Mercury Sable 93 (Taurus) engine knocking/pinging problem

Is it pinging? A tinny quick knocking? It sounds as though you are running rich, check the O2 sensor, you will have to see your workshop manual as I am not sure of the resistances. If your O2 sensor is telling your ECU that you are running lean when you are not then it will max out the timing on the injectors and be running as rich as hell. No power, pinging and usually running on. Does your motor stop immediately when you turn off the key or does it keep running for a few seconds? Either that or your cold start is staying on, check your coolant temeratur sensor as well. Again you will have to find out the resistances yourself as unfortunately I can not tell you. Finally, If both these are fine just check you airflow meter or Manifold Actual Pressure sensor, I am not sure which this car has.

I hope this has helped you. Scott. "Laguna" wrote in message news: snipped-for-privacy@posting.google.com...

Clean or replace the MAF sensor. replace the water temperature sensor (not the gauge sensor, the computer sensor). CHeck ALL little vacuum hoses for cracks and leaks and replace as necessary.

You might also replace the O2 sensors if you never have.

Bob

Start with the often overlooked FUEL FILTER.

I looked at the previous postings a little, and I realize it is "spark knocks" that I have. They get worse when the weather is hot. On a hot weather and engine hot, I press the gas, the car practically can't go uphill, just knocks almost no power, but still runs on. It only happens under load, driving. For example if engine is running parked and I press gas, it goes to 3-4K rpm no problem (as if everything ok) with good engine sound.

I run the KOER test today, I got 538, I guess it is something like "not enough RPM", don't know if related to spark knock problem.

To Scott's question, engine turns off immediately when I turn key off. No weird behaviour on that. Idling is good. Cold or hot, always starts no problem.

I have Hayne's book, it says I have MAP sensor (doesn't mention about MAF). Are they the same thing? I guess I know where it is, but I will take its picture and post it to be sure. How do I clean it?

I located both O2 sensors, plan to change them first.

I checked the hoses, they look ok. But there are many hoses, and some of them I know have hot water in it. Should I check only the vacuum hoses? How do I know which hoses are those?

Since car seemed to heat up a little too much, we changed the thermostat recently. Where is the water (coolant) temperature sensor?

Fuel filter is 8 months old, it should be ok I believe. Thanks in advance

MAF is an air flow meter, MAP is an air pressure meter. They are different ways of achieving similar results. It's all about metering the air coming throught the throttle body. A MAP is more accurate as it allows for temperature changes. But that is kinda beside the point. You should be able to test your 02 sensors, I can't tell you the readings you should get so consult a workshop manual, before you replace them. Start with them. I think you will find they are at fault. The coolant temp sensor is usually located on the side of the head.

Dude, spend the 10 bucks and replace the fuel filter.....A plugged fuel filter will cause the problems you discribe. Low fuel pressure can cause spark knock (ping) and O2 codes......there is no way the O2 sensors will make it run that bad..( allthough it probably needs them because of age, old ones will make it idle rough and run rich, exactly the oposite of your problem sounds like) Always start with the KOEO test first. If you get a live code there, fix it FIRST. Does the car miss/vibrate under a load? Scott M

Having thought about it, Scott M is right, replace your fuel filter. It sounds more like it is running out of fuel when the demand is getting high. Replace the filter and see what happens. If it makes no difference, you might have to attach a fuel pressure guage to the fuel line after the filter. (They have a longer banjo fitting that replaces the original fitting on the top of the filter to fit the fuel line and the line for the guage on the same fitting). But do the filter first and see what happens. Btw this is an injected car isn't it?

Sorry to have been leading you down the garden path, I don't know where my head was at.

Scott.

Just an example, I worked on a small 4wd made by diahatsu, feroza, horrible little things. Any way, it displayed similar symptoms to that you have described. Another tech had been working on it, he had replaced the fuel filter, serviced the injectors (which displayed almost perfect spray patterns) and checked the operation of the key sensors, like MAP sensor and coolant temp sensor. I put a fuel guage on it and found the pressure dropped under heavy load. Meaning a blockage. All I had to do was to trace the problem back down the fuel line and found that it had a small inline filter at the output of the pump. The filter was the type that is actually inside the flexible fuel line, a simple cone shaped net kinda like the ones you have inside your injectors just bigger, which no one knew was there. I replaced it and all was fine.

Sorry it took me so long to remember that.

Scott.

I replaced the fuel filter, drove around a little bit. Problem is still there. But today wasn't very hot, so it felt slightly little better. I swapped the O2 sensors. I will drive some more and dump the diagnostics codes to see if they are any different. Measuring fuel pressure is good idea. (Maybe fuel pump is not very good?). I will have to buy a pressure meter to do that test. Yes, this is a fuel injected car. The car does not miss/vibrate under the load. It simply rejects to speed up and and start knocking even sligtest uphill. On flat highway it speeds up slowly, gradually. How come under no-load (parking) engine is running just fine, going high rpms no problem??

Next thing to check is fuel pressure, also sounds as if the exhaust could be plugged(badly plugged). A good muffler shop will be able to check it for free (in hopes of selling a new cat) Its not overheating is it? Do you have a vacuum gage? Found this for you:

1.Connect Vacuum Gauge to a manifold vacuum source (below or after the throttle plate). 2.Engine warm and at idle, vacuum =_____ in. Hg. (Should be 16 ­ 21 in. Hg.) 3.Engine warm and RPM @2500, transmission in park or neutral, brake firmly applied, vacuum =_____ in. Hg. (Should be same at #2 or slightly higher-if vacuum drops after 15 seconds check for plugged exhaust.) 4.Decelerate vehicle from @2500 RPM suddenly, vacuum jumps up to = _____ in. Hg. (Should be higher than before. Watch rate of vacuum change. It will change differently for plugged exhaust.)

High rps mean more fuel demand. If it is not able to supply enough fuel the pressure will drop and aill not accelerate past a certain point.

Check your codes before doing anything else. Please keep posting your findings as I am keen to see how this turns out for you.

If you pull you spark plugs you should be able to tell if it is running lean or rich, If they are black it is running rich, grey/white lean.

It may be hard for you to distinguish between normal fuel supply and lean mixture by pulling the plugs but you can rule out it being rich.

Generally if it is not running rich it means that the O2 sensors are working, but if you are able to check them it would make sure.

From the other postings it seems that they are about due to fail but that doesn't mean that they have so unless they are really cheap and you are happy to spend the money replacing them for possibly no reason, check them first.

If you do buy a fuel guage to check the pressure, you will have to find out what normal operating pressure is. I can not give you an accurate figure I am afraid. Make sure you buy the right guage and not a high pressure guage for diesel or something like that. It isn't that I think you would but these things can happen to anyone if they don't check.

Scott.

After swapping the O2 sensors, a new code appeared.:

-181 Adaptive fuel rich limit is reached RH).

The previous codes were:

- 189 (Adaptive fuel rich limit is reached LH) and 172 (HEGO sensor indicates system lean RH) were already there.

Does that mean anything? I don't have the tools for fuel pressure and vacuum measurements. I will have to buy them.

I checked the fuel pressure.

- In KOEO, it is 39 psi (the Haynes manual says the same value)

- When engine running in idle, 33 psi

- When I press gas to 3K rpm, it goes up 35 momemtarily and back to 31 psi. If I keep it 3K rpm, it stays at 31 psi.

-When I go back to idle, again 32-33 psi.

Is that the kind of expected behaivour? Ot is it supposed to be at 39 psi for all times, no matter what the rpm is?

Does the manual say 39 with reg disconnected or running or max or....? It is expected to go higher when you rev the engine. The ideal thing to do is drive the car and watch the pressure, leave the head of the gauge sticking out from behind the hood and watch it. See if it goes low when it acts up. Be careful, make sure you have no fuel leaks. BTW, the code you mentioned (not the O2 one) means the computer is trying to adjust the fuel mix richer but is unable to do it (most likely low pressure):) p.s. Didnt I read a post from you about a fuel pump problem before?

Put an old battery in a car and listen to it ping and try to gather power because it is running on mostly alternator.

Haynes manual (for a new beginner like me, I find it not very helpful) only says for idle condition. For idle it is supposed to be 39 psi. Doesn't make a comment for higher rpm's.

I measured the fuel pressure from Schrader valve under the hood (like air valve, if pressed fuel is injected out). During the measurement the hood needs to be open to see the value. So I don't have the option of driving and reading at the same time.

Yes, I had to change the fuel pump lately. The previous one broke on me and I replaced it with another (used) one . But the knocking problem has been there over a few months, so I don't think it is related to fuel pump.

Next I would like to make the vacuum test you suggested. (I also bought a vacuum gauge today). I looked at the throttle assembly but I see many hoses there. Can you give a precise location for how I connect the gauge? (Or a picture, figure etc. would be highly appreciated).

Does previous O2 sensor swapping test confirm if sensors ok?

(I am away until monday, so thanks a lot in advance)

O2 is fine (at lease not causing your major power loss and pinging.) find a vacuum hose that you can "T" into after the throttle plate on the manifold. One with good vacuum at idle will work. Any small vacuum hose that is relatively close to the engine will work and has vacuum at idle would do nicely.

I did some vacuum tests today.

First, I put a T bar on top of the EGR valve. (See picture

On running idle, itshowed zero Hg. I increased the RPM to 2500, in hardly changes to 2-3Hg. So there is almost no vacuum. (We should see some vacuum right? IsEGR valve faulty?)

Second, I put a T bar on top of the fuel pressure regulator. (See picture

). Onidle, it shows 18 Hg, so it is good. When I press accelaration, itdrops to 10 instantly and goes back to 18. If I keep it at 2500, itgoes high to 21 and stays there. When left to idle, it goes back to18. Braking does not effect anything. Sorry, I am a beginner, and there are many things I don't know. Please look at the picture at: Just below the EGRpipe, in front of firewall, passenger side, there is an air plug withhoses connected to it. That thing doesn't feel tight. I can I unplugit off by simply pulling it by my hand. (When it is unplugged, engineidle deoesn't change). Is that the way is it supposed to be?

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