I was wondering if you fine knowledgeable folks could help me diagnose this miss on my 99 Limited?

1999 Limited
153k

I THINK it's a miss but not 100% sure. It only happens during idle or in Park, never while driving. It will be idling just fine and then suddenly it will "thump" which shakes the vehicle slightly and then continue idling normally. Sometimes it does not do it and sometimes it does it 2-3 times during a stop (a couple seconds apart).

I started noticing it a few weeks ago when it would do it once during a drive but now it's more frequent.

I ran out of gas a couple weeks ago (faulty gauge) if that matters.

I'm gonna continue searching but any help is greatly appreciated.

Thanks

Is the CEL on?

Get your codes checked. I recently had a rough idle along with shaking and a CEL. I was getting misfires on 3 and 4. I replaced plugs and wires and that fixed it and just cleared the CEL last night.

But go check codes and maybe pick up some NKG wires and plugs, or Denso plugs. At least you could cross that off the list.

No codes or CEL but I'll scan it anyways. I have a scanner.

I do have plugs, wires, and a WHOLE LOTTA additional parts on my bench ready to go on as soon as it stops being so damn cold out.

Hahaha... I hear you on the weather front. I begrudgingly realized that I couldn't get my lifted vehicle in my garage AND prop my hood up. So, I had to work outside with Low thirties and 20+ MPH wind gusts. I consider myself lucky. At least it was sunny for the most part. And it could have been a lot colder. I can't say that it was fun. But, it was that, or pay someone about $300 to do it. I opted for putting on some warm clothes and taking care of it. LOL.

Yeah the cold makes banging/smashing fingers a whole lot worse!

I'm used to working out in the cold and snow but I recently recovered from a battle with pneumonia so I don't want to push it for a while.

Is your garage lower than normal? I had my 4runner on 6" ramps in my mother's garage and had plenty of room to open the hood. I have 265/75/16's.

It really sucks to have to use ramps just to get to the oil filter. What a PITA that was. I am removing the skid plate next time.

Yeah my garage was made for Hobbits and the support beams are super low, like maybe just 6 feet or less. That's what's called a first house purchase oversight. I won't make the same mistake. I also have 265/75/16s with a SS 1.2 rear lift and about 3" up front with some King COs. I don't think the builders of my house in the mid 1950s had large SUVs in mind when putting hammers to nails. Lol.

Maybe there is somewhere that you can rent a heated workspace.

Being sick just makes the weather suck that much more. I think I read somewhere on here that misfires might not trigger a CEL all the time. But it is still worth checking.

The hobbit garage explains it. LOL. My mother had a similar type garage before she moved into her current house. It was 5 feet high, just enough to get a car in and had no garage door. Weirdest thing ever. You had to duck just to walk into it.

I'm gonna swap in new plugs and wires and see what that does. I did go over the previous owner's maintenance records and I do not recall seeing a tune-up done to it within the last 50k. I have to go over them again and see exactly when it was.

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lolololololololo!!! Great shopping skillz man.

Well done sir. I hardly have enough room for second breakfast, brunch, lunch, supper, dinner, second dinner provisions.

Funny thing is, I fit in okay when I knows Dan the other day to just store it while I went out of town. But when I try to open the hood doing the same thing the top visor was hitting support beam.

So I was like well maybe there's some clearance if I back in. I carefully back then going very slowly but I kept hearing some very light contact. I looked and so am I rear passenger wheel touching a cardboard box and I figured that was the noise. It turns out it was my factory rack rails just kissing the bottoms of the beams.. I got lucky.

Air down the tires to about 8 psi. That'll give you a couple inches. You just need an air compressor to get em back up when done.

Drove it to work today and it started missing continuously once I stopped in the lot. I hope it will get me home.

That sucks. The same thing happened to me. Just keep in mind that if these cylinders aren't firing, they are still getting fuel. I wouldn't drive it too long like that. Like, 'maybe' home and park, as long as home is a short distance. Now, do you want to fix it yourself and freeze, or pay someone gobs of money to do the same?

I'm gonna do it tmw after work. I drove it home and it did not misfire at all. Very strange. I did pop off the cover for the air filter after buying some plugs and it's pretty dirty. I'm guessing the plugs will look like hell.

So the temps were in the 40's today and no precipitation (rare) so I headed outside with some NGK plugs, wires, and air filter. Everything looked good until I got to Plug #3 which was not tight. I could thread it a few more revolutions before it was snug. I believe this may have been causing the miss. The coil pack on that plug was pretty soiled at the tip that goes over the plug so that tells me ignition residue was escaping around the plug. The old plugs were denso and worn a bit but not terrible.

I did notice oil coming out of the tube that connects to the top of the air filter near the throttle body. Some oil residue inside the main air intake tube. I'm not sure what's causing that but it warrants a tear down and cleaning of the throttle body.

I drove around the back roads stopping here and there. There is no miss and the idle is exceptionally smooth. I didn't realize a 153k mile engine can idle that nice.

We'll find out if the miss is gone for sure tomorrow when I take it to work.