Need some genuine help on my Ka24de..

[Kouki_m0n5t3r]

Sorry for the lengthy first post but I am going to try and be as detailed as
possible. First off the car is a 97 s14 with a bone stock motor and A/T. About 207xxx on the chassis. Unsure if the motor is original or not, have not looked it up, but the I/M has some chalk writing on it. Could be a junk yard motor or just the mani alone.

Anyhow..my issue is hesitation during normal driving and acceleration, backfires during deceleration, and stalling at a complete stop or almost a complete stop. I know there a many threads about this but this has been going on for a while and I can not seem to wrap my head around it, usually I am pretty good at figuring out a problem just by searching.

What happens: the problem is intermittent. Sometimes it runs perfectly fine, then suddenly starts acting up and sometimes it acts up from the start. Doesn't matter if the motor is warm or cold. Happens at both times. Sometimes I will be cruising down the highway and will get a random hiccup, almost feels like half a second fuel cut and other times it will just start missing like crazy, like it is only firing on two cylinders, while on the highway or normal driving. At stop signs/lights it wants to stall out. If I keep it alive it spits black smoke, sounds like a cammed v8(but in a bad way), and will only smooth out if I really give it some gas..but that causes my rear tires to spin like I am doing a burnout. Unless I am in neutral, but then when it is time to go if I let off and put it in gear it will die out soon as I let off the gas. If I don't let off the gas I have to do a neutral drop..this is not a race car, lol. If I let it stall out then try to start it again it takes a few seconds and some pumping on the gas before it fires up, even then it still misses like it is on only 2 of the 4 cylinders.

I have had this issue before and to me personally it had all the signs of a failing fuel pump. So I changed that from an oem pump to a walbro, plan on doing a swap that is why I went walbro, and that made it run much better. Still had a small mis but I found out I had oil in cylinder 4 and 3 was slightly wet with oil, so I fixed the VC gasket leak. No more oil.
After the Walbro it ran fine for about a month and a half or 2 and now recently started acting up again. I think I would just have to have bad luck for the pump to be going out again...right?

Things I have done:
Cleaned MAF
Plugs
Dist cap and rotor
Pulled out throttle body and thoroughly cleaned it
Fuel Filter
Fuel Pump
And I pulled the vacuum line off the fpr and ran it for like 10mins to see if it spit back any fuel..nothing. Was checking to see if the diaphragm inside might have been bad. However, once I reconnected it...I started getting some black liquid drops coming out of the exhaust. So that kinda confused me.

I still need to give the IACV a clean, pull the fuel pump and make sure I do not have a loose connection and probably do a smoke test to see if I have a vacuum leak..but tbh..this really seems like it is fuel related. Haven't pulled the injectors yet since I want to have an O ring set in case one rips. Just waiting on that. I also need to check the TPS..but idk, something keeps pulling me back to it being fuel input related. I guess I could also check the o2 sensors but no codes are being thrown for that.

I may just be thinking too hard about this so any idea or suggestions would be a great and appreciated help. Going to run some of that Lucas Extreme fuel treatment through it since I have a bottle laying around..but I doubt that does it.

[Kouki_m0n5t3r]

Also..I haven't really heard anything bad about running a 255lhp fuel pump on a stock motor, from any motor. I have the same thing on my h22 and haven't had any issues. So I just want to make sure that wouldn't be an issue..I would imagine that is the point of the fuel pressure regulator.

[Kingtal0n]

Quickest, easiest thing to do with that kind of intermittent problem, on a KA engine, is start replacing parts. Start with the ECU/Wiring harness / distributor / all ignition components, then move on to the fuel system etc...

Along the way, you might find frayed wire on the distributor plug, or find out that the ECU was not fully tight, or find a huge hole after the maf sensor, or a loose connector on the fuel pump, or a bad CTS sensor/wire, it could literally be any tiny detail.

You can always re-sell parts if they turn out to be good and get your money back.

I just read your full description and find it interesting that the fuel pump fixed it for a while. Surely you changed the fuel filter- WITH the pump? And it ran better... but now its bad again... I wonder if the fuel filter is becoming clogged? Did you change the fuel filter BEFORE the new pump went in? Did you look in the tank for junk? nay, that doesnt make any sense, the car would not spill black smoke. Perhaps the wiring at the fuel pump needs attention. Like I said, replace some parts, sell or keep the spares for more than you paid. You can literally make money diagnosing problems on these cars.

[Kouki_m0n5t3r]

Quickest, easiest thing to do with that kind of intermittent problem, on a KA engine, is start replacing parts. Start with the ECU/Wiring harness / distributor / all ignition components, then move on to the fuel system etc...

Along the way, you might find frayed wire on the distributor plug, or find out that the ECU was not fully tight, or find a huge hole after the maf sensor, or a loose connector on the fuel pump, or a bad CTS sensor/wire, it could literally be any tiny detail.

You can always re-sell parts if they turn out to be good and get your money back.

I just read your full description and find it interesting that the fuel pump fixed it for a while. Surely you changed the fuel filter- WITH the pump? And it ran better... but now its bad again... I wonder if the fuel filter is becoming clogged? Did you change the fuel filter BEFORE the new pump went in? Did you look in the tank for junk? nay, that doesnt make any sense, the car would not spill black smoke. Perhaps the wiring at the fuel pump needs attention. Like I said, replace some parts, sell or keep the spares for more than you paid. You can literally make money diagnosing problems on these cars.

Lol, yeah that was what I was hoping to avoid was just start replacing parts and hoping one fixes the problem. I changed the fuel filter before the pump, however, after the pump, since I still had a miss, I pulled the filter off to check it..felt light and when blowing through it there was no hindrance of air flow. So I reinstalled it, it was only a few weeks older than the new fuel pump. I did check the tank since I had the top open anyway, but didn't see anything. New sock and everything on the pump. The black smoke is what is throwing me off..I mean..it gives signs of running lean, but black smoke coming out? As far as I know that is fuel and running rich..right?
I am going to check the wiring again and also disconnect both ECU and Batt over night.
The weird thing is sometimes it starts up immediately and just fine, other times it struggles and needs help on the gas.
I am hoping it is not a wiring issue, chasing those down is the worst.

Thank you for the reply and solid suggestions!

[nissandrift!]

Well, I wouldn't just randomly replace parts. Look for clues as to what it could be. Try to narrow it down and eliminate possibilities. What an engine needs to run is air, spark and fuel. It needs a certain amount of each to run properly. Check that you're getting good spark. Do a cylinder balance test. Try to see if it's just one cylinder that's acting up or all of them. Take your spark plugs out and see what they look like. Condition of the spark plug can tell you a lot about how that cylinder is running. There are many diagnostic flow charts out there that you could follow instead of randomly throwing parts at it. Find the evidence!

[idlafie]

Just out of curiosity, did your S14 kick any ECU codes?? Does your Check Engine Light come on when you are having these issues?? You might want to check the ground wire on the engine block, (driver side), just above the O2 sensor. If you've got a short in the ground wire, it could cause the issues you are having.

Hope this helps...

ID

[dallasb53]

Quickest, easiest thing to do with that kind of intermittent problem, on a KA engine, is start replacing parts. Start with the ECU/Wiring harness / distributor / all ignition components, then move on to the fuel system etc...

Along the way, you might find frayed wire on the distributor plug, or find out that the ECU was not fully tight, or find a huge hole after the maf sensor, or a loose connector on the fuel pump, or a bad CTS sensor/wire, it could literally be any tiny detail.

You can always re-sell parts if they turn out to be good and get your money back.

I just read your full description and find it interesting that the fuel pump fixed it for a while. Surely you changed the fuel filter- WITH the pump? And it ran better... but now its bad again... I wonder if the fuel filter is becoming clogged? Did you change the fuel filter BEFORE the new pump went in? Did you look in the tank for junk? nay, that doesnt make any sense, the car would not spill black smoke. Perhaps the wiring at the fuel pump needs attention. Like I said, replace some parts, sell or keep the spares for more than you paid. You can literally make money diagnosing problems on these cars.

wtf? are you a mechanic or a parts changer. why in the hell would you just start replacing parts. the fsm tells you how to checks parts for christs sake lol. i think its written on an eighth grade reading level too. :S