'89 CRX HF + D15Z1 troubleshooting...

[1993CivicVX]

Originally Posted by MatHadder

also, my vx has a fairly bad low throttle hesitation. I think it is related to it coming out of the lean burn mode, but I am not sure. It got a lot better after setting the timing, but it is still there. I am in the process of getting a new fuel filter, and having some injectors cleaned and flow tested. I am hoping this will eliminate the hesitation, but it seems like this is a problem that I hear about with the vx a lot, so it might just be the nature of the motor.

Mine used to do this. The ultimate fix was new o2 sensor but the proper spark plugs also helped.

[GasSavers_bobski]

There should be a allen screw/locknut combo that the throttle cable pulley stops against... It sets the closed point. Both the sticking and the low voltage say it's been tampered with. If the throttle closes too far, the plate runs into the throttle body wall and gets wedged there, thus the sticking.

[MakDiesel]

bobski to the rescue again! I sourced a replacement stop screw at the local U-pull-it and now it finally doesn't get stuck. Simple fix. I just hope the sanding on the plate didn't create a gap b/w the plate and TB wall to let air through during idle. I held the assembled TB up the light and could see a faint ring of light, similar to a complete solar eclipse, but it's not a substantial gap. The piece is certainly clean though w/ multiple sprays of carb cleaner and a 2000 grit rub down. I'll be able to put the TB back on the car tomorrow and then adjust the stop screw using the MM to set a .45-.5 spec idle voltage. Hopefully this will clear up my throttle stick and no input cruise bucking so she can be road worthy for a DD. I'll let you know how it and the subsequent test drive goes. Thanks, Mak

[slurp812]

Originally Posted by MakDiesel

I recently test drove my project and a few issues arose. She idles fine but when revving in neutral she hesitates/stumbles below 3k and also has severe rev hang (takes several seconds to return to idle speed, stumbles on the way down too). On the road it's similar with heavy hesitation/intermittent power delivery below 3k and sometimes beyond. It feels like she bucks to get up to speed and that translates into the shifter. I understand this engine is gutless below VTEC/lean burn but VTEC engages approx. at 2200 RPM in these cars, and the hesitation lasts beyond that. Below are specs (engine is stock unless otherwise noted):
If there's anything else I'll update, Thanks, Mak

It sounds like some sorta vacuum leak.....

[MakDiesel]

After replacing the TB (and set closing voltage at .48) and taking her on a 7-mile test drive, the stick problem is gone but the irratic idle, cruise buck surge crap still persists. I may need to check vacuum at the MAP to make sure no air gets past the plate under no throttle input. Slurp, I will try to locate a vacuum leak elsewhere w/ carb cleaner method (I've done this before w/ no luck). I noticed my upshift light is quirky, coming on twice when I steadily accelerate, once in rather low RPM and again before VTEC kicks in (as indicated by my custom amber LED dash light) In cruise/buck mode the light sometimes flickers, other times doesn't even come on. I've noticed the buck problem isn't 100% consistent, sometimes allowing me to cruise all the way down to below 1k RPM, but 70-85% of the time it'll buck/surge/irritate me before it makes it that far. How would I go about testing the O2 sensor? Next time I'll try and get video of the crappy idle and/or cruise buck, which may be harder to make noticeable on video. Mak

[MakDiesel]

I've ordered a spare P07 ECU to try and rule out a faulty ECU, and to have a spare in the future. I'm leaning towards an obscure vaccuum leak, probably from some 15-year old o-ring or maybe my doomed TB. Mak

[MakDiesel]

ok, cleaned IACV (altho it didn't turn out to be very dirty) and drove the car it's longest distance since the swap (85 miles). The jerking is less noticeable but the idle is randomly off, often surging (but not necessarily rise and fall, as is typical for D-series Hondas) but a steady surge at a stoplight to 2 or even 3k. Also, when upshifting w/ no throttle input, the revs actually rise too between shifts enough to notice. Vac leak? I'm checking injectors next per molecule's suggestion, then I may have to find a spare O2 to troubleshoot that expensive fix. Mak

P.S. oh, and I definitely feel the hesitation when coming out of what I presume is lean burn, it's similar to turbo lag in which the engine must be "awoken" after cruising to let it know we need some umph.

[MakDiesel]

more driving (44 mpg on first full tank!) but the idle issue w/ the persistent cruise buck has got to go. The idle is almost different at each stoplight, sometimes surge/fall 1k-1.2k or 1.4-1.7k, etc, or it'll level out near 1.2 or 1.4k and be steady, never 600 like spec. I unhooked the TPS for kicks and drove it, every buck/stutter cleared up and the idle would be perfect if it wasn't for the 2k+ idle. Looks like I need a new TPS or just get another TB and be done with it.....Mak

[neverendingproject]

You might want to double check the TPS wiring. Just make sure pin 1 grn/wht is connected to D22 sensor ground, pin 2 red/blu is connected to D11 sensor input and pin 3 yel/wht is connected to D19 reference voltage.

[suspendedhatch]

Didn't read through the whole thread. Did you sweep the throttle slowly and watch the tps voltage with a multimeter? I'm willing to bet that it's spiking.