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Wet weather causes crappy running, no power

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nedfunnell

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Hello all,
I've got a BMW 325e from 1985. I have a symptom where sometimes, and I've noticed it more when it's wet, I'll have the engine bog down and give me no power. It happens when I'm accelerating away from a stop- I'll get to about 2000 RPM in second gear, then all of a sudden I'll have no power at all. It feels like there's some serious misfiring going on. If I put the clutch in, the engine will rev without trouble, but getting going is very difficult. If I put my foot into it the engine will eventually get some steam going and the problem goes away once I'm up to speed or the RPMs are higher.

I'm guessing this could be caused by a spark issue. I know that my plugs need to be changed from the way they looked when I pulled them out to do my valve adjustment. I will change those. I am wondering also if the wireset and distributor cap need to be changed too. The ones on there don't look to be in awful condition, but they are an OEM brand so they -could- be original with 160k+ miles. I haven't looked under the distributor cap. The wireset and distrubutor cap are non-trivial in price, so I don't want to go for the 'throw parts at it' method of fixing.
Thanks!
 
Sounds like wires are shorting out on the block or head. Always do a cap-rotor-wires-plugs at the same time, even if they "look" ok. But what you say is true, and only happens when it is wet outside, then this is what you need to do.
 
Is it 'bogging down' or 'misfiring like a sonofabitch?'

If the latter; spark issue. Likely a cracked coil, especially if it's mounted in a vulnerable position. VW used to like to put them on the firewall, where water would drip down from the cowl onto them. Dunno about E30's, but I'd wager it's something similar.

'Bogging' is more of just a hesitation issue...the engine is reluctant to actually rev and make power. Misfiring causes the engine to run rough and vibrate excessively, due to the imbalance caused by the erratic power output of one or more cylinders. People not familiar with the term 'misfire' seem to like to use words like 'shaking' and 'bucking' or similar to describe it.
 
Ferzerp: EFI.

Funboy: Wires are in a shroud/holder/runner that keeps them off of the block and head. Why do they need to be done at the same time?

Phucheneh: I'm not sure I understand the difference.

Also, a clarification. This happens somewhat rarely. It's running fine right now.
 
Well, if your stuff is oem to the car, be lucky it lasted this long. It all starts to break down, and really should be replaced every 35-40k or so. Also your taking the wires off, so you may as well change them since they are cheap. Plus its the smart thing to do with that many miles, for it would be like changing a timing belt and not doing the water pump while you have it apart. OH and if that thing has a belt for the timing, you may want to get that done ASAP as well with that many miles on the car. Those need to be changed atleast every 60K.

Come to think of it a bad timing belt could be causing your problem as well since it is stretched out and making the timing of the motor and valves go nuts, and cause you to have no power. And if that goes, chances are its going to take your head with it, bending valves and busted through pistons.
 
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...sometimes when people change the water pump as maintenance, they do a poor job sealing it, or the aftermarket pump goes out sooner than the OEM would've. But I understand the concept; and it generally proves worthwhile.

Plug wires are a little overdone, though. As long as you don't rip the terminals off (hell, even if you do, they can be fixed), wires are always the thing I reuse if someone is low on funds. Cap/rotor and plugs are usually what's causing a generally poor running condition. Wires are more likely to just cause one steady misfire, and it usually only happens when they're torn or abraided.

For the money, it is good practice, though. I just work on cars for poor people too much.
 
funboy6942 said:
Well, if your stuff is oem to the car, be lucky it lasted this long. It all starts to break down, and really should be replaced every 35-40k or so. Also your taking the wires off, so you may as well change them since they are cheap. Plus its the smart thing to do with that many miles, for it would be like changing a timing belt and not doing the water pump while you have it apart. OH and if that thing has a belt for the timing, you may want to get that done ASAP as well with that many miles on the car. Those need to be changed atleast every 60K.
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Autozone wants $113 for a wireset. Not cheap enough to do just because I have the wires off. I'll order a set from Rockauto for $40-60 if I need one, but I don't fall into the camp of "Better replace everything to be safe"

Come to think of it a bad timing belt could be causing your problem as well since it is stretched out and making the timing of the motor and valves go nuts, and cause you to have no power. And if that goes, chances are its going to take your head with it, bending valves and busted through pistons.
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It's occasional, not persistent.
 
My old 89 Mazda 626 had the exact same issue. Would randomly stall every time it rained. Turned out it was moisture getting into the distributor and shorting it out. Tossed a new one in there and it was fine.
 
nedfunnell said:
Autozone wants $113 for a wireset. Not cheap enough to do just because I have the wires off. I'll order a set from Rockauto for $40-60 if I need one, but I don't fall into the camp of "Better replace everything to be safe"



It's occasional, not persistent.
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If wires are causing the issue, you can usually see a visible arc.

As others have said, it's probably the cap/rotor or some other seal on the distributor that's letting moisture in. Or the ignition coil- where is it mounted? It's an epoxy (solid, not oil filled) coil, right?

Good way to troubleshoot this: get a spray bottle with a 'mist' setting and fill it with water. Start engine, and spray parts one by one, looking for a repeat of the problem you experienced. I'd start with the coil, then the dist, and any associated wiring/connectors. If those are all moist and no problem is seen, they make your way down the plug wires.

After spraying each part, you may want to load up the engine; these types of issues often do not manifest at idle. If it's an auto- put the ebrake on, push firmly on the brake pedal, put it in gear, and give it a little gas. This will put a load on the engine similar to acceleration from a stop (but you don't have to go anywhere).

If it's a manual, you may need to just drive it.
 
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I had a 1983 BMW 325e with the same problem. In my case it was caused by a cracked intake tube that had been "patched" with duck tape. When it was REALLY wet, water would get under the tape and make the engine stutter. HEET would help, but not permanently. Replacing the intake tube corrected the problem and it never came back.

That car was a bit of a problem child in other ways, though, and so I traded it for a 1989 Toyota Celica. Eventually it developed the same problem, along with massive leaks in the sunroof due to rust and a whole host of other issues. I never completely figured the wet-weather issue out, but I think it was electrical in that case.

My first two cars were pretty serious beaters.
 
I ordered an intake tube. Mine has some cracks that the PO (manimal) RTV'd but he advised me to replace it before long- looks like before long is now. If that doesn't do it, I'll see about the ignition system.
 
I believe those Bimmers have mass airflow setups, so yeah, that's a good idea. Any air leaking in behind the MAF will cause issues. You usually need a pretty decent hole to make it idle rough, though, and the engine will tend to want to die.
 
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