No Acceleration..Bogging..Yes, I've Searched

[tbradley222]

Hey Guys,

Specs: 92 Nissan 240sx HatchIntake, DC sports exhaust header, Megan 2.5 or 3" cat-back exhaust w/ cat

Gas tank was just replaced as it had a small leak in it.EGR removed and EGR is blocked off on the exhaust header with the 22mm block off.

Problem:

- Car does not accelerate over 3500 - 4000rpm and / 25-30% throttle response- Car only really drives somewhat steady between 3000 - 3500rpm- Sluggish and sounds like it "backfires" (might be wrong term, but i can here it from the exhaust) when I give it more than 30% throttle- Seems to me like it is not getting enough gas to accelerate- When driving and going to downshift or press in the clutch my rpm's drop really low to about 300rpm and car seems like its almost shutting off.- Was not doing this that bad before, problem is getting worse.- Oil is fine

Solutions: ???

Things I want to check are:

1. IACV - Spray Throttle body cleaner for ten seconds while the car is running

2. MAFS- Have done it not to long ago but will do so again with Throttle body cleaner

3. FUEL FILTER- Have not changed it since I have gotten the vehicle in June. Since I did have a rusty tank I feel that this could be clogged up possibly causing this problem. Where can I get a fuel filter from and what am I looking for exactly. Ive heard of people running Z32 fuel filters. Can I get one from a local auto store? (sorry for the noob question, Ive just never dealt with this in the past)

4. FUEL PUMP - When gas tank was replaced the fuel pump was not replaced so a possibility

5. Spark Plugs - Read somewhere here that this could have a factor on the bogging issue and not getting enough gas

6. Fuel injectors - ?

Okay, so any help would be appreciated here. I realise it could be one of several things but if anybody has a better idea of what exactly this sounds like that would be great.

So again,

No Acceleration over 25-30% throttle or 3500 - 4000rpm....when i give it more it bogges and sounds like its backfiring. When i dont give it enough gas (1000 - 2000RPM) its bogges and doesnt barely accelerate either.

Thanks

[tbradley222]

Update: Changed the Fuel filter and upgraded to the Z32. Car is still running horrible. Any suggestions??

[asoomal]

Grab a wire brush and some dielectric grease, time to clean those grounds! :P

[blackRB240]

Clean the MAF, and check fuel pressure. The strainer on the pump may be clogged if the tank was rusty, so check the condition of the strainer and pump. Also, search your intake piping for cracks between the MAF and the throttle body. You may have a crack in the rubber tubing somewhere which can cause problems. To check for vaccum leaks, start the car and run it at idle. Spray all intake hoses, and vaccum lines with starter fluid and if the RPM's raise, you have found a vaccum leak. Also, if you have a catalytic converter still, make sure it isn't clogged. Hope this helps.

[Q45tech]

ACCURATELY measure the rail fuel pressure under acceleration at WOT ~~ 44 psi?

[tbradley222]

Okay thanks a lot guys. I have an aftermarket (ebay i believe) Cold air intake with aluminum piping so I doubt there could be a crack but who knows.

ACCURATELY measure the rail fuel pressure under acceleration at WOT ~~ 44 psi?

Excuse my ignorance but what does WOT mean?

[blackRB240]

wide open throttle

[driftingmy240sx]

sounds like a bad mafs or clogged cat to me. could be fuel pressure related though.

[Q45tech]

Ask the dealer parts person what they sell more of: MAF, CATS or Fuel Pumps......................across US my guess is FUEL PUMPS by 3 to 1!In this case FUEL PUMPS cost half the other two choices.

[blackRB240]

^^^ He speaks truth.

[nichols1992]

I wouldn't start throwing parts at it. You need to check the fuel pressure, maybe there's not enoungh maybe there's too much. If you know the fuel pressure is okay, then I would do a back pressure test on the exhaust. You can also disconnect the exhaust before the cat for a short period, just to see if this is your problem. If you don't have access to the gauges that you need to check the above pressures, that might be the first thing to check.

[blackRB240]

3. FUEL FILTER- Have not changed it since I have gotten the vehicle in June. Since I did have a rusty tank I feel that this could be clogged up possibly causing this problem.

4. FUEL PUMP - When gas tank was replaced the fuel pump was not replaced so a possibility

No Acceleration over 25-30% throttle or 3500 - 4000rpm....when i give it more it bogges and sounds like its backfiring. When i dont give it enough gas (1000 - 2000RPM) its bogges and doesnt barely accelerate either.

I've had this happen MULTIPLE TIMES!!!! Rusty tank + old pump + clogged filter = a car that runs like crap. If there is trash clogging the fuel filter, that means it went through the pump and must certainly either clogged or messed it up on the way through. I'd give a 5% chance that it is something other than a fuel system problem.

[tbradley222]

Yea blackRB240 I totally agree with you. Thanks a lot for the troubleshooting guys. Heading to the shop in a bit to take a look at it ( along with installing my new SPL tie rods ) . Most likely just going to upgrade to the Walbro fuel pump as I am planing on doing a motor swap at some point in the future.

[tbradley222]

okay problem solved!!!!

Installed a Walbro and fixed the issue! The old pump was on its way out and had a tear in the sock.



Thanks again everyone!

[blackRB240]

Glad I could help. +1 for the Walbro!!!