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 |
Jan 16 2015, 03:16 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 |
OK, finally got that stud fixed today.
So, put the manifold back on hooked everything up, reset the timing again. Issue persists. Sprayed carb cleaner all over every nook and cranny - nothing seemed to be sucking it in. Sprayed the intakes at the manifold, at the plenum connections, cold start valve, every hose, and the throttle body. No leaks to be found. New TPS board - adjusted per Pelican's doc. Idle is way low, to the point it will stall out. Adjusting either the ECU knob or the air bypass has no effect. If I pull the hose off the MPS - the car idles better. As soon as I put it back on - no dice. The TB has two hoses that go to the vac on the dizzy. Not sure which is which, but one is high up on the TB and the other is smaller and lower on the TB. If I pull the larger hose off the TB (on top of the TB) the idle goes way up. I haven't adjusted anything. Timing / dwell / leaks / valve adjustment are good. NOW that said. Reminder that this was a CA car and had CAT at some point and speed limiter. Both removed by some PO and I have a replacement FI harness from a 2.0 NON-CA car hooked up. I don't see where that should be an issue, just mentioning it again. I don't know if the ECU is different for one or the other - or if it matters. Finally, I know that at one point there was a short in the FI harness. It was up around the TPS area. I know this because the wires on the old harness were fried. I wonder if that short may have cause a board issue in the ECU. Lastly, I'd love to beg, borrow, steal, (maybe even buy) known good ECU and MPS, to try. I really don't know what else to do. I'm no expert, but since I've started on this issue, I've learned it really is a simple setup. Ain't much going on here. (IMG:style_emoticons/default/headbang.gif) |
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