EGR & burned valves - I see no way it can happen! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-08-2004, 09:57 AM Thread Starter
 
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EGR & burned valves - I see no way it can happen!

OK I've searched for all kinds of info on carb related stuff to cure a high RPM idle up condition when the AC is on. Been checking vacuum valves and such when I decided to clean my EGR valve. Glad I did since the gas port to the regulator was plugged solid with carbon, a soak in lacquer thinner solved that problem.

Now on to the real meat of the issue!

There are many posts on the EGR & possible burned valves resulting from not having the EGR hooked up.
Which is why I cleaned mine!
Many folks claim that if you just drive stop & go around town, without an EGR, you'll never burn a valve. It's hi-speed highway driving that does the damage. I say no way since according to the FSM the EGR doesn't even work due to the fifth gear switch that closes the TWSV and in turn closes the EGR valve. Further more if you drive above 4000 ft elevation at any speed the HAC (high altitude compensator) shuts down the EGR sytem as well. We won't even mention the BVSV that shuts the EGR down until coolant temp is over 116.

So am I "wee Todd did" and don't know chit or is there really no cause for concern over EGR operation / use other than from an emissions view point.

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post #2 of (permalink) Old 06-08-2004, 01:57 PM
 
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Re: EGR & burned valves - I see no way it can happen!

it does help cool down cylinder temps.
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post #3 of (permalink) Old 06-10-2004, 09:34 AM
 
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Re: EGR & burned valves - I see no way it can happen!

So by cleaning up the ERG, did that cure the high idle problem when pressing the AC button?
Mine idles up real high when I press that button, much to high to drive. I put my fingers behind the ERG and did feel movement when pressing on it... so it is not stuck, just probably clogged with carbon build up ???

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post #4 of (permalink) Old 06-10-2004, 11:11 AM Thread Starter
 
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Re: EGR & burned valves - I see no way it can happ

Nope - it did not help that at all. Mine idles up around 2000 RPM when the AC kicks on. Cannot find info in the AC manual as to how many RPM's the idle up actuator should increase idle speed. AC manual just says:
"actuator rod will pull up the throttle lever causing engine idle rpm to rise".
However all the trouble shooting info says to check pressures at 1500 RPM's I would assume that the idle up feature should run at that same speed max.
Looks like any adjustment must be made in the throttle lever / linkage since the actuator is connected to it via a rod which has no adjustment feature that I can see.
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post #5 of (permalink) Old 06-10-2004, 01:34 PM
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Re: EGR & burned valves - I see no way it can happen!

When the compressor comes on it puts a load on the engine, slowing it down. Idle up systems are supposed to restore the idle to what it was before the compressor came on. It shouldn't raise the idle much beyond that.

The reason the EGR moves a little is it's so far out of adustment the R's are getting into mid range -- where the ERG normally starts to open.

Don't know what system you have, but some idle-ups are solenoids, some input the computer, some introduce a small air leak.
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post #6 of (permalink) Old 06-11-2004, 06:00 PM
 
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Re: EGR & burned valves - I see no way it can happen!

OK, mine idles up around 2500 so when I'm on the highway it doubles as a cruse control. I've never recharged the unit so it's probably empty as well, I wonder if recharging it and replacing the seals/ o'rings would create more of a load and bring the rpm's down? Just a thought. I could try another ECM too I suppose.

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post #7 of (permalink) Old 06-11-2004, 09:11 PM
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Re: EGR & burned valves - I see no way it can happen!

If your talking about a samurai, the idle up for the ac unit is adjustable. If the ac is on should idle around 850 to 900.
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post #8 of (permalink) Old 06-11-2004, 09:48 PM Thread Starter
 
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Re: EGR & burned valves - I see no way it can happ

Mine is a carbed Sammi and uses the vacuum solenoid on the throttle linkage. But I don't see a way to adjust it. Help me out a little and tell me how to tweak this thang.
BTW Steve I made more of those clear Lexan door panels but have yet to install any & check the fit. Let me know if your still interested in some as I still need rear panels to serve as templates.
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post #9 of (permalink) Old 06-11-2004, 10:38 PM
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Re: EGR & burned valves - I see no way it can happen!

I used to remove, block off, or disconnect the EGR on all my vehicles. It never seemed to shorten the life of the engines. It seemed to help with off-idle performance in some cases, not make any difference in others. Of course now that 'Big Brother' monitors internet communications, I don't dare do anything against the law (um-humn). I can't beleive any one would sacrifice 10 percent of an engine's horsepower to spin an AC compressor, not to mention the weight of the system. I say do away with it. My '87 Sammy with stock ECM carb runs fine with the electrical load idle up compensator disconnected. The thing that's supposed to idle it up when the alternator is under load. I can't remember why I disconnected it.
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post #10 of (permalink) Old 06-11-2004, 11:15 PM
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Re: EGR & burned valves - I see no way it can happen!

I'm not sure on your system - I don't have one like it. But if it's a vacuum actuator there may be a screw adjustment on the plunger - look for it.
Some actuators you just loosen the mounting screws to adjust.
Some you bend the mounting bracket.
Look on the linkage that contacts it too - there may be an adjustment screw there.

Recharging the system should not make a discernable difference - the load is mostly the compressor turning.

The idle up system is there only to prevent stalling due to the extra load. Properly adjusted it will restore idle back to what it was before the air conditioner was turned on, or slightly higher.

EGR's are used to lower combustion temperatures. NOx forms about 3000 degrees - normal combustion temps are slightly over that "magic number." Adding a tad of inert gas, helium, or burned exhaust lowers the combustion temp slightly. Essentially it spaces the molecules farther apart, not unlike spacing barbeque charcoal briquettes slightly apart to lower the temp.

Engines that were not originally designed to have EGR usually fare better with it disconnected.
But engines that were designed, or the heads modified to use it need it to work. Otherwise the slightly hotter chamber will have pre-ignition - you may not always hear it, but it's destructive.

EGR only operates under cruise conditions anyway -- unless someone that doesn't understand changes things. At idle and lower R's the EGR valve stays closed. At cruise - mid RPM range it opens, letting a tad of exhaust in the chambers. When you punch it, -- Wide Open Throttle, it closes again.

EGR is unrelated to air conditioning fast idle.

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