Horrible mpg vx 17mp

[VX.hatch]

I bought a vx with a siezed engine so I replaced it with a d15b vtece. First tank it got 26mpg and this is the second and its getting 17 mpg. The car starts instantly and idles good. Wot is also good, slow with no power, but smooth and consistent. Part throttle however it has a jerking through the rpm but only when accelerating. I've replaced wires, distributor, plugs with the ngk4, New intake gasket, New O2 ntk, checked timing, New fuel filter, New iacv.

I don't know what's wrong. Please someone help.

[FiShNc]

One thing to avoid is throwing parts at it. Not saying you did; it's just obligatory to get that out up front.

Swaps can be tricky to diagnose because it isn't exactly one car or the other.

Start by checking for CEL codes. Which ECU are you using? Using the correct ECU will be pretty important for getting best performance from the vtec-e.

Then go through a tune up procedure checking for problems. It may be you've already covered that.

Since you just swapped the engine, is it safe to assume you have clean oil, PCV valve, and egr? Also timing belt is on correctly? Double check that. Timing belts on these Honda's can sometimes be easy to screw up.

Did you rebuild the engine before swapping? How do you know it's in good order?

Are you using genuine Honda parts? Sometimes you can get away with other stuff, but there are certain parts that you should just stick with Honda: distributor cap, rotor, wires, thermostat, O2 sensor, etc.

Finally, details. Divulge as many details as you can even if your not sure it's relevant. The more information you give, the easier it is for the experienced people here to help.

Edit: just though of one more thing. What transmission are you using? Selecting the right gearing for your engine can get you better mpgs. The jerking suggests this is not just a gearing issue though.

[Ryland]

the D15b is not a Vtec-e tho...
Fishnc is right about the timing belt, there is a weird set of timing marks that you use instead of lining the normal marks up with the top of the head.
I would pull the valve cover off and start the engine up to make sure that the right number of valves are opening... it might be as simple as it, for whatever reason, is opening up all of the intake valves, that would make it pretty gutless at low revs.

[FiShNc]

I was actually wondering about the engine.

If I'm not mistaken there is a d15b 3 stage VTEC which could be considered to have vtec-e, though 3 stage or dual VTEC would be more descriptive. Otherwise, the engine is a d15b5 imported or vx.hatch meant d15z1, same as the one took out. Or it could just be plain VTEC no E.

In any case, knowing your engine and ecu will help determine they are correctly matched up.

[California98Civic]

Which D15B? For the HF? The VX used the D15Z1. You might have an inappropriate ECU, maybe.

[VX.hatch]

Long post sorry.

First thank you for the replies. Second the seems to some confusion about the d15b. there a 2 versions of the OBD1 d15b. One is the performance d16z6 equivalent and the other is the d15z1 equivalent. To tell then apart you must look at the casting marks. The z6 equiv will has p08 and p28 as marks. Meanwhile the z1 will have p07 just like the z1. Not trying to be mean just want to clear things up.

Onto my car. I do have a vtec-e checked with casting marks and pulled the valve cover. I'm running my stock p07 ecu with stock harness and intake manifold. For things that aren't z1 stock parts are exhaust and intake tube. The exhaust is z6 manifold and magnaflow catback with 2.5" oe replacement cat, I had this from my previous civic and needed it as the vx parts are rusted and bad. The intake tube is an oem z6 as the previous owner of the vx cut the intake to soup can a pod filter. The car also has 14" winter tires on it currently which I now will hurt mileage but not this much. It's also winter here if it matters. All parts are NTK, NGK, or oem Honda. The distributor is the only part I replaced with a used part from another of my working engines. Not saying it's not potentially bad but it ran the other engine fine. I wanted to keep the car OEM but didn't want to spend to much money.

About the engine. It has 125,000km and the original timing belt, I checked. The previous owner that it was the z6 version and swapped the intake manifold and ran a chipped p28. First start up when I got it the car did not fire on #4 and turned out bad distributor. I also smoked solid grey, have a video. The engine still smokes but not nearly as much. It puffs a little on startup and constant under throttle. The smoke smells like its running rich and not like oil or sweet like headgasket. I also put new oil in it along with a filter. I've put a total of 400km on the car and its gone through 1.5 tanks of 87.

About me. I'm a backyard hobby mechanic with friends that are licensed mechanics so I do know my way around a car. I've also swapped engines in civics numerous times before. I mention this as I assume you think I'm a newb who don't know jack and you are rightfully entitled to do so as you don't know me. Also like to mention, when I ask for help I'm really lost. PLEASE HELP!!!!!

[FiShNc]

Thanks for clarifying. So you're running the z1 version, same as your seized one with correct head, ecu, and transmission.

Exhaust will have an affect on mpg but probably not this big.

Are you still running rich even when warmed up? It could be you're never getting to closed loop. That'll make a car run like crap.

[VX.hatch]

Originally Posted by FiShNc

Thanks for clarifying. So you're running the z1 version, same as your seized one with correct head, ecu, and transmission.

Exhaust will have an affect on mpg but probably not this big.

Are you still running rich even when warmed up? It could be you're never getting to closed loop. That'll make a car run like crap.

It actually runs better when the engine is cold. When the engine is cold it doesn't jerk/sputter/misfire. When its warm the car jerks randomly while driving. It runs rich all the time or at least it smells like it.

Also I have no CEL. Had one, O2, but fixed it. If I knew how to upload videos to the forum I would show you what its doing. Anyways I'm going to check the TPS and MAP.

[VX.hatch]

I have to up my post count to post links. sorry for wasted space.

[VX.hatch]

upping post cost to post youtube link