Help, VWDOC! 96 xj pings at idel

Jo Bo did pass the time by typing:

Double check the vac hose to the fuel rail and if you took any ignition wires off or changed plugs, check for a broken plug or crossed wires.

yeah what DougW says. Make sure your vacuum hoses are good to the MAP sensor and you did not damage wiring to the TPS nor 02 sensor.

Pinging could be caused by spark timing too advanced, bad gas, too lean a mixture or low fuel pressure, bad plug causing a hot spot or maybe even a vacuum leak to name a few possible causes.

BTW what did you do since you were all over the engine? later, dave AKA vwdoc1

Well I dropped the transmission pan to replace the filter. That was complicated by the long dipstick/filler tube. I disconnected two connections by the filler tube that were tye wrapped to it. I've rechecked them. Also replaced the thermostat, coolant and air temp sensors were both off in their resistance so I've replaced them. I also changed the oil and filter and had put in the recommended amount of "sea foam" about 2 hundred miles previously. I used the recommended 10-30 oil. I also have removed one quart and put in lucas oil fortifier. This is the first oil change for me on this car with 140k on it and I believe the oil I drained out contained a large amount of "fortifier". I also replaced the distributor a month ago for a worn shaft and "think" I got it in correctly. I'm going to retard the timing by one tooth and see if what happens. Anyway to tell if the timing is correct? Oil pressure is above 1/2 on the guage, engine is quiet above 1k rpms with no or little noise while driving. Only code is "33" then the 55, ac fan clutch and the ac works fine. I've not checked fuel pressure yet. At this point I can't tell if it's a ignition knock or a wear knock. It sounds like my jetta tdi with real good fuel (quiet knock) that's why I'm leaning towards a ignition knock.

Thanks JoBo

Thanks Dave and Doug. Problem resolved! A month ago I put in a new distributor and was very carfull to get it back right. Not carefull enough it turns out. (ONE TOOTH OFF) The noise only showed after I went on my "bing" Sunday. I cleaned all the fittings on all the vacume lines. The ones to the map sensor (the thing on the firewall) were mostly blocked. Carb cleaner fixed that! Now it's a quiet as a 140k mile I6 4.0L with a cracked exhaust manifold an be. Next project, a header or at least a new manifold.

Thanks again JoBo

Jo Bo did pass the time by typing:

Yep. You have to watch that distributor real close. Also helps to have a timing light.

FYI on the Banks manifold. (I had some "fitting" issues) but it works well. a few pics.. I rilly need to do some more for that but I'm lazyand running snot out of every hole in my head. :(

would the timing light help? What would it do?

glad you solved the problem Jo Bo! later, dave AKA vwdoc1

dave AKA vwdoc1 did pass the time by typing:

Even though the base timing isn't adjustable you can still look at the timing mark and see where it lined up. In this case it would have been too far advanced. (about 9 degrees)

You can't change ignition timing at the distributor. Only where the rotor is pointing when the coil fires, which could cause cross-fire. When the coil fires is determined by crank position, which is learned from the crank sensor.

This would mess with injection timing though, which is a whole different bag of worms.

That is what I thought too bllsht! But I am always ready to learn new stuff!

I would think that the ign. timing would/could change due to CPS, CTS, vacuum and the TPS.

I would be interested in finding out how to electronic set the fuel injector timing to get the best power and mileage though!!!!

later, dave AKA vwdoc1

That's right, the computer will use those inputs to alter ignition timing for the current conditions.

Not being an engineer, I'd be interested in seeing how they come up with this stuff, but I don't think it would be worth trying to re-invent the wheel. You can bet the manufacturers do as much as they can to get the best combustion they can already.