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 26 2014, 04:59 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 |
Well, plenum is out.
I'm too tired and sore to do any more tonight. It's time to start drinking! Initial inspection of the plenum - it looks fine. What I thought were loose support rods must have been on something else. It was a long time ago - so I may have the parts confused. In any event, the support tubes do not wiggle. Interesting, I removed the left side manifold to get to what I needed so the plenum would come out. The middle nut - wasn't a nut on a stud at all. It was a bolt. I don't know how deep the stud hole goes - maybe the bolt was bottoming out and it wasn't sealing well? IDK. Anyway, tomorrow I'll check the other manifold - see if it has something similar. Manifold gaskets, injector gaskets - still like new. BTW - how do I test the plenum (now that it is out) for leaks? Was thinking of putting some light inside and plugging all the holes - see if any light comes out in a dark room. Is there a proper way???? Thanks, Len |
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