[4AGE] ignition timing problem -> SOLVED !!

[eg6maxx]

I've got a big problem on my 86.

I used the search engine, I found some threads about the ignition timing issues, but they didn't help me.

About 2 months ago I decided to check the ignition timing on my 86 with a stroblight.
At this time the engine made some backfire but run fine, I though there was too much advance. I was right.
The ignition timing was a pain in the *** to set at 10°, and yes I jumped the diag connector :wink: .
Since that day I can't make my 86 run normaly:

Ignition set @ 10° -> iddle is fine but engine can't rev up, the car can't run without stall.

Ignition set @ ALOT -> iddle very high (1200-1500rpm), engine can rev but a lot off back fire/ missfire, the car can run but it's a mess.

I worked on that sh** about 2 months...
What I've done so far:
- I set the dizzy to all the positions you can imagine, when I bolt it in place I tried with 1 or 2 teeth in advance or retard. I bolt it in place with or without the rotor cap and the cam cover to watch the teeth.
-I changed for OEM BRAND NEW: Coil, Rotor cap & rotor, spark plug Denso Q20R-U11 (My IQ20 weren't very old) spaced to 1.1mm.
-I tried with a brand new distributor.
-The cords are TRD ones about 1 years old (1000 km maybe)
-O ring is new.
-I tested the igniter and the distributor : no problem.
-I checked all the vaccum (map...etc...) for leak : nothing found.
...

The ECU doesn't have any error code.
When I jump the diag connector to set the ignition timing @ 10°, it's very difficult to set, (engine at working temp and iddle set @ 800-850 rpm) the "TDC" mark "jumped" some times. I guess it doesn't have to do that because I jumped the diag connector.



Engine is 4AGE Bluetop, about 150k, it's the original one (1984 Zenki Corolla GT MAP sensored).
Only mods are Apexi Air Intake, Techno pro Spirit header and HKS (Silent Hi-power) Catback.

Maybe the problem is not the ignition timing, I'm kinda lost...Please HELP ! Thank you very much.

[eg6maxx]

Oh yes, I checked the timing belt because the symptoms are like a missing tooth... And no, everything is in place.

[Bean]

Sounds very tricky... so the only thing jumping in to my mind right now are three things.
1. are you sure your diagnostic plug still works? as mine doesn't i.e. if I jumper the terminals the timing doesnt change - means I have to set my timing at idle to 16° instead of 10° (workaround would be to jumper the terminals directly at the ECU)
2. have you done a compressiontest to see if your cylinders have equal and sufficient sealing
3. can't realy tell how to check this in a safely manner but maybe your cold start injector (the one in the plenum) is stuck - this would result in too much fuel and worse an metered fuel being injected... can you make a good picture of your plugs as this will help diagnose the problem...

PS: nice clean engine bay reminds me to clean mine as it more than just dusty right now, but that's no surprise in this country.

[eg6maxx]

Thanks for your answer and the compliment ^^

-The diag plug must work because the "check engine" light blink when I jump it.
-I didn't make a compression check, a friend of me would bring me a checker about 2 weeks ago But I'm gonna do that.
-I'll check this injector.
-The Sparkplugs are brandnew, I don't think we can see anything on them. But My old IQ20 were light brown/grey.

[Bean]

Light brown grey sounds good so it's probably not the injector...

[fax0815]

I´ve had also major problems with my ignition, but my symtoms were a little different.

If you unplug the shortcut wire from the diagnosis plug an keep looking with the timing light does the timing change to 16°? As said above, could be a broken diagniosis plug...

My advice, take a look at the TPS, it caused massive trouble for me! Set the TPS switch acording to the manual, or if thats somehow not possible get a 2nd TPS. My idle switch never closed , well I could set the timing and idle to specs (pretty hard) but the car wasn´t accelerating well and backfireing as fu**. I also remember an unstable jumping TDC mark...

Worth a try

[Ivan141]

Bit of an obvious question, but did you check for error codes while you had the diag. connector bridged?
If all else in the ignition department is in order, then there is little left to check apart from wiring defects, which often result in error codes.
Did you change/touch anything else when you first started experiencing the problem after setting the timing? Some sensors can cause similar problems when not connected properly, but it is unlikely this would happen by itself.

[eg6maxx]

Bean Bandit, I checked the injector it was not clogged, pretty clean in fact.

fax0815, Nothing change (on the TDC mark) if the diag plug is jumped or not, except the "engine check" light that blinking... Weird...
I'll check the TPS.

Ivan141, No error code, le light just blinking without code. The only thing I made (except changed all the parts listed above) was to unbolt and rebolt the distributor a thousand times. So I checked the distributor (yellow) plug because I unpluged/repluged it a thousand times too... But the connectors are OK.

I'll try again tomorrow, thanks for all your advices guys !

[Bean]

if there is no change with the diagnostic plug try setting timing at idle (engine warm etc...) to 16° - I doubt this will fix everything but at least one thing less to worry about.

[fax0815]

eg6maxx Wrote:

[b]fax0815, Nothing change (on the TDC mark) if the diag plug is jumped or not, except the "engine check" light that blinking... Weird...
I'll check the TPS.

I'll try again tomorrow, thanks for all your advices guys !

At least your diagnosis plug seems to work fine.
Getting a strong feeling towards TPS
Had the same thing, no change wheter terminals conected or not.