OK, H-T. I feel like i've done my due diligence on this one and cannot come to a resolution on what may be at fault. Here is the story:

Bought 99' EX 4-door 5-spd for a DD since i cant seem to stand/work on none Hondas for a DD. In my 30's people gave me crap for buying an "old" car to use as a DD. But as an EG owner since 17, i felt that this was the newest of the generations i was familiar with.

Upon purchase immediately changed the following:
Timing belt - Used gates, reset timing via timing gun and reset idle per OEM manual
Water pump
Coolant
Thermostat
Misc coolant hoses as necessary
Fan switch (fan wasn't kicking on per previous owner, this was this issue)
Coolant temp sensor (broken off at the head)
New NGK plugs
Autozone special cap/rotor
New primary o2 (bosch) - was getting p0420 and changed secondary o2 with used o2 i had. Now getting heater circuit code,still stumbles like before and after this change
New gates accessory belts
Pulled vacuum/Refilled A/C with 695 +/- grms of R134a - (compressor was crap as i found out two weeks later, since replaced, new dryer, re-charged)
Oil/filter change
Tranny oil change (Honda MT fluid)
Flushed PS fluid with oem Honda oil
Valve cover gasket
VTEC solenoid gaskets replaced
Distributor o-ring replaced
adjusted valve lash to .007" on in and .009" on ex
Cleaned IACV and TB (left TB on IM)
Reset idle again per OEM specs after all was done.

So as you can see i gave her the full brush up on all the crap that most people neglect/forget/dont do etc. I did not drive it before i did all of this so i cant say it did it before these things were done. By the way honda noobs, that list above is a good run of what you should do to a new 92-00 civic, especially if you get a questionable story at purchase.

So onto the issue at hand. Car starts and runs perfectly in all circumstances EXCEPT no matter cold or hot start the car will act as if the throttle is closed and cut what seems like fuel about 30 seconds to 60 seconds into driving. In fact i know exactly where in my neighborhood this is going to happen. It is that consistent. Hot or cold, i will drive may 500FT and it will do this. I can push in the clutch and give it gas and it will recover fine, i can give it more gas while in gear and it will buck and stumble. If i push in the clutch and don't give it throttle, it will die, seemingly not being able to catch itself at idle. I have driven it for and hour or two after start/stumble and it will never repeat this issue.

ANY input on what to check? I found a thread on what seemed to be the same issue and the dude was an ***, ended up fixing it and not saying how (of course now i cannot find the thread). I truly appreciate any input on this.

 

No new plug wires?

Post all OBD2 codes stored in the ECU.

Reset ECU. Drive. What codes return?

 

Did not do new wires. Reset and drove only has the same code, p0141 - heater circuit malfunction on sensor 2.

It reminds me of when i had a bad TPS on my hatch years ago like your are giving it throttle and the ECU thinks the TB is still closed. Except when mine when mine went bad it gave me trouble all the time under all conditions. This is just so predictably during a certain time then its done.

 

Just a thought as i looked at the car again tonight after the drive. Could it be an issue with the "air injection" thermo valve not being hooked up? I found one of the arms had broken so i just capped the vaccum lines to and from it, but this does allow additional air in the manifold under 149 degrees. I wonder if the car is expecting more air than it is getting since the lines are capped...

Any thoughts or experience with that?

 

^

Also Ohm test the the heater element of the O2 sensor.

 

Ok, Ive ordered NGK wires, a new secondary o2 and picked up a used, but not broken, air injection thermo valve. I should everything in by the end of the week and will report back once installed.

 

Changed the plug wires, no difference

Changed the o2 and installed the air injection valve, no CEL now. But it was idling up at 3500 rpm for a second or two and would accelerate in gear until it started to warm up and it lightly surged then came down to normal and didn't do the bucking. But i let it sit hot for a couple of minutes then re-started it and drove and it did ti again like always, so i am going to say overall no change.

So i am still stuck on this one as to what could be causing the systematic cut out about 30 seconds into running then be fine for the rest of the time its on. Anything next on the list to check?

 

^Post pictures. Do you have a D16Y8 engine and an EX trim?

Also adjust the throttle cable to have proper free play.

Did you bleed the cooling system?

 

Check for vacuum leaks around the intake manifold and throttle body. I would also just replace the front primary oxygen sensor and remove the heat shield to inspect for cracks on the manifold. My old hx had a crack that would only trigger a cel when the heat shield was removed and the hood was opened

 

Ok, i will try to get pics tonight. It is a bone-stock 99 ex and have no intentions of modifying unless the motor died catastrophically i.e. spun bearing thrown rod.

I have adjusted the TB cable. i guess i forgot that on my initial list. I also have bled to coolant system.

 

I will check the manifold, but i have now replaced both o2 sensors.

During the drive this morning it did my hiccup again but otherwise drove and idled great. I did get another CEL, p0420, so i guess the cat has had it. Lucky me in Florida i will likely just do the old fouler trick and bypass the need for a new cat.

 

P0420 can indicate that there is a crack in the exhaust before the catalytic converter. The code can defined as low air flow past the secondary oxygen sensor in some cases

 

Maybe the cat is partially clogged. Remove and inspect.

Bleed the cooling system like this:

https://honda-tech.com/forums/honda-.../#post39830585

How much slack/free play do you have in the throttle cable?

 

Cooling system has been bled. It gets up to temp quickly and holds it like a champ.

I'll have to measure the throttle cable, but i've adjusted it to feel as i have every b/d motor ive had over the last 15 years. Id wager its about 1/8" deflection before the TB opens. Is there an OEM spec on this? As i said, ive always gone based on feel.

Checked the exhaust manifold and found no cracks or leaks. And while it is feasible to have a partially blocked Cat, next time im under there i'll pull it and give it a look see.

As a note i did replace the fuel filter (someone missed that low hanging fruit on the initial full tune) and added the secondary o2 spacer to get no more CEL. Still not change in the 30 second after start bucking.

 

Did you bleed as described at the link?

Just for testing purposes, loosen it more to 1/2" of free play.

It doesn't sound like the car was properly maintained by the previous owner. The cat would be a victim of the neglect.

The cause of the problem will likely fall into this category.

You also may want to test the FPR, and inspect the fuel injectors for partial clogging.

Was the base ignition timing adjusted with the service connector jumped and the engine idling to spec?

 

Which coolant temp sensor did you replace, there are 3 of them. One on the thermostat is the fan switch, one directly under the distributor is the temperature gauge for the dash, and the one in front under the distributor is the ecu coolant temp sensor.

If you have a scan tool try to check the coolant temp readings whenever thr bucking starts, the front ecu coolant temp sensor could be giving bad readings and the engine is giving too much timing because it thinks the car is still cold. I'm going with ron, you keep saying it gets up to temp fine but there still could be an air pocket inside the system that is messing with coolant temp readings. Make sure the interior hvac is set to heat and you bleed the system with the front end of the car elevated and the radiator cap off

 

Coolant bled as spec'd, yes.

I'll drop the tension down and see what happens

I agree the maintenance wasn't perfect, but most of this was changed for my piece of mind. When i dont see receipts i assume the worst. So most of this was changed out of my knowing it was and done and done right.

I agree, 90% of the time ive ever had something go wrong its been relatively simple. I must add here that i had added addition grounds and take off all factory grounds, sanded, cleaned and inspected.

I am seeming to think in the end it is something fuel related, it just seems the most likely cause.

IACV was pulled cleaned and the idle as well as base timing was set just as described in the honda manual. Fans twice, jumped service connector, set ign, then idle, double checked timing after intitial idle adjustment, then headlights on adjust idle, etc. etc.

 

Two coolant temp sensors were replaced. First the fan switch at the thermostat, then the ECU CTS, the larger of the two on the head. The little one wire gauge CTS works fine and has been left alone.

Problem is independent of coolant temp unfortunately. It will do this hot, cold or anywhere in between. The only common thread is it being after the car has sat for about 5 minutes or more it will buck/misfire/shudder about 30-45 second into operation twice (as in two separate and distinct episodes) then be fine for the rest of the operational time.

 

Sorry about the delay in posting the engine bay pic, but here it is in its stock glory. Clean up top after new VTEC solenoid oil seals, dizzy o ring and VC gasket. Hate all that oil leaking. Cooler weather and long weekends will mean rear main and oil pan gaskets get changed, those things are leaking horribly. Darn pillow mount engine mount was toast. Cant believe i had some old hasport b series mounts that solved that problem with style.

 

Your brake booster hose is looking like it's in really poor condition.