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Offline ToniJ1960

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detonation and egr pvs etc
« on: March 23, 2014, 08:22:31 PM »
 For the last year or so maybe longer I notice a detonation  rattling type sound under wot when my engine is hot. I was thinking the egr valve might be bad, but it holds vacuum so I think the diaphragm is probably ok.

 The distributor vacuum advance is connected to a port on the carrb base for venturi vacuum I suppose. Its towards the front of the car next to the mixture screw.

 Theres a second vacuum line going to a port on the right of the mixture screw, and to a 2 port pvs screwed into the water block. It goes to the egr and the pcv valve. I really wonder if the pcv valve should get intake vacuum for its signal?

 But anyway back to the subject question. On the vacuum line to the distributor I get 5-10 inches of vacuum increasing with speed and it doesnt drop when the throttle opens and go back up, so I think thats venturi vacuum, although I wasnt expecting 10 or more inches from the venturi port.

 The second hose from the carb to the pvs, on the output side of the pvs I didnt get anything, but on the hose from the carb side I get the same vacuum measurements as the other hose from the carb base.


 So I guess my egr hasnt been getting vacuum to the diaphragm, or does that 2 port pvs only carry vacuum to the other port above a certain temperature? And is this the correct way to conect the egr? For now I bypased the pvs and connected the carb vacuum straight through.

Offline amc49

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Re: detonation and egr pvs etc
« Reply #1 on: March 23, 2014, 11:30:03 PM »
Hello again.

The PVS needs to be used if it's working. It prevents EGR vacuum from coming on with engine cold, they usually miss then. Engine needs to be warm to tolerate EGR without missing. There can be a PVS used on spark control too if car has it, or the retard above say 35 mph to drop emissions. That gets delayed until car warms up too, retarded spark not well accepted until engine warm either.

You generally use 'spark ported' vacuum for distributor if car is an emission model say '74 or later. That is vacuum that is off with car at idle but it comes on as soon as butterfly opens. You do not really use constant vacuum on much of anything, at least I don't. Older cars did before emissions but the distributor full advance (centrifugal and vacuum together) will be arranged for it. You read base and full advance and see if they make sense. They went to spark port to lower idle emissions, NOx rises with advance at idle. Unless some device requires it to be that way I generally don't use constant baseplate vacuum (Thermactor pump bypass or a/c/heat control or vacuum wipers come to mind). The venturi vacuum is used if you have the vacuum amplifier used on EGR. Other than that not much other equipment uses that either other than back barrels on some vacuum secondary carbs. Venturi vacuum does indeed increase with speed rather than falling off as you open throttle more and more.

PCV should only be a bigger hose not small line. At idle only a small bleed like vacuum leak but it has to be able to flow bigger amounts for when the vacuum falls off and the major flow switches on. That happens when the poppet drops back open to open the bigger restriction inside valve. Why they rattle. You CAN tee smaller lines into PCV as long as it has a big pathway there. I have been known to take like fish aquarium brass air valves for the air pumps (bubbles y'know LOL) and patch one or even two in to the PCV hose to modify the idle air amount by hand in case I think trying to get the proper idle speed is forcing me to screw idle speed screw too far into the linkage to hold throttleplates too far into the transfer ports. Easy way to preset idle speed screw then not have to touch it to get idle faster or slower to get the speed I want.

If still using a stock type air cleaner with the snorkel and taking heat off exhaust, then make sure the vacuum dashpot that flips open the door to pick cold air with warm engine is working. If not, hot exhaust preheated air added to a warmed up engine will ping like nobody's business. I've also on one peculiar car had to add a spark delay valve as well to slow down distributor vacuum building to make the vacuum come on a bit slower, it had a tendency to ping while cold oddly enough, that fixed that.

PCV is a double ended system, the norm at idle is flow through the air filter to valve cover, through engine and then through the restriction in PCV and back to intake to zoop engine clean. Yes, it has to have vacuum to work right and constant vacuum there.  At high engine speeds, the poppet closes to allow the bigger leak to happen then PCV flows like 10X the air and the air filter line on other half then flows backwards, why oil builds in it with worn engine. The engine flows more at that time (blowby) than the PCV can handle and why the flow goes backwards.

If the EGR not working then the timing at that time may be too much and making it ping.

I never memorize the ports by the outside, rather I generally have carb off anyway and easy to trace the vacuum circuits then.

The PVS can drive you nuts, they made many with all kinds of action in them, close, open, different number of ports, you name it. IIRC at least they used to mark the temp at which they work on the side. About all you can do is have known good one and then get motor hot or stone cold and vacuum test for what port does what. Like 50 different ones there. REAL easy for them to give wrong part at the parts store. I've seen 140, 165, 180 degree ones. 2 port, 3 port, 4 port.


Offline amc49

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Re: detonation and egr pvs etc
« Reply #2 on: March 23, 2014, 11:32:02 PM »
If original set up and trying to repeat it, year and motor, May have an emission manual that details it if I can find it.

Offline ToniJ1960

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Re: detonation and egr pvs etc
« Reply #3 on: March 23, 2014, 11:43:11 PM »
 78 2.3 ac 4 spd manual

 Im prety sure it was set up when I got it 28 years ago with spark port vacuum for the distributor and the ege through that 2 port pvs. Chiltons only shows a 3 port one so it can give intake vacuum under certain hot conditions to spped the idle and lower the temp.

 The pcv valve has two large orifices and one barb for a vacuum line. The one large end goes into a hose, the larger barbed port goes into another hose, and the smaller vacuum line at the top.

 Its not really pinging like you get if the timing is lightly too advanced and it only does it when its hot. But there was once a spark delay valve to delay vacuum to the distributor. I wonder if I should put it back in. But if that pvs turns out to be bad it neans I wasnt getting any vacuum to the egr valve. Then again maybe it let vacuum to the egr at higher temps. I guess I would have to take it to test that. Or check with the engine hot.

 Im going to try driving it with the pvs bypassed for a while it sounded strong when I was testing it.

Offline amc49

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Re: detonation and egr pvs etc
« Reply #4 on: March 24, 2014, 04:29:10 PM »
The changes made from 75-80 are bewildering to say the least. I did find out the PVS can be rated by opening temperature and the plastic body color.

black    92-98 degrees
blue    125-131
purple 157-163

On a 3 port PVS two hoses attach to get source and the output, the third is a vent to let output fall off to zero. The locations are not standard, vent can be on the top or bottom, you test for it. Thinking source has to be the middle.

Thinking spark delay valves are rated in delay in seconds by body color too. They delay sucking one way through but pass air freely the other way (internal check valve) so it matters which way installed end for end.

Venturi vacuum amplifier hose locations--O is output to EGR valve, R is to any vacuum reservoir tank in there (may need one if it's missing), M or S is to manifold vacuum, and A is for atmosphere or vent. Doesn't use a carb port at all, rather straight manifold vacuum.

There is a circuit in some engines there called DSSA (dual signal spark advance) that 'improves spark/EGR function under mild acceleration conditions'. See if any EPA hood/engine sticker mentions it as supplied on the car if sticker still there. Maybe that if you are not running the vacuum amplifier but thinking the 2.3L does, so it would not apply.

If EGR valve has ever been changed can be that as well, they flow all over the map and different poppets for different parts, some simply on/off, others increase/decrease flow gradually. On like SBC there could be as many as 8 valves, all fit and most wouldn't work right at all.

I'd disregard what I said about using any carb port like spark and use manifold and venturi vacuum if using the amplifier, they may need full-on flow to make that work, the carb port is a restriction in that case. I've never tried to make a venturi vacuum amplifier work, years ago I could not get them so did things in other ways.

If EGR not coming on because of bad PVS then that is the issue, EGR on kills pinging. Spark delay will help but only as long as the delay is, if the ping still going at cruise after a few seconds and steady state cruise then not spark delay and the EGR needs to be working or too much total timing advance somewhere. I'd make sure again that cold air duct in air cleaner snorkel is working correctly, I had that fail once and got your problem exactly. It must be full open to underhood air with hot engine and the exhaust heat pickup part shut.

Offline dick1172762

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Re: detonation and egr pvs etc
« Reply #5 on: March 24, 2014, 07:02:21 PM »
Tonij1960. I know its a long shot, but have you tried the old water sprayed down the carb? I've seen that old trick work on several car. One thing about it is, that it can't hurt the Pinto, so give it a try.
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Offline 74 PintoWagon

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Re: detonation and egr pvs etc
« Reply #6 on: March 24, 2014, 09:44:06 PM »
I've done the water trick several times works pretty good..
Art
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Offline amc49

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Re: detonation and egr pvs etc
« Reply #7 on: March 25, 2014, 12:48:39 AM »
An even longer shot and rare but I've seen a broken piston when someone did that and big piece of carbon came loose to crunch in a quench flat. Carbon cooked long enough is diamond....... .....it can eat exhaust seats like nobody's business. Other than that rarity it might work, but I've not seen ping to where it could not be cured and without doing that. I personally absolutely do not use water or like seafoam in carb on any vehicle ever.


Offline amc49

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Re: detonation and egr pvs etc
« Reply #8 on: March 25, 2014, 03:10:36 AM »
FYI, just ran across a pic of choke side of carb, 3 vacuum tubes in a rough triangle shape. The top curved one is spark port for distributor, the lower straight one on the right is EGR port and the left lower curved one is a vacuum dump for the Thermactor bypass valve. Per service manual.

Also simple 2 port PVS pictured too. If PVS has 4 ports, top 2 and bottom 2 in pairs, if top one is connected at cold then bottom then bottom one is not, they switch with added temperature. Closed one opens and open one closes.

Offline 74 PintoWagon

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Re: detonation and egr pvs etc
« Reply #9 on: March 25, 2014, 08:31:29 AM »
An even longer shot and rare but I've seen a broken piston when someone did that and big piece of carbon came loose to crunch in a quench flat. Carbon cooked long enough is diamond....... .....it can eat exhaust seats like nobody's business. Other than that rarity it might work, but I've not seen ping to where it could not be cured and without doing that. I personally absolutely do not use water or like seafoam in carb on any vehicle ever.
Well, if you use a garden hose yeah it'll eat up stuff, LOL, gotta control the amount only takes a very slight amount, workrd great in my truck with a self contained camper and pulling the race boat..
Art
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Offline dick1172762

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Re: detonation and egr pvs etc
« Reply #10 on: March 25, 2014, 09:50:29 AM »
Well if your so dumb to use a garden hose, it (your motor) should blow up. I use an old windex pump spray. Works great and is no different from having water injection on your car or truck. I had to use water injection on my car hauler back in the 70's when gas went bad at the pump. It would ping all the time. Put the water injection on it and the ping was gone, that is till water tank ran dry.
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Offline rramjet

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Re: detonation and egr pvs etc
« Reply #11 on: March 25, 2014, 11:53:13 AM »
I remember water/alcohol injection being used on some of the old recip aircraft I worked on in my younger days in the USAF. it was called ADI, (anti detonation injection). Water cools the mixture and alcohol keeps the water from freezing. More HP for take-off.

Offline jeremysdad

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Re: detonation and egr pvs etc
« Reply #12 on: March 25, 2014, 12:41:06 PM »
I personally absolutely do not use water or like seafoam in carb on any vehicle ever.

Out of curiosity, what is your beef with Seafoam, other than the general price?

It is ignitable, by itself, and does at least stabilize fuel for storage.

DO NOT DO THE VACUUM LINE DIRECTIONS if you're over 75,000 miles. If you're over that, add it to the gas tank, and you're golden.

Don't knock a good product, without evidence as to why you're knocking it. :)

You pour any liquid directly down the throat of a carb, and you WILL hydro-lock a motor. But aren't bent rods how mechanics stay in business? lol

Offline Pinto5.0

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Re: detonation and egr pvs etc
« Reply #13 on: March 26, 2014, 05:12:21 PM »
I always used a condiment bottle filled with water to clear carbon. 2500 RPM & a steady stream worked great.
 
On a side note does anyone else think the EGR plate is packed full of carbon & isn't working anyhow?
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Offline 74 PintoWagon

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Re: detonation and egr pvs etc
« Reply #14 on: March 26, 2014, 05:41:09 PM »
Everyone I've taken off that had a lot miles on it were all carboned up..
Art
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Offline ToniJ1960

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Re: detonation and egr pvs etc
« Reply #15 on: March 26, 2014, 08:59:46 PM »
 Once I drive it the way it is with the pvs bypassed for a while, if its not better I plan to take the egr off and check the passages. I have a new gasket allready. The diaphragm holds vacuum so I dont  think Im going to buy a new egr valve just yet
(theyre a little pricey)

Offline 74 PintoWagon

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Re: detonation and egr pvs etc
« Reply #16 on: March 26, 2014, 09:51:44 PM »
Wouldn't hurt to check and see if it's functional.
Art
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Offline Pinto5.0

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Re: detonation and egr pvs etc
« Reply #17 on: March 26, 2014, 10:08:49 PM »
Testing it is easy. With the engine warm & idling push on the EGR valve through one of the slots with a screwdriver. If the engine bobbles it's working.
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Offline 74 PintoWagon

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Re: detonation and egr pvs etc
« Reply #18 on: March 26, 2014, 10:14:33 PM »
Probably wouldn't hurt to clean it out though..
Art
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Offline ToniJ1960

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Re: detonation and egr pvs etc
« Reply #19 on: March 26, 2014, 11:54:33 PM »
Testing it is easy. With the engine warm & idling push on the EGR valve through one of the slots with a screwdriver. If the engine bobbles it's working.

 Thats an ideea too I never saw the slots in the back. What do you push on it with something not sharp? A screwdeiver would be a bad idea?

 Right now my Pinto has two flats in front :( the tires are ok I need to air them up. Every time the weather changes they quit holding air. I had three different places work on  the wheels I suppose theyre too far gone. Time to find some wheels (not real easy to do :(  )

Offline Pinto5.0

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Re: detonation and egr pvs etc
« Reply #20 on: March 27, 2014, 04:41:38 AM »
Thats an ideea too I never saw the slots in the back. What do you push on it with something not sharp? A screwdeiver would be a bad idea?

The valve is steel & it doesn't take much pressure. Certified mechanics recommend this as a quick test of the valve. It wont hurt anything.
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Offline amc49

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Re: detonation and egr pvs etc
« Reply #21 on: March 28, 2014, 08:38:31 PM »
Sorry, lost my dsl for a bit there.

Be careful sticking a screwdriver up in valve if you cock the diaphragm piston to one side you can cut the rubber and junk then. Better to simply add manifold vacuum straight to valve, that'll tell the tale. The EGR block under carb is bad about blocking up with carbon.

Rather not discuss seafoam, I always get flamed for it. Suffice to say I think most auto maintenance chemicals are a ripoff, and do nothing. I use hardly any of them at all.

At our shop I pulled a couple of engines apart that used water injection, the cylinder walls were very finely steam pitted, the blocks had to be bored. I will not argue that water injection does nothing but unless you have a computer dosing it out then you are messing with your engines' durability there. Very easy to get slightly too much and the damage.