1986 Toyota Corolla '86 Corolla, Cylinder Dropping out at L

Tiny
51MINX
  • MEMBER
  • 1986 TOYOTA COROLLA
  • 4 CYL
  • FWD
  • MANUAL
  • 243,000 MILES
This is car model AE82 with the carburated sohc 1.6L model 4A engine.

As fuel consumption increased about 20% since last summer, last week I replaced the oxygen sensor.
That didn't affect the problem much, but after a couple of days, #1 cylinder went dead at idle.

The car runs noticeably rough up to about 2000 RPM where it seems to even out and produce reasonably good power.

The plugs were old and I immediately changed them, but that had no effect on the miss.
#1 cylinder is dead at low speeds, even when spark wires are exchanged between #1 and #2.
The same problem persisted when I substituted the original distributor cap, which I had previously replaced due to a crack causing misfiring in wet weather.
There had never before been a discreet miss problem associated with this cap in dry conditions.

Over the past few months, I had begun to suspect a valve problem was developing due to a few backfires when the car accelerated from a stop from upward inclines during warmup.
This has occured about 5 times since early winter.

Today, I checked compression on #1.
The first surge of the gauge yielded a reading of about 150psi.
Brief cranking brought the reading to 174psi.

I removed the valve cover and everything seemed to be in order.
The valve lash, which I had adjusted last summer, was comparable between #1 and the other cylinders.

The cam lobes looked fine and the valves and springs all appeared to be working normally.

I'm wondering what else might account for one cylinder dropping out under the circumstances I've described?
Thanks.
Dale Myers
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Friday, February 29th, 2008 AT 5:28 PM

2 Replies

Tiny
M8TRIX01
  • MEMBER
I think you might be dealing with a vacume leak. A quick and easy way to rule it out is, with the car running spray some carborator cleaner in short bursts around the base of the carborator and the visible vacume lines and then where the intake manifold meets the head. You will be looking for a change in the way the engine is idleing. If there is no change no vacume leak. If there is a change you found the leak.
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Friday, February 29th, 2008 AT 6:08 PM
Tiny
51MINX
  • MEMBER
Thanks Jeremy.
I'll look at that in the light tomorrow,
That raises another question in my mind, though.
I understand emissions control systems broadly, but not intricately.
I've never serviced the emissions control system in the nine years I've owned the car
This car has numerous tiny steel lines running all over the place connected with rubber hoses to what look like little check valves and other devices.
I have inspected the components, visually and haven't detected deterioration.
I don't understand these little piping systems at all, but there is one lead to a device screwed into the intake manifold just behind the #1 cylinder.
I wondered if the Emissions system could be implicated in this problem, other than by vacuum leaks caused by deterioration.

I'm also concerned about carb cleaner damaging the hoses and wonder if it might be better to spray an oil, instead.
I'm going to have to logoff now.
Thanks again.
Dale
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Friday, February 29th, 2008 AT 6:31 PM

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