Dreaded CEL

From what I can gather basically the car starts fine and then once warm runs rough. You found fouled plugs, replaced them, no change. Have you pulled the new plugs and checked for fouling? As for the CTS, if it's open, yes it would cause rich running but typically not to the point of fouling plugs and running rough. Additionally, you said you had fouled plugs on both sides which, if CTS related, would indicated both CTSs were shot. Also, what did the other plugs look like? As I recall, you said two fouled on each side. If the other two looked good it would suggest something associated with specific cylinders, not something that effects all cylinders of one side or the other. Lastly, what happens when you hit the throttle? Is it still rough, or does it clear out?

 

So does "runs rough from the start" mean even when still cold?

 

David

I had a bad running issue on my 95 355 after the engine out service where I replaced all the crimps. I must have done 150 of them. I started the trouble shooting by changing components including a different MAF and Coolant temp sensor.

Then I thought better. It was something I did, nothing broke.

I went back to every single wire that I touched, and measured the continuity from each connector pin to the ECU (two ECUs on the 2.7) and I found that I have swapped 2 pins at the left bank idle valve. Swapped them back and it was purring again.

You have done a lot to this car, and perhaps you should back up a bit and start measuring every pin to the ECU. If you need wiring diagrams and where things go, I have that.

Good luck man, it is a painful learning process with these things.

 

If it's running bad from cold and hot, IMO it would place doubt on the CTS. FWIW, my 355 had a bad CTS when I got it (open). There were no drivability/starting problems, but it smelled rich and had high (measured) HC before the cats.

I would pull the plugs again and see what they look like. If they are all the same great. If some are different then it's relates to specific cylinders.


Also, you said you replaced the phase and RPM (TDC) sensors. Did you correctly gap the RPM sensor? If not you could be getting a weak or intermittent signal and injection timing could be off.

 

Using the old spacers doesn't mean the gap is correct. The gap between the tip of the sensor and the toothed wheel on the crank should be measured to assure it's correct. So, it could be off.

 

Lots of spark testers. http://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/oem-in-line-ignition-spark-tester/900800_0_0/?checkfit=true

This one you just place over the wire http://www.amazon.com/Lisle-19380-Spark-Tester/dp/B0002STS3U

In use https://www.youtube.com/watch?v=NUrKFNSTlzU

 

David, earlier in the thread you mentioned that the exhaust fumes smelled very rich, enough so that it bothered you being in the garage with the engine running. Is that no longer the case?

The easiest way to determine whether the plug in question is firing would be to put one of the old plugs back in the hole, take the new plug and connect it to the spark plug lead, ground the base of the plug, and then fire up the car and look for a spark. If there is no spark try testing an old plug in the same fashion. If you get spark then you have a bad plug, which does happen on occasion. If neither plug will fire then the chances are good that the wire is bad (or perhaps there is a problem with the connector in the coil).

 

I did same thing with my engine out when replacing all pins with the gold connector kit. I was lucky everything worked but i did same thing with the water temp sensor. When i reversed the one wire it worked as well. I have learned coincidences are not usually the case.

 

Your cylinder one is not getting spark if it looks like that. Get a timing light or spark tester just to prove it to your self.

I had this happen and on my 355 it was a pin in the main ecu harness that tells the coil to fire.
Thanks were to Mitchell for the ecu pinout. When mine did it the obd2 caught it as a miss fire and the slowdown came on due to cat overheat on that bank.

 

The 348 has a wasted spark system like the 355. Thus, if cylinder 4 is getting spark it should not be ECU related. 1 and 4, and 2 and 3 are paired. That is, for each pair, the plugs fire on the compression and exhaust stroke. If 1 is not firing and 4 is there must be a short to ground somewhere between the coil and plug 1.
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David, if you search the archives long enough you'll find mention of a company that builds original style plug wire sets for around half that price. I don't recall their name, nor do I have any experience with them, but some here seemed to have had good success with them.

I've been very busy so I haven't been keeping up with your posts all that well but if all the plug wires showed continuity it may not be a bad wire (although it certainly could be). As JohnK (to whom I owe an apology by PM when I get a chance, for confusing him with someone else) posted, two plugs fire at the same time, so you could swap the two wires at the coil and see if the miss moves to the other cylinder as a means of checking the connectors in the coil. More later, hopefully, when I have a little more time.

 

No problem Mike. No harm, no foul.

 

Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry

 

You rock, Dave.

 

Dave, I didn't want to bring this up before it was confirmed that cylinder 1 has or doesn't have spark, but did you happen to noticed if the plus from 1 was wet, as with raw fuel? If it was dry it just might be that the injector is clogged, inoperative, or not getting the signal from the ECU.