Vacuum Problem...Never seen this before...
Vacuum Problem...Never seen this before... Hey Everyone...I'm helping to diagnose a problem with a 1995 Trans Am at my friends shop...Its a stock bottom end LT1 with LPE ported stockers and the 211/219 cam which were previously installed by another shop...It came in with all kinds of issues but this one has me stumped...The thing is pulling 20 psi of vacuum at idle into the hole on the rear of the passenger side valve cover! When you take off the hose the damn thing wants to suck your finger into the valve cover! PCV on intake is working backwards also...We removed and resealed the intake and the problem is still there. We also installed a new Holley TB in place of the clapped out BBK at the owners request and still the same issues...The EGR has been previously deleted and capped off at back of intake...and its got plenty of compression...and all vacuum lines are good...
The only thing we can think of is that the intake itself is cracked somewhere...The motor is acting like its an intake...sucking into itself...Anyone alse ever heard/seen this before? Its gotta be something simple I'm just not seeing it...Any help or booze would be greatly appreciated...There's been lots of other questionable shop's hand in this thing and we've been fighting to get everything right...I feel bad for the car's owner...
--Alan
The only thing we can think of is that the intake itself is cracked somewhere...The motor is acting like its an intake...sucking into itself...Anyone alse ever heard/seen this before? Its gotta be something simple I'm just not seeing it...Any help or booze would be greatly appreciated...There's been lots of other questionable shop's hand in this thing and we've been fighting to get everything right...I feel bad for the car's owner...
--Alan
--Alan
Havent had it running long enough to tell...Does not seem to be using oil...from the condition of the intake I'd say it got dropped at some point...Spoke to the owner and he seems to think its ran 'weird' for a while...There's so many issues we've been tackling...one at a time...Motor came in with a squeeling bearing noise...20,000 mile replacement shortblock from GM...oil pick up was trashed, mains were scored...replaced bearings..the guy thought he had gotten a Vig 3000 converter, but got some kind of ATI garbage, but paid Vig price...found loose nuts/bolts all over the engine bay, in the headers, brackets not mounted, wiring all rigged, plug wires wrapped around A/C unit....Unreal...I guess we'll try to dig up a used intake...I can't see him spending $450 for the edelbrock junk...
--Alan
--Alan
--Alan
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Well the general consensus is that the manifold must be cracked somewhere...We're gonna get a new/used intake and try that...I'll post up if thats the culprit...or if its not...
--Alan
--Alan
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Update...Well we found a good used intake and installed it checking to make sure all plugs under the shield were installed and tightened...The damn thing still does the same thing! I've never seen anything like this before...We used all new vacuum lines and pcv valve and triple checked the work...Been working on these motors since 1992 and am stumped...Its pulling vacuum into the engine from every hole: passenger side valve cover, TB, pcv hole and corresponding port in the front of the intake...If you were to hook the system up as its supposed to be each end of the hose is pulling vacuum against itself...valve cover to TB and pcv to manifold port...
Any other suggestions are welcomed...
--Alan
Any other suggestions are welcomed...
--Alan
--Alan
I'll have totalk to shop owner, but I think he did a compression test and all cylinders were fine...We haven't done a leak down test, but thats next on the agenda as long as the car owner gives the go ahead...I'm also thinkin we just pull the motor and start going thru it one part at a time...Its easy enough to drop it out of the bottom and start checking that other shops work as they installed the heads and did the cam swap...The fuel pump is also bad as it is 36 at idle and drops to 20 under load..This is after the other shop supposedly installed a walbro (twice)...I can't wait to see the job they did on that when we drop the tank or cut a hole in the floor...
I really feel sorry for the car's owner as all he wants is his car done right...Which is what he paid for once already...
--Alan
I really feel sorry for the car's owner as all he wants is his car done right...Which is what he paid for once already...
--Alan
So if you take the oil fill cap off and put your hand on it it sucks?
so unhook the PCV vac source and plug it, still does it? unhook the vent tube....still?
I say it could be a few things...... but something that frikkin big has got to be easy to find. Dont feel bad, we been working a car tuning all week and couldn't figure it ou running 6.60's...well we found the problem last night, carb studs were loose. tightened them bitch went a 6.19 112..... dont know how we missed that
so unhook the PCV vac source and plug it, still does it? unhook the vent tube....still?
I say it could be a few things...... but something that frikkin big has got to be easy to find. Dont feel bad, we been working a car tuning all week and couldn't figure it ou running 6.60's...well we found the problem last night, carb studs were loose. tightened them bitch went a 6.19 112..... dont know how we missed that
Update:
Well, we decided to pull the heads and did the driver's side first. Found a hole in an intake runner all the way to the push rod. The heads were done by LPE and they must have had a bad casting, or casting shift, or who the hell knows... Don't know how they could've missed it unless it was real thin and passed whatever QC and testing they do before shipping, and then it broke apart at start up. Anyway, Lingenfelter is standing behind their stuff and replacing the head and valve train at no charge and taking care of all shipping. finally the poor owner of the car caught a break! Its nice to see that LPE stands behind their stuff. We were all anticipating an argument and got great customer service...
Thanks again for everyone's suggestions...
--Alan
Well, we decided to pull the heads and did the driver's side first. Found a hole in an intake runner all the way to the push rod. The heads were done by LPE and they must have had a bad casting, or casting shift, or who the hell knows... Don't know how they could've missed it unless it was real thin and passed whatever QC and testing they do before shipping, and then it broke apart at start up. Anyway, Lingenfelter is standing behind their stuff and replacing the head and valve train at no charge and taking care of all shipping. finally the poor owner of the car caught a break! Its nice to see that LPE stands behind their stuff. We were all anticipating an argument and got great customer service...
Thanks again for everyone's suggestions...
--Alan