Hi Folks, I've been doing some poking around my 84 308 QV US spec car (as you do when bored!). No actually, it has only recently come into my ownership, and I noted the following: Aftermarket exhaust (no cat) OEM Cat Sensor cable tied to engine bay Both the highlighted relays in the image below pulled somewhat out! The car runs and drives fine, but on startup it pumps out a lot on NOX fumes (not smoke). On poking around I found the above mods. The two relays where in place but seemed half pulled out (so not sure if they were making contact or not?). I pushed them back in initially thinking they worked their way out (which is not really likely). Once I noticed the NOX fumes I wondered if a previous owner pulled them as part of some disabling of the CAT system? Can someone enlighten me on what these two relays do? I assume by the name #D is for the throttle position sensor (switch as they call it)? Not so sure about #E electro-valve cut-off? I'm not familiar with the working of the CAT system on 308's. Any enlightenment would be much appreciated BB Image Unavailable, Please Login
Hi All, I found a Bosch K Jetronic Technical Instruction book. Reading through I couldn't find any reference to item E in my above attachment. So I assume this a Ferrari item rather than part of the Bosch K-Jet system? Only thing that came close is the below, but I assume this is item B from above? The Bosch book also mentions emission control via lambda sensor. But I don't think that is what is installed in the 308, it looks more like a temperature thermocouple? Either way, its not connected hence my investigation of the strong NOX fumes. Can anyone assist? Thanks, BB Image Unavailable, Please Login
No, it is a throttle position switch (not a throttle position sensor). It is actually two switches built into a single housing -- one switch that closes at idle and another switch that closes at WOT. for relay D: At idle, relay D actuated -- this ensures that the cold start injector is disabled by disconnecting the cold start injector from the differential pressure switch (so that, no matter what the differential pressure switch is doing, the cold start injector will never wrongly add fuel when the throttle plate is in the idle position. At anything other than idle, relay D is not actuated -- this allows the differential pressure switch to fire (squirt) the cold start injector if a rapid throttle movement causes the intake manifold pressure to change quickly. For relay E: During cold running (water thermoswitch closed), if not at WOT, and the oil temp is not super cold = relay E is not actuated = the air injection electrovalve is actuated = vacuum reaches the air injection cutoff valve and opens it = the air injection system is "on". During cold running (water thermoswitch closed) if at WOT or if the oil temp is super cold = relay E is actuated = the air injection electrovalve is not actuated = vacuum does not reach the air injection cutoff valve so it remains closed = the air injection system is "off". During warm running (water thermoswitch open) = the air injection electrovalve remains not actuated (no matter what relay E is doing) = air injection "off". Do you have a copy of your 307/84 OM?
Hi Steve, Thanks for the detailed description. I have a digital copy of the owners manual, and on looking at it again I found a section on these systems (not sure how I missed it!!!!!). I'll take a better read and see if it answers some of my questions. From your description above, it does not sound like a good idea for those two relays to be left unplugged? Maybe they were just not fully pushed in but still making contact? What won't be in the owners manual is if someone removes the CAT from the system. What do people do when aftermarket exhausts are installed? Do they disable some components like the oxygen sensor? As I imagine if the sensor is constantly reading ambient temperature because there is no CAT - then this must impact the engine operation? Rgds, BB
You are approaching this as though it is a modern car, stop it. ;-) As I recall, and Steve will be quick to correct me, the O2 sensor is not used for much at all, the fuel injection system is all mechanical, ok, MOSTLY mechanical, so there isn't the reading of the mixture using O2 sensors that you get in a modern car. I think that it mostly operates the "Slow Down " light on the dash when the mixture gets VERY rich. How much did I get right Steve?
Yes, no reasons to unplug those relays -- nothing "positive" would result, only "negatives". Depends -- some aftermarket exhaust systems, or test pipes, provide a port for mounting the O2 sensor so the Lambda system can remain operational even if there is no cat. If there is no O2 port provided in the exhaust stream, then the O2 sensor must be unplugged and removed (and the '84-'85 US system will default to open-loop operation more like the '83 US system). If the O2 sensor is not unplugged and just left in the ambient atmosphere it would (wrongly) report "I'm way lean (too much O2)" to the injection ECU and the injection ECU would (wrongly) tell the frequency valve to add more fuel. However, many reports here of unwanted "surging" on an '84-'85 US with the Lambda system working (with or without cat) so many do get unplugged (although I don't like that ). Don't confuse the "cat temperature sensor" with the O2 sensor -- on a system with no cat, there is no reason to mount the cat temp sensor (which is a thermocouple) in the exhaust stream, although, again, many test pipes provide a fitting to keep it mounted in the exhaust stream just as a handy place to keep it. If your system has no cat and no fitting for the cat temp sensor, perfectly OK to just "tie up" this cat temp sensor somewhere convenient; however, this cat temp sensor still need to stay plugged in to the warning light ECU (if unplugged, the "slowdown light" would constantly illuminate).
Thanks Steve - looks like my magnaflow exhaust has no temp sensor port or O2 sensor port. The temp sensor I found cable tied to the back of the engine bay. So from what you said above this can just stay there! I haven't been able to find the O2 sensor so can assume it has been removed, but I will try locate the wiring loom to make sure this is the case. Would it be worth the effort to have a bung fitted to the exhaust and re-activate the closed loop system? Or is the KJet so basic that there is no real benefit? Cheers, BB
Without a cat, it's probably less important to have the Lambda system working (and many do get unplugged here in the US on the '84-'85 V8s even with a cat because of the "surging" symptom). Still, both no cat and no O2 sensor would be a deduction for me as a Buyer .
