SOLVED: 1998 S70 base - rough idle, odor, undrivable (culprit was distributor cap) Topic is solved

[MagicBus]

That's not enough to go on?

If you turn a garden hose on to a trickle the water flows without any opposition. If you turn on the water full blast the water has to fight to get through the hose. If you restrict the flow with a hose nozzle it has to fight even more.

Your trying to find out if large volumes of exhaust gasses are fighting like hell to get through. If large volumes of exhaust gasses are fighting like hell to get through, there is only one thing that can cause it, excessive opposition to flow ...a clog.

I'll be more definitive tomorrow, but I started the S70 this morning briefly and had no trouble getting to 5K. Didn't put the window down to listen, but will do so tomorrow.

[wizechatmgr]

Does it sound like there are a bunch of marbles (rattling) in the exhaust? I had a converter melt down that once had some of those symptoms. Little rattle at idle, but no rattle at speed and no power either. It was what was left of the converter jamming up against the exit of the converter.

[MagicBus]

Does it sound like there are a bunch of marbles (rattling) in the exhaust? I had a converter melt down that once had some of those symptoms. Little rattle at idle, but no rattle at speed and no power either. It was what was left of the converter jamming up against the exit of the converter.

Not a bit, at least not at the moment. I do know that sound, and will listen for it today when I check things. Just starting my day here.

[MagicBus]

OK - so here's the update, and it's not looking good.

I want to stress that the car has been running flawlessly since I bought it in September, 2016, and I haven't had to add any oil between oil changes, with the exception of half a quart this past cycle (now due for an oil change).

So, this morning I started the car (started fine), but definitely ran like it was missing (at least sometimes) on one cylinder. I warmed it up a few minutes and revved to 5K without any issue. Windows down, no teakettle noise. I don't think I have an exhaust restriction. I let the car run a few minutes to warm up. I still had some misfiring as evidenced by the blinking light, but not constant.

Then I pulled the fuel pump relay. The car started with a sputter and then stopped when it ran out of fuel. I want to stress that I've started the car maybe 10-20 times since I got stuck on the side of the road. So, I'm now reasonably sure the fuel system is OK (which was my first suspect). Then I disconnected the new coil (which may or may not have been wonky - I'm sure the car is running better with the new one).

Then I pulled the plugs. Once was noticeably carboned. Cylinder 4, I think. Then I ran a compression test. The numbers weren't good. The numbers I found online were for a 1993-1997 non-turbo 850, but I imagine they'd be the same for my 1998 S70:
1993-1997 850 Non-Turbo: 185-213psi

I don't think my compression tester was making a perfect seal (I discovered a missing o-ring near the end of this process), but here's what I got:
cylinder 1: 185 PSI
cylinder 2: 179 PSI
cylinder 3: apx 75 PSI
cylinder 4: apx 150 PSI
cylinder 5: apx 150 PSI

At the end of the process, I noticed that the o-ring where the compression tester seals into the engine was gone. So, I suspect that I didn't get a perfect seal and my numbers may have been a little low as a result. I may check cylinders 4 and 5 again...

I replaced the o-ring with a new one and re-ran the test several times on cylinder 3. Unfortunately, the numbers came up the same.

At that point, I decided to do a wet compression test on that cylinder. I may have added too much oil (it really only felt like a little bit), because the compression went up in that cylinder over 300.


So, unless I'm having difficulty just getting the tester to seal in that cylinder, I'd say that the valves are good, but there's something piston/cylinder/ring going on there. Probably no longer worth my time. I don't have the time to put a used engine in it nor the money to have a shop do it, so barring a miracle, I may be car shopping soon.

If I can, I'll tinker with it and see if I can get it good enough to get me in and out of the office this winter.

[MagicBus]

Edited - see below

I re-ran the compression test with the new o-ring and all cylinders showed big improvement. It's icy out there, so I have to think the engine cooled down a bit, still skewing the numbers. Cylinder 3 is still problematic, compression-wise.


I put everything back together and started the car. Still ran like crap. Tried to move it forward and back in the driveway - still stalling.

I wanted to leave no stone unturned, so I took out the airbox and removed the distributor cap... AND FOUND A BUNCH OF MOISTURE INSIDE. Where it came from and how it got there, I don't know. I'm not offroading this car. I drive through the suburbs to a desk job in this car, for the most part.

Anyhow, I dried the cap and rotor and put it all back together. The car sprang to life and sounded perfectly healthy again. I moved it back and forth in the driveway with no issues. I'm going to take it for a spin, but it looks like I'm back in business. If cylinder 3 stays quiet, I won't question it.

Interestingly enough, and this was a clue, the first time I started the car again after the compression test and clearing the codes, the misfire I got was for cylinder 2.


Thanks again everyone for your input.


Update - I let the car warm up a bit and then took it for a spin around the block. It's still low on power, stumbling, and feels like it's missing on a cylinder. I'm currently at a loss. Going to have some lunch, pop the distributor cap off again and go from there.

[RickHaleParker]

At that point, I decided to do a wet compression test on that cylinder. I may have added too much oil (it really only felt like a little bit), because the compression went up in that cylinder over 300.

1 tablespoon of oil measured, don't guess. Plastic Measuring spoons are dirt cheap.

Anyhow, I dried the cap and rotor and put it all back together. The car sprang to life and sounded perfectly healthy again.

Good to hear you got it drivable again. You might want to put a thin bead of RTV on the edge of the cap to prevent this from happening again.

Cylinder 3 is still problematic, compression-wise.

The rings on #3 maybe stuck due to carbon buildup.

• Pull the plugs out
  Pour 1/5 bottle of Seafoam in each cylinder.
  Stuff a rag in each spark plug well.
  Let sit for 24 hours.
  With the rag still in the spark plug wells, crank the engine to push out the Seafoam.
  Remove rags, reinstall plugs.
  Start engine and bump the RPM up to 1500 and hold.

The exhaust may turn black, this is carbon that the Seafoam ate up, it will pass. It might take 20-30 minutes to clear up but it will.

Take the car out for a drive, give it some hell to knock out stubborn carbon.

Get it home, let her cool down. Redo the compression test on #3.
With luck, the rings are unstuck and you got compression back.



the

[MagicBus]

Final update - car back to normal. I'm a dumbass. When I put everything back together after looking at the distributor cap, I neglected to properly re-seat the intake boot, introducing a new problem with eerily similar driveability symptoms. I re-seated the boot and all is good.

As for cylinder 3, I'm still thinking that maybe I didn't get the compression gauge to seat properly in that cylinder. The car just runs too smoothly to be running with one cylinder that low on compression. Maybe sometime in the future, when it's not so cold, I may try that Seafoam trick.

I just picked up a new distributor cap from the store, just in case the old one is cracked and that's how moisture got in there. Though I may try with RTV like you said.


Anyhow, I just drove the car approximately ten miles and all seems to be perfectly back to normal. Tomorrow, I'll change the oil and get on with my life.

[wizechatmgr]

Good deal.

You could also smear generous amounts of dielectric grease around the seal of the distributor cap.

I used to have that intake problem when working on the older "new beetles." Their intake boot is/was some sort of what felt like rubber and over time it deteriorates to the point where you have a fight to the death to get it on - just to find out it isn't sealing...

[RickHaleParker]

I just picked up a new distributor cap from the store, just in case the old one is cracked and that's how moisture got in there.

With the engine running, lift the hood in the dark, see if you have a personal thunderstorm under the hood.

[wizechatmgr]

The electric light show =)

Also doesn't hurt to mist it. Occasionally wires may not have boots in great condition. I've previously used wire dryer in a can. Believe it was some form of light weight silicone or oil like liquid - it helps if the wires are marginal.