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2009-09-03 06:50:17
OK guys, I'm a little rusty on my sr20 tech, and I'm at that point where the car is starting, but not running, and I'm a little at a loss. The background is that I just finished a motor swap from DE+T to DET w/calum RT ECU, s4's, disco, nismo 740's, z32 maf, etc. etc. Yesterday, the car would start and idle, but it was idling really high and very rough. I tested spark, injectors, and compression, and all are good on all 4 cylinders. Consult shows no codes being thrown. Today I went back to set my timing and idle, and now it won't idle at all. It surges up to about 2500rpms and then falls on its face. It's struggling a little to start, and I think my battery is about toast, but I don't feel like that should be the real issue. I have checked for vac leaks, and can't find any, I've checked for fuel leaks and can't find any, so I'm unsure of what my next step is. I can't check timing if it won't idle. I don't think I should mess with the idle screw unless I get it in timing mode. Any ideas guys? Thanks in advance!
2009-09-03 14:14:36
It won't hurt to adjust the idle screw while not being in timing mode. It might be the only thing that helps.

Check throttle cable, make sure it's not too tight.

You could play with ignition timing as well. Put the distributor maybe 7 degrees forward and see if it helps any, then try 7 degrees backward. Put it back in the middle if that doesn't help any.

Triple check the intake system. Pretend you are the air going into the filter and as you flow through the system and pass pipes, make sure they are all plugged properly if they should be.

It's possible your idle control valve is broken or disconnected.

Did you re-use the old harness or swap to a DET harness? Which accessories did you carry over from the old motor and which are from the DET?

Do tests in a controlled manner so you're not left wondering "What if I did ___?".
2009-09-03 14:22:23
I have all new custom pipes, with the only one going off the actual intake pipes being the port for the IACV. The IACV is brand new, by the way, never used. I double checked it and it's indeed plugged in. I kept my old DE harness, but made sure to keep the DE sensors. No accessories from the DET went in, it was really only a longblock. I eliminated AC, h2o, and PS. I put on a brand new IACV, brand new injectors, brand new injector harness, new plugs, wires, dist, dist cap, etc. etc.

I have pushed the dist back and forth a little, but with no good results. I'll try messing with the idle screw, and I can check the throttle cable, haven't really considered it.
2009-09-03 14:35:16
Originally Posted by dr.fowler

if i give it pretty good gas as the rpms climb, i can keep the revs up and keep it running, but as soon as i let off it falls flat on its face.

That's a different story... So it'll stay running as long as you keep giving it throttle?

It's most likely an idle air problem then.

Check that the air-way is clear from the tube connected to your custom pipes all the way to the idle valve. You could always try removing the idle control valve from the side of the intake completely and then try to start the car and see what happens. It might idle at like 5k rpm (in which case I'd maybe suggest putting some tape of the gaping hole in the intake manifold so that the opening is no bigger than a dime) but that would tell us a lot. it would let us know if the engine is willing to idle or not, and if it's the idle air path way that's the problem.

Edit: On second thought this is probably a bad test. I keep forgetting about the MAF (I don't run one) and you'd run lean doing this and it might not tell us anything.

How well does it run while you keep the throttle applied? It is smooth, or giving you lots of trouble?
Can you keep it running by applying like 5% throttle? Or do you need like 50% or more?
2009-09-03 14:47:00
It kin of sounds like a MAF issue... bad ground perhaps. I'd recheck the harness, and check the ground from the MAF to intake manifold connection.

Ben's right; whatever you do, be methodical in your diagnostic to avoid overlooking something.

2009-09-03 15:26:22
OK, I did ground the maf with new wires directly to the intake mani. To keep the car going requires 50% throttle or better. It runs pretty rough, lots of fuel and quite a big of backfiring. I've considered getting into the tunerpro software and pulling down on the fuel maps and latency to see if it's just a case of dumping fuel for some reason. I may pull the injectors just to see what's happening, but I don't believe they're the true problem, they're all firing just fine. I guess I can unhook the idle air path and see if I can run something clear through the idle air path. I never really considered a physical obstruction in the tube.
2009-09-03 15:29:36
If it takes that much throttle and it's still not running right, it's not a simple idle air problem then. It does sound like a fuel delivery problem, which could be MAF related, ECU related, or injector related.
2009-09-03 15:30:46
when you put in the new engine, did you swap the intake manifold? this same problem I had, ended up being the intake manifold gaskets (2/3 of them actually!)

also, if it's a MAF issue, when you increase the throttle in neutral, does it bog between certain points? That would also indicate a maf or air issue.
2009-09-03 16:27:58
I didn't swap the intake mani, I just left the DET one on there. I am fully prepared to get a new maf on there, this one is real old, but it was working fine on my last setup. I'll have to dig around to find one. The voltage looks ok on it, but I suppose it could have a problem.
2009-09-03 17:50:37
per our conversation on the phone, I say the bin for the ecu may need to be double checked to ensure it is for 740cc injectors. sounds like it is dumping a **** ton of a fuel. i have a bin for z32 and 555cc, you want to try that and see what happens.
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