How To Stop Pre-Detination Rattle?

[scottryana]

OEM or aftermarket?

No chance of getting a real wideband on it? The old O2's the 80's use are narrowband.

If there is detonation 9 times out of 10 it is timing, bad fuel or lean.

 

[Funner]

No doubt about that! In my mower I've seen it turn to gel in as little as 3 weeks & turn to crystals in 6 months. Damn EPA sleeping w/corn farmers or something!!!! But if it was only ****ty fuel then a ton more 80 owners would be complaining.

I live in a relatively small town (<40K people) so I don't have the options of all the different fuel stations. Right now I'm trying Shell fuel but it seems to rattle as bad, or worse, than Valero & Murphy (Wal-Mart). I don't use Quick-Trip, RaceTrac or the other jumbo gas stations.

All the gas in your town is coming from the same source with varying degrees of additives depending on the brand. In a small town I would be buying gas from the busiest station as it will be freshest.

 

[Reelitchy]

Like you idea about the dist being off science you mentioned taking it out a while ago. Also with new o2 sensor - wouldnt the ecu still be using old and long term info. Would resetting the ecu cause it to use new information?

 

[LFD2037]

OEM or aftermarket?

No chance of getting a real wideband on it? The old O2's the 80's use are narrowband.

If there is detonation 9 times out of 10 it is timing, bad fuel or lean.

Denso so OEM. I have no way of getting a high dollar scanner on it. It's not timing or it'd do it even with higher octane fuel. It's not bad fuel because its done it with every fuel I've used except high octane. It's not a lean condition or it'd only get worse (hotter) with higher octane fuel. Am I correct on these 3 scenarios?

 

[LFD2037]

Like you idea about the dist being off science you mentioned taking it out a while ago. Also with new o2 sensor - wouldnt the ecu still be using old and long term info. Would resetting the ecu cause it to use new information?

But wouldn't it be really obvious if it was off a tooth? The only issue I'm having is pinging, that's it.

 

[scottryana]

I don't believe that you are correct with it not being timing or lean related. Higher octane fuel even if it is timing will will resist knock, depending on how much the advance is and what the octane is. If you are getting relief using high octane than timing would be my first check. If it is lean the octane would not matter much octane is more closely related to the ability of a fuel not to detonate and allow you to advance the timing and make more power. It is not the fuel itself that runs hot or makes the power.

 

[LFD2037]

I don't believe that you are correct with it not being timing or lean related. Higher octane fuel even if it is timing will will resist knock, depending on how much the advance is and what the octane is. If you are getting relief using high octane than timing would be my first check. If it is lean the octane would not matter much octane is more closely related to the ability of a fuel not to detonate and allow you to advance the timing and make more power. It is not the fuel itself that runs hot or makes the power.

We've established it's not timing because it does it at even the stock 3*. So lets say its lean. Why is it lean? No vacuum leaks, FPRegulator and FPRelay appear to be working properly, its not running hot. What else could cause it to run lean (by Friday I should have my new fuel filter and new fuel pump filter but others with the same issue have replaced those with no improvement)?

 

[hammerheadfistpunch]

Update on mine:
I had my mechanic pull the valve cover and pull the cam with the spring loaded cam gears and re-tension the cam gear spring (on the exhaust side). He said it was properly tensioned before but did it again and it hasn't been an issue. Granted it hasn't been as hot and it still feels like my engine is down on power...but its better. According to him, they had trouble with timing on another 1fzfe where they couldn't get the timing right and they went in there and discovered that whoever was in there before hadn't torqued things down right and the exhaust cam kept going out of time. They kept playing with the dizzy to get the timing right and it would keep going out. Something to consider. Has the head been off your rig yet?

 

[LFD2037]

Update on mine:
I had my mechanic pull the valve cover and pull the cam with the spring loaded cam gears and re-tension the cam gear spring (on the exhaust side). He said it was properly tensioned before but did it again and it hasn't been an issue. Granted it hasn't been as hot and it still feels like my engine is down on power...but its better. According to him, they had trouble with timing on another 1fzfe where they couldn't get the timing right and they went in there and discovered that whoever was in there before hadn't torqued things down right and the exhaust cam kept going out of time. They kept playing with the dizzy to get the timing right and it would keep going out. Something to consider. Has the head been off your rig yet?

My heads never been off. Thanks for the update on yours.

 

[Reelitchy]

But wouldn't it be really obvious if it was off a tooth? The only issue I'm having is pinging, that's it.

Not sure it would be off as much as you think. One tooth could probably be 10-17 degrees off either before or after depending which way it is turned. I would for sure check it. Also did you reset the ecu? Since the o2 gives info for the mixture get rid of the old info.

 

[scottryana]

You can't know for sure if it is a true 3 degrees if your distributor is off by a gear. Any reading you get will likely be wrong.

 

[mtullis]

Just fixed mine.
My Timing was set to 10 with the jumper in, backed it down to 5 and my problem went away.
If your distributor was off by a gear looks like your timing would be way off when checked by a timing light.

 

[LFD2037]

You can't know for sure if it is a true 3 degrees if your distributor is off by a gear. Any reading you get will likely be wrong.

Wouldn't it of read 13* timing or -7* timing when I checked it before changing it?

 

[LFD2037]

Not sure it would be off as much as you think. One tooth could probably be 10-17 degrees off either before or after depending which way it is turned. I would for sure check it. Also did you reset the ecu? Since the o2 gives info for the mixture get rid of the old info.

I've checked it, I'm not just guessing. It was at +3* before I changed it to +7*. This was months AFTER I took the dizzy out.

 

[Reelitchy]

Wouldn't it of read 13* timing or -7* timing when I checked it before changing it?

Not sure what you are saying exactly but if it's a tooth off and you set it at 0. It will actually be 10 or -10 but still read 0. The crank sensor etc is in the dist and thinks its correct. If I set your watch 20 min back and you don't know it - your always going to be late

 

[scottryana]

Reelitchy has it right. If it was a tooth off and you had it advanced 7* it would have not been a true 7 and could have been just getting it back to 0.

 

[mtullis]

A timing light is going to give you a true reading (with the jumper in) the light only fires when the plug does.

 

[scottryana]

Yep timing light will, OBD2 will not.

 

[94SRUNNER]

Between 6 and 7*. That's my estimate of it between 3 and 10* on the timing plate.

Your "estimate"? Did you actually check the engine timing per the FSM?

 

[LFD2037]

Yep timing light will, OBD2 will not.

I used a timing light. I used the jumper in the diagnostic box. Timing measured, with the light, was 3*. I advanced it to 7*.
Your saying my timing could actually be off even though the timing light showed between 6 and 7*?