98 Nissan Maxima runs good for about 5 minutes and
the egr on most cars , is a 50k mile service point (cleaning)ever do the 60k mile tuneup (service sch. list? )? if tuned up (spark parts, (list) all filters )then it can be ? EGR sticking open, love to do that just before a stop sign, is its hallmark of messup.So is the ISC (idle speed contr. valve,electric) this stick , yes clean it. barring that..with all otto cycle engine, there are 3 simple paths.1: good engine, (some fail hot only)2: good spark (yes, tuneup deal)3: bad fueling, yes, as you said, too lean or too rich.if the engine is good, (compression good)and the tuneup gives you good spark and good timing.we land on bad fueling , in that order.going backwards can result is 3 weekends shot.so fueling, Ill pretend its fueling and that 1 and 2 are ok.in the service manual they cover this with tests.Is the check engine lamp on key on the goes out running,if not, why not connect a scan tool, (USA answers, all mine)In canada , the EGR and other errors (misfire) are ignored by the ECU (no CEL warning) so not posting country puts me in hand cuffs.fueling.1: remove spark plugs. are the they soaked in fuel, 1 or all.?2: if dry , good.if wet , check for bad injector rates and root cause.if dry. then you need a scan tool to see if 2 things are good.1: engine idles hot, in closed loop, if not fix that.2: light fast cruise, (no hill) does ECU hold Closed loop status.?3: if those are ok, does the LTFT say near center.most cars run -4% not -25+ or +25%LTFT means long term fuel trim. when running look for pending errors. and live errors and stored errors, they are called DTCs Drive-ablity issues are the most complex , just before intermittent.huge books exist on topic.here is one more of the many,(misfire )induction air leakswhat we call this is gathering evidence. (after the tuneup)
