'03 Z with minor mods- Intake, high flow cats, cat back exhaust.

Idle is not consistent and when engine temps reach around 140 degrees, the idle starts dropping down to the 400s. When e-fans are running full, idle drops bad and car starts to choke and will bog down and cut off at times. I've checked fuel pressure and it's good at 51 psi, cleaned the MAF and throttle body, have done all the relearn procedures, have no codes on the ECU at all, and changed plugs to try to help the problem.

Checked compression (at 124 degrees per my aem gauge)
Cylinder 1: 180
Cylinder 2: 185
Cylinder 3: 190
Cylinder 4: 185
Cylinder 5: 185
Cylinder 6: 185

These were taken dry and I did not get around to getting it done quick enough to consider it truly up to operating temp however they were pretty consistent across the board so I think I'm ok there.

When I try to drive it, the car hesitates and sputters/ backfires a little to begin with and feels like it doesn't have any power. I imaging the ECU senses something isn't right and is messing with the timing thus pulling power. I'm just not really sure where to go from here.

 

Any luck so far? What else have you tried?

 

Knock sensor, crank position, both cam position, and 02 sensors all new. I have one more guess and that is the gas. I have not experienced having old/ bad gas before but at this point that's all I got. Car sat for over a year without being more than started with a half tank due to an injury and many surgeries.

 

Have you tried cleaning your MAF? I'm asking because before cleaning mine, I had a problem with erratic idle, and engine cutting off when coming to a stop. After cleaning it, engine idles perfect.

 

A few things to consider.
Siphon gas and get new 93 octane.
It's an 03. Change plugs if over 75k.
Get a load test on alternator and battery. Good luck.

 

I forgot the additional things I've done after reading those posts. Cleaned maf and throttle body (yes I did all resets after), and changed spark plugs this past weekend to rule that out.

Going to siphon gas Sunday and pray that does it. Haven't thought of a load test so that'll b next if the gas doesn't work.

 

Car is still being an ***. Syphon ed old gas and put 5 gallons of new in and no change. Checked load on alternator and battery and both stayed between 13.5 and 14.2 even when it almost stalled out.

 

So, to clarify. Does it idle ok until it reaches 140F? Test resistance on coolant temperature sender when hot and cold. In Ohms if resistance is 0 sender is bad.
Possible leaks in air intake system.
Dirty air filter.
Put a cheap vaccuum guage on the intake manifold. When mine was acting erratic, the vaccuum was around 13 and horrible idle. (Spacer install). Tore it apart and coated each surface with clear silicone and retorqued. Vaccuum went to 22.5 , problem solved.
Hope some of this helps!

 

I'll grab a vacuum gauge tomorrow and try that. Are you saying put it in line between the intake manifold and the brake booster to check it there or elsewhere? The coolant temp sensor is actually new. As in 2 weeks old because I got that code on my scanner. After replacing, the code went away. I checked voltage to that sensor and it was good when I checked it.

I will say I know I have 2 of the bolts that attach upper and lower intake manifolds that will not tighten due to stripped threads. I'm guessing this could be causing a problem going by what you're saying.

 

Took off upper plenum and retorted all bolts in correct order and fixed the 2 that were bad. Vacuum is at 22 so I'm good there no question however.... same issue. No chang at all I'm afraid. Sprayed throttle body cleaner on all vacuum lines to make sure and no change in idle. I'm really wondering if I can get it tuned to get this crap fixed.

 

Sounds like you definitely have a troublesome issue... Theres a few more things that could be going on here that will cause the same issue. 1. Your catalytic converters could be plugged do to previous issues. 2. you could have bad fuel injectors that arent flowing correctly. 3. Even though you cleaned your MAF sensor that doesnt mean that the sensor itself is not bad I've seen them go bad with no check engine light before. 4. You could have a faulty cam/crank sensor even though they are new that doesnt mean somebody didnt return a bad one and the parts guys put it back on the shelf. Personally if I were you and this far into the issue I would take the car to a nissan dealer or someone that has the proper diagnostic tools to look at all the sensor read outs that way if somethings off you have a starting point of where the issue is coming from. Hell it could also be a faulty throttle body not wanting to open. Good luck man!

 

If you have access to a fuel pressure tester i would check pressure. Also leaning toward a faulty throttle body.

 

Hey man, sorry for the necro but I'm having a very similar issue. How did you get this sorted?