here we go....

[carsonk9]

What's up guys. Terrible first post I'd say but I need some help with my z (who hasn't heard this before)
I'll give you a quick rundown. The car is hesitant between idle at 3000rpm then it launches like a bat out of hell. It's a 93 n/a.
I had two check codes, one for egr, and one for knock. Knock sensor was dead so I bypassed it for now. No codes in 500 miles. Still hesitates. Coming down from a long 65mph cruise I drop to neutral to come to a stop and my Rpms drop to about 350 and then shoot up to 750-800. Sometimes it will randomly missfire on warm idle but it's intermediate, after you gas it. It doesn't happen for the entire day again. Can find a dead cylinder, spark plugs are new ngk plats, coils tested good, injectors tested good, iac got cleaned and tested good. Maf is good when warm...when cold I only got .47 v...but when it's warm it's normal, no vacuum leaks, no broken hoses that I haven't replaced, egr is getting vacuum but Idk if it's stuck open or closed. Not sure if that would cause a problem in only a certain point in my rpm range though. Fuel pressure was 37psi at idle, though it does make a loud prime noise when warm only. Voltage is good. Just cleaned all my ground contacts. I'm out of ideas really. No check codes. Just a small hesitation/bucking like motion between idle and 3k. Help...anyone?

[solaire]

Well it could be a lot. By bypass did you mean you got the z1 harness and new Nissan knock sensor and relocate? Those can cause it. Also what was the code number? These will say exhaust sensor and u think egr at first but its for the o2 sensors. Also the Maf is somewhat isolated from the engine so it won't experience as drastic temp changes as other parts. If its not reading right it can cause tons of issues. Its the computers right hand man for determining engine load to adjust fuel trims. Another thing to check is tps. They can get corrosion in the connector and yield bogus voltage and make the computer think throttle is open or closed too. That misfire could be corrosion at the ignition module on the timing cover and it could be causing a miss under load which may feel more like a hesitation than actual miss. I've seen 2 dead cylinders on 1 bank make the engine feel sluggish but you wouldn't think its a miss. They run surprisingly smooth when that happens. A dead cylinder can cause idle to drop low until computer picks it up also. There's a few threads up here about checking ptu outputs, which exact plug part numbers to use, etc. These cars are surprisingly picky about that stuff. I know it seems like a lot but I've been where you are and you've got to check 1 thing at a time because most efi issues on these cars have the same symptoms but different culprits

[carsonk9]

Yeah everything you said I've checked. The code was egr and det sensor. The bypass is a 1mohm in line. My knock sensor is dead so I did this as a quick fix. 02 sensors are also fine. Maf gave a ready of .47 v when cold which isn't in spec but when warm it was in spec and thatsbwhen my problem occurs. Tps was checked a and in spec ignition module is also fine. Only thing I can truly think of is a fouled out plug from the knock sensor changing my mapping when it though it was knocking. I put irrudium plugs in (big mistake) and the car started missfiring and stumbling badso I went back to the old plugs until I can get new ones today. I'm trying to see what could cause it to lose power only when hot. Not cold.

[RED_DET]

TPS reading correct voltage?

[carsonk9]

Tps was spot on. Checked timing last night. Off by about a degree. Corrected it and the problem still remains.

[carsonk9]

Well after all the trouble shooting and nobody with any type of lead of solution(including not being able to pin point the problem myself) I've decided to just buy a jdm motor and put new belts and seals on it and call it a day. Now. I'm not going to drop that motor in until this one goes (compression read 150-157 on four cylinders, 139 on 2 and 119 on 3) so I'd like to figure out this problem directly. Now pulling up to a stop sign or light above 65 mph, the cars idle drops to about 250-300rpm and holds until I get under 50 mph. Then it returns to 1200 then down to 750-850. It only occurs above 65 mph and obviously when the clutch is in. If I come down from 80 mph and coast same thing until I get under 45 mph, the faster a decel the faster I get my normal idle back. Now am I getting some type of ram air issue? No aftermarket air filters but they are new filters and they are paper(old owner) or am I looking at some type of other issue?

[nexus08]

Have you cleaned your MAF sensor?

[carsonk9]

Have you cleaned your MAF sensor?

Yes to no prevail.

[RED_DET]

I'm not liking that last compression # of 119 when comparing all the rest.

[carsonk9]

I'm not liking that last compression # of 119 when comparing all the rest.

Yeah that's why I just went ahead and bought a jdm motor. Not gonna bother trying to rebuild it when it's at 226k.

[RED_DET]

Just be sure you change out all vital seals on that JDM engine, to include rear main seal and especially the front.