Re: '85 Corolla AE82 4AC hesitations?

"Hammo" <hbaj@aapt.net.au.nob> wrote in message
news:C08D11CF.14B%hbaj@aapt.net.au.nob...[color=blue]
> Greetings Brains Trust
>
> Have a question regarding the above mentioned machine that is equipped
> with
> a 5 speed manual.
>
> It was hesitating under load (2, 3 and 4th gears), ok in 1st and top.
>
> Changed plugs, distributor cap, checked plug lead resistance (all under 20
> K
> ohms/metre) as well as obligatory fluid change with filters, carb cleaner
> down carby and new fuel filter. Adjusted timing, and changed coil
> (outside
> of resistance specs). So far, the car has improved dramatically, yet when
> it gets upto operating temp begins to hesitate and miss in the 3000-4500
> range. The tacho is jumping about 200-700 rpm jumps and I am at a loss to
> discover why
>
> What is going on?
>
> Also, I changed the dizzy cap as the plug poles showed an odd corrosion on
> them. This corrosion has returned in under 300 kays of driving.
>[/color]

What brand ignition parts are you using?
[color=blue]
> The mech advance and vac advance are working on the dizzy (confirmed with
> timing light).
>[/color]

Have you checked manifold vacuum at idle and at higher RPM?
[color=blue]
> Are the electronic ignition systems on these things responsible for this
> erratic tacho behaviour as well as the poor acceleration and missing in
> the
> 3000-4500 rpm range?[/color]

I doubt it.
[color=blue]
>
> How can I get the tach to behave?
>
> Very interested in any ideas that are out there!
>
> Cheers
>
> Hammo
>[/color]

IIRC, this vintage Corolla had carburetor and drivability issues with
hesitation under acceleration but erratic engine speed and missing were not
part of the symptoms.
--

Ray O
(correct punctuation to reply)

"Hammo" <hbaj@aapt.net.au.nob> wrote in message
news:C08E0E1C.4BBA%hbaj@aapt.net.au.nob...[color=blue]
>
>
>
> On 15/5/06 2:59 AM, in article
> 26aff$4467644f$180fead6$5636@msgid.meganewsservers.com, "Ray O"
> <rokigawa@tristarassociatesDOTcomn> wrote:
>[color=green]
>>
>> "Hammo" <hbaj@aapt.net.au.nob> wrote in message
>> news:C08D11CF.14B%hbaj@aapt.net.au.nob...[color=darkred]
>>> Greetings Brains Trust[/color][/color]
> snippo[color=green][color=darkred]
>>>
>>> Also, I changed the dizzy cap as the plug poles showed an odd corrosion
>>> on
>>> them. This corrosion has returned in under 300 kays of driving.
>>>[/color]
>>
>> What brand ignition parts are you using?[/color]
>
> Bosch, for both the dizzy cap and coil, NGK for plugs and Repco brand HT
> leads.[/color]

I'm not familiar with Repco. While Bosch is a well known and respected
brand, for some reason, they sometimes perform poorly in Toyotas. For that
reason, I stick with OEM - Nippon Denso or NGK. You may wish to stick to
OEM ignition parts next time you change them.

Seeing as how you have measured the resistance, the ignition parts are
probably OK.
[color=blue][color=green]
>>[color=darkred]
>>> The mech advance and vac advance are working on the dizzy (confirmed
>>> with
>>> timing light).
>>>[/color]
>>
>> Have you checked manifold vacuum at idle and at higher RPM?[/color]
>
> Yep. Confirmed that I have advance with higher rpm that is greater than
> that of just mechanical advance. Have suction on the vac lines, but only
> know that it is there, not how much it is pulling.[/color]

I've seen the plastic T junctions and vacuum switching valves develop very
fine cracks that allow just enough of a vacuum leak to cause problems.
Sometimes the amount of vacuum leak varies with how much the engine mounts
allow the engine to move, sometimes the variance is caused by temperature.
Take a close look at the hoses, junctions, and vauum switching valves.

[color=blue][color=green]
>>[color=darkred]
>>> Are the electronic ignition systems on these things responsible for this
>>> erratic tacho behaviour as well as the poor acceleration and missing in
>>> the
>>> 3000-4500 rpm range?[/color]
>>
>> I doubt it.
>>[color=darkred]
>>>
>>> How can I get the tach to behave?
>>>
>>> Very interested in any ideas that are out there!
>>>
>>> Cheers
>>>
>>> Hammo
>>>[/color]
>>
>> IIRC, this vintage Corolla had carburetor and drivability issues with
>> hesitation under acceleration but erratic engine speed and missing were
>> not
>> part of the symptoms.[/color]
>
> I'm not convinced the engine speed is erratic, just the tacho is
> indicating
> that it is. I have yet to check the AAP diaphragm for signs of leaking,
> as
> It has been reported that this is more of a concern when cold, not hot?!
> I
> have a sneaky suspicion that the electronic ignition module is the root
> cause of it all, but have not got a wiring diagram to help me diagnose it.
> The Haynes manual I have looks at the latter models, or combines all
> machines under 1987 together!
>
> Cheers
>
> H
>[/color]
While you're looking at the AAP diaphragm, take a look at the fuel level in
the sight glass for the bowl to see if it is even with the notches in the
middle of the glass.

You may also wish to hook up an external tachometer to see if it matches the
one on the gauge.

This vintage also had problems with igniters, but they tended to be a
complete failure and cause a no-spark condition.

Good luck!
--

Ray O
(correct punctuation to reply)

"Hammo" <hbaj@aapt.net.au.nob> wrote in message
news:C08FFF58.D52%hbaj@aapt.net.au.nob...[color=blue]
>
>
>[color=green][color=darkred]
>>>
>>>>
>>>> "Hammo" <hbaj@aapt.net.au.nob> wrote in message
>>>> news:C08D11CF.14B%hbaj@aapt.net.au.nob...
>>>>> Greetings Brains Trust
>>> snippo
>>>>>
>>>>> Also, I changed the dizzy cap as the plug poles showed an odd
>>>>> corrosion
>>>>> on
>>>>> them. This corrosion has returned in under 300 kays of driving.
>>>>>
>>>>
>>>> What brand ignition parts are you using?
>>>
>>> Bosch, for both the dizzy cap and coil, NGK for plugs and Repco brand HT
>>> leads.[/color]
>>
>> I'm not familiar with Repco. While Bosch is a well known and respected
>> brand, for some reason, they sometimes perform poorly in Toyotas. For
>> that
>> reason, I stick with OEM - Nippon Denso or NGK. You may wish to stick to
>> OEM ignition parts next time you change them.[/color]
>
> Interesting. What problems have been encountered?[/color]

I've encountered vehicles with driveability problems when accelerating and
missing. Some aftermarket parts work fine with no problems, and others do
not, and an aftermarket igniti part that works fine in one Toyota may not
work correctly in another. I do not have an explanation for this, and
rather than experiment, I just use and recommend OEM ignition parts.
[color=blue][color=green]
>>
>> Seeing as how you have measured the resistance, the ignition parts are
>> probably OK.[/color][/color]

<snipped>
[color=blue][color=green][color=darkred]
>>>>
>>>>> The mech advance and vac advance are working on the dizzy (confirmed
>>>>> with
>>>>> timing light).
>>>>>
>>>>
>>>> Have you checked manifold vacuum at idle and at higher RPM?
>>>
>>> Yep. Confirmed that I have advance with higher rpm that is greater than
>>> that of just mechanical advance. Have suction on the vac lines, but
>>> only
>>> know that it is there, not how much it is pulling.[/color]
>>
>> I've seen the plastic T junctions and vacuum switching valves develop
>> very
>> fine cracks that allow just enough of a vacuum leak to cause problems.
>> Sometimes the amount of vacuum leak varies with how much the engine
>> mounts
>> allow the engine to move, sometimes the variance is caused by
>> temperature.
>> Take a close look at the hoses, junctions, and vauum switching valves.[/color]
>
> This is a probable, I know that there is indeed vacuum, but to actual
> amount
> of vacuum and how much is required, I am at a loss. There is bound to be
> a
> line that requires replacing in there _somewhere_!!!![color=green]
>>[/color][/color]

You can probably buy, borrow, or rent a vacuum gauge at an auto parts store.

Also, you will need a repair manual to check whether all of those vacuum
switching valves are functioning properly. Unfortunately, there is no easy
way to check their operation without a manual.


<snipped>
[color=blue]
> While you're looking at the AAP diaphragm, take a look at the fuel level
> in[color=green]
>> the sight glass for the bowl to see if it is even with the notches in the
>> middle of the glass.[/color]
>
> In the middle as in the centre? The Haynes (book of lies) I have shows
> the
> level to be anywhere to be from the middle to top or the bottom of the
> sight
> glass. It is hard to describe, but the glass has that indentation and
> some,
> you reckon the centre is the best place to set it?
>
> ____
> /_ _\
> | |
>
> Agh, the ASCII is terrible, but imagine the same above and below and I
> have
> the manual saying the minimum is the bottom bit.[/color]

The sight glass has notches on the sides of the metal perimeter of the
glass, centered horizontally. The fuel level should be roughly even with
those notches.
[color=blue]
>[color=green]
>>
>> You may also wish to hook up an external tachometer to see if it matches
>> the
>> one on the gauge.
>>[/color]
>
> Yeah, it reflects the crazy signal on the tacho in the car. The dwell
> gauge, shows a very stable and realistic representation of the changing
> dwell during acceleration and idle etc.
>[color=green]
>> This vintage also had problems with igniters, but they tended to be a
>> complete failure and cause a no-spark condition.[/color]
>
> Bugger! Is there an aftermarket one that you know of? OEM again?[color=green]
>>[/color][/color]

I am not aware of any aftermarket sources of igniters, but as I mentioned
before, when working on Toyotas, I stick to OEM ignition parts so I've never
searched. I have not priced one for a long time, but my wild guess is that
they are in the $175 to $200 range. Fortunately, it is highly unlikely that
the igniter is the cause of the problems you are encountering. When an
igniter fails, you have no spark and the engine will not run, and since your
engine does run, I would not spend time chasing the igniter.

Going back over your previous posts, I just caught that the problem occurs
when the engine is cold. Problems with the choke and with vacuum switching
valves could cause the symptoms you're describing. Check to make sure that
the choke pull-off it not working too soon.
--

Ray O
(correct punctuation to reply)

For what it's worth the electronic ignition module on this year and
model was recalled in 1990 or '91. We waited until it died to take it
in and that was in '93 I seem to recall. The car just wouldn't start
one day. No other indication of problems before or after. It runs
fine to this day.

-L

On Tue, 16 May 2006 11:30:13 -0500, "Ray O"
<rokigawa@tristarassociatesDOTcomn> wrote:
[color=blue]
>
>"Hammo" <hbaj@aapt.net.au.nob> wrote in message
>news:C08FFF58.D52%hbaj@aapt.net.au.nob...[color=green]
>>
>>
>>[color=darkred]
>>>>
>>>>>
>>>>> "Hammo" <hbaj@aapt.net.au.nob> wrote in message
>>>>> news:C08D11CF.14B%hbaj@aapt.net.au.nob...
>>>>>> Greetings Brains Trust
>>>> snippo
>>>>>>
>>>>>> Also, I changed the dizzy cap as the plug poles showed an odd
>>>>>> corrosion
>>>>>> on
>>>>>> them. This corrosion has returned in under 300 kays of driving.
>>>>>>
>>>>>
>>>>> What brand ignition parts are you using?
>>>>
>>>> Bosch, for both the dizzy cap and coil, NGK for plugs and Repco brand HT
>>>> leads.
>>>
>>> I'm not familiar with Repco. While Bosch is a well known and respected
>>> brand, for some reason, they sometimes perform poorly in Toyotas. For
>>> that
>>> reason, I stick with OEM - Nippon Denso or NGK. You may wish to stick to
>>> OEM ignition parts next time you change them.[/color]
>>
>> Interesting. What problems have been encountered?[/color]
>
>I've encountered vehicles with driveability problems when accelerating and
>missing. Some aftermarket parts work fine with no problems, and others do
>not, and an aftermarket igniti part that works fine in one Toyota may not
>work correctly in another. I do not have an explanation for this, and
>rather than experiment, I just use and recommend OEM ignition parts.
>[color=green][color=darkred]
>>>
>>> Seeing as how you have measured the resistance, the ignition parts are
>>> probably OK.[/color][/color]
>
><snipped>
>[color=green][color=darkred]
>>>>>
>>>>>> The mech advance and vac advance are working on the dizzy (confirmed
>>>>>> with
>>>>>> timing light).
>>>>>>
>>>>>
>>>>> Have you checked manifold vacuum at idle and at higher RPM?
>>>>
>>>> Yep. Confirmed that I have advance with higher rpm that is greater than
>>>> that of just mechanical advance. Have suction on the vac lines, but
>>>> only
>>>> know that it is there, not how much it is pulling.
>>>
>>> I've seen the plastic T junctions and vacuum switching valves develop
>>> very
>>> fine cracks that allow just enough of a vacuum leak to cause problems.
>>> Sometimes the amount of vacuum leak varies with how much the engine
>>> mounts
>>> allow the engine to move, sometimes the variance is caused by
>>> temperature.
>>> Take a close look at the hoses, junctions, and vauum switching valves.[/color]
>>
>> This is a probable, I know that there is indeed vacuum, but to actual
>> amount
>> of vacuum and how much is required, I am at a loss. There is bound to be
>> a
>> line that requires replacing in there _somewhere_!!!![color=darkred]
>>>[/color][/color]
>
>You can probably buy, borrow, or rent a vacuum gauge at an auto parts store.
>
>Also, you will need a repair manual to check whether all of those vacuum
>switching valves are functioning properly. Unfortunately, there is no easy
>way to check their operation without a manual.
>
>
><snipped>
>[color=green]
>> While you're looking at the AAP diaphragm, take a look at the fuel level
>> in[color=darkred]
>>> the sight glass for the bowl to see if it is even with the notches in the
>>> middle of the glass.[/color]
>>
>> In the middle as in the centre? The Haynes (book of lies) I have shows
>> the
>> level to be anywhere to be from the middle to top or the bottom of the
>> sight
>> glass. It is hard to describe, but the glass has that indentation and
>> some,
>> you reckon the centre is the best place to set it?
>>
>> ____
>> /_ _\
>> | |
>>
>> Agh, the ASCII is terrible, but imagine the same above and below and I
>> have
>> the manual saying the minimum is the bottom bit.[/color]
>
>The sight glass has notches on the sides of the metal perimeter of the
>glass, centered horizontally. The fuel level should be roughly even with
>those notches.
>[color=green]
>>[color=darkred]
>>>
>>> You may also wish to hook up an external tachometer to see if it matches
>>> the
>>> one on the gauge.
>>>[/color]
>>
>> Yeah, it reflects the crazy signal on the tacho in the car. The dwell
>> gauge, shows a very stable and realistic representation of the changing
>> dwell during acceleration and idle etc.
>>[color=darkred]
>>> This vintage also had problems with igniters, but they tended to be a
>>> complete failure and cause a no-spark condition.[/color]
>>
>> Bugger! Is there an aftermarket one that you know of? OEM again?[color=darkred]
>>>[/color][/color]
>
>I am not aware of any aftermarket sources of igniters, but as I mentioned
>before, when working on Toyotas, I stick to OEM ignition parts so I've never
>searched. I have not priced one for a long time, but my wild guess is that
>they are in the $175 to $200 range. Fortunately, it is highly unlikely that
>the igniter is the cause of the problems you are encountering. When an
>igniter fails, you have no spark and the engine will not run, and since your
>engine does run, I would not spend time chasing the igniter.
>
>Going back over your previous posts, I just caught that the problem occurs
>when the engine is cold. Problems with the choke and with vacuum switching
>valves could cause the symptoms you're describing. Check to make sure that
>the choke pull-off it not working too soon.[/color]

Lou Donayre wrote:
[color=blue]
> For what it's worth the electronic ignition module on this year and
> model was recalled in 1990 or '91. We waited until it died to take it
> in and that was in '93 I seem to recall. The car just wouldn't start
> one day. No other indication of problems before or after. It runs
> fine to this day.[/color]

The module would usually stop working but would be OK again after a
20-minute cool-down. We had several replaced in fleet 1985 Chevy Novas
(reskinned Corollas).

Toyota issued a few TSBs about hesitation problems with 1985-87 AE82s,
including a final one that recomended, among other things:

1. Raising the float level to the top of the permitted range (must
readjust idle mixture);

2. Reducing the amount of EGR by adding a restrictor to one of the
vacuum lines of the EGR valve or EGR valve modulator;

3. Changing the accelerator pump arm (not for 1985)

4. Replacing the primary main jet.

I noticed significant improvement after these modifications were done,
although the car was still limited by its 75 HP engine.