KA24DE bogging/hesitation until 3000 RPM and stalls coming to a stop

[CrypticDemise]

The car is a 1991 hatchback with factory dual cam KA, 140k miles, factory auto, 5 speed swapped. I've always noticed the car seemed to have a bit of hesitation and never seemed as fast as my previous s13s. Valve stem seals went bad and I finally got around to replacing them as well as a ton of parts on the car because I also pulled the IM to delete PCV/fix vacuum leaks.

After I replaced all this stuff, I wanted to tackle the hesitation, and it seems more present now than ever. At first, I noticed taking off in first gear, the car would really bog down, but was smooth after that. Now, just about anything under 3000 RPMs in any gear with more than 1/4 throttle makes the car misfire/bog/stutter really bad. If I go easy on the throttle, it's fine. After 3k RPM, car smooths out, but feels gutless (may just be that I forgot how slow an NA KA is).

First, I checked the ECU codes, and got 34. Replaced the knock sensor and it was still there. Wasn't getting voltage at the ECU so I checked the harness and found a break above the fuel rail area. Fixed that, ECU now sends 5 volts KOEO as it should, 2.5 volts with engine running/sensor connected. No more code 34.

Then it started showing code 13. This is where I'm stuck. CTS is brand new nissan, PN 22630-51E02. Checked resistance and it was reading normal, around 1300-1600 kOhms with engine cold, 300-ish kOhms at operating temp. Spliced in a new connector because it was cracked and corroded. Connector pins have 5 volts disconnected, KOEO, but when I connect the plug into the sensor, it reads around 2 volts. I assume this is normal? There is continuity from the connector to ECU pin for both power and ground. Swapped the ECU for a manual one I had from a parts car (verified working) and code 13 still comes up.

I replaced the sensor for the dash gauge because it was starting to act erratic, jumping to hot and cold randomly. Now, the gauge just never gets to operating temp. Bleeding the coolant system for 10-15 mins and the gauge just starts to touch the C. Driving it for half an hour, I managed to get it to the second tick mark above C, but it just goes back to C randomly whenever it chooses to.

Upper rad hose is hot, lower rad hose is fairly cool, but I figure this is normal since the KA has a reverse-flow coolant system. Cracking open the bleeder screw, burning hot coolant comes out, so surely the temp sensors are submerged in hot coolant, but both seem to be malfunctioning. I figured my gauge cluster may be the issue, not my temp sender, but it is odd that the ECU says the 2 pin CTS isn't working properly either.

Car has a 248/248 cam swap and idles pretty good when I first start it. Once the rad gets hot, the idle seems to raise up from 900-ish to 1300-1500 RPM, which seems to be a symptom of code 13 from the research I've done. Driving around, the car dies anytime I put the clutch in while the car is still moving.
I really don't suspect MAF (usually causes issues in higher RPM range) or vacuum leaks (would present more idling issues), nor do I suspect fuel (unless its FPR?). TPS is set at 0.49 volts with throttle closed. I was convinced it was a sensor, and the CTS would really explain these issues, but why does my ECU think there is a problem if I have continuity, a new sensor, and hot coolant? Are both ECUs screwed up and reading code 13 somehow or is there something else that can cause code 13? Is it possible I just need more engine bay grounds after my battery relocation?



Parts replaced:
Swapped fuel rail/injectors for a rail and injectors from a known working KA, didn't remove injectors from rail so I highly doubt injector seals are the issue, car tries to die at idle when unplugging any injector
Spark plugs/wires less than a year old, NGKs
Z32 fuel filter less than a year ago
Walbro 255 installed yesterday
CTS for ECU and dash gauge replaced last week, OEM nissan replacements
New coolant, bled properly, car has shrouded clutch fan, dual e-fans, ebay radiator
Lots of vacuum hoses replaced, EGR and literally just about every emissions system has been deleted properly
Battery relocated last week, cleaned engine bay grounds and replaced ground strap at back of head above headers
Knock sensor
Cleaned IACV a week ago

[mechanicalmoron]

What do your plugs look like, oil coolant gas dry and sooty dry and lean etc? Got your firing order right? Check compression, maybe running compression?

A stock KA feels like a pretty normal quick-enough car, not a broken boggy car - if you can't tell the difference, you should probably get a town and country or some shit.

Maybe you screwed up the cam timing playing with those exhaust cams. Or lost some shims or something. Kind of sounds like a head problem.

What's coming out the tailpipe?

You deleted the PCV? How? And what the fuck were you thinking?

[CrypticDemise]

Originally Posted by mechanicalmoron

What do your plugs look like, oil coolant gas dry and sooty dry and lean etc? Got your firing order right? Check compression, maybe running compression?

A stock KA feels like a pretty normal quick-enough car, not a broken boggy car - if you can't tell the difference, you should probably get a town and country or some shit.

Maybe you screwed up the cam timing playing with those exhaust cams. Or lost some shims or something. Kind of sounds like a head problem.

What's coming out the tailpipe?

You deleted the PCV? How? And what the fuck were you thinking?

Just pulled the plugs, they're OEM spec NGKs I bought last year and the gaps were all around 0.035" so I re-gapped them all to the 0.044" range. All the plugs looked the same: black around the edge (keep in mind I did have a valve stem seal issue recently so I assume that's just the burned oil) with a white ground electrode. None were wet.




After gapping the plugs, the car did feel a bit smoother, but definitely still has bad hesitation. Temp needle didn't move from cold during the 10 minutes I drove it, still died at stop signs, 1300 RPM idle. Car also seems to have factory distributor cap and rotor with the nissan logo cap cover, factory ignition coil too. Double checked firing order and it seems correct: looking directly at distributor from the engine bay, plug wire 2 on top, 3 on bottom, 1 on the left, and 4 on the right.

Forgot to mention, I did a compression check a couple months ago before I replaced the valve stem seals:
Cylinder 1: 151 psi
Cylinder 2: 166 psi
Cylinder 3: 161 psi
Cylinder 4: 161 psi

Seems to be within spec of 151-179 psi. Wet test, all went between 170-180 psi.

I just haven't driven the S13 in a while since the valve stem seals went bad, and my daily is definitely quicker than the 240 even if it had full power. But like I said, it definitely feels down on power past 3000 RPM despite revving smoothly compared to 1-3k RPM.

I haven't checked distributor timing, but I put it exactly where it was when I went to take it apart, dead center of adjustment, made sure I reinstalled the distributor according to paint pen marks I made when disassembling it. Would dist. timing make the car feel this bad?

Almost positive the engine timing is good. In fact, I was putting the top end back together when I noticed my timing marks were off, so I pulled it all off and made sure I did it right. Cam lobes lined up properly with 4 teeth CCW for the intake cam (which is actually an exhaust cam), counted proper number of chain link pins between timing marks, and I put a ratchet on the crank bolt and ran it through a few cycles to ensure everything was as it should be. All buckets had shims, buckets spun freely, cam caps torqued properly, etc...

After the valve stem seal job, the tailpipe is free of any smoke when I rev the car up while sitting in my yard, and haven't noticed any smoke when driving the car. Don't see or smell anything odd for a straight piped car.

Believe me, I did days of research on the PCV system before deciding to delete it. Previous owner decided to leave the valve cover PCV port open and it was puking oil out, I assumed because blowby was easily getting past the bad valve stem seals. So I pulled the IM, followed a guide on ka-t forums on pulling/tapping/plugging the 4 PCV ports with pipe plugs, sealed with teflon tape and ultra grey RTV on top of plugs for extra security. Straight through fitting in place of the PCV valve, with a hose from the straight fitting to the catch can, valve cover port to catch can, and third port for a vacuum source that I used on the stock intake, utilizing a factory nipple that was capped because it was for an emissions piece I had deleted. SO all that to say, blowby is effectively being evacuated from the crankcase using an intake vacuum source (car is NA).

I'm just stumped that both the coolant temp sensor and sender seem to be acting odd. Is it possible both are bad/wrong part # despite being brand new in nissan packaging? I have both sensors on a spare KA that I know to be working, should I just try swapping them out with those so I know the sensors aren't the culprit? If the sensors are good, the wiring is good, and the ECU is good, wouldn't that have to mean I have some constant air bubble in my cooling system that is affecting both of the sensors? I mean, I bled the coolant with the front end on ramps, massive rad funnel to make it the highest point in the cooling system, and squeezed upper/low rad hoses with heater on, and eventually I wasn't getting anymore bubbles. Overflow tank between max and min lines, 70/30 water to coolant. Is there anything else that would cause a code 13 to be thrown?

[CrypticDemise]

So I swapped out the coolant temp sensor and sender for the ones on my spare KA and now the temp gauge reads properly and I have no more code 13. I have no idea why the brand new ones I just bought didn't work properly. Double checked on nissan part dealer sites to see and they matched up to the sensors I bought.

Anyways, the car still has hesitation, though it's not as pronounced. TPS voltage is at 0.49v closed. Did an ohm test too and it read 1.2 kOhms closed, 8.7 kOhm WOT, and the TPS on my spare motor reads about the same. Injectors all read between 11-13 ohms. Really not sure where to go from here, ECU reading code 55 (no codes).

Things I haven't checked/replaced:
Ignition coil (factory)
Distributor cap and rotor (factory)
CAS (cleaned connector, figure it would throw a code if it was bad)
MAF (same as above, also bad MAF symptoms are pretty different from mine)
FPR
O2 sensor (it does look to be OEM and looks pretty dirty, but isn't the O2 responsible for cruising drivability? Disconnecting it at idle does nothing)

[mechanicalmoron]

I don't know that it's your problem, but by your description you have a PCV system that would be a shitty band-aid for a haggared turbo setup, that puts full intake vacuum on your crankcase - with no fucking turbo? Why do you have a catch can at all? You're probably pulling past all sorts of seals and stuff. A positive crankcase ventilation system doesn't put uber vacuum on your crankcase, it creates a positive flow and a mild vacuum, to pull fresh air into your engine to flush out the vapors.

It sounds like you've done plenty that will confuse the shit out of the stock computer, while managing to do absolutely nothing that would make the car faster.

[CrypticDemise]

So you would consider my current setup, if it were on a turbo KA, a bandaid for a haggard setup, and even worse while NA? I'd like to hear what you consider a proper PCV setup. I don't wanna get into this because you and I should both know the PCV catch can setup has NOTHING to do with how my car is running, but since you wanna bring it up...

People run far simpler catch can setups on KA-Ts, with lines to PCV and valve cover vent running to a VTA catch can with no problems. On the facebook groups, I've seen tons of people running a catch can this way no issues. Running a straight fitting instead of a PCV valve allows less restricted flow of crankcase gases, and having these two sources hooked up to a vacuum is the PROPER way to do it, because putting these to a vacuum source improves ring seal and helps evacuate blowby more effectively. The valve cover vent is literally hooked up to the intake from the factory, and the PCV valve gets vacuum from the manifold from the factory.

Keep in mind, on my setup, the one vacuum source has plenty of restrictions: the tap for the intake is only 1/4" diameter, which is much smaller than the 5/8 intake vacuum hose the valve cover is hooked up to from the factory; I'm running a check valve so positive intake pressure at WOT isn't going through the crankcase; the catch can has a filter on the vacuum port so it doesn't suck up any oil from the other two ports, and finally, this vacuum is split between 2 sources: the valve cover vent and the PCV.

Putting my finger over the PCV/valve cover vent sources at the catch can only produces a small vacuum, hardly noticeable. The oil cap isn't hard to pull off, nor is the dipstick. The vacuum that is being pulled is not nearly as significant as you may think. Just to prove it wasn't the issue, I disconnected the vacuum hose, capped off the port for it, and ran the PCV and valve cover hoses to atmosphere. Car felt no different.

Yes, I know a catch can isn't something important on an NA car. I was trying to get rid of vacuum leaks (PCV hoses were destroyed anyway) and get this out of the way while I had the IM off, because I plan to go turbo eventually. No, obviously this doesn't make my car faster (though in high HP applications, a sealed catch can setup that provides crankcase vacuum has been proven to net 10-20whp increase on 500whp+ R35s), but I see this as a modification that improves function and health of my engine. You should see the stuff that the catch can accumulates. And how on earth would a catch can setup confuse the computer? You think the computer gets readings off the PCV system or something? Using a sealed catch can setup ensures all air going into/out of the crankcase is metered by the computer.

[CrypticDemise]

Pretty sure I know what the problem is now. I remembered that while I was doing the valve stem seals, I ran into an issue with my valve stem holder attachment for my air compressor. The compressor had too much pressure and actually cycled the motor when I first connected it. After that, I lowered the pressure and had no issue, but that means the lower timing chain moved while the upper timing chain was off.

I put the crank pulley back to the TDC mark after that happened, but its possible I left some slack in the chain so the lower chain may be a tooth or two off in relation to the upper chain. So while I properly timed the cams to the idler sprocket, I most likely didn't properly time the upper chain relative to the lower chain on the idler sprocket.

Doing some research on the timing chain being off by a tooth or two, the symptoms sound like mine. Exhaust is noticeably louder than it was before (thought it was just because I installed headers at the same time as the valve stem seals), feels slower than a KA should, and bogging/hesitation.

Thank you mechanicalmoron for suggesting this. While I was confident I had timed the cams properly, I figure the lower chain might have been slightly off because I just went by the crankshaft mark rather than the idler sprocket timing dimple. I'll update with my findings, whenever I am able to get to it.

[mechanicalmoron]

The chain sure sounds reasonable.

As to PCV, that extra power probably comes from the elimination of air pumping losses (crank, backs of pistons), according to the ring explanation the vacuum should just suck all the power right past the ring gaps, right?

Excessive vacuum is not healthy for a motor, and not only allows strange air leaks, but can also do things like fold seals over, suck gaskets in, and effectively make an air reservoir that the MAF can't see. The PCV doesn't just vacuum the crankcase, it replaces the fumes, while quite intentionally avoiding excessive vacuum by orifice and valve sizing, type, placement, etc.

It's a problem that some stock cars develop on their own, and instead of getting super fast, they develop leaking, oil burning, and drivibility problems, and get taken to the shop.