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Old 05-29-2012, 11:26 AM   #15
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Could still be one of the components you have already replaced, or the wiring to it. You can put a new diaper on a baby...

I'd start unplugging things one at a time. It'll run, and it should set a code fairly quickly. For example, if it runs better with the airmeter unplugged, good chance it's the airmeter or an air leak. I also wouldn't put 100% trust in what you are seeing for coolant temp. If the sensor IS bad, the ECM will synthesize a coolant temp that starts at ambient and warms up to a "normal" value. You could be looking at the defaulted value, and not the raw value.

Also curious what the short and long term fuel trims are. Could help diagnose an air leak.

It does have stock manifolds, right? I have Banks headers and the location of the O2 sensors further downstream makes them run a little cooler, it occasionally tries to go closed loop too soon and runs rough.

One more thing...should have thought about it sooner, I was discounting fuel issues due to it acting up on LPG or gas.
Have you checked out the fuel pressure regulator? It's a common failure. If the diaphragm ruptures it can send fuel directly into the intake manifold. It would still do that in LPG mode. Just need to pull the vacuum line to it. If there's fuel there, you found your problem.
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Old 05-30-2012, 04:09 AM   #16
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Thankyou again for the latest replies.
Some of the content is a little over my head since I was bred in the times of carburettors and distributors, but I have learned a lot and continue to learn.
Another difficulty is that, here in Spain and most of Europe, there is practically no service for these vehicles at all! So, I have to send to Rockauto for parts, and read about problems mostly on forums and on Alldata. It seems that I have tested and replaced endlessly, but still have a motor that purrs when hot and is a dog when cold.
I get live data from an Autel scanner and can record it when I want to.
As I've said, there are no codes, and all sensors give sensible indications.
In addition, just in case, I have replaced many sensors at least once!
Vacuum and leak tests are good. Fuel pressure(40) and regulator are good.
On cold start, all fuel trims show rich at first, then it goes into closed loop
after a couple of minutes. The STFTs cut to low values between + and -
3.0%, but the LTFTs stay high around 13%. At 110 deg., the LTFTs suddenly decrease to bank 1 3.1%, and bank 2 6.3 %. These values remain even when the motor is hot. At about 170 deg., the motor smooths out completely but all the scanner readings stay the same.
There is nothing in the readings to indicate why this happens at this temperature, and it continues warming up to 195 deg..

Someting has just occurred to me!
If, after a couple of minutes, it goes into closed loop and the STFTs drop to very low values, and the O2 sensors are switching as they should, surely this is saying the fuelling is correct?
So how is it possible for neat fuel to be pumping out of the tailpipe???
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Old 05-30-2012, 10:36 AM   #17
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Great info.

Fuel trims don't seem too out of whack, but aren't perfect either.

I've been guessing that it smooths out when it goes closed loop. Sounds like that may not be the case? That is, it goes closed loop and still runs rough until it gets warm?

And you're right. Assuming all cylinders are firing, you shouldn't be getting excess fuel in closed loop. Regulator checked out ok, did you pull the vacuum line to it? If the diaphragm has a pinhole in it, it'll still function, but could pass fuel into the vacuum chamber.

It is interesting that the LTFTs are positive though. As long as the tool you are using is applying the signs right, that means it's learning ADDED fuel (it only learns in closed loop of course). A non or misfiring cylinder can cause that, the O2 sensor sees the oxygen from the non-burning cylinder and adds fuel to compensate.

Might check if there is vacuum at the EGR valve when it's running rough (I'm leaning back towards the EGR system....). I know, new parts, but you never know if they are good, and maybe something got hooked up wrong when parts were swapped. It does smooth out when warm, so it's probably not a junk EGR valve (seen those idles bad ALL the time).

Pretty good puzzler on your hands. Being in Spain really adds to the challenge (I googled Chella just to see where you were, too far to help!).
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Old 05-30-2012, 12:32 PM   #18
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If, after a couple of minutes, it goes into closed loop and the STFTs drop to very low values, and the O2 sensors are switching as they should, surely this is saying the fuelling is correct?
So how is it possible for neat fuel to be pumping out of the tailpipe???
I don't know what STFTs are, but properly working O2 sensors and tuned EFI will dither across lean/rich very rapidly under cruise conditions.. Note, not at idle and not at full throttle, but partial throttle cruise.

Then again, you're indicating that you're rich until you're warm.

The "smell" of hydrocarbons in the exhaust could simply be a bad cat converter... If you're rich, your 02 sensors should indicate very rich (pegged rich) - narrow band 02 sensors really have 3 positions - rich, lean, and stoich (14.7:1) - they cannot indicate how lean or how rich... If you need how lean/rich, you'll need a wideband.
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Old 05-30-2012, 01:41 PM   #19
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Thankyou, tderonne and cb1000rider.

Nothing happened with the motor or the regulator when I pulled the vacuum line. But, the regulator is worth changing for it's cost!
Excess fuel is still getting in when running on LPG, but I presume the gasolene pump would not then be running!
I like your idea about a misfiring cylinder, and I will go faithfully through the disconnecting routine again!
Personally, I'm happy with the functioning of the EGR system. It only gets really hot when driving. And I have experienced the power loss when it isn't working! The EGR vacuum pulses, and I believe this is correct? However, I will check the three components again.

cb1000rider, the O2 sensors switch quickly in between zero and 1 volt, and in closed loop which it enters after a couple of minutes, the short term fuel trims are less than +/- 3.0%. This is really my number one puzzle!
By the way, this model F53 has no cat converter, and the two O2 sensors are just after the exhaust manifolds.
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Old 05-30-2012, 03:17 PM   #20
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chellaman,

Years ago when I first got my Catalina, I had a tune up done. Ran great at power. I was having some stumbling at low speed, with no codes. I got under the dog house and was checking for vacuum leaks, missing/loose wires, etc. Checked the distributor too. Still couldn't find anything. I then checked the firing order. The mechanic had swapped two wires adjacent to each other on the distributor. Fixed both problems, the firing order and the ex-mechanic. Why did I tell this story, because I don't think swapped plug wires would register as a misfire code. Tderonne stated that it seems to be ADDing fuel during the learn in close loop. Could this be the extra fuel that is being injected but not ignited in two cylinders at cold conditions (open-loop) and the problem is not apparent, but still there, when warm (in closed loop). This condition would follow from gas to LPG to gas. Some thoughts, and again, Just my two cents...
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Old 05-30-2012, 03:19 PM   #21
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When the #5 piston on my V10 broke, you couldn't tell by listening to it idle or rev'd up. It was just sluggish. I don't remember it blowing black smoke, but the MPG doubled with that one cylinder out. It did not set any codes either.
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Old 05-30-2012, 09:29 PM   #22
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cb1000rider, the O2 sensors switch quickly in between zero and 1 volt, and in closed loop which it enters after a couple of minutes, the short term fuel trims are less than +/- 3.0%. This is really my number one puzzle!
By the way, this model F53 has no cat converter, and the two O2 sensors are just after the exhaust manifolds.
So that sounds like correct behavior (in closed loop).
The fuel trims, if I understand correctly are 02-based fuel amount correction. 3% means the base tune is pretty well on spec for target.

With no cat converter, it's going to smell pig rich. Literally, you'll be able to smell it at a stop light. Back in my younger days, I removed the H-pipe (and 4 associated converters) on a 5.0L Mustang and had the same symptoms. I stopped doing that sort of thing when I found that the HP improvement was marginal and the resulting hydrocarbons increased by literal factor of 10x.

So if you're not finding a single log measurement - especially that of temperature sensors that indicates a colder than reality value, I'm a bit stumped.... As an experiment, I think I'd determine the resistor value of the CLT (coolant temp sensor) that corresponds to 180-190 degrees, stick it in there, and see if that improves your situation.

Second, without a cat or a wideband you really can't tell if you're rich enough to trigger misfire. Your misfire might not be mixture related - the indication of rich seems to be somewhat subjective - no offense intended...

A second test could be to change the plugs (yea, not a small job on a V10 that may have plug blow-out issues), replace them. Go through start-up, cool-down, and restart... Then read the plugs. See if you can see a specific cylinder or two that is misfiring. Like other posters above, the misfire diagnostics on the V10 don't seem to be that great, at least not on my 99...... Note there is a KOER Key On Engine Running test that *may* be able to detect a misfiring cylinder, but I'm still trying to get that sorted out at home.
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Old 05-31-2012, 09:48 AM   #23
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Shucks, just install a block heater so the engine will have some heat in it on cold start ups.
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Old 06-05-2012, 11:57 PM   #24
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chellaman,

Your OBD-II scanner may be able to show you the results of a "cylinder contribution" test. The engine control computer checks the acceleration increase of the crankshaft each time a cyl has a power stroke and stores this. Finds things like bad injector, spark etc.

Another thing to check is the IAC (idle air controller), it's mounted on the throttle body and controls a small solenoid that operates VERY fast with short pulses of current to maintain the correct position for that engine temp. The IAC has a small passage the allows air to bypass what we used to call the "butterfly" in a carb. Before closed loop the engine comp uses a "lookup" table for temp to determine the correct position for air at the current fueling rate.

It has, if I remember right an electrical connector on it with three wires. At cold idle unplug this and see it there is any chage. This is a non-serviceable part also according to Ford.

Re-post with the solution if you've found the problem...
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Old 06-26-2012, 08:16 PM   #25
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Any update?
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Old 06-26-2012, 08:44 PM   #26
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Don't know if CC considers their IACs as serviceable or not, but when my Dodge Ram 5.9L kept stalling last year, I soaked it in PB Blaster overnight and it's been working fines since.
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Old 06-27-2012, 06:03 AM   #27
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Bad IAC, in my experience, would result in low idle or fast idle.. Not a rich mixture.
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Old 06-27-2012, 09:39 AM   #28
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Bingo!

Or stalling as I experienced.
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