QuestionQUESTION: Hi Howard,
I removed/cleaned the throttle, oil breather screen and tubes. I also removed the oil in the intake manifold. I found there is a drain plug in the manifold on the opposite side of the throttle, so it must not be too much of a problem. Spark plugs are cleaned and gapped correctly.
Unfortunately, I still have the poor idle/drive problem. I've also noticed that the idle seems to go up and down slightly when it is acting up.
The O2 sensor has two identical white wires that go to a plug, and a black one by itself that connects to a thicker blue wire, which is where I connected the voltmeter. The reading would quickly cycle from .66v to .54 to .33 then nearly nothing before starting again. I unplugged it and the O2 sensor gave me a .75v constant reading.
Timing was hard to read since I can't get hand on the pulley to clean it. If there are numbers, I can't see them. I did see the marks, though. My timing seems right in the middle...about 6 marks from the right. The A/C compressor is in the way and it is hard to see it straight on.
I removed all the plugs and did another compression test. Engine was not hot, so dry readings are a bit higher. This time I used only a teaspoon of oil.
1=150/160wet
2=145/160
3=160/170
4=160/165
5=155/170
6=150/155
Just so you know, the night before the car started acting up I had installed a different radio and replaced an A/C hose and tested it for pressure. The very first thing I checked were the wires and connections around those things when I had engine problems. I'm assuming it is a coincidence, but thought I'd mention it.
Thanks again,
Dave
ANSWER: The compression readings look ok but the 0/2 readings of .75 v(unplugged)if this was a warmed up engine is too rich on mixture. It should be close to .50 v to be correct. Things to look for that can cause this are, Mixture adjustment on air flow meter set too rich, coolant sensor readings off when hot (should be about 100 ohm.), leaking injector (difficult to test) (however it may show up as a single spark plug showing flat black color when left idling for a good length of time after a good cleaning), Cold start valve leaking (may show up as flat black color on several plugs)
The ser III are noted for rough idle but even when they had a rough idle they should run good above idle.
A rough idle and poor acceleration off idle was a symptom of carboned up intake valves also. If all else fails try to find someone who has a bore scope and remove an injector and it's seal sleeve to look at the valve. If you can't locate a bore scope you might be able to see if you get one of those tiny probe lights and set a cylinder so the intake valve is open and pull that spark plug and with the little light dropped into the spark plug hole, look at the under side of the valve head. The coked up valve gets so much carbon that it disrupts flow and absorbs much of the fuel sprayed in by the injector that it gives a rough idle and poor accel off idle. Even though the same volume of fuel gets through, it comes off of the valve in droplets instead of a spray thus poor vaporization. My ser III suffered from that at about 65,000 miles. Many of the Jags I had the head off of also suffered from it too.
Howard
---------- FOLLOW-UP ----------
QUESTION: Yes, engine was warmed up for the O2 sensor readings. Bad o2 sensor maybe?
I have a different MAF on the car now then when the symptoms first started. This one still has the seal over the mixture screw.
I think I'm going to start with the cold start sensor leaking possibility. All the plugs were black. Also, I had it out early in the summer when my car wouldn't start (which turned out to be water in the gas tank). Maybe I encouraged it to start leaking somehow.
Thanks again. I'll let you know...
Dave
ANSWER: Dave, you already got a reading from the 0/2 sensor why do you not believe what it tells you? Clean all of the plugs and run the engine at the RPM that it runs bad (idle) then after letting it run for a while remove the plugs and look for the signs of a rich mixture (flat black dusting of the plug) This would confirm the 0/2 reading you already have. You have done this and you have conformation that it is running too rich.
Now all you need to do is track down why it is too rich. The possible reasons are,
1. Fuel pressure too high
2. Air Flow Meter set too rich
3. Cold start valve on or sticking open
4. Injectors leaking (this would only effect that cylinder)
5. Fuel pressure regulator diaphragm leaking
6. Injection coolant sensor feeding false info to ECU
One or more of these is causing it to run rich.
Let me know,
Howard
---------- FOLLOW-UP ----------
QUESTION: Only reason I mentioned the O2 being bad is I thought a symptom was making a computer run rich, making the plugs have the black coating.
However, you are right. I pulled the plugs out tonight that I installed yesterday. They were dirty again (black). I removed the throttle ducts and looked down the throttle valve...again I had about a teaspoon of oily black liquid. When I cleaned it out, it smelled like fuel. It is not coming from the breather...I checked the line and it is clean (since I just cleaned that yesterday, too).
Tonight I pulled the cold start injector and tested it with the pump running. It did not leak. I also pulled all the injectors and tested them for leaking...they didn't. They also spray gas when cranking the engine like they should.
However, with the key on and pushing on the air flow meter flap (engaging the fuel pump), I heard what sounded like gas spraying. I tracked the sound down by using a screwdriver like a stethoscope. It was coming from the fuel regulator. It sounds like fuel rushing through it even though it isn't going anywhere. Could that be indicative of a leak in the diaphragm? It's really the only thing left on that list.
I appreciate your patience and wisdom in helping me get the Jag back on the road.
Dave
AnswerDave, the regulator does operate when the pump is on because most of the fuel that is pumped up to the regulator is sent back to which ever tank you have selected. This fuel goes to the AC cooler unit mounted on the AC compressor. Then it returns to the tank. So you should have fuel passing through the regulator. It is easy to test by just activating the pump as you did and remove the vacuum line from the regulator and see if any fuel at all comes out of the regulator. You can at that time shake the vacuum line to see if any fuel is in it as a regulator can leak just at times.
The 0/2 sensor is just a trim on fuel mixture. The coolant temp sensor for the ECU is a major fuel mixture control as is the air flow meter. The cold start injector should never run when the engine is running as it is only opened in the ignition "Start" position and it is disabled by it's temp sensor in the coolant rail even in the start position. The air temp sensor in the air flow meter is also only a trim control.
How many miles did you say were on this engine? Most XJ-6s I worked on carboned up the intake valves at from 60 K on up to 100 K miles.
Howard
