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HELP PLEASE #2

NoVaGT

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I've been struggling with a low RPM (1500-2100RPM) subtle bucking/shuddering, that felt like an engine miss-fire. Subtle, but annoying as hell as it is most noticeable when just cruising in 5th or 6th. It happens in every gear, but it's really noticeable when you just want to cruise in a relaxed manner.

During free-way cruising, right in the RPM range where the bucking/shuddering would occur, I would get a CEL with engine misfire code(s) that would require a crank-position sensor relearn.

So I dropped the car off at the dealership yesterday. Today the service manager called with what they think is the issue;

Air getting into the intake system past the MAFS.

Some sort of crack in either the intake manifold, or the intake tubing past the MAFS. This would lead to a very lean stoichiometric rate, too much air, not enough fuel. So what I was feeling at low RPMs was knock/detonation??? Basically combustion skipping a cycle?

Head temps did not get high, so I hope I don't have to fear any major damage. The engine pulled strong and clean past 2100RPM.

Now, I would figure the stoichiometric rate was waaay too lean. And of course there were engine miss-fire (random) codes and CELs. Does that mean the engine could tell that detonation was happening due to the mixture being too lean? Or the ECU could tell that normal combustion wasn't happening at the correct time because of the lean condition?

Are these conditions the ECU can detect and then threw misfire codes? For some reason I figured a misfire code meant an electrical gremlin in the ignition system the ECU was detecting.

Also, should I change the plugs?
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jhatley7

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Not sure if Bama lets you datalog for revisions, but that's what needs to be done. Sounds to me like a tune issue.
 

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some people have posted about their intake manifolds cracking and causing such issues, can't find the thread at this moment though.
 

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I had this same exact issue with BAMA, had 11 revisions until they got it working with out the suddering or surging, it was back and forth between Brandon and Ryan, Ryan actually solved the issue. In total from adding more parts and BAMA issues I've had 30+ revisions. Not joking, ported tb 5+ revisions, ported intake 5+ revisions, ported manifold 5+ revisions, 47lbs injectors, 5+ revisions, flex-fuel tune 5+ revisions, point is they can get it done, it's most likely the tune from BAMA that has the issues it's just very time consuming working with them.
 

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I have a similar issue as well... i got a P0316 code which is for misfire at startup but the misfire happens when I'm driving normally like u, at around 1500-2200rpm. I cleared the code but haven't got any back even though it still bucks....
 

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I've gone through much of the sub-forum here for issues, and it appears as if cracked intake manifolds happen. It appears to be a known issue, as replacement intake manifolds have a new part number.

So, hopefully I'll get the car back this week, with the manifold replaced fixing the misfire issue, a replaced tachometer glass (plastic), and a replaced steering wheel (weird wear after 8400 miles).
 

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I've gone through much of the sub-forum here for issues, and it appears as if cracked intake manifolds happen. It appears to be a known issue, as replacement intake manifolds have a new part number.

So, hopefully I'll get the car back this week, with the manifold replaced fixing the misfire issue, a replaced tachometer glass (plastic), and a replaced steering wheel (weird wear after 8400 miles).
Hmmmmm maybe I have a cracked IM??? It did start to happen after a hard launch at the track. This misfire is driving me crazy!
 
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Hmmmmm maybe I have a cracked IM??? It did start to happen after a hard launch at the track. This misfire is driving me crazy!
Many people have reported this issue, but the instances have never been collated into one thread. Perhaps it's time we did so.

I do think that many people have cracked intake manifolds, but they're never properly diagnosed. There was one member here that had exactly the same issues, and went through something like 14 revisions of tune with BAMA to "fix" the issue.

And I bet that the tune was just manipulated to mask the issue.

Another poster here stated he just had the misfire CELs shut off, and lived with the bucking shuddering.
 
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I have a similar issue as well... i got a P0316 code which is for misfire at startup but the misfire happens when I'm driving normally like u, at around 1500-2200rpm. I cleared the code but haven't got any back even though it still bucks....
I'd bet a lot of money your IM is cracked. That is exactly what my car was doing.

Annoying as hell, ain't it?
 

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Yeah now it's got me thinking... it did happen right after a hard launch at the track. Hell yeah it's driving my crazy! I can't stand it, makes me mad just think about it lol.
So how can you determine if it is a cracked IM? Is there any kind of test or something?
 

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Yeah now it's got me thinking... it did happen right after a hard launch at the track. Hell yeah it's driving my crazy! I can't stand it, makes me mad just think about it lol.
So how can you determine if it is a cracked IM? Is there any kind of test or something?
All I can say is your car's symptoms are identical to mine. And it's a known issue. Just drop your car off at the dealership and tell them you think it has a cracked I.M., and let them take it from there.

My dealership had seen enough of them for the techs & service advisor to know exactly what was wrong.
 
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I got my car back today, after they installed a new I.M.

Everything is fixed. The bucking/shuddering (misfiring) is gone, and the engine is much smoother.

Un-metered air getting in and fucking with the ECU really had the engine running like dog guano......go figure.

They also replaced the steering wheel (bad wear after 8400 miles) and the tachometer lens, which was scratched when I bought it.

The new steering wheel has a really weird effect, like the car is brand new.
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