pspees

Hi everyone, my 92 pickup/22re has developed a noticeable and annoying knock or ping around the 70 mph range. It's fine until I have to push it a little, like up a slight hill. Then it sounds like shaking a can of spray paint. Original engine has 300k and otherwise runs smooth.


I started using higher octane gas with little to no improvement. Changed the timing chain set with no improvement. No check engine light, timing is set to factory spec. Always keep it tuned up.


I'm just wondering if this is common for these engines and if there's something typical that usually causes this or is this something that's leading to big problems? Thanks.

nothingbetter

not sure if its a common problem but check your valve clearances. I had an exhaust valve that was way to tight. It got really hot from not touching the head long enough and would preignite the fuel.

Also check the usual things like your timing and spark plugs.

pspees

Thanks, I'll be checking the valves soon. I'll follow up when I'm done.

Nogarage

I would check the EGR valve. Could be stuck closed. They get crudded and stick open or closed. Not hard to check.

pspees

So it's been a few months but I've adjusted the valves, didn't help. Had the EFI serviced/cleaned. Didn't help either. The only thing that made a difference was backing the timing off to about 2 degrees; a band-aid repair and a sacrifice of power and gas mileage.


I'm curious now if the distributor is the problem. That or something else is screwing with the advance and allowing too much at high speed. I know that the distributor's advance is controlled by the computer with some kind of sensor. Maybe the distributor's advance function isn't right? What can cause that? Thanks.

millball

Did you check the EGR for correct function as previously suggested??

EGR acts during high speed cruise conditions, and if it does'nt, a lean condition can exist that will cause pinging.

pspees

Haven't checked EGR. Checking I guess is done by applying vacuum to the EGR valve with engine running and noticing a change? Thanks!

millball

Applying vacuum to the EGR valve while the engine is idling should make a big difference, probably kill the engine if the egr valve is good. This only proves the valve itself though.
I don't know the procedure for checking the control circuit, maybe someone else will chime in, or you could consult the Factory Service Manual.

pspees

Applied vacuum to the EGR valve, engine almost died so I'd say at least the valve is good.


Good point about the vacuum circuit. I wonder if one of those vacuum switches or control thingies on top of the engine isn't working right? I had a problem with the EGR modulator in the past but that caused the engine to run really bad. As of now it's running great but pinging like a mother on the freeway!

combatcarl

Might see if the modulator is operating correctly, or all it's vacuum lines are routed right/functional. I don't have my book, I'm at work. But if your valve appears to work, I'd look at the modulator. It's what tells the EGR valve when to open. Should be open at part throttle (to varying degrees) and closed at WOT and idle. Here's a little info, it's what I could turn up on my phone at work. Maybe not quite correct year, but they're all pretty close in function and operation/design.
http://forum.ih8mud.com/threads/egr-...orrect.389631/

Mr. No SPAM

Do you still have the vacuum system diagram sticker on the inside of the hood? If so it's an easy way to check things being connected properly.

pspees

So I found something. Connected a vacuum gauge to the EGR valve and only got 2 in. of vacuum driving around the block. Based on the vacuum diagram under the hood everything is connected right but one of the hard lines "R" between the throttle body and the EGR vacuum modulator is clogged. It's one-way so I'll bypass it with a hose and see what that does. I'm guessing that the EGR valve isn't seeing as much vacuum as it needs to open all the way due to the modulator not working right. I'll be back later...

combatcarl

Might be headed in the right direction, then. I have no idea how much vacuum is sent to the modulator. But bypassing the hard line will probably tell you if that's the issue. I've seen fine wire run through those hard lines, to check which end goes to which other end, maybe doing that would remove any clog?

RustBucket

iTrader: (1)

I had a bit of this issue when I removed my EGR. Running colder plugs helped. If I recall you switch the 16 with 20 on the denso plug part number or something like that.

Mr. No SPAM

A clog that was causing problems in my system was in the line that runs off the EGR manifold to the bottom of the modulator. The steel fitting that comes off the manifold was clogged. Running a piece of solid cable wire attached to a drill down that hole cleared it out and restored good EGR behavior. I had the EGR valve assembly off for that job.

300k on that engine? How's compression? How do the plugs look? Any hint that it burns oil? Carbon deposits on the piston top and in the combustion chamber in the head can cause pre-ignition too.

kcaudill

Mine was doing this as well, Found a couple lose manifold studs around number 4 cylinder. Had to replace the gasket. after that all was good again

pspees

Backstory:
Had a NEW head put on at about 250,000 miles. Ran great for a while but started pinging some time after the install. NEVER did before. Compression test shows ~180 psi in all 4 cylinders. Oil consumption isn't an issue after getting the new head and mechanic said cylinder bores looked good. It does foul the plug in #4 pretty bad since the head job. Other 3 are clean.


Back to the EGR: I found that a couple vacuum hoses were switched around at the throttle body, put them where the diagram says. Also, throttle body port "E", which the diagram says goes to "P" on the vacuum modulator was plugged so I cleared it out. Checked the modulator, checked the vacuum lines. Still pinging like a SOB. So bad sometimes it scares me. It's driving me nuts.

bswarm

What kind of plug fouling? If it's oil fouling, that might be your ping.

pspees

Best I could get with my old camera. It's black but not oily.










It's only one plug, it looks black, but not oily, with a bunch of gray stuff plastered to it.

This pic is a little better. It just looks burnt when the other 3 are clean.

combatcarl

Yeah, there's some buildup in that cylinder, somewhere. And possibly others. The other three look like this?