codizz88

Currently diagnosing a car i just bought has a hesitation that is sometimes subtle and sometimes more aggressive making a pain to drive. Yet no CEL... In the process of troubleshooting everything by the Helms manual, not quite done yet next going to troubleshoot the LAF, Intake air temp and Spool valve for heck of it. All tuneup stuff is new, VX distributor is new, and has new NTK LAF sensor that was put in when previous owner swapped out the cali ECU with a 49 state, today i redid all the engine grounds since they looked like crap and honda likes to expose 25% of the wire on their grounds.

My main question for now is when i was checking MAP sensor towards end of the trouble chart is asks if there is approx 3 V key on then 1 V at idle. Im thinking how approximate is approximate i wish they mentioned a + / - value. my readings were 2.850 and .750, come to think of it i backprobed connector instead of probing ECU, maybe small voltage drop from ECU to connector? ill re check for hell of it at the ECU...

Then also when diagnosing my egr valve going down the trouble chart everything is passing then i get to where it says connect power directly to the EGR control solenoid valve from the battery (which i did with alligator clips) and it asks if there was approx 8" of vacuum in 1 second and i only got 6" so here again i come to not knowing how approximate is approximate. Every vacuum line i pulled off and made sure they were clear and leak free, the chart ended with me needing an EGR control valve solenoid but that is assuming 6" of vacuum isnt sufficient since it asks for 8".

This weeking im looking at the LAF circuit for sure, was just leaving it for last since its a new sensor. I have a spare NTK sensor that came with car i might swap in, or just drive it with it unplugged from what others have said if my hesitation goes away then its sensor related...sorry for the novel and thanks for help to any of my questions.

Txdragon

Trying to diagnose something like hesitation without a CEL is like going to the doctor asking him to diagnose an illness based upon nausea and vomiting. It simply can't be done!
You mentioned a few things here that could either be a problem or THE problem, it's hard to say. This kind of issue leading to a bad solenoid or sensor would almost definitely trip a CEL. I would look a bit closer at fuel delivery and go from there.

Former User

Did you check the ignition timing? If so, give details.

Does the CEL work?

codizz88

Yea i know its one of those problems, it is likely something bad enough to make it run crappy but not trip the light....with OBD1 unless its a major issue it wont trip a CEL annoying at times. yea CEL works, i also did a fuel pressure test and its within spec. Ill probably ohm the injectors out and other things later if it gets that far, and probably test the new dizzy components and wiring just because. The timing is good 16 btdc, Coolant temp sensor tested good, same with throttle angle sensor. Correct zfr4f plugs and all tuneup stuff, was mainly concerned with those testing numbers, still a lot of troubleshooting to do, before i start getting really stumped.

Former User

My single cam

check all of your wiring harness and such as well, something may be corroded, not grounded or disconnected.

codizz88

What are you getting at? i said 16 BTDC, z1 is a 16 +/- 2 engine... verified mechanical timing, jumped service connector, timing gun reads at 16btdc with engine at operating temp no load. which roughly is the middle mark, supposed to be red mark, TDC mark is located clockwise of your 10,15,20 marks on pulley used to verify mechanical timing. Some engines go by cylinder head surface flush with TDC marks on cam gear other engines go by the TDC mark and pointer. Z1 goes by the pointers on the back timing cover.

Former User

I am trying to figure out whether you checked/adjusted the timing correctly. Were you monitoring the engine rpm with an external tach during the procedure? What was it?

jlk16188

mine gave me hesitation when the O2 sensor failed but no CEL (with functional CEL). I also had to change out my TPS and calibrate it bc of a dead spot at low throttle. must have been where i cruised on the highway with the throttle position constant.

codizz88

Yea i checked the TPS hot and cold and carefully ran it through a few times good smooth voltage and passes all other checks. Id hate for that o2 to be bad but i have another older one that should still be good ill use if i have to. I found a few problems and fixed them but it may or may not fix the actual issue. Ill release my findings when its all said and done.

jlk16188

I changed my O2 sensor and seemed to still have a hesitation issue so i did the following:

The ground at the thermostat housing on mine was broken somewhere in the harness between the O2 sensor and the grounding point. I ended up cutting the ground wire at the harness after the o2 sensor plug and running a new pigtail to the grounding point. I also ran a tap through all the ground point threads in the engine bay and polished the ground connectors to ensure proper ground.

this solved all of my hesitation issues

codizz88

Well one interesting thing i found, i unplugged my o2 and it runs fine now. Yet it never had an o2 CEL, or one at all. So i went through the entire LAF(o2) flow chart from helms and all my voltages passed for the 02 sensor wiring, and the o2 is a new NTK one...So with the o2 unplugged i think it goes into a limp mode and doesnt use input from other sensors as well besides the o2 sensor yet all other sensors passed tests regardless.

eghatch9295

iTrader: (1)

keeps it in open loop, with pre programmed fuel maps, among other things. have you opened your ecu up to check for bad resistors/burn marks?

codizz88

The ECU was originally a cali model and replaced with a 49 state to use lean burn, one thing i did notice was that there was some corrosion on a few wires entering ECU from water leaking from im guessing the cowl somewhere gotta figure that one out still...

So that is one thing i need to mess with, i noticed it few weeks ago and cleaned the ecu terminals and sprayed contact cleaner on the harness plug and let it dry but it didnt make a difference. Next thing i might do is open up ECU and take a look and then Ohm out those corroded wires and maybe have to end up fixing them it was hard to tell how bad they were, i bought 5 large and 5 small ecu pins just incase, i was thinking that my voltages for o2 sensor were going to be off because of that corrosion but they werent and i backprobed right at the o2 sensor.

codizz88

Best way in my opinion of how it runs is it feels like its hitting lean burn and hesitating when its going into it, as if its leaning way to much and erratic, does at various cruising rpms and all speeds.

eghatch9295

iTrader: (1)

distributor new as in parts store new?

codizz88

Yea distributor is brand new when i got it, i also made sure it was a vx distributor. It came with the original dizzy, i have it apart now have to fix a few wires for it that were ruined from a bad oil seal in it. The coil tests good still so if i fix the wiring to the sensors in it should be good to go and then ill swap them just to see because i know new ones are hit and miss.

What else should i look at with fuel? i did a fuel pressure test from the manual and pressure is good, regulator is working.

jlk16188

did you rewire the car to accept a 49 state O2 sensor when you swapped to the 49 state ECU from the 4 wire O2 senor and Cali ECU???

The is a big difference and the O2 sensors matter. You have to have the matching sensor with ECU and the Cali model has to be modified to accept the 49 state ecu

eghatch9295

iTrader: (1)

z1/z6 distributors are the same. parts store distributors are extremely problematic. i have a large milk crate full of dead honda distributors in my basement, 75% of them are aftermarket or rebuilt.

codizz88

The previous owner did it not me, i just know it has a new NTK 5 wire o2 and he changed the ecu, is there an additional wire that needs to be ran from ECU to the o2 connector or something im unsure if he did that. Weird thing is the old o2 is a NTK 5 wire as well, i was thinking the cali model o2 were a 4 wire.

EDIT: According to this 92 cali models came equipped with the 5 wire which explains why this one had one installed and that you would just simply have to swap the ECU. http://ecomodder.com/forum/showthrea...n-vx-7295.html

cvcrcr99

my 92 vx did the same thing years back, unplugged the o2 and it ran perfectly, but with a CEL. Previous owner put on all new ignition parts etc etc, but never looked at the o2 sensor. Swapped out with a good, used unit and the problem went away magically.

TheException

So, it seems like you need to be a rocket scientist to figure out the VX stalling/bucking/hesitation? Mine does the same thing, I've replaced with new parts:
-MAP sensor
-Distributor
-Cap/Rotor
-Plugs/Wires
-TPS
-Fuel Filter
-Cleaned the IAC and checked the fuel injectors
-blead/burped the cooling system

I guess Ill B swap it!...

Is this what your car is doing? Here's mine:

The muffler rusted off, there are no engine noises, just low quality.

eghatch9295

iTrader: (1)

/\ verify mechanical and ignition timing. compression and leakdown.

TheException

I am lol-ing at myself so hard right now... After about a year of troubleshooting/guessing, I finally chased the vacuum lines, and I had the #16 and #7 lines mixed up.... Stupidity is expensive! Haha, good luck OP.