Flat Spots - But only under load

[darkwolf]

MY 1989 ST183 3S-GE ACIS (2nd Gen I think) Front Wheel Drive Celica is having some trouble with flat spots. Or rather - I'm getting a sweet spot.

~3000RPM the engine seems to stutter like its being starved of fuel/air/spark. Almost like its missing.

3000 - 4500RPM engine seems perfect no worries.

4500+ Engine repeats range 1. Stuttering, feeling starved etc.

NOW.

When it happens if I put the clutch in - no worries. In fact the stuttering goes away, the engine revs up about 1,000 RPM more than it was at before I put the clutch in.

My initial thought were air, so I have replaced the air filter with a pod filter to see what that did. Same symptoms, though the sweet spot if you will seems better (no changes to plumbing at all)

Replaced spark plugs, same deal. NO changes at all.

MY next thoughts are maybe the HT leads, though I can't figure out why it would lead to a problem only under load.

This leads me to believe it may be a problem with my drivetrain. Clutch/Gearbox/Diff.

But again if it is one of these which one, why and what would I need to replace to fix the issue?

Any help appreciated. Thanks.

[rollaholic]

get coil pack(s) checked by auto sparky

[darkwolf]

get coil pack(s) checked by auto sparky

Really? Why would the coil cause this effect though? I could understand if the problem was throughout the range, and with or without load.

Will have a ring around anyway.

[Adamal]

Tried injector cleaner?

[RunningRich]

My thoughts would be ignition. The car probably has the original cap and rotor for a start. Take the cap off and check for oil within the dizzy, leakage is common.

[rollaholic]

get coil pack(s) checked by auto sparky

Really? Why would the coil cause this effect though? I could understand if the problem was throughout the range, and with or without load.

Will have a ring around anyway.

because its possible for coils to malfunction intermittently, or only under certain conditions - even similar to those you've described.

diagnosing faults over the net is never easy, but like someone else said it sounds like an ignition problem.

[sergei]

had similar problem on 20v, turned out to be coil.

[20v_rollaboy]

Also make sure the coil has proper grounding, I had the same problem in one of my wagons.

[matt dunn]

a flat spot or a miss, very different things and causes,


for a miss ht like as said,


for flatspots try checking for leaks in the map sensor line,
or oil in it,
check fuel pressure and injectors, ( unlikely though)
and retard the ign timing by 5 deg to see if it fixes it,
if it does look at fuel type, knock sensor, or detonation due to carbon build up in the head etc etc.

3SGE isn't it?

[darkwolf]

It is a 3S-GE.

Going to get a new fuel filter and check the coil.

Heard a clicking noise from north east corner of engine bay while it was off. Had stereo running for a while before it happened. (if you know what I mean).

Am actually wondering if it is an electrical short...

[sergei]

Clicking noise might be charcoal box venting the pressure from tank.