggested. Check the CTS. Both are simple. Read page C14 in the 355 manual..it shows the temp/resistance curve for the CTS. Very easy. I looked at both of mine this weekend. Both CTS where reading the exact same thing, and the temp matched my IR temp readings on the block.

I am trying to understand why Ketel is starting with the most complicated things first, then working backwards? How do you tear into the engine and do the Tstat without testing these?

Ernie...he obviously listens to you....what do you think?

 

I think, sure why not, put the multimeter on them and have a looksy. I could be totally wrong and the O2 sensors could be roasted, maybe even all 4 , or the cts gave up the ghost. Only takes a few seconds to check the resistance. So have at it.

Yo Mitch, remember to take your multimeter to ketel's pad and check out the readings. Unless you already have one ketel.

If they all check out fine, then will you guys be okay with swapping out the t-stat?

 

any updates?

 

Yes, but since it is Ketel's car, I will respectfully let him do the update.

 

Still no update? yelcab...come on and spill the beans

 

I think he discovered that he neglected to refill the coolant reservoir.

 

OK, Ketel gave me permission to post.

The swatters blue 1997 F355 spider came to my garage running poorly with the Slow Down Light permanently on. That means the car is in slow down mode and not running at its full performance state. Car has been bought out of Carolinas and has never passed CA smog due to the 11 CEL codes. The major was done 18 months ago but that is extent of the history as far as I know. Up on the rack it goes.

Leaky valve cover / cam seal on bank 2.
Leaky oil lines to the tank in 2 places.
Broken CV boot on left axle.
Nasty fiberglass bits soaked with CV grease and oil all around the left side.
The good news is it has a set of factory cat converters and the headers have been replaced with some non-insulated units (forgot brand).

The Thermocouple from the bypass valve was removed from the valve, zip-tied off to the side under the bumper. All 3 Thermocouple control units have date codes of 2000, of the green variety.

Cursory look indicates one O2 sensor mis-wired at the connector.
A voltage check with the engine running indicates both Precat O2 sensors putting out 330mV when 700-900mV is expected. Both post cat O2 sensors putting out zero (nada) volts. All four O2 sensors are pronounced dead at the scene.

All three TCU came out on the bench to be tested.

Battery voltage applied, Thermocouple plugged in, voltage meter at the signal pin indicates that the TCU for the bypass valve has the 12V and ground shorted together inside the unit and was pulling my test battery down. That explains why the thermocouple was removed and zipped to the side. That TCU is dead.

The other 2 TCU for the cats tested with signal pins permanently at 8V where 4.75V is the maximum that is expected. Both TCUs are also toast and also explains why the car is running in limp home mode.

The new O2 sensors did not arrive on time so we did not change them out. There was no Thermostat on hand so we did not remove the old thermostat. Plus, I think the limp home mode is likely responsible for the cool temperature.

So far, the count stands at 4 dead O2 sensors, 3 dead Thermocouple control units. Replacement of those 7 devices will take care of the 10 out of 11 CEL codes that the car suffers.

The remaining one code about the Cam position sensor, I think I know what that is but let's wait for the others to go away first.

Ketel took the opportunity to finish installing the last GCK bits at the bottom of the engine and I sent the car home with the instruction to replace the O2 sensors (which we slightly loosened on the rack), and the TCUs, before any more driving should be done. Then, we will tackle the remaining issues whatever that is.

I kept the donuts.

 

Hey, Mitch, are you sure those O2 sensors are ded? Mine have an extra ground wire soldered to the housing and attached to a grounding screw on each cam cover. I have seen several 348's like this and some without. Without is the stock setup, but I am sure people have figured out that there is a grounding problem with these things. 4 dead O2 sensors seems pretty rare unless they were murdered. Thermocouples are pretty unsophisticated pieces - it's hard to imagine 3 dead ones. Still I don't have a 355 or an OBD II car. Thankfully.

Sounds like you are on the path to making all correct and I am sure Ketel is stoked.

 

Mitchell, let me know if any homes go up for sale on your block. I'm moving in to your neighborhood!

 

"OH THE HUMANITY!"

Son of a biscuit that is a whole slew of problems. Your a good man for helpin him out Mitch!

 

You just missed your chance, twice in the last 6 months, right across the street.

 

So.....fault codes were correct form day 1, or so it seems.

The cat TCUs can possibly repaired. There was a thread here on how to do it.

As you probably know, having factory cats cans on the car does not mean the cats are good. When I got my car it had factory cats cans. One was hollow, and the core in the other was breaking up. If the cores are breaking up it might explain why the O2 sensors are shot. Thankfully, being a 95 the ECU doesn't care.

Are you sure all the fiber glass in the CV grease isn't particles of cat core?

Glad to here the car is being finally diagnosed and hopefully corrected.

Lesson learned, if your car is throwing codes they just might be for real.

 

Very, very nice of you to help and I'm glad the car is on the way to a proper correction. ;-)

 

Now THAT is how a professional helps out a brother. Well done.

 

One question. If it's in slow down mode (light on, not flashing) should not at least one bank be shut off, i.e. ECU cuts fuel to the affected bank? That's a little more serious than not at full performance. I'm getting the feeling there is more to this story.

Also, are we saying that all these problems (CELs and others) were present during the PPI?

 

My understanding is ...

Flashing: cat overheating, slow down
Steady light: still overheating, slow way down and seek help soon
Steady light & power cut off: overheating, you have not really sought help, I am cutting you off. Although, if only one cat is sending the overheat signal, you can shut down that one bank. If both cats are sending the overheat signals, which banks does the ECU shut down? Dunno.

As for the ppi, that is a question for the owner. Ketel is getting the o2 sensors and the TCUs ordered this week and he will install them. Then we will see where we are. My humble opinion is there are more wiring issues (beyond the one O2 sensor) to sort out yet.

 

97 manual:
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That is ominous. Lets hope not.

This is one of two threads to "bypass" the SDECU on 5.2 motronics and later. In this thread I started there is the down and dirty bypass and cribj's elegant aftermarket SDECU which is the way to go if you want a problem free SDECU system with data logging. Explaination of how the system works is there too. There is another thread on this board for a home made SDECU circuit which is also quite good. Ferrari has failed here since at least the 348. I think of the oem Ferrari system as Ferrari's retirement plan.

http://www.ferrarichat.com/forum/technical-q/328364-exhaust-ecu-aka-sdecu.html

http://www.ferrarichat.com/forum/348-355/378429-thermocouples-slow-down-lights-related-cel%92s-how-conquer-them-4.html

If either of those two threads are followed with as simple and cheap as a temporary 1.5V battery those associated codes can be eliminated and taken out of the equation for this part of the technical troubleshooting.

Mitch has got us some real datapoints and now the problems can be solved. He knows how I feel about that. I also commend everyone for having a rational technical discussion.