Surge / Idle |
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Surge / Idle |
lsintampa |
Dec 22 2014, 08:53 AM
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#1
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Senior Member Group: Members Posts: 520 Joined: 28-January 13 From: Tampa, FL Member No.: 15,441 Region Association: South East States |
75 2.0 FI
I'm in Florida - so the weather outside is somewhat warm (50's maybe right now). I'll try to be as detailed as I can. I've had this issue since I started driving the car - about 8 months ago. It underwent a motor rebuild - along with some other mechanical repairs. All hoses are new (air supply, and fuel). ECU and other FI components are original - best I can tell. When I start the car - it starts right up. At idle RPMs go to about 1500 with a very slight surge (maybe 1450 - 1550). If I pull the air supply that goes to the AAR from the air filter and plug it, the idle goes down to what I'd expect - about 900 RPM still with a little surge. This is while the motor is "cold" - so to speak. Within like a minute of starting. As the car warms - just at idle, the RMPs start to come down and the vacuum from the AAR isn't as strong - but still present. However now the surge is crazy - like from almost a stall up to maybe 1200, back down, back up, etc. Pulling the hose from the AAR - does nothing - I can plug it or leave it and the air filter wide open and there is no change. I put the hose back on - again no change. I did not let it get to a full warm state - IE the temp gauge just started to move up. I've heard there are three states (cold, pre-warm, and fully warm) that come into play. Various tinkering, like turning the air mixture valve to a total closed state, and mucking with the ECU dial has had some success, but at BEST, I get like a 1200 RPM idle still with some surging. To the best of my knowledge there are no air leaks - at least not from any hoses. I've some concerns that the air plenum may have some stress cracks around the support studs. But I don't know that would cause the surging? I'd think the idle would just be high - period. YES / NO? I don't know where to begin to figure out why it behaves this way. Thanks, Len |
lsintampa |
Dec 23 2014, 12:57 PM
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#2
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Senior Member Group: Members Posts: 520 Joined: 28-January 13 From: Tampa, FL Member No.: 15,441 Region Association: South East States |
Maybe I'm onto something here....
I don't have any carb cleaner, but I do have starter fluid and a fire extinguisher (IMG:style_emoticons/default/piratenanner.gif) With the idle surge as good as I can get it, I started up at idle and started spraying about areas where no air should enter. Left side fuel runners - nothing - no change. Right side however did change the idle. At first I thought it might be the fuel runner gaskets, but I don't think so. The runner gaskets, manifold gaskets, TB gasket, all are new, as are the injector seals. So I don't think that's the issue. HOWEVER, I do now suspect the plenum itself is an issue. I had asked this once before, but I wasn't really sure if my question was understood. Simply put, there are two support tubes (columns) that support the plenum. They are on opposing sides, and the tubes are hollow - they go directly through the plenum. I recall that MY tubes are "loose" - by loose, I mean I can turn them, the ends are not connected to body of the plenum. They don't fall out, but they certainly are not "welded" to the plenum body. I'm thinking the plenum needs to be taken out - OUCH - and repaired. ???? No / Yes? Is there an easy way to get that puppy out without having to remove the manifolds? I guess I could cut the runner gaskets. Not sure how easy it would be however to put new ones on - once I yank that puppy. |
DRPHIL914 |
Dec 23 2014, 01:45 PM
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#3
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Dr. Phil Group: Members Posts: 5,766 Joined: 9-December 09 From: Bluffton, SC Member No.: 11,106 Region Association: South East States |
Maybe I'm onto something here.... I don't have any carb cleaner, but I do have starter fluid and a fire extinguisher (IMG:style_emoticons/default/piratenanner.gif) With the idle surge as good as I can get it, I started up at idle and started spraying about areas where no air should enter. Left side fuel runners - nothing - no change. Right side however did change the idle. At first I thought it might be the fuel runner gaskets, but I don't think so. The runner gaskets, manifold gaskets, TB gasket, all are new, as are the injector seals. So I don't think that's the issue. HOWEVER, I do now suspect the plenum itself is an issue. I had asked this once before, but I wasn't really sure if my question was understood. Simply put, there are two support tubes (columns) that support the plenum. They are on opposing sides, and the tubes are hollow - they go directly through the plenum. I recall that MY tubes are "loose" - by loose, I mean I can turn them, the ends are not connected to body of the plenum. They don't fall out, but they certainly are not "welded" to the plenum body. I'm thinking the plenum needs to be taken out - OUCH - and repaired. ???? No / Yes? Is there an easy way to get that puppy out without having to remove the manifolds? I guess I could cut the runner gaskets. Not sure how easy it would be however to put new ones on - once I yank that puppy. sounds like you probably found your leak, those should not be loose. Get ahold of Bruce Stone, he will have a nice newly powdercoated one most likely or have one done for you - in the mean time can you tape over those to seal them off just to test it? Phil |
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