Problems with non-Jeep vehicle. 93 Nissan Sentra

[Knucklehead97]

Howdy guys. My family has had this 93 Nissan Sentra for about 2 years now. Great little car, even with 212k miles the little 1.6l still runs PERFECTLY... when it will start. It all of a sudden got a hard start and I can't trace it. If you pat the gas pedal while cranking it then it will start after a little while. That doesn't make sense to me because it is fuel injected, so pressing the pedal shouldn't effect it till it starts, right? We had the fuel pump changed and it started perfectly for about 3 days. And now it's right back where it was. Fuel pressure was correct. I'm thinking fuel pressure regulator or TPS but the mechanic says it isn't. On another note, I no longer use that mechanic.

[gogmorgo]

If it's overfueling, i.e. flooding, opening the throttle will lean the mixture back out enough to start.

 

How do the injectors look? Could be they're leaking, or stuck open, or some sensor or other part is malfunctioning, leading it to run way rich. Could also be intermittent ignition system issues not letting it fire until you've cranked it long enough it floods and won't fire until you clear out the flood by opening the throttle. When was the last time it got plugs, wires, cap, rotor, etc?

[Knucklehead97]

Cap and rotor about 20k miles ago. Plugs and wires maybe 1k ago. I looked at the rotor and cap and they looked good still two injectors were replaced due to failure when we first got it, they were replaced with used ones. Not sure how to tell if the injectors are leaking or if it's being overfueled. Also if I get it to start, and it warms up, then it starts without patting the pedal. It still takes long to start but it doesn't need to have the pedal patted.

[gogmorgo]

Sio a similar thing happened the last couple weeks with my MJ on very cold days, like nearly -40, if the block heater didn't get plugged in or something between the plug and the hydroelectric plants malfunctions. It'll crank really slowly, and eventually pick up speed and start coughing as it's trying to start, and then quit coughing until I step on the pedal. My theory is that the truck is dumping too much fuel in due to the cold and eventually floods out. It's only been a problem on severely cold days. I'm thinking the coolant temp sensor may be starting to fail, because -40 is about at the bottom of its range which is where failures start to become apparent (the edges of the range) and my understanding is the computer dumps in extra fuel if the CTS is reading cold as a bit of a "choke" feature. Something about open vs closed loops that I don't remember about.

But coolant temp sensors are usually pretty cheap. If I remember next time I'm in there I'll pull the CTS out of the old engine that didn't ever have issues with cold starts, see if anything changes. My O2 sensor's only a little more than a year old, much less old than the one I didn't even bother trying to pull out of the old exhaust, but the O2 sensor's about the only other thing I can think of right now, although I don't think its relevant to cold starts, something something open vs closed loop that I don't remember about.

[shelbyluvv]

Bad fuel pressure regulator letting the fuel drain back into the tank. Try to double cycle the key to prime the rail before cranking the engine.

[gogmorgo]

Me or him?

[Knucklehead97]

Bad fuel pressure regulator letting the fuel drain back into the tank. Try to double cycle the key to prime the rail before cranking the engine.

I cycled the key multiple times and it doesn't change anything. I think the FPR might just be absolutely shot on this thing.

[gogmorgo]

Cycling the key didn't do me any good either, although I didn't do it too many times cause it's @#$%ing hard to turn at -40.

[Knucklehead97]

Cycling the key didn't do me any good either, although I didn't do it too many times cause it's @#$%ing hard to turn at -40.

it's about 50 degrees here and I'm cold... I couldn't stand -40

[Knucklehead97]

As a update for the car... my sister said when she was driving behind me today (I was driving the Sentra) it smelled badly of gas. So overfueling?

[gogmorgo]

Frostbit my finger on the key last time it happened, lol.

Probably overfuelling, yeah. Although all that really means is not all the fuel going in is being burnt.

Does it have any sort of self-diagnostic abilities? If it's not switching to closed loop it's probably either the O2 or coolant temp sensors, but could also be an issue with MAP/MAF sensors, or a vacuum leak or a bunch of other potential things, including failed injectors. If you can pull trouble codes it might help pinpoint an issue.

Only reason I can think of a fuel pressure regulator could cause it is if it's regulating too high, but I'd expect a properly functioning injection system would detect the extra fuel and turn the injectors down.

[Hippie66]

Failed regulator will cause too much fuel in some vehicles. TBI Chevy would dump so much fuel that it'd dilute the oil and I have seen signs of exhaust catching

on fire.

[Knucklehead97]

The car is OBD1 so scanning it is possible but I don't know anyone with a scanner.

[gogmorgo]

No trick for counting check engine light flashes? Turning the key, or a paper clip in the diagnostic port? I don't know a heck of a lot about Nissans

[Knucklehead97]

No trick for counting check engine light flashes? Turning the key, or a paper clip in the diagnostic port? I don't know a heck of a lot about Nissans

I haven't checked into this due to being on vacation in Gatlinburg and working super long shifts for the holidays. But there isn't a CEL on so does that mean it's not even throwing a code? If it's not throwing a code then I'm thinking even more that it's the FPR...

[gogmorgo]

I've rarely seen the check engine light on my MJ come on, even though it's thrown a handful of codes over the years. I think the only two times the CEL ever came on was once for the TPS and once for a charging issue, bur i've had all manner of codes that didn't trigger the light, CPS, CmPS, coolant temp sensor, and a couple others I can't remember right now. OBD1 isn't necessarily like like OBD2 in that it may not throw a light for less-than-critical reasons.

But I can't really comment on how Nissan's OBD1 would work, as the purpose of OBD2 was to standardize all the crazy systems that the various manufacturers had come up with.

[Knucklehead97]

I've rarely seen the check engine light on my MJ come on, even though it's thrown a handful of codes over the years. I think the only two times the CEL ever came on was once for the TPS and once for a charging issue, bur i've had all manner of codes that didn't trigger the light, CPS, CmPS, coolant temp sensor, and a couple others I can't remember right now. OBD1 isn't necessarily like like OBD2 in that it may not throw a light for less-than-critical reasons.

But I can't really comment on how Nissan's OBD1 would work, as the purpose of OBD2 was to standardize all the crazy systems that the various manufacturers had come up with.

I'll hopefully get to mess with it tomorrow or Tuesday. I'm going to run seafoam through the TB and fuel system and see if I get anything from it. Sadly another car has broken down in my family... my idiot brother decided to not check his oil and his POS Mercury seems to be knocking now. Never ends.