'93 Civic VTEC-E skipping - Fuel Economy, Hypermiling, EcoModding News and Forum

tim3058 · 09-22-2009, 09:03 AM

Hey guys, just thought I'd pick your brains before I start replacing stuff. My '93 Civic DX has the VX D15Z1 swap. I just got the car so I don't know the whole history of how well the swap was done, the owner claimed he swapped the computer and everything, all the underhood parts look connected (no missing/hanging/cut wires, etc). I get a fairly constant skipping at most any speed, most noticeable when I'm at 55 or so, let off the gas, then re-apply the gas. It almost sputters, then smooths out, with an occasional skip. Compression in all 4 cylinders is 185-190psi, just replaced plugs/wires/cap/rotor and the plugs all look ok, light tan. It did throw a check engine light yesterday, but it went off after 5 or 10 minutes and didn't leave a code. I'm going to check the injectors/fuel system the next few days. Anyone encountered this? It's getting 45mpg so things can't be too bad. Thanks for the help guys.

TomO · 09-22-2009, 11:21 AM

I'd start off by making sure the right plugs are in there.

Double check the ECU to make sure it's a P07 (located in the passenger side footwell near the door under the carpet).

Is the EGR hooked up with the control box?

There is a normal stuttering that is inherent to the Z1 motor, coming into and leaving lean burn, but it shouldn't horribly noticeable.

Start here: VX Info Thread

Ryland · 09-22-2009, 01:01 PM

This is the same problem as I had the last three times I had a bad o2 sensor in my VX's.

tim3058 · 09-22-2009, 10:01 PM

Thanks for the insight guys, I will look into the plugs tomorrow, the local Advance Auto gave me Bosch's... maybe I want the NGKs. I noticed today that the first 5 minutes or so of running are stutter free also, if thats any clue. I didn't get to check the fuel pressure tonight, I did put a new fuel filter in, still stuttering though. Will update as I discover more.

Ryland · 09-23-2009, 12:34 AM

if it runs good for the first 3 to 5 minutes then starts sputtering then I'm sticking with o2 sensor, as the computer is waiting for the engine to warm up in that time and waiting for the o2 sensor to warm up as well.

Christ · 09-23-2009, 01:03 AM

O2, TPS, or MAP. All three are affected by engine temps, but the O2 is the most likely culprit for a light stumble while cruising.

tim3058 · 09-23-2009, 09:38 AM

Thanks for the advice, I'll check the o2 this week also. This morning on my way to work the car did the usual, ran smooth for 5 minutes then started sputtering here and there. For the first time, the check engine light came on and stayed on the rest of the drive, and the car ran smooth the rest of the way. I'm guessing if its o2 the computer just ignored the signal?

TomO · 09-23-2009, 12:09 PM

NGK V Power are the only plugs that should go into the VX motor, seriously.

tim3058 · 09-24-2009, 11:56 AM

Ok, went to Advance Auto last night, the wires I got are the same part # as for the Si, so should be correct for the VX engine. Got NGK plugs, have to install them tonight. I unplugged the O2 sensor last night, and car runs like a top now (check engine light is on obviously). Would that be a sure sign its the O2? (or could it be another sensor, just computer operating in closed loop, ignoring everything). Don't mean to sound clueless, I've always wrenched on carburetor V8s so this is new terrain to me, and haven't had much time to actually dig in and check stuff this week. Thanks again for the help

TomO · 09-24-2009, 12:47 PM

Yup, the VX plug wires are the same as the Si ones.
And the model of the plugs were NGK V-Power ZFR4F-11 right?

Unplugging the O2 will make the car run smoother, but isn't the best way to determine if the O2 is bad. Best way would be to measure the output of the O2 and see if it's getting "lazy". The info on how to test the O2 was in that VX Info link I posted before.

You'll catch on to the PGMFI world in no time at all with our help