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socalsuperhero 07-13-2008 02:18 PM

D15Z1 Engine surging, help needed...
Got the d15z1 full swapped into my crx. Engine started up no problem, no cels. Engine idles great, revs fine, but has a hesitation/surging problem around ~1500rpm at part throttle (think trying to take off in first gear). Have gone through all the vacuum diagrams and everything is hooked up right. Any ideas?

SVOboy 07-13-2008 02:23 PM

Vacuum leak? Where's it idling?

socalsuperhero 07-13-2008 02:25 PM

idling at 600rpm, checked vacuum equals 15psi at idle, timing is set right on as well.

SVOboy 07-13-2008 02:54 PM

Can you monitor the afrs and see what they're doing around the time of the stumble?

socalsuperhero 07-13-2008 03:12 PM

Not really, I can monitor the voltage on the o2 sensor, but thats about it without a afr guage

vtec-e 07-13-2008 04:32 PM

Is it the lean burn? My civic does that when i drive gently and hesitates when i bring on the throttle a little. I heard its the lean burn being weak and it takes the ecu a second to come out of lean burn. I dunno. Me heads fried, the hatchets are gone to bed and i'm skulling a few cans to settle me nerves!!


SVOboy 07-13-2008 04:46 PM

^ I'm also thinking it might be lean-burn. Monitoring the volts should be enough, since you can see the change to tell whether you're in lean burn or not.

socalsuperhero 07-13-2008 09:37 PM

Ok, so i measured the voltage across vs+/vs- and ip+/ip-. I also tested a few more things. the engine runs fine at part throttle up until 1450rpm, then the engine starts surging at any speed at part throttle, but runs fine at full throttle. So, that being said here's what I came up with:

vs+ idle +.5v, drops to +.39v while surging
ip+ idle pretty steady at +.47-.5v with the occasional drop to 0v. at 1300rpm it picks up to +.65v with the occasional drop to 0v. while surging it goes back and forth from +1.07v to +.7v

vtec-e 07-14-2008 12:43 PM

ok, i'm lost!

SVOboy 07-14-2008 12:45 PM


Originally Posted by vtec-e (Post 43844)
ok, i'm lost!

Yeah, me too. I wonder if the o2 is just dead and being funky. Try unplugging it and seeing if it still does it.

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