'96 Q acceleration issue

[rickymartinakasgk]

125K on my '96 Q with a problem that Infiniti service (nor anyone) cannot seem to verify/fix. This car was a rocket (kind-of) when new.Problem: lack of power on even minor inclines. On long upgrades need to really floor it to downshift just to keep up with even Kia's passing me.At full throttle from stop, the Q will shift to 2nd at 6000rpm, which I have been told is a good thing. Full throttle does not seem to be a problem, it's the slow 30-40, 40-60mph accelerations on the inclines that are.No buzzing noice from fuel tank.Any thoughts?

alex

[Q45tech]

The usual culprits for the problem you describe are cracked knock sensor/s and low fuel pressure [under load] from old worn out fuel pump.

What do actual measured physical tests of these components show?

[goody90q45]

Problem: lack of power on even minor inclines. On long upgrades need to really floor it to downshift just to keep up with even Kia's passing me.......Any thoughts?

You're living in the wrong town to not be able to accelerate up a hill. There should be very few cars than can out-accelerate you on the streets of San Francisco. (Sorry, I had to get that in.) With the mileage you have on your car I'd say Tech's advice is spot on. Ohming your injectors and knock sensors (see pic) is an excellent starting point and will tell you a lot about the health of your engine. It will take you all of 10 minutes and a voltmeter.

I agree with Tech that your problem is most likely fuel pump and/or fuel pump control unit (FPCU) related. They should both be replaced at the same time. Measuring fuel pressure under load will tell you if it's starving for fuel.

[rickymartinakasgk]

Thanks for the help....Will check it out today.

[elwesso]

since its a 96, taking it to autozone or something similar that does free OBDII diagnosis will be your easiest bet.

[Q45tech]

Unfortunately OBD2 scanner will only show if KS are functional [not throwing a code] but it's a start.

As with all 96-99 OBD2 was a wing and a prayer, kinda, ifa, shoulda, maybe useful and maybe not while they worked the diagnostic bugs out of software.

[captainluigi]

dennis, would you expand on that thought a wee bit please?

[Q45tech]

Each different code has a range of normal and early OBD2 was wider than necessary to avoid codes unless it was serious.

Good enough emission may not necessary be as good as brand new performance. After 2000 LEV and ULEV requirements tightened up the ranges significantly.

In 96-99 just because no codes doesn't mean you stop looking for problems.

[Lenneo]

brother i had the exact same problem as you, and no1 could figure it out. All you have is a dirty camshaft sensor, and this prevents the cylinders from working properly

[maxwell867]

Where is the camshaft sensor and how did you come to that conclusion because my 96q has the same problem with acceleration. I changed the plugs, fuel pump and fpcu, cleaned mass air and connectors but very little improvement. Next job was the knock sensors which i was not looking forward to. When i ohm the injectors and knock sensors i am not getting any readings.

[rickymartinakasgk]

So now I'm trying to find a Infiniti Service here in San francisco who knows what a camshaft sensor is So far they haven't a clue.So I'll keep trying.Thanks for that idea.

[96Qowner]

Known as a Crank Angle Sensor (CAS) or Camshaft Position Sensor (CMPS) in the Infiniti manual.

[qsiguy]

Regardless of what else you do I'd definitely test the knock sensors. I actually had my car on a dyno with a bad knock sensor and it was down 70-80 hp from normal just from a bad knock sensor. You'll feel that on those hills for sure.

[rickymartinakasgk]

I have questioned 3 Infiniti tech here in the city and one regular tech.

If it's the Knock sensors, it should be throwing a code. (it's not) It's a long job (5 hours in the book) to test/replace the sensors and they said since we down there might as well replace then and include the harness, since it's probably corroded. God know what's atached to all that.Price $2237.00.Nobody thinks it's the camshaft sensors (no code).As I said before the fuel pressure is right on.Are the knock sensors that hard to get to?

[AlabamaDan]

I'd trust Q45Tech over most dealer techs. It's been a long time since Q45s where regulars in the service bay of a dealership.

You say fuel pressure is good. Have you actually measured it. There's a thread around here that says it's not difficult. Just T into the fuel line after the fuel filter with a gauge. (RIGHT?)

As far as throwing a code, I believe Q45Tech is saying that on a 96 it will only throw a code if it's broken. If it's not performing 100% or even 75% it will not throw a code. This OBD stuff isn't quite as smart as people would like to think.

I may just test my KS, fuel pressure and Injectors to see how they are.

[96Qowner]

OBDII will code for KS but won't light the CEL.

One more thing to discuss is the FPCU. Has fuel pressure been measured at all three FPCU voltages? Wouldn't hurt to pull the FPCU and inspect it for a burnt plug terminal or damaged circuit board- not hard.

[maxnix]

Start with fuel pressure, then look at CAS and MAF connectors very carefully. Report back, please.

[Infinitiguy19]

Regardless of what else you do I'd definitely test the knock sensors. I actually had my car on a dyno with a bad knock sensor and it was down 70-80 hp from normal just from a bad knock sensor. You'll feel that on those hills for sure.