Civic VX severe part throttle hesitation!!

[steffen707]

Originally Posted by TomO

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.

I got my mpguino hooked up and was monitoring the MPG while cruising below 50mph, HOLY COW! This thing is sweet.

On the highway, IT SUCKS. It will go into lean burn and the mpg will shoot up to like 50-70 depending on the grade. Then the car will slowly decelerate and i'll have to push the pedal down like you stated to richen it up, and then BAM, 28mpg until i accelerate like 4-5 mph, then great gas mileage again, until BAM 28mpg.

I cleared the trip data on the mpguino while already going 70mph on the highway and i was impressed that I kept 64 mpg for like 1/8 mile, then it started slowing down and then dropped out of lean burn to 28mpg. After averaging the mpg over my highway only jaunt averaging 64 mph, I only got 35mpg.

This is like 3mpg better than the previous engine.

[TomO]

There still may be a problem with your setup Steffen...I'm wondering if your intake air temp sensor is going out or perhaps your TPS is getting old.

[steffen707]

Originally Posted by TomO

There still may be a problem with your setup Steffen...I'm wondering if your intake air temp sensor is going out or perhaps your TPS is getting old.

HEY! I don't have the clutch switch hooked up yet either. So maybe the ECU thinks I constantly have the clutch pedal pressed, and idling, and the EGR isn't suppose to do anything when idling???

[TomO]

You may have something there. EGR is only active at low throttle positions when cruising above a certain speed if I recall correctly.

Get that switch hooked up, lol.

[steffen707]

I checked the tps and the map sensor per the repair manuals trouble shooting tests and they both are in spec.

I have a 2nd O2 sensor I was going to test in the car, and i also tested another p07 A00 ecu that I have laying around. The ecu didn't change anything; however, i took out the crappy bosch platinum plugs and put in a fresh set of the OEM ngk plugs, and BOY DID THEY MAKE A DIFFERENCE.

For anybody that reads this thread and has a hesitation issue as well, try new plugs first. I gained 12 mpg on the highway, and I think it eliminated the hesitation completely. Now what i feel I believe to the the "normal" lean burn transition. Mpguino verified!

Before I couldn't hold 70mph with the bosch plugs, and now I have no problem holding 70, except that i'm trying to keep it in lean burn as hard as possible and sometimes just have to give in and give it more gas to maintain speed.

I did this swap to get better gas mileage of course, but I don't want to change my highway driving habits of 70mph on cruise. We will see how it turns out.

[93_VX_Guy]

Originally Posted by steffen707

I checked the tps and the map sensor per the repair manuals trouble shooting tests and they both are in spec.

I have a 2nd O2 sensor I was going to test in the car, and i also tested another p07 A00 ecu that I have laying around. The ecu didn't change anything; however, i took out the crappy bosch platinum plugs and put in a fresh set of the OEM ngk plugs, and BOY DID THEY MAKE A DIFFERENCE.

For anybody that reads this thread and has a hesitation issue as well, try new plugs first. I gained 12 mpg on the highway, and I think it eliminated the hesitation completely. Now what i feel I believe to the the "normal" lean burn transition. Mpguino verified!

Before I couldn't hold 70mph with the bosch plugs, and now I have no problem holding 70, except that i'm trying to keep it in lean burn as hard as possible and sometimes just have to give in and give it more gas to maintain speed.

I did this swap to get better gas mileage of course, but I don't want to change my highway driving habits of 70mph on cruise. We will see how it turns out.

I noticed a slight improvement in holding lean burn when I changed to the correct plugs but very very slight. MPG didn't improve at all, possibly got worse for me. Your symptoms sound very similar to mine though.

Also, I'd like to add that I have 60psi in my tires and still only averaging 42-44mpg now. When I get a chance I'm going to check out the resisters in the L1H1 per TomO's request.

[steffen707]

keep in mind i havn't even driven 300 miles on this setup yet, so I don't know for sure what an "average mpg" would be.

But i checked my 2 L1H1 O2 and the resistance was 6.24 and 2.40. Now this was on setting 20k of my cheap multimeter, so I don't know if that means 6,240 and 2,400 ohms or if its 6.24 and 2.40ohms. My guess is the former is correct.

Also, my mileage numbers are in a 2500lb 97 civic dx hatch, including me 175lbs, A/C a full tank of gas. It was 2500 exact.

[BrickHouseVX]

Did you check your fuel pressure? Mine was out of spec but still running, but poorly.
I checked the pressure and it was 29psi and 36psi.
After new pump the pressures were 35, 45psi

Runs awesome now. No hesitation, mpg up, more power, better idle. All fixed with new pump.