Hi all,
I've scoured the archives and read everything in the 700-900 FAQs (all good stuff..but to no avail.). The car starts fine, but within minutes begins to stumble and blow black smoke, especially under hard exceleration. The check engine light comes on within minutes after reaching cruising speed. The codes are: 2-1-3 (throttle switch faulty at full throttle), 2-2-1 (fuel system compensating for rich or lean mixture), 1-1-3 (fault in fuel injectors).

WHAT I'VE DONE SO FAR:

1. Replaced 02 sensor (weeks ago the OBD indicated it was bad)
2. Replaced Fuel Pressure Regulator and spark plugs(seemed to work...for about 50 mi.)
3. Replaced ignition wires, cap, rotor.
4. Checked the Coil (Bosch)
- Primary Resistance: 1.2 ohms
- Secondary Resistance: 7.4k ohms
QUESTION: Does my vehicle have a Breakerless, Computerized, or EZ-116k ignition system? I'm guessing its the EZ system because the PR is just 0.2 over spec, and the SR is right in the middle of spec.
5. Listened to Injectors (all are clicking the same)
6. Removed and Cleaned the Throttle Body (my dentist wishes I'd brush this well)
7. Throttle Position Switch passes the "click" test.
8. Currently running a can of BG44K through it (this and gas in oil reduced viscosity to near water....changed it out today).
9. Performed my first Compression Test (fun!):
- #1 180 psi, #2 179 psi, #3 180 psi, #4 180 psi (waited until guage didn't rise any higher in each cylinder). These values are impressively consistent and about 6% above the 170 psi spec. I suspect carbon deposits from rich burn (when I pulled the new plugs to test compression all were equally blackened with soot.)

RUNNING OUT OF MULTIPLE WORKING HYPOTHESES:
1. Could it be the coil? (need to know which system I've got.)
2. Could it be worn injectors - either leaking or opening too early and for too long (I've ordered new ones because after 150,000 miles they've got to be tired)
3. Could it be the Throttle Position Switch (maybe it's worn out)
4. Or could it be the ECT sensor? What I've read indicates when it fails it tells the ECU the engine is cold and wants more gas (is there a code for this?)

Given that the cylinders have good even compression and ALL plugs are equally fouled, I'm leaning toward the ECT. I doubt all four injectors would fail equally within a month...something seems to be telling the FI to spray extra fuel at all times. Have read about Base Idle Setting impacting driving performance, but idle seems to be set correctly....just stumbling and missing due to too much fuel.

FINAL WEIRD NOTE: When I pulled the fuel pump relay and main fuel pump fuse to relieve the fuel line pressure by idling the engine until it stalled I cut the grass for an hour and when I came back it was still stumbling along and puffing rich exhaust smoke. Huh???? This made me think the injectors were really leaky and engine vacuum was sucking fuel through them. Or, perhaps there was so much gas in the oil the engine was sucking and burning crankcase fumes. It wouldn't die!

OK...Sorry for the length of this...plenty here to chew on.
Jon

Looks like you're finding the ECT by elimination. You may be committed to replacing it already, but you'd be more satisfied if you could indict it positively first, by measuring its resistance from the ECU connector. The technique is in the book. Of course, if it is intermittent mechanically or with temperature, you wouldn't vindicate it with a good reading.

Not sure exactly which early 90's 240 may have eliminated the 5th injector so if yours has one, consider that could be a goner. With the LH2.4 OBD test sequence, you can activate it, the other injectors and the idle motor to test. See the FAQs if you're not familiar with this.

Also on your final wierd note: It should not run with the fuel pump relay removed. It will not run with the main fuse removed. At all.

The confusion comes from the labeling on the fuse panel and the info in the owners manual which is wrong in most cases. The main pump fuse is the FI system fuse under the hood, not fuse #6 -- until 91. If you pull the plug on the main pump, under the seat, you'll still get enough fuel from the transfer (tank) pump (fuse 4) to idle, after a fashion.

When the FPR (which would have been my guess) was replaced, you say it was OK for a while. Do you discount the possibility of having killed the replacement somehow?

Also, a note-- the LH2.4 ECU remembers its default mixture setting, or limp home. Maybe this is my "wierd note" but I think I've caught it remembering this fuel map after doing both an OBD reset, and once, pulling the main fuse for a few seconds. Pulling the plug of the ECU always flushed its memory. And your ignition is EZ if you have the OBD.


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Art Benstein near Baltimore

Thanks Art,
Now I have a few more things to check (oh Joy!)...I also really felt it was the FPR...especially when it started running so much better (even before the new plugs were installed). How could I kill a new FPR just by driving the car? It seems to me only excessively high fuel pressure would damage something with a a diaphram in it (and cause rich running). I'll pull the vacuum hose to see if fuel drips out...but if not should I assume it is OK? Could I check it by applying vacuum to the unit?
Jon

While you are checking the vacuum hose for gas, also pull off the return line to make sure it is clear all the way to the tank. A clogged return line will nullify the action of the FPR.
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Art Benstein near Baltimore

Great idea....but how do I check for a clear return line?
Jon

jon,
I'm going through similar problems. David Hunter, Art and other gurus suggest the coolant temp. sensor. This thing runs the car a bit rich until the temp comes up and then leans the car out through a signal to the ECU. $40 part if that's the culprit. Went to change mine last night and it's in a tight location under the #3 intake port (OK, it's a bitch!). I couldn't get it done...yet. I think removing the entire intake manifold is the besy way to do the job. You didn't say what year the car is, but on my kid's 92 240 if you look on the drivers side of the engine you'll see the knock sensor(mine had a 12mm bolt attaching it) and right above that you'll see another sensor with one wire attached. I'm guessing that one is for the temp gauge. The one we need to get at is further back and pretty much buried by the fuel injection connections and intake manifold. I haven't yet even gotten the bail clip connector off and was getting pissed so I gave it a rest for the night. I'll try again fresh and probably take the intake off completly. Hope this helps. Looks like the only thing you haven't yet changed or considered. Good luck.
Eric

Sorry....1990 240 DL Wagon with somewhere between 150,000+ and 160,000 miles (previous owner had to fix odometer...I'm not sure how long it was driven before the fix...but they changed their oil every 3k so they probably noticed it pretty quick). It was fixed and set to zero when it had 57,791. Now it reads 96,175. The car is in great shape overall and VERY clean, so tend to think the true miles are in this range.

Thanks Eric,
Unless I have crazy high fuel pressure I think it is the ECT sensor. I tried to fiddle with connection....Snaking my arm in there was a real pain. I will probably just take the intake off and replace the sensor. It will also be a good time to clean a very gunky intake manifold.
Jon

hi there i removed mine with the intake manifold in place. you might need some peroxide and band aids when you are done.

Hmmm....I'm wondering if it would actually be faster to remove the intake manifold :)
Jon

I ran out of peroxide. Used several boxes of nitrile gloves over last 5 years. So far only once have I done damage all the way through the skin, and you can be ready for dinner in 5 minutes. Good luck with your lambda restoration, btw.
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Art Benstein near Baltimore