Momentary valve tapping at high speeds

[emfjsullivan]

I've got a '93 Navajo (Sport) with about 120k miles on it. It's a 5 speed manual.

Looking for ideas on isolating an intermittent problem I've been experiencing.

Symptoms: About 2-3 hours into a long trip (typically 6-13 hour trips), while going about 65-70mph with my cruise control on, all of a sudden, I hear a short burst of valve tapping (2-5 seconds). This is usually accompanied by the check engine light coming on either before or after (can't remember which). The tapping will go away, but then the check engine light may come on intermittenly for a while (next hour or 2), as well as the tapping may come back intermittenly.

The only other info I have that may be relevent (I say may because this has happened before I did all this), is that I'm using 20w50 vs. the 5w30 speced (the shop that did the oil pan gasket replacement put in the 20w50); I just replaced the intake manifold gaskets (all) and valve cover gaskets; plugs; inition wires and cleaned the MAF. I used to have the octane plug shorted, but no more once I learned about the leaky intake manifold and MAF cleaning.

Any ideas on how to isolate the problem? I do have an OBD tester if I need to drive around w/ it connected.

Thanks

 

[JDraper]

I'd start by looking at the oil pressure. There was an issue with some of the older 4.0's having a problem with the oil pump pressure spring breaking and causing intermittent loss of oil pressure. The oil pressure gauge on your dash is not a true pressure gauge, it's more of an idiot light. If I remember correctly, it just measures no pressure, good pressure or high pressure, but nowhere inbetween. You might want to consider looking into hooking up a true oil pressure gauge to see if a loss of pressure is causing your problems.

 

[410Fortune]

Also the speed you are traveling is irrelevant, the RPM of the engine are relevant, so at 65-70 with OD on I am guessing your RPM's are around 2000?

20W 50 is heavy stuff, asking more from your oil pump..........


Did it ever do this with the 5w30?

 

[emfjsullivan]

The oil pressure gauge is an analog one, and I assume measures a range of pressures. What would be the best way for a do-it-yourselfer to measure pressure? Are there cheap gauges out there?

The RPMs are about 2000-2200.

I do believe it did it w/ the 5w30 as well. I originally put synthetic in, and thats how I found my oil pan leak. Put normal oil (5w30) in after that, and it still occassionally happened. Doesn't happen alot, but it is noticeable when it does.

Thanks

 

[JDraper]

Originally posted by emfjsullivan
The oil pressure gauge is an analog one, and I assume measures a range of pressures. What would be the best way for a do-it-yourselfer to measure pressure? Are there cheap gauges out there?

If you're talking about the factory gauge, it looks like an analog gauge, but it's really a 3 position switch with a resistor on the back to make it look like it's functioning as an analog gauge. There are bunch of threads on the board about it.

You can add a true oil pressure gauge to your truck fairly cheaply. Dead Link Removed sells a mechanical dual water temp and oil pressure gauge set for $17.99 (P/N SUM-G2924). You would also probably need a tee adapter to hook it up with your normal dash gauge.

 

[410Fortune]

I have mechanical oil and coolant temp gages on my 4.0L, the stock gages make great paperweights, thats about it...........
The good news is the oil level light still works even if you use an aftermarket pressure gage.......