maxxximus

Its kinda funny that as I glance at the first page on the forum today there are like 5 different threads on power/pinging/hesitation problems, but no one seems to have the same symptom as I am seeing:

After installing a new Frankencar intake and cleaning the throttle body in early October, I effectively solved my early morning hesitation/rough idle problems. However, now that it is colder, I have felt on several occasions my engine bogging down/feeling weaker when getting beyond ~3200 RPM on the tach. By no means does this happen all the time or at the same temperature/outdoor conditions. On a hunch, while this was acting up last night, I pulled over and shut the car off for about 10sec then fired back up. NO bogging/hesitation even after just doing it moments before.

- No SES Light
- ALWAYS 93 octane gas
- Different outdoor temps

I am open for suggestion or like experiences. It is annoying to the point of taking it in, but my FNND are retarded monkeys and I have yet to find a competent shop around here that can do engine diagnosis well. It almost sounds like it could be the ECM acting crazy. Does the 2000SE have a variable intake?

UMD_MaxSE

iTrader: (1)

bogging around 3500 rpm on a 2k/2k1 may indicate that the swirl control valves in the IM are not opening smoothly... (all 2k1 and 2k cali spec have these).

spirilis

iTrader: (2)

If your 2000 is Cali-spec emissions, maybe the Swirl Control Valve isn't opening properly after it warms up?

Swirl Control Valve is a Cali-spec emissions-related device which restricts the inside of the intake manifold (to add swirl to the intake air) when the engine is warming up, with engine coolant temperature somewhere between 50 and 120F. It stays closed from idle all the way up to 3200-3600RPM or so, where it's supposed to open.
Maybe when it's colder, the Swirl Control valve isn't opening up properly as the engine warms up beyond 120F?
Or, maybe the Engine Coolant Temperature sensor is giving the ECU bad numbers...?

Also, forgot to add above: The Swirl Control Valve should be OPEN ALL the time when the Engine Coolant Temp. is above 120F.

Also be aware: if you disconnect the Swirl Control Valve Solenoid harness, the SES light should come on eventually, but it will be one way to determine if your Swirl Control Valve is causing the problem. With the harness disconnected, the Swirl Control Valve will stay open all the time.

For reference:
The Swirl Control Valve Solenoid harness is the brown-colored electrical connector you see in the picture below:


Try disconnecting this and see if the problem goes away.

If your car is Fed-spec and you don't have one of those... then the problem will be something else, since Fed-spec 2000 Maximas don't have the Swirl Control Valve system.

maxxximus

Wow...

That is the most comprehensive diagnosis I have heard on this issue (I have posted it several times ). Thank you very much. Even if it doesn't pan out it is something to try. I am unsure if I am Cali or Fed spec. Which part of the VIN would I check to find out?

Wow...

-Sean

spirilis

iTrader: (2)

Not sure about the VIN, but if you got 3 O2 sensors, you're Fed-spec, and if you have 4 O2 sensors, you're Cali-spec.

maxxximus

Bummer... that isn't it as that junction looks entirely different on my Max. Would having the Air Temp Sensor removed and replaced with a resistor (for constant 32F ) cause this issue (in place to solve the cold start/stutter issue that is now gone)

-Sean