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Discussion Starter · #1 ·
Ok so gas prices on the rise again.. I use premium 93oct in my 89si because anything less and I get that pinging..or shopping cart wheel rattling kinda sound coming from my engine when I accelerate.
Well the other day Im driving past those concrete divider walls with my window down and I stomp the gas, and sure enough, i hear that sound..thats the only way I can hear it with premium though..
Anyways, its time I actually fixed this instead of buying super expensive gas,

So then, 87 octane blows up a little bit sooner than 93 octane, so if I retard my timing, I can make 87 work like 93..or just plain work normally like it should?

Let me know if im wrong or there is a different way..
but if im right, how much am I going to adjust it? i dont even know how to yet..
 

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What you are refering to is "detonation". Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. Some common causes of detonation are....advanced timing, like u said. It could also be, an egr valve, knock sensor, your spark plug rating could be too hot, you car could be overheating, or you could also have a lean fuel mixture. But I think your heading towards the right path.....i'de start with retarding the timing a degree or two. If that doesn't help....i'de start eliminating some of these other causes. If you need help diagnosing some of these, let me know.
 

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^ ditto to dano. if you dont have a manual, look in the FAQ for the online manual. check to see what your timing is currently, its probably way advanced from stock. and adjust the timing properly to the stock setting. at stock timing you should be able to use 87 octane without any detonation no matter what, unless its junk gas, or something else is wrong with your car.
 

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Discussion Starter · #5 ·
Well, im kinda strapped for money, and a timing light is kinda expensive..cant I just adjust the timing from the distributor? Or would it be a whole lot better idea to just get a timing light..or have a shop do it?
 

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um, thats how you adjust the timing, thats the only way to adjust the timing: at the distributor. but you cant just turn it and think its ok. you NEED a timing light to adjust the timing. no ifs ands or buts.

you NEED a timing light to adjust it, and you NEED to adjust it at the distributor lol. if you think either of those aspects is wrong, or not the only way, then im going to tell you to take it to a shop and tell them to set it for you to 15 degrees BTDC, mark is on the flywheel.

i am curious though, how else did you think you could adjust the timing other than using a timing light and turning the distributor while using the light? and have you ever attempted to set the timing yourself without a timing light? how did you do it and what made you think it was set ok?
 

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Discussion Starter · #7 ·
lol no no no, ive NEVER touched my timing, and I honestly had no idea how to change it. And I had no idea you needed a timing light which is exactly why I came here to ask lol..
This is like the only part of my car I dont understand and have been afraid to touch..
Guess I'll be getting a timing light then.. and perhaps now ill figure out how to change my timing belt also
 

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Discussion Starter · #8 · (Edited)
I just got a timing light and checked my cars timing. Its right about at the red line.. My gas mileage is pretty decent, 27mpg ish, so I dont think its running lean.
Should I just go ahead and retard the timing more, or should I move on to spark plugs.. and if someone could explain the egr valve and knock sensor and how they could cause detonation?

Edit : Oh also, is it supposed to fall further and further behind as you rev it up? Because I dont think so but thats what it does.. I think I remembered reading somewhere on here someone had a problem like this...

Is my timing belt off a tooth? oh noes.....
 

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Did you jumper wire the ignition timing service port thingy ? If not :

Look back on the firewall just to the left (looking over the front bumper) of the vacuum box of doom that has all the vacuum lines running out of it.

There is a little wire connector looking thing that should have a yellow rubber cover on it. Pull the cover off and put a jumper wire of some sort between the two holes.

This takes the ECU out of the loop which you need to do because it can be fiddleing with the timing while you are trying to adjust it.

Now use your timing light and set the timing.

Oh yeah..to answer your question, timing is suppossed to advance as RPMs go up. In fact, your saying that made me suspect the you hadn't jumpered the service port.
 

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again, what dano said^ lol. you gotta jumper that plug to bypass/disable the electronic ignition advance when checking/adjusting your timing.
if your timing is practically dead on with that said and done, i dont understand why you would be getting detonation with anything less then 93 octane. cuz i'd assume you have the right spark plugs in the car lol. and our cars dont have knock sensors, and i doubt our egr system would have an effect on detonation unless its stuck open.

maybe you're hearing something different and mistaking it for detonation?
 

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If the EGR system has failed closed you can get some mid throttle detonation, as the computer runs the timing assuming that the damping effects of the exhaust gasses will keep detonation under control.

My car, with stock timing, knocks at low rpm high load with anything less then premium(91 R+M/2), and would knock at medium-high load partial throttle on hot days, even with premium. That was due to a short ram intake, now that i have a CAI it gets enough colder air to keep it from detonating.
 

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Discussion Starter · #12 · (Edited)
ok so I jumpered those stupid wires, but I didnt get a CEL or anything, or notice a difference. I checked the timing and it was the same.
If timing advances as rpms go up, wouldnt that mean it'd be getting closer to the white mark, moving clockwise, down, isntead of counterclockwise,up like it is with me?

Just to be clear - the marks are moving up from the pointer. No marks get any closer to the pointer as the RPMs go up
 

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Thats the direction they should be going.
The timing gun is firing when the computer fires the #1 plug
The marks are at 15BTDC.
If the spark fires at 15btdc, the gun flashes on the marks.
If the spark fires before that (advanced timing), the gun fires before the marks get to the pointer.
 

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Discussion Starter · #14 · (Edited)
Hmm, I think i get it..
Well anyways, I replaced my spark plugs, they havent been done, ever, by me and I got the car 26kms ago. No difference there, still heard that sound. Then I flushed my coolant, god knows when that was done last, the stuff was brooowwn. Afterwards I drove it around and was driving hard (When I most often heard it), and I didnt hear the sound.. so perhaps my engine was overheating, or just a coincidence...
Ohwell atleast I did 2 things I had been putting off for a long time.
But still, I dont understand what else it could be if I can only hear that ..sound.. when I use 87 octane. Last year when I noticed it my dad told me to try higher grade gas, and it went away, or was way less pronounced.
Im not using crappy gas.
Im confused


Edit - Wow im stupid, I understand it now. For some reason I was thinking that the closer the pointer was to the white mark, the more advanced it was..
Well im going to fill it up with 87 octane, if the problem persists i'll retard the timing a little bit, see if it doesnt help..
 

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how does advancing/retarding timing affect power output/delivery?

my distributor looks to have the timing advanced as far as it can go....
is it usually necassary to have the preludes timing advanced all the way to acheive the stock 15 btdc timing?
or shouldn't it be in the middle somewhere?
and if my timing is too far advanced, would there be a severe lack of low-rpm power?
because my car bogs bad below 2,000 and seems to be down on power through the whole rev range.
I cant say Ive heard any pinging or knock though....
thanks
 

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If you don't have a timing light, don't me making assumptions about your timing.

Regarding your lack of low-end power, are your secondaries functioning correctly? On a B20A(5) lude, a failure of the IAB solenoid will make it so the secondary butterfly plate is stuck open at all times, which will destroy low-end power. Check your cams to make sure they're both at TDC, and borrow a timing light to check ignition timing.
 

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If you don't have a timing light, don't me making assumptions about your timing.

Regarding your lack of low-end power, are your secondaries functioning correctly? On a B20A(5) lude, a failure of the IAB solenoid will make it so the secondary butterfly plate is stuck open at all times, which will destroy low-end power. Check your cams to make sure they're both at TDC, and borrow a timing light to check ignition timing.
okay, i wont fiddle with the timing... but this is the first i've heard of the IAB solenoid. Tell me, would failure of the IAB solenoid trigger a CEL? I throw no codes. If you could tell me the exact location of the solenoid, I could try one from my parts car, a 88 si that ran great. Thanks,
 

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how is your valve adjustment?

maybe you have a bad O2 sensor.

the other posters provided good material but i just wanted to add a few things to it. maybe what you hear is actually loose valves. maybe the O2 sensor is reading slightly off and doesnt throw a code. i think that ignition timing is important but there are other things to check out too.
 

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No light for the IAB solenoid.

Here is a real quick and dirty test though.
Start the car and let it idle.
Get out and pop the hood (make sure the e-brake is on! :p).
Now, from standing in front of the bumper and looking in, look on the right end of the intake manifold just to the left of the brake and clutch master cylinders.
You'll see a brassish round metal thing with a vacuum line come out the top.

Coming out of the bottem is a shaft, that shaft actuates the secondary butterflies.
Watch that shaft, then pull the vacuum line off the round metal thing.
The shaft should come out, and the doodad it's attached to should rotate.
When you plug the vacuum line back in, it should suck the shaft back in and rotate the doodad the other direction.

If it doesn't, the solenoid is shot.
 

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how is your valve adjustment?

maybe you have a bad O2 sensor.

the other posters provided good material but i just wanted to add a few things to it. maybe what you hear is actually loose valves. maybe the O2 sensor is reading slightly off and doesnt throw a code. i think that ignition timing is important but there are other things to check out too.
The valves are quiet and they never sound "clanky" like some 3rd gen's...

the car is an 88 si and has new:
plugs
wires
dist cap, rotor
air filter
fuel filter
both O2's sensors

and right now i just swapped in the whole control unit in the vacuum box from the parts car that was fast as hell and it was a 88 Si AUTO...

maybe the engine in the stick cars get dragged around alot and just get tired...

im going to run an errand and test drive the car to see if the new bypass solenoid and map sensor helped it...
 
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