Vacuum leak causing low boost? (UPDATE: Still low boost, TPS?)
03-10-2005, 11:17 AM
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Vacuum leak causing low boost? [UPDATE2: At the shop]
Just bought an 87 turbo. I had a PPI done at Tom Charlesworth in Tulsa and it came back very clean. However, on the way home, I was unable to get more than around .2 bar of boost at WOT. I called Tom this morning and he said that maybe a hose came loose and I have a vaccuum leak somewhere. He had checked the Recirculator Valve and said it held a vaccuum when he tested it and that he had full boost when he drove it. What should I check to see if I have a leak? I thought maybe it was just a weak wastegate spring, but now I'm not sure.
Ideas?
Ideas?
Last edited by danny951; 03-30-2005 at 06:08 PM.
03-10-2005, 12:41 PM
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Pop the hood and start looking around for loose hoses. Theres a pile under the intake manifold to look at.
Is it having trouble idling? If the idle is rough thats another big hint towards a vacuum leak.
Is it having trouble idling? If the idle is rough thats another big hint towards a vacuum leak.
03-10-2005, 01:33 PM
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Check the two vacuum hoses that go to the intercooler banjo bolt and the j-boot since these two are inlined with the CV (Cycling Valve) and maybe you're problem.
03-10-2005, 02:06 PM
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Yeah, thanks, I just saw your post from last July..
and you fixed it with a new hose? Exactly which hose is this? I'll have to check it when I go to lunch.
My factory boost gauge reads 1.2-1.3 boost under full throttle. After searching, turns out it could be the wastegate, cycling valve and/or a vacuum leak.
Looking under the hood for a vacuum leak, i found the banjo bolt on the IC pipe hose that goes to the venturi tube is eaten. I can see the white threads of the hose itself.
The engine stumbles SLIGHTLY when started, if i give it just a touch of gas, everything is normal.
Could this be the problem? i am suspecting so.
Looking under the hood for a vacuum leak, i found the banjo bolt on the IC pipe hose that goes to the venturi tube is eaten. I can see the white threads of the hose itself.
The engine stumbles SLIGHTLY when started, if i give it just a touch of gas, everything is normal.
Could this be the problem? i am suspecting so.
03-10-2005, 02:23 PM
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To not have an idle problem and only be running that much boost tells me it's one of two things:
1. The cycling valve, it's either broken or the electrical connector has come loose, this will default to sending all boost pressure to the top of the wastegate and only pull about .2-.3 bar. If it were the KLR defaulting it due to overboost, it would reset the next time you started it.
2. The vacuum line to the blow-off (recirc) valve, without boost pressure to the valve diaphram it will open early and only hold about .4 bar.
I have had a loose hose, like one to the blow-off, which would seal up under vacuum but let massive amounts of air out under boost but this was not a smooth (un-noticable) transition!
Check those two things out first, that's all I can think it would be. Gook luck.
1. The cycling valve, it's either broken or the electrical connector has come loose, this will default to sending all boost pressure to the top of the wastegate and only pull about .2-.3 bar. If it were the KLR defaulting it due to overboost, it would reset the next time you started it.
2. The vacuum line to the blow-off (recirc) valve, without boost pressure to the valve diaphram it will open early and only hold about .4 bar.
I have had a loose hose, like one to the blow-off, which would seal up under vacuum but let massive amounts of air out under boost but this was not a smooth (un-noticable) transition!
Check those two things out first, that's all I can think it would be. Gook luck.
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03-10-2005, 04:30 PM
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Yes, really make sure the little line that goes to the recir. valve is connected. I just my car back from having work done and first time I hit boost the line just popped off. After I hooked it back up, WOW I really felt my new WG kick in sooner!!
03-10-2005, 09:58 PM
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Originally Posted by danny951
Just bought an 87 turbo. I had a PPI done at Tom Charlesworth in Tulsa and it came back very clean. However, on the way home, I was unable to get more than around .2 bar of boost at WOT. I called Tom this morning and he said that maybe a hose came loose and I have a vaccuum leak somewhere. He had checked the Recirculator Valve and said it held a vaccuum when he tested it and that he had full boost when he drove it. What should I check to see if I have a leak? I thought maybe it was just a weak wastegate spring, but now I'm not sure.
Ideas?
Ideas?
2) could be a problem with the recirculating valve. Really east to test. Take it off and if you can blow through any of the holes then it's bad. Doubt it.
Charlesworth did the PPI eh? Strange he didn't find this. Did you get the list of stuff he checked? Did he provide any paperwork? Did he tell you anything specific about the car? Impressions? Stuff the needs to be done? Brake pad thickness? Compression? Oil leaks? etc?
Intake hoses don't just pop off all of a sudden.
Good luck!
Dal.
03-10-2005, 10:11 PM
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I was pretty shocked that it was happening after he didn't say anything about it.. I was stupid for not opening it up full boost when driving it around, but we were in the middle of the city and it was not easy to find a place to do this. Evan, a guy on here that looked at the car for me, didn't say anything about not getting full boost either.. the recirculating valve is okay and holds a vacuum. On the way home tonight I had a few instances where I could get more than .2 bar of boost (I say .2 bar -- basically it gets just to the first line on the stock boost gauge after the 1 in the middle). there were a couple times i could make around .5 bar or so, but it would hesitate, stutter a bit and then drop to around .2.. the motor is very smooth until i try to get into some boost and it feels like hesitation and stutter..
Can someone tell me where to find the Cycling Valve and how I can test it or bypass it altogether if that is safe?
Can someone tell me where to find the Cycling Valve and how I can test it or bypass it altogether if that is safe?
Last edited by danny951; 03-11-2005 at 11:18 AM.
03-11-2005, 11:22 AM
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I also got a suggestion to check the TPS. On the way into work this morning, I noticed that I can get a little more boost if I let off the throttle at around 4k RPM in 3rd gear and then floor it, but the boost dies back down to around 1.2 bar. I checked the TPS and I do hear a click at the idle position, but can't tell about at WOT position. I'll have to have someone sit in the car for me and mash the pedal. I may need to get someone who knows what to look for help me out at the swap meet on Saturday at Zim's.
