I drove my '94 Toyota pickup DLX 350 miles down to Illinois over the holiday, and then a couple hundred miles into Wisonsin yesterday, when I started hearing this ticking sound coming from under the hood - directly related to the rpms. I could only hear it when I'm asking the truck to drive somewhere (if I step on the gas while in neutral, no strange noises....only when accelerating and driving). Any ideas what could be going on....I've heard rumors it could be a sticky lifter, also wondering if the exhaust manifold is leaking? It was dark and I didn't have a flashlight, so I don't know yet if there are obvious signs of anything leaking, but I'll look closely tonight.

Any ideas of what to look for and how to diagnose this?

Thanks!

Jeff

Which engine?

22R

Your *rockers* probably have worn valve adjustment screws. When they wear flat, they'll start making noise. Easy enough to replace.

Exhaust leak, carefully hold your hand near the exhaust manifold to feel for a leak. I sometimes use a scrap of rag to see if it'll blow around; less likely to get burned. A leak will allow noise to amplify.

well, I just started it up and did feel an exhaust leak towards the front of the manifold. I'll try tightening up the mounts tomorrow to see if that helps. Otherwise I guess it's time for a new gasket?

Might want to check if a exhaust manifold stud backed out, it happened to me last week ... driving down the highway when I heard a loud "ticking" noise. Initial thought was someone had an exhaust leak and then realized that person was ME! <img src="/forums/images/graemlins/lol.gif" alt="" />

Well, I tightened up the manifold and exhaust-to-manifold bolts, and still get the loud ticking when accelerating. If it were worn valve adjustment screws, wouldn't the noise be loud all the time? Is it as easy as taking the valve cover off to check the condition of those screws? I also noticed a very slight wetting around the edge of the valve cover...could be a bad valve cover gasket, but would that cause (or allow to be heard) the loud ticking?

One last idea I had is to put a quart of Lucas bros oil stabilizer in there. I always use that when I change the oil, but I recently had my oil pan resealed and the shop changed the oil for me. Don't exactly know why, but for some reason I think my engine really likes that stuff.

>>>*One thing that might be happening is that exhaust leak is probably still there. Just snugging up the bolts may not completely seal the leak.

A leak around one exhaust port will make a noise similar to the one you describe, which is demonstrate under load yet quiet down at idle.

I would suggest changing the gasket, and while off check for the fairly common vertical crack on the inside of the manifold right in the center of the inside curve.

We see that quite a bit and it makes a sound like something banging around in there at engine speed while under load.

*The valve cover gasket will not cause any noise although an overly tightened valve cover can cause the rocker arm to contact the inside of the cover. We snug those holdown bolts just enough for the grommets to begin to bulge out, it won't fall off.

Another under load noise we find outselves chasing is a single cylinder ping. This is a bit like a soft tapping noise, the cause is usually carbon buildup from a cylinder using a small amount of oil. The stock compression ratio on the 22RE engine is pretty close to the edge for regular fuel, it doesn't take much to create some pinging.

If suspicious of that, run a tank of premium fuel through her, if the noise goes away then you know for sure.

One fix that often works if you do have some carbon buildup is to head out to the drag strip. Some nice full throttle runs will usually blow the carbon out..Besides, the Mitsubishi guys will have to give you a good head start....*LOL**....*EB

Thanks for the very informative response and suggestions! I'm awefully tempted to go check into that right NOW, but new years eve is calling (and it's freakin cold out - I have only a snowy gravel driveway to work in)! I will pull the manifold off this weekend, check for that vertical crack, and replace the gasket....hopefully that does it.

I've run a fuel injector cleaner through one tank, and I'm working through another full tank with injector cleaner right now (I also have a surging idle, checking to see if something in the throttle body's getting stuck, but I have a feeling it's a vacuum leak). Once that tank's empty, I'll try out the premium fuel idea, if the new manifold gasket doesn't cure the issue.

Thanks again, happy new years everyone!