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.
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