Code 34 (93 LT1
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From: Detroit's West Side MI
Code 34 (93 LT1
In the ongoing issue with my rebuild I replaced the timing set and opti to the '95 version, no change.
Various checks and I have bad vacuum (-5 in/hg), and a code 34 (MAP sensor signal voltage was too low (high vacuum) when engine speed was under 700 RPM, or when TPS was greater than 20% with an engine speed above 700 RPM)
Could my new cam have a bad grind?
EGR is removed, could I have a leak or a problem with the EGR system?
What about vacuum lines routed incorrectly or not connected?
Various checks and I have bad vacuum (-5 in/hg), and a code 34 (MAP sensor signal voltage was too low (high vacuum) when engine speed was under 700 RPM, or when TPS was greater than 20% with an engine speed above 700 RPM)
Could my new cam have a bad grind?
EGR is removed, could I have a leak or a problem with the EGR system?
What about vacuum lines routed incorrectly or not connected?
Last edited by ScaryFast; Mar 15, 2006 at 06:17 PM.
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From: South Carolina
St. Jude Donor '03 & '05
Originally Posted by ScaryFast
In the ongoing issue with my rebuild I replaced the timing set and opti to the '95 version, no change.
Various checks and I have bad vacuum (-5 in/hg), and a code 34 (MAP sensor signal voltage was too low (high vacuum) when engine speed was under 700 RPM, or when TPS was greater than 20% with an engine speed above 700 RPM)
Could my new cam have a bad grind?
EGR is removed, could I have a leak or a problem with the EGR system?
What about vacuum lines routed incorrectly or not connected?
Various checks and I have bad vacuum (-5 in/hg), and a code 34 (MAP sensor signal voltage was too low (high vacuum) when engine speed was under 700 RPM, or when TPS was greater than 20% with an engine speed above 700 RPM)
Could my new cam have a bad grind?
EGR is removed, could I have a leak or a problem with the EGR system?
What about vacuum lines routed incorrectly or not connected?
Thread Starter
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Joined: Jul 2001
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From: Detroit's West Side MI
Originally Posted by steve40th
Did you replace the MAP?
Plus, we actually measured low vacuum in the cylinder, so I would assume the MAP reading is accurate.
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Looks like you have a massive vacuum leak to me it should be ~19inHg.You listed all the good candidates.Does it run?How about Valve adjustments?They could be stuck open causing that low a vacuum.Backfiring?
Thread Starter
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From: Detroit's West Side MI
Originally Posted by Redeasysport
Looks like you have a massive vacuum leak to me it should be ~19inHg.You listed all the good candidates.Does it run?How about Valve adjustments?They could be stuck open causing that low a vacuum.Backfiring?
It runs terribly and has severe spark knock. I've been trying to fix it as a severely advanced timing issue until today.
No backfiring, but running very rich, lots of smoke, etc.
With my cam (I added specs below in sig) I'd expect a little less pressure, like maybe 16.
Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Have you tried the torch/starting fluid tests at all the possible vacuum leak areas?
That is a pretty hefty cam.Have you run the 30# injectors before or are they new too?If new that would be why it is rich your gonna need a tune for those.
That is a pretty hefty cam.Have you run the 30# injectors before or are they new too?If new that would be why it is rich your gonna need a tune for those.
Last edited by Redeasysport; Mar 15, 2006 at 07:31 PM.
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From: Myrtle Beach SC
St. Jude Donor '05-'06
You could try plugging all the vacuum lines except for the FPR and re add them one at a time.Check the EGR plug too if it is not sealing it could be a problem.Got the old egr? Put it on to eliminate that.
You said "low vacuum at the cylinder" what does it read on the intake?
You said "low vacuum at the cylinder" what does it read on the intake?
Last edited by Redeasysport; Mar 15, 2006 at 07:38 PM.
Thread Starter
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From: Detroit's West Side MI
Originally Posted by Redeasysport
You could try plugging all the vacuum lines except for the FPR and re add them one at a time.Check the EGR plug too if it is not sealing it could be a problem.Got the old egr? Put it on to eliminate that.
You said "low vacuum at the cylinder" what does it read on the intake?
You said "low vacuum at the cylinder" what does it read on the intake?
We checked the EGR plug, it had a slight leak but it didn't change when we fixed it. I'll check the other lines, but there really aren't many without EGR.
The injectors are new with the cam/heads. I will try a fluid test at each. I hope I have enough fluid...everyone's closed now.
Oh, and I have a custom PROM from Alvin for the updates.
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Le Mans Master
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Well you know if there is no external vacuum leak that only leaves.........Don't wanna say it
Just because there is no external leak on the EGR it does not mean the plate is sealing across the 2 ports.I would put the old EGR on to eliminate that.
Then there is are you 100%sure the opti is installed right.You know it can be off but with no backfiring I doubt it.Have you checked for spark at each plug yet and/or pulled them to check for wetness?
Just because there is no external leak on the EGR it does not mean the plate is sealing across the 2 ports.I would put the old EGR on to eliminate that.
Then there is are you 100%sure the opti is installed right.You know it can be off but with no backfiring I doubt it.Have you checked for spark at each plug yet and/or pulled them to check for wetness?
Last edited by Redeasysport; Mar 15, 2006 at 07:54 PM.
Thread Starter
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From: Detroit's West Side MI
Originally Posted by Redeasysport
Well you know if there is no external vacuum leak that only leaves.........Don't wanna say it
Just because there is no external leak on the EGR it does not mean the plate is sealing across the 2 ports.I would put the old EGR on to eliminate that.
Then there is are you 100%sure the opti is installed right.You know it can be off but with no backfiring I doubt it.Have you checked for spark at each plug yet and/or pulled them to check for wetness?
Just because there is no external leak on the EGR it does not mean the plate is sealing across the 2 ports.I would put the old EGR on to eliminate that.
Then there is are you 100%sure the opti is installed right.You know it can be off but with no backfiring I doubt it.Have you checked for spark at each plug yet and/or pulled them to check for wetness?
We just replaced the opti. It's fine. Plugs are soaked with fuel, I've replaced them several times just to keep them fresh.
The old EGR valve had a leak, too. I just need to check the seal again.
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From: Slidell Louisiana
I would bet on an vacuum leak prior to a faulty cam.
Did you have your heads decked?
If the heads were decked were your intake surfaces machined in order to maintain proper alignment/fit of the intake manifold ?
On some of the other sites guys are writing threads about intake fitment issues when they get their heads back due to the geometry change imparted by decking the heads.
Mike
Did you have your heads decked?
If the heads were decked were your intake surfaces machined in order to maintain proper alignment/fit of the intake manifold ?
On some of the other sites guys are writing threads about intake fitment issues when they get their heads back due to the geometry change imparted by decking the heads.
Mike
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St. Jude Donor '05-'06
I wasn't headed for the cam yet but something along what Aboatguy said.Some kind of internal intake leak.Untill you can get a vaccum even when turning over I would not go there.Soaked plugs aren't a good thing either.Are you sure it is firing on all cylinders?Coil?ICM?.I would be trying to find out for sure if your getting enough spark too.
Thread Starter
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From: Detroit's West Side MI
Originally Posted by aboatguy
I would bet on an vacuum leak prior to a faulty cam.
Did you have your heads decked?
If the heads were decked were your intake surfaces machined in order to maintain proper alignment/fit of the intake manifold ?
On some of the other sites guys are writing threads about intake fitment issues when they get their heads back due to the geometry change imparted by decking the heads.
Did you have your heads decked?
If the heads were decked were your intake surfaces machined in order to maintain proper alignment/fit of the intake manifold ?
On some of the other sites guys are writing threads about intake fitment issues when they get their heads back due to the geometry change imparted by decking the heads.
If there's a fitment issue between heads and block wouldn't the head gasket fix it? So the fitment could be between heads and intake?
How do I:
1) test to see if this is a problem
2) fix it?
So when you say geometry change, I assume you mean that the top of the heads are further apart because they sit lower on the block, causing the intake to not seal?
Opened topic up (I think code 34 was too specific a subject) to here:
http://forums.corvetteforum.com/show...post1554444569
Last edited by ScaryFast; Mar 15, 2006 at 11:07 PM.
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From: Slidell Louisiana
Originally Posted by ScaryFast
No, the heads weren't decked (nor the block). But the heads and intake were a swap, I sent my cores and got back a (supposed) matched intake to the heads.
If there's a fitment issue between heads and block wouldn't the head gasket fix it? So the fitment could be between heads and intake?
How do I:
1) test to see if this is a problem
2) fix it?
So when you say geometry change, I assume you mean that the top of the heads are further apart because they sit lower on the block, causing the intake to not seal?
Opened topic up (I think code 34 was too specific a subject) to here:
http://forums.corvetteforum.com/show...post1554444569
If there's a fitment issue between heads and block wouldn't the head gasket fix it? So the fitment could be between heads and intake?
How do I:
1) test to see if this is a problem
2) fix it?
So when you say geometry change, I assume you mean that the top of the heads are further apart because they sit lower on the block, causing the intake to not seal?
Opened topic up (I think code 34 was too specific a subject) to here:
http://forums.corvetteforum.com/show...post1554444569
However, you may have an intake leak, or a vacuum leak. If it were my car:
I would retorque the manifold, check all of the vacuum lines, plug the brake booster line, check for external manifold vacuum leaks, using propane.
If that did not fix the problem I would pull the intake check the gaskets/mating surfaces. Did you degree your cam?
Mike
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From: Slidell Louisiana
Originally Posted by ScaryFast
PS - Mike, did you get your head flow numbers yet?
Not yet! Probably tomorrow or Monday. However, they probably will flow about 10cfm less than what you have in your sig at .550.
Mike
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From: Detroit's West Side MI
Originally Posted by aboatguy
However, you may have an intake leak, or a vacuum leak. If it were my car:
I would retorque the manifold, check all of the vacuum lines, plug the brake booster line, check for external manifold vacuum leaks, using propane.
If that did not fix the problem I would pull the intake check the gaskets/mating surfaces. Did you degree your cam?
Mike
I would retorque the manifold, check all of the vacuum lines, plug the brake booster line, check for external manifold vacuum leaks, using propane.
If that did not fix the problem I would pull the intake check the gaskets/mating surfaces. Did you degree your cam?
Mike
We did not degree the cam, but I just re-did the timing gears and Opti Tuesday and the cam pin is where it should be. I suppose it could be slightly off and not visible to the eye, but it's damn close.
I guess we'll have to do that if there are no leaks.
