How far to retard timing - or is it something else?

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
My fj60 knocks under load, and on hill starts. Just did a valve adjust, new plugs, etc. Everything seems right, so I'm trying to get the timing so that I don't knock anymore. Can't seem to however...

I've removed and plugged the vacuum advance lines to the dizzy, and with it adjusted so that the bb is exactly under the pointer, it knocks. (Vacuum at this point is 21.5 inches by the way - for those of you who've suggested timing by vacuum).

I've retarded the timing, bit by bit. Now the bb has moved to be just under the edge of the window, and vacuum is 20 inches. Knocking still on hill starts, and just a little rattle under load at higher rpm.

From reading the FSM and Haynes the only thing that I can think of is that the pistons are carbonized, due to many miles with a carb running rich. Right solution would be to have the carb rebuilt, and to yank the head to clean the pistons.

However, I don't know enough about engine tune-up/timing/etc to spend this kind of money and time w/out some smarter folks chiming in first...

Any advice appreciated.
 
Joined
Aug 26, 2002
Messages
1,484
Location
One of Four Presidential Flying Saucers
First, check to make sure your smog pump is pushing enough air into the heads. You may not be running rich at all - the error could be in the air injection system.

Second, time for a little Sea Foam. Do a search and you'll find a ton of info on the stuff. It'll burn the carbon off of everything and might take care of the pinging (if it's caused by carbon, that is) Be sure to reset your timing back to the right setting, as well.
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
swank60 said:
First, check to make sure your smog pump is pushing enough air into the heads. You may not be running rich at all - the error could be in the air injection system.

Second, time for a little Sea Foam. Do a search and you'll find a ton of info on the stuff. It'll burn the carbon off of everything and might take care of the pinging (if it's caused by carbon, that is) Be sure to reset your timing back to the right setting, as well.
I had to take it to a shop recently, since I failed emissions (high CO). The shop said my air injection was good, and all I needed was a new cat. CO went to zero, and I passed emissions. So, I assumed my air injection was OK...but maybe I should recheck.

I did a can of Sea Foam. 1/3 in carb, 2/3 in tank. Any value in doing it a second time?

Thanks!
 

Doc

 
Joined
Apr 26, 2004
Messages
5,918
Location
Utah
Run the entire can of sea foam in the carb or PCV. It'll eventually clean out the carbon.
 

FJ40Jim

The Cruiser Whisperer
 
Joined
Sep 26, 2003
Messages
10,390
Location
Lancaster, Ohio, USA
swank60 said:
First, check to make sure your smog pump is pushing enough air into the heads. You may not be running rich at all - the error could be in the air injection system.
Swank is half right. Something needs pushed into the engine to lower the compression and keep the aggresively curved ignition from rattling. The system that does this is EGR. If the EGR is not opening fully, then cylinder pressure and burn rate will both be too high, causing spark knock.

Mixture can also be a contributing factor. Gunked carb or vac leaks will lean the mix which leads to knocking.

The Air Injection Reaction (AIR) system does shove air into the exhaust, but that is downstream and after the combustion event. It doesn't affect combustion process, but does have a big effect on tailpipe emissions.

One other common problem on old electronic distributors is the advance stop pin gets eroded inside the distributor. This increases the amount of mechanical advance. The stock distributor already has way too much advance for good performance. Add several more degrees w/ the worn stop pin and it only gets worse. Check the mechanical advance to make sure it is not more than spec'ed in the FSM.

HTH!
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
Based on the advice given, I've done a few things to try to nail this down a bit further.

Ran another can of Seafoam through the carb (in 1/3 increments). Lots of smoke each time.

Worked through the EGR section in the Emission Control Repair Manual. Here are the problems I found.

1. Filter in t he vacuum modulator looks like crap - you can blow through it, but barely. Cleaning didn't seem to help. Thus checking air flow through the vacuum modulator with engine off and with engine at 2500 rpm is hard. Supposed to be free air flow w/engine off, and strong resistance at 2500 rpm. I got strong resistance in both conditions. Also removed the filter, and still had strong resistance in both conditions.

2. With port R on the Vacuum Modulator connected directly to manifold, at 2500 rpm manual says I should get high vacuum and engine misfire. Instead, I get zero on the vacuum guage, and engine runs smooth.

3. Blowing into port F on VSV at 1500 rpm, VSV should open and air should come out of port E. I get no air out of port E.

4. Inspected VSV more closely. Blowing air into pipe E when VSV is connected to battery and air should come out of pipe F - but no air comes out.

I did not remove and inspect the EGR valve, as I've read on here that this can be quite difficult. However, the Repair Manual gives a test of the EGR valve, which it passed. (Apply vacuum directly to the EGR valve at idle, engine should run rough and/or die.)

Based on the above, it appears that my Vacuum Modulator and VSV need replacing.

Further advice before I drop coin highly appreciated.
 

FJ40Jim

The Cruiser Whisperer
 
Joined
Sep 26, 2003
Messages
10,390
Location
Lancaster, Ohio, USA
Doug,
Congratulations :bounce:

You've followed the FSM test procedures and gotten results. :)

Sounds like the EGRVM and VSV are bad. They are throwaway items, so it's time for new ones. :crybaby:
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
Thanks Jim for the words of encouragement. I'll work through a couple of the other sections in the Emissions Repair Manual, and see what else needs to be replaced. Guess an order to C-Dan is in the making.
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
Here's an update...and two questions...

I've run another can of seafoam through the engine, and looked at the top of the pistons. They are grey, not black, not silver. Is this correct?

I've replaced a few parts, and seem to have no pre-ignition at higher rpm - say over 2500 rpm at WOT.

However, the most severe knocking is at very low rpm - 700 rpm for example. It happens even with very little throttle. Most noticable on moderate hill starts.

Based on the advice from above, I still have some other things to check, but wondered if it's meaningful that the knocking is worse at low rpm...that is, does knowing this help to isolate the likely cause?

Thanks for the help.
 

dd113

 
Joined
Jun 13, 2003
Messages
2,922
DOug, Are you sure this is spark knock and not rod knock? Will it do it not under load?
 

60wag

SILVER Star
 
Joined
Jun 25, 2003
Messages
1,929
Location
Boulder, CO
Did you ever look into the distributor advance limit pin? I was told that there is supposed to be a rubber sleeve on the pin. Mine had no sleeve so I added one to reduce the amount of total advance. A slice of nylon air hose fit nicely - I think it was 5/32". As with my subtle knocking problem, it seemed to fix it, for a while. I still get a bit of knock but its at wide open throttle at high rpm. I need to take a look in the dizzy to see if the pin sleeve is still there. I'll also likely replace the EGR vacuum modulator one of these days. I get the knock more noticeably at the beginning of a trip rather than later on. It'll do the same thing two days in a row so I don't think its related to carbon buildup. I'm gussing its more of a thermal issue. Maybe the old vacuum modulator changes a bit as it gets heated up? Your problem is different in that its low rpm rather than high. Are you SURE you've got the distributor advance vacuum hoses connected properly especially on the engine side of carb.
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
dd113 said:
DOug, Are you sure this is spark knock and not rod knock? Will it do it not under load?
I don't know what rod knock sounds like, so I can't rule that out. However, I hear the sound only under load. No sound when revving the engine in neutral, no sound when accerating under light load. I can drive so that I don't get the noise, and I can drive so that I do get it.

Does that help?
 

lovetoski

SILVER Star
 
Joined
Jul 13, 2003
Messages
4,628
60wag said:
Did you ever look into the distributor advance limit pin? Are you SURE you've got the distributor advance vacuum hoses connected properly especially on the engine side of carb.
I haven't checked the dist advance limit pin, but plan to this evening. Thanks for the tip on a fix...
Regarding the vacuum advance hoses...I have checked all the hoses at least twice, but obviously something is still wrong, so I'll check these again tonight when I'm futzing w/the dizzy.
 
Top Bottom