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 |
DRPHIL914 |
Dec 22 2014, 01:16 PM
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#2
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Dr. Phil Group: Members Posts: 5,768 Joined: 9-December 09 From: Bluffton, SC Member No.: 11,106 Region Association: South East States |
"To the best of my knowledge there are no air leaks - at least not from any hoses." Well, you need to "know" because your the mechanic. I chased this same scenario for months before I found one of the new injector seals had not sealed because I inserted the injector at an off angle so to speak. Once that was addressed I found that the MPS was also out of tune since the rebuild. Installed an AFR gage, tuned the MPS and all was great. EDIT-Pull that plenum and inspect it. Pour some liquid into it to see if there are any leaks at suspected areas, check intake runner hoses, oil filler gasket, throttle shaft for excessive wear. Also, disconnect everything from the vacuum source except the MPS. If it runs better re-attach each item, one at a time until you find it. (IMG:style_emoticons/default/agree.gif) its either a vac leak you have not found OR you are still running lean so ild will be high, and if it goes lower it will start to surge. lean running, could be CHT issue and/or MPS but probably with MPS - is the MPS a stock original?( they tend to be a bit on the lean side) - oh, then of course re-verify your timing if you have not already. pw Checked timing... maybe you missed my last reply - If I pull the hose off of the MPS - the car seems to idle just as I'd expect. Put the hose back on and the surging kicks right in. yes- i admit, jumped to the reply before reading down thru all of the responses- Another case of a car running better without the MPS?? If that's the case, then you probably are running super lean due to some major vacuum leak and removing the MPS is making the mixture "acceptably" richer to compensate. The only time of had that kind of surging is when I've forgotten to reconnect a hose or make sure it was tight. maybe- and a bad vac leak like rich suggested could dot his - in my case recently it's the MPS gone bad electronically, making it SUPER lean, so disconnecting the mPS makes it default rich, but in this case still run |
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