Civic VX severe part throttle hesitation!!
 

First off I'd like to apologize to Nachtritter for thread jacking. I thought it best that I start my own thread for this issue.

This is in regard to the 49 state conversion I just completed following Nachtritter's instructions.

Since that post I've replaced the MAP with no improvement, seafoamed the intake manifold, again no improvement, cleaned out the EGR and intake/exhaust ports with no improvement.

What did work strangely was unplugging the brand new NTK/NGK L1H1. I drove it home today like this and it ran perfectly aside from the check engine light coming on. I'm stumped because I tried this before when the car had the P07-L01 (Cali) ECU and 4 wire 02 and there was no improvement to the hesitation issue whatsoever.

I even went back today through Natch and TomO's wiring instructions and made sure everything was connected properly.

Any help would be greatly appreciated!

Dang, I'm stumped here... I know I can feel the lean burn kick in on mine when I'm at part throttle on the freeway and it feels like a bit of a hesitation, but what you're talking about seems quite a bit more severe.

For me, I can use lean burn when cruising on level ground, but any up grade requires a bit more throttle (and I can usually feel it get out of lean burn mode). Typically, I'll accelerate above target speed then let it go into lean burn and try to maintain speed for as long as possible while in that mode. Eventually I slow down enough that I have to get it out of lean burn again and repeat the process...

I used an mpquino to watch my FE and it was fairly easy to tell (when the MPG readout increased noticeably) when it went into lean burn.

At first it seemed like a hesitation problem, but once I got the feel of it, I was able to take max advantage of the lean burn mode.

Came across another oddity. I decided to unplug the EGR all together in troubleshooting and I'm not getting any "check engine" light. You reference

I'm thinking something's not right between the 02 and the EGR valve or from the EGR to C129... What do you think?

I can tell what you mean about keeping it in leanburn on level ground and having to give it more gas up steep grades coming out of that mode. For me I can't maintain speed at all in leanburn unless i'm going DOWN a steep grade... lol. Even then, it wants to herky jerk and slow down. On rare occasion i can get the gas pedal just right to where it will maintain speed on a downhill run but usually it will just slow down unless I accelerate past leanburn mode.

Just thought I'd post an update, I've kind of gotten used to the hesitation issue. Haven't tried anything new other than installing the correct NGK plugs. I still believe there's something wrong but have given up on the issue for now... Driving a little faster is helping me not notice so much but affecting my MPG of course. I'm only averaging about 42mpg... :confused: Best tank so far was 47mpg with mostly city. Strangely it does better in the city then on the highway, I guess because that's where it struggles the most with the lean burn hesitation problem.

Also I thought I'd add I'm getting worse MPG with the new Sumitomo 165/70/13s then I was with the old 175/70s on there... I just can't win with this car it seems :(

Have you Ohm'ed out your fuel injectors? Just a random thought, perhaps one of them is intermittently failing. If you have a shop locally that can clean/rebuild/flow balance them, it's totally worth the peace of mind and potential mpg gain, not to mention if a bad injector is the source of your severe hesitation that would fix it.

I know that when I extended my O2 sensor in my VX to its new home, I had forgotten to swap out the new calibration resistor that was matched to the new L1H1...that was some severe hesitation for a few miles until I pulled over and swapped it to the correct resistor.

I mention this because I would like to know what value your calibration resistors are in your L1H1s. Would you be able to use some needle nose pliers to pull out the white insert on the sensor connector and look at the numbers on the flat side of the calibration resistor? Or just use an Ohm meter and measure the resistance of pins 3 and 4 and post here if you don't want to pop out the resistor from the connector.

Here's a little topic about the resistor.

HA! I just started having an issue with this in my vx swap. My egr control box isn't hooked up properly and no check engine light either. Similar to your egr not being hooked up. I'm gunna test some stuff tomorrow after work to see if there is vacuum between the egr control box and egr valve while driving. Gotta hook up a t fitting and a vacuum gauge.

Hmmm, mines not herky jerky at all, but smooth; however, its still seeming to show not necessarily hesitation but slow to respond to gas pedal pressing. It will be going at 70mph and then slowly slows down (don't remember if it was uphill on flat ground or what, mostly flat ground I belive), then I have to give more and more pedal to get it to pickup speed or to maintain speed, then it like starts to accelerate and i gotta ease off the pedal to get it to slow down accelerating to then maintain back at 70mph.

Is this a problem or the nature of the lean burn machine?

I can ohm my L1H1 for you tomorrow. Not sure how this will help, but its curious information non-the-less.

This is part of the normal behavior of the d15Z1...At a constant cruise speed it will lean out as much as it can. Lean running makes less power and wind resistance will eventually start to slow the car down. When you start to push the pedal down to compensate, it takes a second for the mixture to richen up to where it makes more power.

Also, when cruising steady state, the ECU will periodically run rich a bit in order to keep the catalytic converter up to temp as running lean will cool off the catalytic converter.