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Old 12-07-2011, 05:05 PM   #31
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Car "stumbles"


It pumps the exhaust gas into the intake system. Not the other way around.

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Old 12-07-2011, 05:09 PM   #32
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Car "stumbles"


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It pumps the exhaust gas into the intake system. Not the other way around.
Thaks, House, but still- how can it pump exhaust gas if its mounted on the imntake manifold? I dont get it.
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Old 12-09-2011, 06:06 AM   #33
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It's mounted on the intake manifold, but there should still be some type of EGR tube coming from the exhaust system. When the EGR valve opens the vacuum and pressure from the exhaust pumps the spent gases back into the intake.
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Old 12-09-2011, 07:11 AM   #34
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It's mounted on the intake manifold, but there should still be some type of EGR tube coming from the exhaust system. When the EGR valve opens the vacuum and pressure from the exhaust pumps the spent gases back into the intake.
LOL....Hey man, I know youre trying to help me understand this,. but there is NO "some type of EGR tube coming from the exhaust system", period.

Unless, perhaps you mean to say that somehow, the exhaust kinda blows back into the cylinder and makes its way through the intake valves BACK out to the egr??

Thanks again, house.
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Old 12-09-2011, 07:18 AM   #35
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Car "stumbles"


I don't know what your system looks like but perhaps there is an internal exhaust port through the intake manifold and head.
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Old 12-09-2011, 02:48 PM   #36
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OK, I get ya now. maybe. Guess if I want I can look up the drawing in the shop manual- maybe theres something in there that may show the port innards. But, thanks for the persistence in helping me understand, house!
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Old 12-09-2011, 06:07 PM   #37
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OK, after searching /rresearching more, Ive concluded the only thing it could be is its a defective/off spec EGR valve. It IS aftermarket, and Ive learned lots of people warn of this- too late for me to return it- bought it 9 yrs ago. For now, Im gonna unplug the vac hose and stopper it up. I also have not noticed any pinging/knocking as a result. Whats the harm, right?
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Old 12-10-2011, 11:24 AM   #38
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No harm. They are not open during idle or WOT I believe. Only cruising at partial throttle. Just emmisions junk.
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Old 12-10-2011, 02:32 PM   #39
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No harm. They are not open during idle or WOT I believe. Only cruising at partial throttle. Just emmisions junk.
Right , house, no egr on both idle and WOT (I learnt this in all my research...LOL). You do need to be aware of pinging though- can be serious. If pinging is that "ticking" noise when one cruises/accelerates (timing too advanced), I dont have it (although, I understand, the ECM does correct for it if it happens).

Thanks, Man!

(on to my honda civic ac comp project.......other thread)
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Old 12-16-2011, 07:22 PM   #40
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Oh Boy

I don't think this is a type of problem for a DIYer. You had a very good reply about checking codes, did you? It has nothing to do with your check engine lite, also in these years GM has what called a "data stream" which is a valuable tool for a competent technician. The fact that you unplugged your EGR for years can lead to problem of carbon caking giving other symptom exactly of what you are describing. Yes there is an internal exhaust port and an vacume port in the Intake manifold. EGR is MUCH more then an anti pollution device, in the 80s when computerized engine controls came mainstream, lots of old school techs and backyard mechanics blew them off as "anti-pollution". False.

My suggestion would be research intake valve deposits, problematic TB gasket and TB warpage, GM data stream and pid values.

Sorry to be so vague on the reply but rough idle problem are rarely an easy fix.

Good luck
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Old 12-17-2011, 01:10 PM   #41
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Oh Boy

I don't think this is a type of problem for a DIYer. You had a very good reply about checking codes, did you? It has nothing to do with your check engine lite, also in these years GM has what called a "data stream" which is a valuable tool for a competent technician. The fact that you unplugged your EGR for years can lead to problem of carbon caking giving other symptom exactly of what you are describing. Yes there is an internal exhaust port and an vacume port in the Intake manifold. EGR is MUCH more then an anti pollution device, in the 80s when computerized engine controls came mainstream, lots of old school techs and backyard mechanics blew them off as "anti-pollution". False.

My suggestion would be research intake valve deposits, problematic TB gasket and TB warpage, GM data stream and pid values.

Sorry to be so vague on the reply but rough idle problem are rarely an easy fix.

Good luck
Thnaks. No "check engine light " on. But, do you mean a Scan Tool? I could buy one if it comes up for sale on ebay. If you think that would help. Now, to you, running without the rge could show up as pinging. If YOU would not hear any pinging or clickety clackety (or tick-tick-tick) in the engine while running, would you conclude you are running the engine timing as safe? isnt the ECM for 87 GM suppose to compensate for pinging should it happen?

Thanks
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Old 12-17-2011, 03:48 PM   #42
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Ok I'll try to answer these
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Thnaks. No "check engine light " on. But, do you mean a Scan Tool? I could buy one if it comes up for sale on ebay. If you think that would help.
In all OBD systems there are priority to the codes, not all will give a "CE" (check engine) on dash, some are secondary faults that won't lite the dash but will give you a indication on whats going on. Did the unplugged EGR give a CE lite? I don't remember, its been a while since I worked on an older GM here in the salt belt they are long gone. Buying a scanner with a the capabilities of reading a data stream could be useful altho depending on your skill level could be overwelming as well. Mid to late 80's car were a piss off to diagnose, the first generation OBD systems where unreliable and not vary precise to say the least.

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Now, to you, running without the rge could show up as pinging. If YOU would not hear any pinging or clickety clackety (or tick-tick-tick) in the engine while running, would you conclude you are running the engine timing as safe?
No, if you hear ping things are already going way bad, knock sensors pick up small frequency noises and are often problematic of of being over sensitive.

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isnt the ECM for 87 GM suppose to compensate for pinging should it happen?
Yes

Two different things here, static and calculated (computed) timing
The job of an egr has nothing directly to do with ping, ping is a symptom not a fault. Ping = Pre ignition. The job of an EGR is to lower the temperature of the combustion chamber, reducing certain pollutants, (true high combustion temp can cause ping among other things), thus giving the ECM a easier time to adjust other perimeters that effect performance, fuel economy, and anti-pollution. An ECM (brain) thinks in 3D, its usually called strategies. This is way too complicated for me post, I type real slow but basically unplugging an egr shift many calculation to the left a bit effecting mostly fine tuning, like a car with a funny stumble or whatnot. Unplugged whatever puts your car into a limp mode, not optimal for anything.

What I think is going on with your car, -put a "without looking at it" disclaimer here - unplugging the EGR for so long causing #1 combustion temperatures to run too hot, in turn causing carbon deposits on the intake valves outside of combustion chamber #2 in turn playing with fuel mixture #3 ECM is trying to adjust timing #4 ECM is trying to adjust fuel mixture #5 normal wear and tear of motor after 25 years These cars are known for a bad TB gasket and sometimes the TB warping. All these symptoms altho nothing is majorly f-ed up, show up as poor performance between hot and cold. Again very difficult to diagnose even for a licensed tech.
What I would do in your shoes, check for a vacum leak around the base of the TB, take it to a shop and pay a one hour diagnosis, it might cost you less in the long run.

I am sorry if my posts come off as arrogant, its not meant to be so, its just on forums I have a hard time expressing my demeanor. Sorry if I missed something.

Good luck
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Old 12-19-2011, 06:24 AM   #43
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Yes, GM tries using EGR to compensate from running water temps WAY too hot. I learned this from working on C4 Corvettes. If you do block off the EGR, I'd recommend keeping an eye on water temps and possible putting in a lower temp T-stat and a fan switch.
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Old 12-21-2011, 04:04 PM   #44
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Sorry for delay- ben busy putting together my civic ac (other thread). But, thanks, Mac and house. Guess some history is in order:

My egr is not elec, but just vac type, so wouldnt give "feedback" to the ecm. Still, when unplugged, no check engine light. Yes, I know unplugging it is bad, but man, the car runs so sloppy with it connected (cruise only), and soooooo smooth without. Funny you brought up the hotter radiator/engine, and I did install a simple toggele switch a year ago for the fan!!

Mac, I did spend some $$ on this years ago- got me nowhere. They just done get excited on working on sunbirds. The dealer told me I needed a new cat, AND FI. They were grasping at straws. I still have the same cat. Bought myself a new FI and was for nothing. Dealers......

I dunno- I always heard an egr is responsible to lower temps in combustion , higher temps which can cause detonation (or pre ignition?), oh well, whatever- can never get them 2 straight- either of whioch is not good for engine, thats the point. You say its just for lowering NO3/NO2, (by allowing for lower temps, without which the no3/no2 gasses would be worse. )

So, where to go from here. I will be osting a link to a youtube soon- think t will help? Its showing the vac gauge at idle. Maybe its a shot, eh?
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Old 12-21-2011, 06:35 PM   #45
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OK, here it is- not sure if it is relevant to my egr problem, but this is what I have on my car:

http://www.youtube.com/watch?v=Zs4QT...ature=youtu.be

undulating vacuum at idle, fluctuating about 1-2 " mercury. Any ideas? This I believe may be even unrelated to my egr running roght at cruise speed. Still, if I can fix this bad vac, its a win.

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