I know this has been discussed to death here, but my situation is a little different. Friday I changed the oil and filter on my 348. After taking off the air cleaner housing to get to the oil filter, I thought I would do a little preventative maintenance and clean all the electrical contacts I could see while I had the air filter box off. So I disconnected the battery and began to spray electrical contact cleaner on all the unplugged connector contacts that I could reach. I then took a low pressure air hose and blew the remainder of the contact cleaner out of the sockets and re-connected them. After I was done changing the oil, I re-connected the battery and started the car. I waited about 15 minutes before shutting her down. Then 45 minutes later I took it out for a test drive and immediately the check engine lights started coming on and off and the idle was galloping. I drove it home, checked all the connectors and reset the ecu's. Yesterday I got in and drove to town and the check engine lights started coming on again. First the 1/4 light then the 5/8 light came on and off. Then they both started coming on and off simultaneously. By the time I got home they both had stayed on. Then I disconnected the battery for a couple of hours and started it again last night and let it idle for 15 minutes. In abiout 5-8 minutes the idle started galloping from 2000 rpm to almost stalling, and the CEL's started going on and off. I checked the ECU codes and 1211 (lambda regulation) came up. Question is, what connector is at fault here? Which connector has both sides of the lambda's plugged into it? I've disconnected and re-sprayed every connector 3 or 4 times that I had sprayed previously. I used Caig electrical connector conditioner. I can't imagine both O2 sensors going out simultaneously. What I don't understand is why both sides CE lights are going on and off at the same time.
Sounds like you may have filled the back side of the connector(s) with cleaner, assuming you didn't peel the boots back, and the cleaner is shorting the sensor wires together. Blowing them out with compressed air with the boots pulled back may solve it. Side note, each connector has a small silicone seal that is easily lost during cleaning, important for keeping the connection water tight.
Have you read the codes on the ECUs? That should tell whats wrong or at least get you started in the right direction. Also are you letting the spay dry before you reconnect? Regards, Vern
SpannerMan: I peeled back the rubber and blew out anything that was in there. Standig: I thought about that as well, but no. vern cornell: Yes, I pulled a 1211 (lambda regulation) first. Then when I disconnected both O2 sensors I got a 1114 (lambda sensor} code. And yes I blew out each connector after letting the cleaner/re-conditioner work for a couple of minutes. Brian: Bet you've seen lots of "Dumb", eh?
Simple question: Are you SURE you erased the stored codes from the Motronics using the procedure in the manual (not just disconnecting the battery)? Sorry, I had to ask.
I belive lambda regulation sets when the sensor is out of the expected range for that time, temp, throttle position, etc. since you stated that the codes came back after 5-8 minutes from a cold start, the sensors may have been too cold to begin reading, when the computer was expecting them to be working. Each sensor has a heater that is supposed to bring the sensor up to operating temperature quickly (1-5 minutes max). Chances are the heater in the sensor(s) are bad. Clearing the codes cleared out any adaptive memory that could have compensated for the poor sensor response. Question...did the code(s) return on both banks, or just one? If both, than you may have a running problem that is affecting the mixture enough to put the o2 sensor out of range. Possible fuel pressure regulator leaking into vacuum port, vacuum leak etc. If only one bank, then a bad sensor is most likely. Or a problem that is only associated with that bank, missfire, injector unplugged etc. Also, I have had better luck clearing or checking codes with engine running than just key on engine off.
Erik, the code returned on both banks. I've reset the ECU's when the motor has been at operating temp, to no avail. I also noticed yesterday that I could hear the AC pump leaking air somewhere near the pump, so it won't hold a freon charge. This wouldn't have anything to do with it would it? I know that when the pump engages it sends a signal to the ECU's to compensate idle speed parameters. When the car has been driven for awhile, the idle speed is fine when stopping. But when I turn it off then start it again shortly, for a few minutes, the idle gallops up and down to the point of stalling out. John
The reason your car continues to gallop is because you did the relearn with the engine warm. You must do it when the engine is COLD. So, disconnect the battery, wait about a minute, reconnect it, then start the car and let it relearn everything. Again do it when the engine is stone COLD. Remember NOT to touch anything at all when the car is relearning the process. Have you tried to attach an additinal ground wire to the O2 sensors yet? It's easy. A peice of wire & hose clamp will do the job.
My 348 kept getting the Lambda codes and I tried the extra ground with no improvement. A trip to the auto parts store and a couple of Bosch generic O2 sensors for less than $60 each and the car runs perfect. You need to cut and splice the connectors, but the splice kit comes with the sensors. If you want the OE sensors they are about $150 each and need to be ordered. My Advance Auto Parts store had the generic sensors in stock.
Oh I'm not saying his O2 sensors aren't shot. I just think a .25 cent hose clamp and some wire that was laying around could save him at least $60/per O2 sensor. But the problem started after he cleaned the connectors, so that's why I suggested that.
ernie, I have reset the ECU's when the car was stone cold. I've also done it when it was warmed up. I've also done it when it was luke warm. Doesn't seem to matter when or how many times I do it, still get the CEL's. The ground wire trick is something I haven't tried yet, but I will tonight. brm, I started getting the CEL's after changing the oil and deciding to clean some connectors. For both O2 sensors to go out at the same time is pretty coincidental. Although I have 2 brand new Bosch ones sitting on my work bench, I was reluctant to put them on if the old ones weren't bad. But maybe I'll do that anyway. This problem has me absolutely bewildered. I consider myself a fairly decent mechanic when it comes to my personal vehicles. But this thing is nuts. I've disconnected and reconnected every connector that I touched while cleaning, a hundred times. I've checked the continuity of the wires to all those connectors, and even said a little prayer one night in the privacy of my own garage, all to no avail.
i see you checked conti but you really should check the circuit under load.continuity is a bad only test.i'm thinking you may have pulled/broken a wire.what other connectors did you clean? good luck.
Frank, I cleaned the 2 maf's, the 2 electrovalves, 2 engine idle controllers, the 2 fuel injection plugs, the 2 throttle pots., the water temp sensor, the 4 O2 sensors plugs, a plug under the oil filter (has one contact in it, not sure what it is for), and the positive battery connector under the air box. How would one run a continuity test under load without tearing up the wire insulation and housing?
The best way to get readings from wiring without hurting anything is backprobing the connector. As you stated, the lights came on after the oil change-clean connectors, reason says that it must have been something you did. most sensor connections are very sensitive to resistance changes and even the slightest corrosion can offset the signal enough to cause radical running problems. Here is what i would do first: Using a dvom (digital volt meter) backprobe one of the O2 sensors (before the catalytic converters). Four wire sensors have 2 white, 1 black, and 1 grey wire. The signal wire is black. With key on engine off compare the left and right bank sensors. should be reading near the same voltage aprox .3 to .6 volts. Check white wires for 12 volts and grey should be ground. Now start the car and let it idle for 3-5 minutes and while it is running, check the signal wire again, say every minute or so. What your looking for is the general time when the sensors begin to start working. When the voltage starts to cross above and below .45 volts, it is working- telling the ecu what the O2 content is in the exhaust. As the mixture goes rich, voltage goes up, lean down. The range is generaly .2-.8 volts- going up and down. This is the key to this test. The mixture is a range that the computer is trying to stay within, and the rise and fall of O2 sensor output voltage is showing that the computer is doing its job of keeping the engine in that range. If the O2 sensor output (signal) never changes the ecu can't use the O2 sensors to control mixture and sets code(s) The sensors won't change if they are bad (not working) or there is something keeping the mixture rich or lean. If the sensor voltages stay above .45 volts even if you hold the car at say 2500 rpm for 10-30 seconds than the mixture is very rich. So then below .45 volts would be too lean. Coolant temp sensors will cause both depending on if it is shorted or open. Maf will cause both. Vacuum leak-lean Fuel pressure regulator-rich. Pull the vacuum line off the FPR if you see fuel, its leaking. This is only one test, but it's a start. Re-check everything-even if it means doing over what you've already done. I have found that I step on my own toes more often than I care to admit. E-
Erik, I really appreciate your input. I must say I'm getting a real lesson in automotive electronics. A couple of questions I have though and one is the water temp sensor. I cleaned and checked it earlier. If it was shorted or open would the temp. guage still continue to work? Also, I read that to check the intake air flow you run a resistance test between pins 1 and 6 on the MAF's. It should be 383 ohms. True? Also can you run load tests on the MAF's?
eric thanks for finishing a thought.i was thinking voltage integrity.or min/max at the least.lets check the battery connections and grounds.again.then O2 's. forza i have a '90 348 in the shop is morning and will look it over for any thoughts but hope following O2 toggle points you in the direction.
Very interested that you have detailed informationon the 348 check lights do you have similar detailed information for the 355 slow down light ( 5.2 system ) ie voltage readings at thermocouple ECU s .I have replaced both ECU s and both thermocouples but still have an intermitant slow down light coming on from start up .( both Cats have been checked ok ) Any coments appreciated .
ernie-thanks, no sckool like old sckool..... rivee- There are two temp senders, one for the gauge and one for the computer. Don't remember which is which, but pulling a connector off will either set a code or change the gauge reading...I run load tests on maf's It can be done with engine off, just measure output voltage (don't know off hand what terminal number- will check tomorrow) then blow through sensor with compressed air. Best to check them with the car running though, and watch response at different throttle positions (rpm). If you have access to an occiliscope, you can see a nice graph at different rpm's, and catch glitches more reliably. Actually an o-scope is the best way to check O2 sensors too..Snap-on Vantage scope is overkill for the weekender though...oh and I don't think the a/c is a problem..it should not engage if the freon charge is low. A pressure sensor on the receiver-drier acts as a safety for the compressor. wlracing-I found that the later OBD2 355's will set a different code for each one of the three modules, and will not clear unless a scanner clears the codes and the part is replaced. The slow down light would blink after startup, no check engine light, can't remember the code numbers, something like 1145,1146,1149-will check my notes. If it's not an OBD2 car then you may want to check the sensor probe(s) for continuity to ground, the two wires in the sensor should not be shorted to the shielding. Those pesky little boxes really piss me off....I would like to find or build a test bench for them to ensure I am spending my customers money wisely, but alas, I am a mechanic not an engineer. in time I will have more data to work with. Happy turkey day everyone E
take a look at 328 ignition problem thread by ctnbop.....everything looked good, but on a second look he saw that the connector pins were too wide to make good contact.
For anyone looking to learn more about how modern fuel injection systems work, I recommend: "How to Tune and Modify Engine Management Systems" by Jeff Hartman Mostly tuner stuff, but has some cool Bob Norwood tuned fcar pics.
I searched for my electrical gremlin off and on for more than two months, and was two days away from having it towed to the shop when I isolated the bad connector. I've learned to be more meticulous when it comes to electrical issues. I disconnected/reconnected everything many times, and in the process probably made the connector wider each time. In the end, I learned a lot and the car runs noticeably smoother now after having cleaned most all the connectors. Good luck...you'll find it.
