Slow Sluggish q45

[DuckmanEG]

Ok i did search and read a couple threads. But nothing to sure. So i will state my problem and see where we can go.

Pick up a 93 Q45. Now driving for a little while. I notice the little things i need to improve on. The car runs awesome when cold. It seems to be set more at a time thing. About 15 minutes into my drive, it just becomes a dog. Doesnt really want to downshift. Real sluggish. I can get on it, super slow till about 4000 rpm, takes some time to get to 4500 rpms then goes back to its slow pace to a little higher rpm.

So where do i start. I am going to check knock sensors when i get a chance. Also do a oil change, spark plug and what ever other little things. Just looking for people who had this similar problem and what you did.

[goody90q45]

Is the Check Engine Light on?

If no CEL then it could be the fuel pump or fuel pump control unit. How many miles on your Q (120-140k?)? Knock sensors are the least of your worries at this point.

[duckman240sx]

The check engine light right now is always going to be on. I put a 94 ECU into my 93. Its looking for TCS which i dont have. I have yet to check it to see if anything else has been stored. That was also going to be my first thing to do actually.

The car has 160k. Brand new fuel pump was installed and a used module was put in around Feb by previous owner. I have the receipt showing this. So i was not guessing those things.

[goody90q45]

Pulling ECU codes is the best next step rather than guessing.....although the EGR starts working about 15 minutes into a drive. Do you have any leaky hoses? Plugged EGR path? The codes will tell all.

[duckman240sx]

Guess that will be the next thing to check real fast some time tomorrow, hopefully.

I will have to check my hoses after i read into the EGR system on this car.

[maxnix]

Ok i did search and read a couple threads. But nothing to sure. So i will state my problem and see where we can go.

Without a maintenance history, I am afraid all we can do is whizz in the dark with you. So many items not addressed.

Fuel pump pressure? Fuel filter? Then On and On into fuel intake system.

[Q451990]

Why did you put the 1994 ECU in? I would certainly reinstall your old ECU or look for another compatible '93 ECU for your car - or upgrade to the NICO ECU.

I don't know that your problem is there, but it's worth eliminating that as a cause.

Heath

[duckman240sx]

A new filter was also installed along with the new fuel pump and a used module in Feb. By previous owner.

I can check pressure.

I put a 94 because that's all the junkyard had. I bought the car in non running condition and that was the problem before. I check and erased the codes when I first put the ecu and was only throwing the tcs error but I haven't check it since I installed it and drove on it. Also I put that in because elwes something something said it would work. So for the mean time that's going to have to do until I have money for the correct model

[elwesso]

TCS will never throw a CEL.. You need to check the codes! Running a 94 ECU in a 90-93 will not result in a CEL and everything should work the same!!

If Im running a 90-93 ECU in my 94 theres no reason why they're not cross compatible. My guess is you've got an issue with the EGR causing the CEL.

But you also need to check your fuel pump! Fuel pressure is key and I bet anything you've got a bad pump!

[duckman240sx]

Ok since everyone keeps sayinf pump. I pop the trunk and its whining. Not good from what I rear in the past. The module is also hot as f***. So maybe replace module first as seeing the pump was new?

[elwesso]

no dont do that, the module may still be OK or salvageable... Replace the pump real stat like..

[maxnix]

New OEM pump? Should be fine if you also used new O ring. Did you inspect used FPCU?

[Equinox]

My car acts similarly to the OP. Bogs down low...if i can somehow get it to 4000rpms or so, it takes off like a bat out of hell and pulls all the way to redline. Fuel pump makes a loud constant moan.

What's the best place to buy a fuel pump and FPCU?

[maxnix]

What's the best place to buy a fuel pump and FPCU?

Fuel pump and O ring

http://www.infinitipartsusa.com

Call them

FPCU can be culled from wrecks, but be careful as more bad ones are present now.

[paranoidjack]

Maybe this is just me as I've done this job on 2 Infiniti's, but this sounds 1,000,000x over like bad knock sensors. I know you already said it but everyone seems to be running down the fuel pump path...

If the fuel pump was bad, wouldn't they have more difficulty in higher rpm's than the other way around? (genuine question)

Anyway, 3900RPM was the magic number for responsive car when my KS's were bad...

I'd bet money on it!

[duckman240sx]

Ok finally got time to check the codes. Yeah for no second job today. Any how.

34 Knock Sensor 35 EGR Temperature Sensor (RH) 46 Secondary Throttle Sensor 51 Injector Analysis

The 46 is the obvious one. Which is what i had confused. The secondary is needed for the TCS, which i dont have, which the ecu is looking for. Correct?

So theres that. Where do i go from here. Which one might led to the other failing or throwing a code.

Also i had tried to ground out the FPCU to put the pump on and it does the same thing, if that matters for anything.

[goody90q45]

....Also i had tried to ground out the FPCU to put the pump on and it does the same thing, if that matters for anything.

You ran a jumper from the pin in the pic (lower left) to ground and no change? Was that a new fuel pump and used FPCU put in by the PO? The used FPCU may have burned out the new fuel pump. Pull apart the FPCU and look for evidence of melted solder joints, especially the ground circuit and where the connector pins tie into the circuit board. If it looks scorched then resolder.

34 Knock Sensor 35 EGR Temperature Sensor (RH) 46 Secondary Throttle Sensor 51 Injector Analysis

The 46 is the obvious one. Which is what i had confused. The secondary is needed for the TCS, which i dont have, which the ecu is looking for. Correct?.....

Correct. Code 35 may be the same thing. Do you have a fed emissions engine and a CA ECU? Is there a single wire temp sensor at the EGR inlet mounted on the plenum? Post your ECU P/N and we'll tell you what you've got.

Ignore code 34 for now or until you can ohm test the injectors at the harness connector. The KS code should come on when there's engine issues but it's a stored code and does not light up the CEL.

That leaves code 51- Injector Analysis. Have you ohm tested the injectors yet? The connector is in the same bundle as the KS connector.



Unless you have 2 or more bad injectors it's the fuel pump and FPCU gone bad. Good luck.

[duckman240sx]

I grounded it out just like that.

I have just the bolt.

Everything that was on the ecu:4GA18-B18-P953212

[goody90q45]

I have a 14 page list of Nissan ECU's and your number is not one of them. There's 21 ECU's for the 1991 Q45 alone.

I'm pretty sure the EGR sensor being gone is the source of the ECU code.

[maxnix]

I have a 14 page list of Nissan ECU's and your number is not one of them. There's 21 ECU's for the 1991 Q45 alone.

I'm pretty sure the EGR sensor being gone is the source of the ECU code.

Yes, and grounding the fuel pump proves nothing. One must measure the pressure under operating conditions.

[JOSHIE88]

my car was doing the same thing... i changed the knock sensors and it made a world of difference im almost positive thats what your problem is

[FarAboveDaClouds]

I have the same issue with my 95 Q45t... Sluggish off the line but flies after 3500-4000RPM's. Fuel pump was replaced with OEM Japanese equivalent from WorldPac parts. Fuel pressure is 37PSI tested in the lines which is within OEM requirements. Cold weather (rarely in FL.) and occasional random times, it pulls off the line like I think it should always. FAST AND HARD!!! Can't figure it out... Transmission problem maybe?? 2nd gear take-off? HELP!!

[Infinitiguy19]

Did you read the post above your first post?