04nissan xterra xe 2.4 Sluggish no Power?

[JT]

Hi ive been trying to diagnose this problem at work.
a 04 nissan xterra xe 2.4 L motor manual.
it came in customer says lack of power after changing the sparkplugs/wires, cap and rotor. ran fine but didn’t drive it for a while then the problem started happening. :stick: they did something to it.
i took it for a test drive and the car dosn’t respond well. I give it gas it feels like i am towing a very large heavy boat going up hill. It seems to not have power also seems to cut off at 3k rpm. feels somethings plugged like a large bananna near the muffler banana: .
when driving 1st gear/ 2nd gear it cant even accelerate from a dead stop. feels dangerous when driving it on the roads. I managed to turn around and drove back to the shop. im like what the hell. 👿 this feels like the motor is cutting off fuel or something. POS rubbish this piece belongs in the dump. :angry:
so no check engine codes. i used the scanner first thing, no codes.
i inspected the firing order seems correct on the dizzy wires.
i cross referenced the spark plugs it is platinum spark plugs looks new. gaps seems within specs.
i rechecked resistance in those sp wires. seems ok. inspected cap/rotor.
threw in some new dizzy did the timing unplugged the two connectors at tps sensor and mechanical ok. timing on the dot.

i see data on the verus snapon scanner. map/ etc seems to be moving o2 seems to move. no codes.
i checked ignititon timing see it advances but then somehow retards the timing when the engine boggs if i rap the motor faster or try to accelerate regular.

checked the TPS max WOT is 3.8V and min is idle at .4V
specs are .46 min and 4.8V max
idk why its at this i adjusted the tps sensors engine off key on with scanner to spec. max i got where 3.9 and min .46

i cant adjust it to 4.8V max?
if i bottom it out max seems to be up to 4.2???

new TPS, New MAF,

knock sensor seems not within specs
replaced the knock sensor.
still same issue.

same problem everything is fine when revving very slow. fine up to 5k rpm
then i stomp or give it gas it seems to bogg out cut off no power at all. i removed the throttle body cover same thing.
sounds like it is blocked off by something. when i rap the throttle or give it pedal boggs out slugish motor. :blink:
with the filter only throttle body off sounds like a weird engine air noise that is barfing/farting cutting off noise?

so i checked fuel pressure at the fuel rail. i did the unplug vacumm lines idle and key on test pressure seems within specs.
i rev rev the motor it seems to have constant fuel pressure. seems okay. i pressed the fuel pressure gauge injector drop test filling up a cup of fuel cars seems okay pressure flows with no drop of pressure at idle.

so fuel pressure is good. pump is ok.

i checked vacuum lines for cracks etc no nothing. i did the vacuum gauge test. at the intake mani.
the car seems to have very good engine vacuum 21 to 20 inch vacumm. then i removed the first o2 sensor and test for vacuum gauge with it zero psi gauge vacuum at the first 02 sensor. seems flow easy.

comp test passed.

so i removed the pipe after the first cat converter. The converter i reved the engine and checked the engine vacuum gauge with first 02 sensor before 1st cat. i rev the engine until it seems to bogg a little same problem.
i see the gauge and it seems to move slightly to 2 to 3psi vacuum gauge.
is this a bad cat? is 2 to 3psi?
2 to 3 psi jumps sometimes when i give it gas.
i will remove the cat converter later just run the header? is the cat bad 2/3psi at first o2 sensor? vacuum gauge?

anybody have any info on what can i check next?
any info would be helpfull :woohoo: :blink:

Topic

[dan]

now the funny thing i see here is the ignition should ADVANCE with increase in RPM not retard, the faster the engine spins the earlier the plugs must spark too ignite the air fuel mixture in time too press down on the piston at the right time…

if the ignition retards too far the air fuel mixture will combust too late causing the engine too feel down on power sometimes even missing… the only time that i know of the PCM retarding ignition timing is in the case of traction control, or knock…

[EricTheCarGuy]

You might want to check for leaks in the air tube that goes from the MAF sensor to the engine. Any leaks here can cause performance issues like you describe. Also, I know you say you checked the firing order but given that was one of the things that was done before the problem showed up, going over that work is a very good idea. More info here.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Good luck and keep us posted.

[JT]

[quote=”EricTheCarGuy” post=104029]You might want to check for leaks in the air tube that goes from the MAF sensor to the engine. Any leaks here can cause performance issues like you describe. Also, I know you say you checked the firing order but given that was one of the things that was done before the problem showed up, going over that work is a very good idea. More info here.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Good luck and keep us posted.[/quote]

okay i found out this vehicle don’t have any trac control.
i put everything back did a smoke down test and i have no leaks. good vacuum with the vacuum gauge. also with a new MAF knocksensor/ new distributor.
i removed the cat converter and reved the engine. no power laggy problem still like it still wants to cut off. slugish.
i put everything back again and still no check engine light.
it still have the same problem it did when it came in.
im stuck i don’t know what else should i check.

[Lorrin Barth]

Cam timing?

[college man]

What was the fuel pressure when checked with the fpr
vac line unplugged and on? You may need to tape the gauge
to the windshield to see what the fuel is doing at that time
of problem. There is a fuel filter on that vehicle. fuel spec
is 34 psi at idle and 43 psi with the fpr line off. also the
plugs should be NGK double platinum tipped.PFR5G-11 What are
ST and LT fuel trims at idle and 3,000 rpm? what does the o2
voltage do at idle and the 3,000 rpm? Is the o2 going into closed loop?

[JT]

[quote=”college man” post=104134]What was the fuel pressure when checked with the fpr
vac line unplugged and on? You may need to tape the gauge
to the windshield to see what the fuel is doing at that time
of problem. There is a fuel filter on that vehicle. fuel spec
is 34 psi at idle and 43 psi with the fpr line off. also the
plugs should be NGK double platinum tipped.PFR5G-11 What are
ST and LT fuel trims at idle and 3,000 rpm? what does the o2
voltage do at idle and the 3,000 rpm? Is the o2 going into closed loop?[/quote]

okay, heres what happened ordered an ECU. replaced it and wala thats the problem :woohoo:
bad ECU. :woohoo: problem fixed, i sent the other one back for core

[EricTheCarGuy]

Thanks for reporting the fix. Any idea what caused the ECU problem?

[johnfkimmel@yahoo.com]

On especially older model Nissan vehicles with driveability incidents it is a good idea to also check near ecm’s main harness connector for any signs of moisture penetration.Plugged hvac drain tubes,replaced windshields urethane seal leaks,etc.A lot of times no dtc present and you may be stumped.

[Author]

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