This problem has been plaguing me for months and I've had no success. Essentially what's happening is I start my car and everything is fine. Once it gets warm however, the engine has really rough idle and the acceleration seems to be stuck until it finally takes off. I've posted about this before, and somebody suggested I might have fouled spark plugs from a previous bad fuel injector problem I've since fixed. I've replaced the spark plugs with platinum NGK ones, which didn't help, however I've heard this issue can occur if you use platinum opposed to iridium, which doesn't make sense to me. The only codes I have are p0300 (random/multiple misfire) and p1320 (ignition signal). This leads me to believe that it's the coil packs which I've heard can go bad on old qs, and so far the only measure I've taken since is performing a sort of crude power balance test by buying a single coil pack and testing it in each cylinder, to see if it changes anything. That and replacing the fuel filter and using fuel cleaner additives. I know it's not the best idea but it's the best I could think of. I'd really rather not sink like > $800 into new coil packs without being sure, and I'm really lost as to what it could be besides that. Anyone have a problem similar and been able to fix it?
Sorry for the long post, I appreciate everyone who helps.
Thanks

I have a 93 J30 was plagued waaay back with hesitation gettin to @3000rpm , in the end it seemed to have taken close to the "shotgun" approach , and I and many others can't quite put their finger on the root , or even contributory causes !!!!
But listening to your story - you " Did Plugs " , OK , one thing I noticed on my coil on plug type coils was a little spring inside the boot , way back , which gives a kind of "pressured electrical contact" to the plugs end AND many get loose and fall out . Like they fall out into the "tube " , into your hand , the floor , THE CHAMBER maybe ?????
Go see if one of the misfires is like this , AND IF'n a spring supposed to reside inside the coil boot , it IS IN FACT still in there ???? ............ May have to check each one , ie. ALL of them though .

p.s. IF lost spring , and you have a 'good' junk box 'o springs , it's like a small pen clicker spring 1/4" long

Wow I would not have thought of that. It's totally possible that one or more fell out when doing plugs.
Thanks! I'll check on that soon.

Cause I assume you have'nt started yet on this ,I'm comin back like Columbo - ONE MORE THING!
Like that guy Scotty Kilmer emphasizes is "Use the factory brand / part # for plugs - period " .We all know a motor may have miles , or issues that may warrant , even NEED adjusting plug specs . Colder , more or less nose projection , material ie. PT , CU ,IR ,RH whatever whatever - been there done that . He also suggests to hold up the removed old plug and 'match it' to what you're now gonna put in there ! Better , know your thread depth , nose projection , need colder ?hotter? , etc. But see that plug TERMINAL at end of insulator is NOT shorter !!!!! A little longer (1-2mm??) - judge that one yourself .

So IF'n the plugs you put in are at all " short " , PLUS one or more of the little 'contact' springs , if in there, have come out - I believe the scenario would show as seen by you ??? Maybe .

Cause all mfr's can stray more or less in these dimensions , especially if changing ANY aspect of factory brand/part # . Hell even after 21 years , ya never know even 'OEM proper' part may have 'drifted' dimensions and a lost spring(s) will add a huge pre-gap before spark passes through the plug?

p.s. Waaaaay back , J.C. Whitney sold a pre-gapping , inline attachment for distr, cap center terminal . They really sold SOME SH!&#TT back in the day......... LOL

Update: I checked all the ignition coil springs like macgiver suggested and they were all there and seemingly in fine shape. I replaced the spark plugs with iridium ones to be safe and no progress. Any help is welcome and I'm kinda desperate for help at this point.
Thanks!

Have you cleaned out the MAF?

So I think the iridium ones were a bit different in size than the platinum ones. I have cleaned out the MAF to no avail, using specified MAF cleaner. I'm fresh outta ideas.

First thing is, see if it's a lean problem. Try some Brakleen or Gumout down the barrel while it's running and see if it's better, worse, or the same. That will give you some idea of what tree to bark up. Could be a vacuum leak, crappy fuel pressure, bad engine grounds, a lot of things. If Brakleen makes it better then it's probably one of the first two, monitoring the STFT (short term fuel trim) will tell you which. If the STFT is way rich at idle but normalizes when you raise the RPM's then it's a vacuum leak, if it's normal at both ends then it's a fuel delivery problem. Monitor the MAF too, if it's all over the place or isn't moving much then it may just be bad.

FWIW the ten things probly responsible for my poor performance under 3000rpm , blasted the MAF w/cleaner , de-oxit ALL connectors ( coils & inj's for sure ) , R&R both PCV valves , checked per FSM the "Igniter" (power x-sistor cluster which energize ea. coil-pack) , spray throttle bodies , vac hose check , timing advanced by 2 more degrees BTDC , put in an alternate TPS( backup TPS had on hand) , did ecm reset many times along the way - is all I can remember for now . Problem for me was in the late 90's up to 2006 . But after all these accumulations of steps done , I have'nt had ANY problems since , up till now even.

I think , and hope some finicky thing you find and fix , and youl'll enjoy that '45 , like I do my J , good luck !

So I used some seafoam air intake cleaner, so I ran the engine and sprayed that stuff in as instructed. It seemed to get slightly better afterwards, but I'm not sure if that was random. It has really rough that's around 500 rpms and fluctuates. Recently it's been stalling occasionally. I haven't looked much into fuel pressure or vacuum mostly because I don't know if my OBD2 can do it, or what the normal numbers are. I had to put the seafoam in the air intake tubing, which the car didn't seem to like, since it broke the seal, it also created white smoke and I noticed a lower coolant reservoir after, not sure if it's related or how that would happen. I feel as though I can fix any of these problems if I could just diagnose it, I'm just tired of throwing parts at it because of hunches to no avail.
Thanks again

I'm not sure if this is significant, but it's something I just remembered. The gas tank seems to depressurize when I remove the cap to fill up.

Then try leaving it off / loosened even . But , my J30 would usually make a strong whoooshing sound , never knew if pressure or a vacuum actually , and now that I remember that would be the 1oth possible factor cause I've gone through 3 gas-caps in 22 years on the J . This whooosh -removing the cap - was more intense when hotter , when driven long , and when tank was less than 2/3rds !!! ......????

What the hell , leave it very loossy-goosy for a day , what to lose ?

Well I tried the loosened gas cap and it didn't seem to do anything. Iridium spark plugs still haven't seemed to make any difference.

If it's sucking air in and not venting it out, on a car that age, you might have a full evap and a purge volume valve that's stuck wide open. That will essentially create a huge vacuum leak that can't be detected externally and can't vent completely till you pop the cap. I'm not all that familiar with the Q plumbing, but if it has metered purge then that's a possibility.

Would I still be getting the occasional code for Ignition Signal if it's the EVAP or purge valve?
Edit: How would I go about finding/ fixing that?

The P1320 is a little weird with a P0300, because it generally indicates unusual feedback from the secondary of a single coil and not a bunch of them. Your new coil pack might actually be causing that, especially if it's aftermarket.

Checking a malfunctioning purge valve is rough without a scanner that has work-support, but checking for one that's stuck wide open is easy. The purge should never be open any amount at idle speed, so if you pinch off the line to it on either side and the idle improves, it's stuck.

Thanks! I'll look into that tomorrow when I get the chance, I appreciate the help.

Well I just went and fiddled with my EVAP system a bit and compared my vacuum tubing to the nifty diagram on the underside of the hood. Turns out I've had the EVAP purge solenoid hooked up backwards for the past few months because I didn't install it correctly after taking apart my intake manifold. I appreciate everyone's help! I wouldn't have noticed that in my own.

That sounds like good news! curious if problem solved?

Ah ........ "The Human Factor !! " ( Outer Limits Nov '63 )

An accident causes the brain of a dangerous paranoid and an Army psychiatrist to be switched

..............................................................

It worked when I first started it back up. Then about an hour later it was running rough again, once up to highway speeds it seemed to even out though. It's kinda up and down with performance now, I'm thinking it's just the ECU trying to reaclimate after trying to compensate for an error the past few months.

It maybe adjusting to that "Human Factor"

How funny...this is similar to my MAF sensor thread.

I noticed after cleaning and compressed air blowing my purge line of old charcoal, and sea foaming the purge valve, I was getting some weird acceleration issues, even triggered a knock sensor code and my engine ran hot.

Once I turned off engine and filled tank up, issue went away. Drove from Kansas to Arizona and only experienced the issue briefly once.

However, it's odd because the issue first occurred out of nowhere one morning at startup. And mainly with the AC on. It was so intermittent though. But lately the issue seems to have been mitigated,

My purge line was so clogged up with carbon, I had to buy a little plug in tire inflator to clear all the crap out. But it must have been that way for months or even years.

98_Q45 wrote: ↑

Fri Sep 10, 2021 10:30 pm

How funny...this is similar to my MAF sensor thread.

I noticed after cleaning and compressed air blowing my purge line of old charcoal, and sea foaming the purge valve, I was getting some weird acceleration issues, even triggered a knock sensor code and my engine ran hot.

Once I turned off engine and filled tank up, issue went away. Drove from Kansas to Arizona and only experienced the issue briefly once.

However, it's odd because the issue first occurred out of nowhere one morning at startup. And mainly with the AC on. It was so intermittent though. But lately the issue seems to have been mitigated,

My purge line was so clogged up with carbon, I had to buy a little plug in tire inflator to clear all the crap out. But it must have been that way for months or even years.

Hopefully you replaced the evap canister? If not, you'll have the same problem over and over again. That charcoal is from a broken canister bag, and there are pounds of it in there...

VStar650CL wrote: ↑

Sat Sep 11, 2021 4:33 am

98_Q45 wrote: ↑

Fri Sep 10, 2021 10:30 pm

How funny...this is similar to my MAF sensor thread.

I noticed after cleaning and compressed air blowing my purge line of old charcoal, and sea foaming the purge valve, I was getting some weird acceleration issues, even triggered a knock sensor code and my engine ran hot.

Once I turned off engine and filled tank up, issue went away. Drove from Kansas to Arizona and only experienced the issue briefly once.

However, it's odd because the issue first occurred out of nowhere one morning at startup. And mainly with the AC on. It was so intermittent though. But lately the issue seems to have been mitigated,

My purge line was so clogged up with carbon, I had to buy a little plug in tire inflator to clear all the crap out. But it must have been that way for months or even years.

Hopefully you replaced the evap canister? If not, you'll have the same problem over and over again. That charcoal is from a broken canister bag, and there are pounds of it in there...

Yes, I did. But instead of the $200 one, I got a $60 one. Same manufacturer, and it fits the vent valve. But had to install it upside down and add a longer hose to one of the purge or line valves.

Did this on my Maxima, so ordered 2 at the same time to compare and contrast. I just checked the other day, no carbon in the lines. Finally got all the crap out after blowing it out thru the front and the back. Can't really say it made much of a difference with anything though. It cleared some codes and mitigated the weird hesitation issue (which probably wasn't even my MAF sensor after all) butt Still only getting 21-22 mpg with the a/c on lol.

Scan your IAT and see if maybe it thinks your car is in Alaska. That's a very common cause of poor mpg without any real performance issues.

If only you could get the car to think it's in Hawaii , ya climb right in

macgiver wrote: ↑

Sun Sep 12, 2021 12:04 pm

If only you could get the car to think it's in Hawaii , ya climb right in

Funny. Nissan IAT's go to -22F or -40F when they're open-circuit, hence "Alaska". That causes the ECM to over-rich the mixture thinking the incoming air charge is very cold, hence poor mileage. It ain't a joke.

That Alaska part walked right into it ,VStar... LOL ... I know your usually breaking things down even past the nitty-gritty with your Tech Mojo - some crackerjack techs have come and gone - keep daizin & amaizin like ya do

macgiver wrote: ↑

Sun Sep 12, 2021 5:08 pm

That Alaska part walked right into it ,VStar... LOL ... I know your usually breaking things down even past the nitty-gritty with your Tech Mojo - some crackerjack techs have come and gone - keep daizin & amaizin like ya do

By the way, for those interested, that's exactly how "dry shot" nitrous-oxide systems work. By injecting the very-cold NOx ahead of the IAT sensor, the gas fools the ECM into temporarily dialing the mixture to full-rich whenever it's injected. That obviates the need for a separate fuel solenoid like a "wet shot" system, but it's of course limited by the maximum fuel the injectors can deliver. Thus, wet shots are needed for very large HP gains.