Rough idle, and EGR troubles

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pippo

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People,

Posted this on the J car forum with little response/interest, so here it goes:

1987 Sunbird GT NON turbo, original owner. New EGR connected, car has rough idle and runs very badly- kicks/coughs/spits/sputters/buckles, in every RPM range, even at higher rpm's like 4-5000.

Disconnect EGR (and plug vac line to it) and car still has rough idle BUT at acceleration runs GREAT! No hesitation/spitting at all.

My EGR has no electronics to it- just the vac line. This has been going on for years now. I drive it every day to work. I have check for vac leaks and found none so far.

So, conclusion is why rough car running WITH egr, and why rough idle with either egr both connected/disconnected?

Any tips greatly appreciated.

Thanks.
 
how many miles on the engine?
have you done a compression test?
have you checked the spark plug wire resistance?
do all the plugs look the same and are any of them fouled?
 
melsg5 said:
how many miles on the engine?
have you done a compression test?
have you checked the spark plug wire resistance?
do all the plugs look the same and are any of them fouled?
Click to expand...

Thanks, Mel. I did a comp test a few years ago, and they differed by only about 15 psi (145, 140, 135, 150). Car has 209,000 miles on it. But started to behave this way years ago, actually, when it had say, 125,000 on it.

No oil burning at all. Oil level never changes on dip stick. So, isnt that one indicator of good piston rings?

I did install new spark plugs a year ago. Old ones looked decent.

Interesting idea- spark plug wire resistance. Being that they are different lengths, should they register a different resistance between them? What ohms should I expect if I test them?

Remember- car runs excellently when gas pedal floored/accelerating aggressively. No rough engine signs at all. Its just when I re connect that EGR valve. Then it runs like HE@$. (Oh- also same rough idle connected/disconnected).

Thanks again.
 
Plug wire resistance is 1k/foot of wire.
Does the vacuum line going to the EGR valve connect to a solenoid?
If it does have you checked if vacuum is always going to the EGR valve regardless of engine speed which would then point to a solenoid problem?
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melsg5 said:
Plug wire resistance is 1k/foot of wire.
Does the vacuum line going to the EGR valve connect to a solenoid?
If it does have you checked if vacuum is always going to the EGR valve regardless of engine speed which would then point to a solenoid problem?
Click to expand...

Thanks again, Mel. Vac line goes from EGR directly to back of intake manifold port- no solenoid at all. very simple/rudimentary. Guess that makes it easy, huh? Eliminated anything else.

I have even tried 2 different EGR's over the years. Now I have 2 "good" ones, which are basically not even used. Both behave same way. Gotta be something else.
 
OOps, I goofed- you are correct, Mel. I should have said the EGR goes to the TBI port, not directly to the intake manifold. A port in BACK of the TBI.

It sure helps talking about it. Anyway, now that we are clear on that, guess we go to the next step.

I mentioned that I checked for vac leaks. If I missed one, think that could be the cause of bad behavior upon acceleration at all RPM's? I doubt it. If we rule that out, we can chase something else, right, Mel?

Thanks for the continued support/advice/patience.
 
disconnecting the EGR vacuum line at the valve and plugging it causing the engine to run better points to an EGR problem. Do you have vacuum at that line at idle speed and as you open the throttle does the vacuum fade away?
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melsg5 said:
disconnecting the EGR vacuum line at the valve and plugging it causing the engine to run better points to an EGR problem. Do you have vacuum at that line at idle speed and as you open the throttle does the vacuum fade away?
Click to expand...

will check this out asap and let you know.........
 
melsg5 said:
disconnecting the EGR vacuum line at the valve and plugging it causing the engine to run better points to an EGR problem. Do you have vacuum at that line at idle speed and as you open the throttle does the vacuum fade away?
Click to expand...

At idle I have no vac at the end of the line! And when I watch the vac guage as I increase the engine speed by hand (by throttle cable assembly) the vac goes up! It goes up gradually with the RPM's. I could not tell what vac went with what rpm cuz I was under the hood all the time with no assistant (dont know if that even matters).

So, Mel, what does this mean that I have no vac at idle?
 
Is manifold vac and TBI vac different Mel? I understand that manifold vac goes down upon acceleration. But after testing my TBI vac that vac goes UP with acceleration/RPM increase.
 
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Is there more than one port on the TBI and the hose is perhaps hooked to the wrong port?
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melsg5 said:
Is there more than one port on the TBI and the hose is perhaps hooked to the wrong port?
Click to expand...

Figure #13 , on the AZ link you posted on your post #9 (for 1987 sunbird) shows it. I believe it is corrrect. Hey- I can try swapping the vac lines betweeen the MAP sensor and the EGR.

So, After thinking about it a bit I think manifold vac is different than TBI vac. That confused be for a bit.

Anyway, thanks again, Mel.

Maybe if we persist we will finally get it. After many many years.
 
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Just checked under the hood itself and there is a sticker from factory with diagram of that. Even better/more accurate than that AZ diagram. Drivers side port is Evap canister. Middle port is EGR. Pass side port is MAP sensor. All hooked up correctly.

I removed the egr vac tubing and even blew in it to make sure no obstruction. Also, on the fuel evap canister port- think I can disconnect that as that canister is useless anymore. The rubber tubing set )going to/from intake manifold) is rotted at the connection nearest the canister. Also, no way that charcoal is not depleted after 31 years. Not sure if that rotted tubing would cause my problem(?).
 
it would cause a vacuum leak
 
I installed a new rubber hose to that evap canister, so should not be a problem now.

Heres an idea- was reading about harmonic balancers (engine pulley) that can go bad from rotten/cracked rubber which is sandwiched between the pullley parts. Adfter inspection yes, there are some small cracks, but doesnt seem to be serious cracking.

Any idea on if our cars are known for pulleys to be the cause of shaking/rough idle? I thibnk it is remote, but at this point I will consider anything.

I wanted to buy a new one buy cant seem to find one anywhere- the ones on ebay etc all have 3 mounting "holes", where mine has 4. Very strange.......
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pippo said:
Just checked under the hood itself and there is a sticker from factory with diagram of that. Even better/more accurate than that AZ diagram. Drivers side port is Evap canister. Middle port is EGR. Pass side port is MAP sensor. All hooked up correctly.

I removed the egr vac tubing and even blew in it to make sure no obstruction. Also, on the fuel evap canister port- think I can disconnect that as that canister is useless anymore. The rubber tubing set )going to/from intake manifold) is rotted at the connection nearest the canister. Also, no way that charcoal is not depleted after 31 years. Not sure if that rotted tubing would cause my problem(?).
Click to expand...

The evap cannisters can be eliminated by just running a clear plastic universal fuel filter in it's place, one line to vacuum, one line to the gas tank vent .

Doug in P.R.:)
 
Rough idle is either the throttle body is dirty or the idle control valve is dirty,or it needs replacing, or the port it sits in is dirty and or the intake manifold is full of junk-carbon.

Gets some throttle body cleaner and spray those mentioned above out.

Another idea is to use a can of Seafoam in the tank or run it off a good vacuum hose in the can directly while idleing.



Junkyard or Europe is the probally the only place to get the balancer.

Doug in P.R.:)
 
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92 Sunbird LE said:
Rough idle is either the throttle body is dirty or the idle control valve is dirty,or it needs replacing, or the port it sits in is dirty and or the intake manifold is full of junk-carbon.

Gets some throttle body cleaner and spray those mentioned above out.

Another idea is to use a can of Seafoam in the tank or run it off a good vacuum hose in the can directly while idleing.



Junkyard or Europe is the probally the only place to get the balancer.

Doug in P.R.:)
Click to expand...

Thanks, Doug. So, you think it is remote chance that my rough idle is caused from the balancer, right? That would be good news as I would rather chase other components because, as you said, a new balancer is difficult to find.....
 
Know why when I spray cleaner into the TBI the engine stalls? Yes, I did that, about a month ago, tried to clean the tbi with FI cleaner. The engine stalls/dies out completely. Im scared to do it again......
 
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