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Discussion Starter · #1 ·
So new to the forum , but have a question for the community hopefully will be inciteful
We own a 2004 Astro van , has about 225k on the engine and transmission. we are the 2nd owner and purchased it with 200k . I own a transmission shop and am reaching out because we have been unsuccessful in determining why this engine vibrates in drive at idle.

So we replaced the cap and rotor , spark plugs , wire set all a/c delco parts. when we first bought the van . and this issue was not present untill recently. When the vibrations started there was also a power loss and a thump on take off so , we first addressed the obvious. The motor mounts were shot and dry rotted. i replaced them with new ones autozone, and before you say AFTERMARKET! i know not factory ,but the mounts did fix the acceleration and the thump , but not the vibration . so i racked it back up on the drive on and put a pole jack on the oil pan while it was in gear and taking the load off the engine and trans mounts ,but the issue was still there.

So i pulled the cowl off the inside of the engine and checked for vacuum leaks . i found one for the purge solenoid and replaced the hose with a new one . Sadly this did not work either. What i can say for sure is the power steering lines are leaking at the hydro boost and behind the hydro boost. I feel as the engine is idling low maybe creating the vibration . If i barley increase the throttle percentage the vibration practically goes away.

any help would be much appreciated on this.
 

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Discussion Starter · #2 ·
So afternoon update . the engine vibrates badly at idle in drive. i watched the pids on my scan tool and sitting at a fast food restaurant drive thru the idle sits at 540 rpm .If i barely get the idle up like 100 rpm its smooth as silk. also my bank 2 fuel trims seemed to be high . the range is from 0-25 % on my scanner and it was reading high 40s . i wonder if my o2 is bad and increasing the fuel trim
 

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so the throttle body is so dirty . i wonder if this would cause a low idle. im going to clean it and re install it
Rough idle was the 1st sign of intake gaskets going bad on my 2001 Astro. Ultimately it started consuming coolant then overheating as the coolant level dropped faster and faster over time. I suggest check your exhaust for signs of burning coolant (odor, excessive moisture etc) and pay attention to your coolant levels. You could check your spark plugs for evidence.....
 

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Rough idle was the 1st sign of intake gaskets going bad on my 2001 Astro. Ultimately it started consuming coolant then overheating as the coolant level dropped faster and faster over time. I suggest check your exhaust for signs of burning coolant (odor, excessive moisture etc) and pay attention to your coolant levels. You could check your spark plugs for evidence.....
came here to say the same thing

I was not aware that it was the issue, so I replaced the engine and trans mounts that looked worn.

also realized I have a LIM gasket leak (as evidenced by spark plugs, and a positive lab test for coolant in oil)

LIM repaired, rough idle seems better
 

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Discussion Starter · #6 ·
came here to say the same thing

I was not aware that it was the issue, so I replaced the engine and trans mounts that looked worn.

also realized I have a LIM gasket leak (as evidenced by spark plugs, and a positive lab test for coolant in oil)

LIM repaired, rough idle seems better
Im going to start with the obvious before having a fun lower intake to replace gaskets on . Im going to clean the throttle body and see what happens . But i will take into account the possible coolant leaks i know that dexcool is a gasket eater. checking my coolant levels today
 

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Im going to start with the obvious before having a fun lower intake to replace gaskets on . Im going to clean the throttle body and see what happens . But i will take into account the possible coolant leaks i know that dexcool is a gasket eater. checking my coolant levels today
well the OEM gaskets are plastic junk. And they typically fail at around that mileage. Mine was at 206k and probably failed sooner. Not saying for sure that this is your issue, but a lot of people recommend replacing the gasket preventatively at that mileage. With the Fel Pro metal core gasket that won’t fail again. So I was going to replace mine anyway.

I did not notice any coolant consumption or leaking with mine at all. I only knew because of the spark plug contamination, and sending an oil sample to BlackStone labs for $30.
 

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Discussion Starter · #8 ·
well the OEM gaskets are plastic junk. And they typically fail at around that mileage. Mine was at 206k and probably failed sooner. Not saying for sure that this is your issue, but a lot of people recommend replacing the gasket preventatively at that mileage. With the Fel Pro metal core gasket that won’t fail again. So I was going to replace mine anyway.

I did not notice any coolant consumption or leaking with mine at all. I only knew because of the spark plug contamination, and sending an oil sample to BlackStone labs for $30.
good advice . i will defiantly look into this and return with my results. Do you think a combustion test would sniff the exhaust fumes
 

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good advice . i will defiantly look into this and return with my results. Do you think a combustion test would sniff the exhaust fumes
I’m a total novice mechanic. Everyone on here is more experienced than me. I’m just repeatwhat I’ve learned.

FWIW I only did the last oil test because I am a VW owner and a lot of the VW people were adamant that the recommended 10,000 mile oil interval changes were acceptable, and to have your oil tested if you don’t believe it. I figured what the hell, I’ll see what the Astro oil reveals. Lab results showed coolant in oil, and signs of bearing interface wear, likely due to the coolant reducing lubricity I think. That and a guy I know said “that spark plug looks coolant fouled.” It was the spark plug in the rear passenger side, where the LIM gasket is known to often go. I believe if I remember correctly it’s common for it to leak into the cylinder there. I didn’t notice any coolant consumption, so it prob was a small leak into the cylinder

the only test I can think of like that is one where it tests the coolant for combustion products, to rule out a head gasket leak.

again I’m no expert. But I have heard that it is totally worth having the LIM gasket replaced at that mileage since it’s a known failure point
 

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Discussion Starter · #10 ·
So update. Throttle body was filthy so i took it off and cleaned it re installed it and still the same issue persists . I will say there may be something to the intake leaking coolant. the radiator was a 1/2 gallon low so i am going to smoke test the intake this week
 

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I mean, they aren't the smoothest idling engines to begin with, but there are so many things that can cause the idle to be worse. Don't forget to inspect your engine mounts.


If it's losing coolant internally, most of the time it's the LIM gaskets, I wouldn't wait too long before replacing them :)
 
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