Nice 93' HB w/VG30 Intermittent surging...SOLVED

[MauiRick]

Long time fan first time post. Man…I have a very nice low mile 93’ HB VG30 4x4. I have been going crazy trying to track a intermittent surge. Mainly under a load and you can feel it go in and out on a steady 2-3 sec interval. Replaced MAS and TPS…have scanner hooked up and all I could find is that the o2 sensors goes full rich over 2k rpm’s. But I know this is a early set up so might be normal? Truck has 130k on it and is in very nice shape. Getting about 17-20 mpg…installed headers and k&N. Any ideas? Thanks for looking!

[MauiRick]

Found out today scanner showed O2 sensor going in and out at 2200+ rpm's which at the same time is the actual surging! Surge in and out 2 seconds...scanner lean-rich...surge...lean rich surge.Any ideas guys?

[Q451990]

to NICO!

Is there a certain RPM where this happens? I had another truck with a surging issue that turned out to be a bad EGR... Nissan EGR valves tend to be fairly bulletproof, but do need cleaning from time to time.

Heath

[MauiRick]

2200-2700 rpm"s depending how much load is on the motor.Never sugures cold...seems to pop up after a good long warm up.

[Q451990]

That would kind of follow an EGR issue... The ECU will lock out the EGR while the engine is cold, at idle, and at higher RPMs. It's designed to open at cruise speeds to help keep the cylinders cool and slow combustion by putting exhaust gas into the combustion chamber.

Check out the FSM (factory service manual) for your truck at www.nicoclub.com/FSM/

The oldest manual available is for the 1994 model year, but I don't think there's much of a difference between the 93 and 94. The Truck and Pathfinder manuals are combined, so look under the Pathfinder. There is a diagnostic for surge on EF&EC-75.

Good luck!

Heath

[MauiRick]

Mucho thanko for the link to the manual....very cool. Ok...so I removed the egr valve and it was clean...but I still soaked it and cleaned and noted the needle could move very freely with vac (my big old lips).Took it for a test drive surge still there. The manual stated egr,o2 sensor or ecu (but rare). I got a good buy on a o2 local and just installed.Will drive today to see...any idea's on where to get a ecu? Man I search everywhere on the net including ebay. Ecu # mecm v131 a1 2917. Thank you thank you!!

[Q451990]

One thing we see with the Q45s especially, is that the port in the intake will get clogged with carbon, but you won't see any (or very little) in the valve itself. If you can push the valve up manually at idle, you should notice the idle speed drop significantly, or even choke down. When you rev the engine into the 2000-3000 RPM range, feel the bottom of the valve to make sure it lifts. It'll kind of lift up and flutter. If there's no movement, you probably have a vacuum leak or bad control solenoid.

Check http://www.car-part.com for an ECU - but I really really really doubt that it's the problem. ECU failures are very rare unless they're physically damaged by water or an accident. It would be worth checking any ground wires near the ECU and it's connector to make sure it's secure though...

Good luck!

Heath

[MauiRick]

Well...here we go its FIXED! Lazy O2 Sensor!!! Runs like a new truck...never seen a early OBD1 car respond to a new sensor before. The sweeps I saw on the scanner must of been to slow. She now pulls hard all the way through the rpm's and even sounds better! I installed Pacesetter headers and modified intake and never got a advantage until now.I was getting 20 mpg wonder what she will get now!?? FYI...NAPA Auto Parts had a NGK O2 Sensor for $73.88...the Bosch was $150...YIKES!!
It is now just a pleasure to drive around town and go through the gears!Smoooooth! Have fun out there!!

[Q451990]

That's great news! The NTK/NGK sensors work nicely. I've used one before in my old Hardbody 2.4L.

Heath