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Hey guys,

i have this problem since a few months since i've got a brand new vacuum advance cuz my old one was leaked all air and didn't do anything and the car had a lot of power leak. My carb was rebuilt in march, then i got this advance in may from rockauto (same as the original). Since then, the car is running great, i feel all 70 hps, i have a 6-7 l/100km fuel consuption ( about 33.6 - 39.2 mpg if i'm correct ) instead of 7-9,5l/100km. But since i've installed the new vacuum advance there was an engine clanking (sounds like its detonating) when i stepped on the gas. The carb was set again, this problem seemed to solve, but now, when i barely touch the gas pedal, it clanks again (only sometimes, not always!) if i step on it, it immediately ends. My emissions results are perfect, i don't know if its because of the poor mixture, cuz its only started since the new advance.. my ignition timing (dunno correct term in english) is at 3 degrees ATDC if i remember correctly (factory data is 5+-2 ATDC if i'm correct, will pop up the hood to confirm). need help guys, because i'm really frustrated of this. next thing i'm thinking of is the ecu/ecm (located under the heating radiator), didn't find anything about this on the web, i have a spare ecm. What do you think, could the ecu/ecm cause this? thx in advance and sry for the long letter.

gab

Your ignition timing will always occur BTDC (before top dead center), so I would recheck that, or maybe it was not translated well.
Your engine is detonating/pinging if your timing is that far off. You need to set the timing with the vacuum advance disconnected and plugged (the hose has to be plugged), this takes the advance out of the equation, and allows the base timing to be set.

So, remove the hose for the vacuum advance, plug the hose and recheck your timing. Also be aware that the timing marks on the crank pulley can move if the rubber has allowed the top of the crank pulley to slip. Not likely with a small engine like this, but worst case scenario. Check that timing, and ask other people if they get issues with the gas they buy from the same gas station as you.

Now this is how you would have set your timing on a carburetted motor that I am used to before computers, but you say your car has an ECM/ECU, so does that mean you have an oxygen sensor too? Someone else here must know a bit about these motors too.

Thanks for the advice, i will try it as you said. I usually get my fuel from different stations as i use the car for long distances. Yes, it has an O2 sensor. Oh, and the car says the default ignition timing is 5+-2 degrees BTDC, and mine is at 3 degrees BTDC now. I wonder that the ECM is for only the O2 sensor. It has an IC like we use in computers nowadays. That was in '84/'86.....

And i forgot to say, the problem only starts when the engine is heated up. Until it's cold, everything is fine.

Check the coolant temperature sensor.

_________________
05 wrx wagon
99 Benz ML 320
91 eagle summit swapped - 6/4 bolt combo
94 Audi s4 - sold
88 Eagle Vista Turbo LX sedan, RIP

Does that affect it? I think its fine..

So, finally the clanking is over. I simply changed the hoses connected to the vacuum advance. Seems it wasn't been installed properly.

Help guys,

I wrote into this thread a year ago... I believed that the vacuum hoses were connected wrong, caused the engine to crank. No. They were installed correctly. Thats why I need your help now. If everything is in place they should be, the engine cranks badly. The vacuum advance must advance too much. If I change the hoses, no cranking, but loss of some power. If I set ignition timing to 0 degree, nothing happens. So far, checked the ECM, the vacuum switches, (ignition cables+spark plugs), dunno what to do next. I'm afraid the vacuum advance is not working good. Or the last idea is that the carburettor is causing too much vacuum which cause the distributor to advance too much. What should I do? Thx guys, and sorry for my English.

No one? My engine is crazy, now, if I go with an even pace, the car jerks crazily. Also jerks while accelerating. Please help!! I need to find a solution, I'm out of ideas. Had to choose: 1) detonating engine and runs like it has 200 horses, 2) jerking but no detonating and running like it has 40 hps... Maybe Rockauto.com sent me a wrong piece? Why my car detonating when everything is in place? wtf?????
Just passed over 140.000 km today, don't want to bury my engine.

Are u sure you installed the distributor correctly? I'd check it at tdc or with a timing light. Also you can test it out at idle with a vacumn pump.

This sound like the same problem I had with a leaky vac advance ( or retard ) on my old tbi g32b set up.

_________________
05 wrx wagon
99 Benz ML 320
91 eagle summit swapped - 6/4 bolt combo
94 Audi s4 - sold
88 Eagle Vista Turbo LX sedan, RIP

The timing was set to 4-5° BTDC, it was tested with a timing light. The distributor must be installed correctly (u think might be not? my mechanic did the job). No, the vacuum advance doesn't leak. Its 1 year old (also tested it 2 days ago, both lines holds vacuum). Recently, I changed the basic timing to about 0° again to see what happens. Nothing. Everything is the same. The vac.adv. simply pulls the distributor too much i think (thats why the engine is detonating). Thats when i give small gas. If i step on it harder, then the detonating is over, but again if i barely press the gas pedal the detonating comes back. The vac.advance can be installed in only one way right? It seemed simply to put one bolt thingy to place.
Could be my distributor goes crazy? I have spare one. Or some vacuum line/hose/switch issue?

If your confident about the timing then it must be running lean to be knocking like that. Perhaps a bad fuel pump or carb? Could be a bad air leak at the carb or IM?

Do you still have the vac hose diagram on the hood?

_________________
05 wrx wagon
99 Benz ML 320
91 eagle summit swapped - 6/4 bolt combo
94 Audi s4 - sold
88 Eagle Vista Turbo LX sedan, RIP

Fuel pump is new too, its working well (it did the same with the old one). It musn't run lean, the emissions values were good when my exhaust manifold was in one piece (now it has a bad crack so we are unable to measure true values, need to fix that too). Other thing, if I change the two vacuum hoses connected to the advancer, then if the engine is cold, its detonating, when is hot, it doesn't (but jerking remains, thats how i use it now..). Also, if I change the two upper hoses connected to the second solenoid valve located at the left side of the motor (which connects directly the advancer's upper line with the switch), then it detonates at greater load, and doesn't detonates at lower load. Also, you cannot adjust the mixture at this type of carb, you can only adjust it for cold conditions.
Btw, what do u mean under bad carb? My mechanic told me, the only thing he can believe, that my carb generates too much vacuum (because of worn carb gaskets) causes the advance to immediately pull maximum timing for the distributor at wrong throttle standings (sry for composition, hope you understand what i mean). He advices to rebuild the carb but i doubt that it causes the problem (i don't have much talent in cars tho). Rebuilding it would only consume a lot of time, energy and money again with no result, i fear. Plus its almost impossible to get a rebuild kit...

So tomorrow im gonna compare the advancer's advancing range with the old one to see if it really pulls too much...and check every solenoid valve and vacuum hose related with the advance..no other idea.. the map..:

Checked the vacuum advance, all solenoid valves, vacuum hoses.. Everything is fine, but the car doesn't.. Got another tip, that the throttle position sensor could be wrong.. gonna check as soon as i can.. what do u think? gonna find a solution damn quick, i'll go on a 2000 km holiday trip abroad, don't want to have problems because of this.. please help guys..my only hope is here..

As a shot in the dark, are you able to read any codes off the ecu? A bad sensor, like a TPS should be caught by the ecu.

_________________
05 wrx wagon
99 Benz ML 320
91 eagle summit swapped - 6/4 bolt combo
94 Audi s4 - sold
88 Eagle Vista Turbo LX sedan, RIP