Elusive problem, Previa intermittently running poorly

[mountainhick]

OK, It finally has warmed up enough to do some work outside. I checked for diagnostic codes... nothing. Started her up, seems fine. I am still afraid to drive anywhere without an escort vehicle. Here's why:

A couple months ago I went to town on a very cold day. Filled with gas and headed home. Under any load (uphill) it lost power to where I had to down shift 2-3 gears lower just to pull the hill, and felt like it was going to stall. It alternately felt like the power broke through a little here and there, so it would lurch a bit then fall back into powerless awfulness like it's going to die. I limped it home and parked it.

First thought, bad fuel. I went travelling for over a month and came home to the Prev snowed in with a kicked battery, I added a bottle of HEET to the fuel tank, Jump started on a warm day and it ran OK. Didn't go far, just out to the mailbox, a few miles. Figured we should give it a longer test so had my wife follow me for about 15 miles pulling hills etc (also on a relatively warmer day). It did fine.

Then the weather got very cold for a while, more snow and very wet. I went to drive again, this time just to the mailbox and here's what it did:

Hard start: did not kick right in and the cold start increased idle also did not kick in. It felt like it was missing on a cylinder and was running at about 700 rpm. I sat for a while giving a little gas to get it to warm up as it seemed like it wanted to stall. Then went to drive. Exact same behavior as the bad day I had driving home. and I noticed that when I stopped the idle was around 500rpm and again it felt like it wanted to stall.

So I posted the thread asking about engine codes. Checked codes today (it's warmer again), no codes, started right up, seems to be running fine.

So my conclusions: it is having trouble when very cold and or wet/high humidity, otherwise seems OK. Still could be a bad tank of fuel, possibly a line icing up.

Otherwise I have no idea.

Any ideas?


Update: just took it for a drive maybe 12 miles, seems fine. Happy :dance2: but WTF? :wall:

[pdgizwiz]

Here's one:

Check the coil wire, where it plugs into the coil and the distributor cap. I've found that these connections can be seriously corroded. The boots are designed to keep water out, but after 20 years in 'the mountains' it wouldn't be surprising to find that the seal had failed. And they're on the underside of the vehicle instead of on the top of a nice warm engine.
Since your symptoms are intermittent and weather related, it smells electrical.

[sited faith]

I've had this occur when my aftermarket cat had its innards break up. If they get turned sideways it blocks the exhaust. It'll idle fine but there won't be any power for hills.

mike h. '97 335k miles

[mountainhick]

Thanks guys I'll check the coil and plug wires at the distributor.)

I don't think it is the cat, I had it off a short while ago replacing a bad exhaust gasket and it seemed fine. I'll keep it in mind though.

[timsrv]

Pull the distributor cap and check for oil inside the distributor housing.

[mountainhick]

Wires and distributor are clean.

[TheMAN]

What kind of plug wires are these and how old are they? If they're the Toyota OEM Sumitomo wires, there should be a manufacture date stamped on the wires
Just because they look clean, doesn't mean they're good... if there are pin holes or a break in the carbon wires, problems will crop up during humid weather. The only way you can check wires is checking the resistance. But, all bets are off when it comes to the condition of the cable jacket.

I'd start by just replacing all of the wires and spark plugs (stock are Denso dual platinum, get at least NGK or Denso dual platinums). Check the distributor cap gasket and the look inside the distributor for any signs of oil leakage. There are also heat shields below the distributor and valve cover to prevent exhaust heat from cooking the ignition system... make sure they are there

[mountainhick]

Thanks TheMAN, I agree it's a good idea to just replace the wires at this point.

Yes, heat shields are in place.

[Tjsprevia]

I've had this occur when my aftermarket cat had its innards break up. If they get turned sideways it blocks the exhaust. It'll idle fine but there won't be any power for hills.

mike h. '97 335k miles


had the same thing happen with my prevue , aftermarket parts suck on theres things