Brand New D15Z1 - Lean Burn Stutter / Hesitation
 

Hi all, I am new to ECOmodder, but have been dealing with honda swaps for 10+ years. I have a 94 civic VX with a DX tranny. Sorry for the wordiness but its necessary :)

I am having the lean burn stutter/hesitation issue with. Once at operating temperature and cruising at light throttle the car struggles and hesitates, as soon as I give it gas it runs perfectly. It also runs perfectly when the brand new Honda O2 sensor is unplugged.

I have searched and have done a ton of troubleshooting - many people post this issue but I have spent hours combing through threads and I haven't seen a fix??!!! Most threads just end with the person having tried EVERYTHING with no solution posted.

Engine:

Brand new OEM D15z1 that had never been started. (Got it from a Technical College, it was donated from Honda in 1992. It sat on a engine stand it's entire life) It was completely brand new when I installed it and had never ran. It was only missing a distributor. (Of course I replaced front and rear main seals and head gasket and checked the valves/springs cylinder walls and everything just in case- It was perfect.)

My car was a 94 DX but I did an entire cabin harness swap from a VX. The D15z1 also had a brand new engine harness on it. So my swap was plug and play. The car started instantly after swapping the engine in and everything was great with no engine lights. But once at operating temp I get the hesitation while cruising as it goes in and out of lean burn. I will stress that it runs FLAWLESSLY with the 02 unplugged.

Things I have done/tried:

-Checked all wiring, no shorts/open wires
-Set proper base timing with timing light
-Brand new distributor, wires, NGK ZFR4F-11 plugs, fuel filter
-Changed the brand new injectors out for some other VX injectors (did nothing)
-Changed out the brand new O2 sensor out for an older oem O2 sensor (did nothing)
-Checked Voltage/Resistance on TPS, IAT and MAP sensor - all were good. Also changed those 3 sensors with others just in case (did nothing)
-Checked function of EGR, the ports were spotless as the intake mani and EGR valve are brand new.

One thing to note : I am using a VX exhaust manifold but I fabricated a catalytic converter bypass pipe and am using a DX downpipe. The DX cat is still in the OEM location under the car as well. I am concerned that perhaps it needs some backpressure at the O2 sensor to read correctly or something??!!

I'm totally stumped. Any insight at all would be greatly appreciated :)

Anyone have any ideas? Would a PCV issue cause cruising hesitation in lean burn?? Or would a PCV problem just mainly affect the car at idle??

I have no clue where to go from here :(

problems start at operating temp? check your coolant temp sensor, does it get too hot? maybe a bad, incorrectly installed t-stat?

as far as i know, the vx uses a wideband sensor.
is the new o2 location farther from the head than stock?

I'm not 100% tracking what you are saying here, If it's that you are running a DX exhaust manifold to a cat-delete, then I'd say this has something to do with it!

Non stock VX exhaust will screw up the o2 sensor because it tends to be over sized, it's not back pressure from small exhaust, it's the smooth exhaust pulses that a correctly tuned exhaust creates.

Thanks for the replies, my thermostat is brand new OEM, but maybe I should check the Coolant Temp Sensor??

I suspected too large of an exhaust may be an issue, but hadn't seen any info about it. I did find two people in a post who claimed that it didn't matter what happened after the first O2 sensor, but I was skeptical.

Just to clarify: I'm running a VX exhaust manifold that connects to a short custom pipe that then runs into a DX down pipe and then through the OEM DX catalytic converter that is under the car and then out through the muffler.

Basically with the exception of the exhaust manifold and custom little pipe, the exhaust system is OEM DX.

I will work on installing the VX down pipe, in the mean time I'm open to any other suggestions :)

The VX exhaust is around 1/3 smaller then the DX, because the DX engine tends to run that much faster with the torque at higher RPM as well.
On my first VX I ruined an o2 sensor in less then a year by having a slightly over sized exhaust and it's something that I noticed on my current VX along with my brothers VX is that a large or open exhaust seems to lead to lean burn not working right and a shorter o2 sensor life.

Thanks for the info, I'm going to order an OEM VX mid pipe - I already have the down pipe. I swear I've tried everything else. Now it's just a matter of finding a CAT somehow...sheeshh they're expensive.

When I get the correct exhaust on I'll let everyone know if the stutter went away. Stay tuned...

My cat has been hollowed out and my 02 is dead. But I have questioned the need for it on the hondatec board a couple of guys have vxs with no cats. So... Possibly they don't notice the hesitation or...
http://honda-tech.com/showthread.php...t=cat+hollowed

After checking out that link in the above post, I'm not too sure that those who are posting are very familiar with the VX exhaust system. Who knows though, when you get an O2 sensor thats good let us know how lean burn works with your hollowed out cat...... my situation is still quite different than a hollowed out cat, I have custom little 3" wide straight pipe into a larger than OEM exhaust.

On top of my lean burn hesitation issue I noticed today that my shift light no longer comes on, but the bulb is still good :( super annoying, not sure why that would happen. No CEL on.

According to TomO (a moderator on ECO modders), "The upshift indicator (as Honda calls it) reads the MAP sensor, TPS sensor, and rpm signal to determine the best upshift timing."

I wonder if it's possible that my TPS has a bit of a light throttle dead spot, I tried a different MAP sensor and nothing changed.

Except for a hollowed cat my exhaust is 100% vx . Leanburn works fine just incase someone is wondering.

mine is hollowed on my z1 in the vlx as well and lean burn is smooth. its a vx manifold to vx cat and a vx downpipe and that bolts up to the lx converter (i would recomend doing this to your dx as well) that way you know the engine is getting the correct backpressure.

what kind of hesitation is it? does it stumble and carry on? or does it just bleed off like you are losing power?

grab some numbers off of the 02 sensor. should have the ngk part number and then underneath that it should read A09 or A08 or A07 etc. the correct one is the A09.
the actual part numbers on the box are the same but different ones are made in different places and the federal vx calls for the A09. check out my thread for more info with pics.

http://ecomodder.com/forum/showthrea...5z1-23433.html

7th page has pics

I'm not sure that I will put an 02 on the car I might have a tuned ecu and either a 02 delete or calibrate the ecu to run a less expensive wideband. I have many ideas and options. But as you see a hodgepodge of exhaust will work as to weather or not the 02 will last I don't know. Today the tuner told me to move the 02 way past the cat downstream. As the heat kills them. The are just as accurate farther back if the exhaust is sealed properly???? So all the more ideas now.

You cannot tune the P07 ECU. I wouldn't mess with the O2 sensor location either, I'm sure Honda put it there for a reason.

My shift light started working again on the way to work this morning. Weird.

your o2 sensor is where it is because it needs to be there to stay hot enough to work right, the vx's engine run slower and cooler so the exhaust doesn't get as hot, that is why the cat is close up to the engine block as well.

Thanks for the input :) I have tried two different O2 sensors and still had the same result. I am currenty running a brand new OEM Honda O2.

The car does go into closed loop but it hesitates a little, still maintains speed and all but it sputters and seems to have a dead spot at light throttle while in closed loop only. I ordered a VX mid pipe and am searching hard for a cat, then everything will be completely OEM and I will know for sure if that was the problem.

I know one thing, if the O2 needs some heat or proper exhaust pulsation to work properly like Ryland is suggesting and has seen by experience, then there are definitely issues with my 3" wide bypass pipe into a DX downpipe.

I will keep you all posted... in the meantime some pics of the motor pre install:

Brand new had never been started D15z1:

You can see the custom pipe (I since changed to new plug wires)

http://imageshack.us/a/img541/2651/20121224141223.jpg

http://imageshack.us/a/img827/9/20121215125053.jpg


http://imageshack.us/a/img405/2917/20121215183511.jpg

http://imageshack.us/a/img339/6168/20121215135506.jpg

Lean is mean and generates alot of heat. You melt your pistons when you get to lean with a load. No I will not be tuning a p07 it's maps will be put into another ecu that us tunable.

PROBLEM SOLVED!!!!...

So after going over everything again and again, I took off the valve cover and realized that the timing plates on the rocker arms were damaged. There are little tabs on the timing plates that sit on top of the primary rocker arms. The tabs butt up against a casting on the rocker arm caps. These tabs allow the car to disengage VTEC once it is engaged. The tabs on mine were all broken off!!

I had to change all the timing plates. (They must have been damaged by students since the engine spent it's entire life at a technical college). I didn't realize they were messed up when I originally put the engine together. When the valve cover was off I could see that the primary rocker arm pistons were all engaged into the secondary. A flick of the spring by hand disengaged the little pistons in the rocker arm, freeing the primary rocker arms from the secondarys.

So what was happening is that the engine was constantly in VTEC!! This caused it to run with a stumble in leanburn. It's surprising how well it ran overall considering this issue, but now it runs PERFECTLY.

Can't wait to see how the mileage will be!!!

Note: It doesn't look like a catalytic converter is necessary for proper leanburn operation. I have installed an innovate LM1 wideband 02 sensor right beside the OEM sensor and the car is entering leanburn just fine with no stuttering or problems. (I drilled and tapped the OEM manifold right beside the stock 02 sensor. )

Thanks to everyone for their suggestions!

Could you post a pic of where you mounted the wideband on the manifold? I mounted my vlx one in the converter because it's gutted but I plan on putting one in my vx hatch and that converter is not gutted.

I used an innovat wideband as well. I love it

finished the input shaft bearing, clutch kit, radiator, and brakes on my VX, so i took it for a big drive yesterday. i have the common complaint of hesitation at times and want to check the TPS and MAP but i can't find any test procedures for them in the FSM. i'd also like to find a test procedure for the o2 sensor. can anyone direct me to what pages to look at, or tell me how to do the tests?

fwiw, here are the symptoms i'm experiencing:

- periodically, while keeping the throttle steady, the car will slightly lose power. this is more noticeable when taking a hill. it usually last for a few seconds, and then while continuing to keep the throttle steady, the power will kick back in. this loss of/return of power is a smooth transition, there is no bucking or jolting.

- often, the throttle does not respond to minimal increases, and will only respond after several of them, but by then it's too much and i need to back off the throttle. so it's like: i'm cruising but need to accelerate slightly so i give it a tad more throttle; no response; i give it a tad more throttle; still no response; i give it a tad more throttle, and the car acts as if i suddenly gave it substantial throttle—which i did, when you add up all the minimal throttle increases—and i need to back off the throttle to get the light acceleration i wanted in the first place.

- lastly, when keeping the throttle steady upon starting climbing a hill, there is a noticeable power increase, as if i just gave it substantial throttle.

thanks gang.

oops, just found a few of the tests. for those interested, they are in the FSM on the following pages:

o2 sensor - page 227
MAP sensor - page 244

unfortunately, i have no CELs and the manual pretty much says "if no CELs, everything's fine right now. look for bad wires or connections." oh, FSMs.

Sounds like to me that lean burn is kicking in, at least the symptoms that you are describing are like my car (98 HX) when it is engaging leanburn. Do you have a MPGuino?

no, i do not have an mpguino.

Yea sounds like normal operation in lean burn. That power increase is it coming out if lean burn= worse mileage. Keep it in that soft low power area for best mpg. Instrumentation helps a lot I have far gauge but you can go with Mpguino for a lot less

Could be lean burn could be wrong or going bad 02. You can still check for stored codes.

the o2 sensor looks brand new, and the PO mentioned that he installed it recently. i did see some of slownugly's other posts that mention how not all o2's are created equal so i will eventually compare the part #s and go from there. i have a feeling it might be difficult getting the correct sensor since the boxes have the same part # but if it looks like an issue, i'll dig into it.

i remembered today that i checked the timing when i first got the car, and that it was substantially retarded. i advanced it as far as it would go but it is still retarded so next on the to do list is accessing the timing belt and advancing it. i'm familiar with 80s toyotas where you could pull the dizzy to advance it a tooth, which is not possible with these cars. which way should i rotate the crank or cam pulleys to advance the timing by one 'tooth?' i guess that term still applies since the timing belt has teeth on it.

No you can't put the dizzy in wrong it could be a tOoth off though. You do have to put a jumper wire in a connector when checking timing. If you didn't know. Looks new doesn't always matter look at the wire colors or 02 and look that it has the rubber grommets in slow and uglys post. Good luck.

right, i understand the dizzy cannot be put in wrong. however, the cam and crank pulleys can be aligned inccorectly. that appears to be the case with this car since after jumping the connecter and advancing the timing as far as possible, it is still quite off to the left (looking over from the driver side fender, of course). i guess i will just remove the timing covers, set the crank to TDC on the #1 cylinder, and confirm that the cam and crank pulleys are in fact off. if they are, i guess i'll remove the timing belt, rotate either pulley the small amount required until both are TDC, and then put the belt back on.

what are the correct wire colours for the o2? i haven't seen that mentioned. i have checked the PCV grommet and it appears fine.

Look at slow and uglys post look at his wire colors. He had a bad stumble with the wrong 02. The harmonic balincet has 3 lines on it make sure you are trying to time it to the correct one. Put the car at top dead center on the crank pull of top timing cover and check the cam.

moving this to another thread, found here:

http://ecomodder.com/forum/showthrea...tml#post366773