Misfire / Stuble 20+% throttle?

[XtremeHKS]

Guys my car runs like **** when I give it 20% or more throttle, it stumbles hesistates and misfires. It runs smoother with the MAF unplugged rather then with it in

[r34 gtr]

clean that MAF and try it. if not, look for a vacuum or intercooler piping leak. thats about all i can think of.

- tim

[Notchbackca]

does it do it WOT or just partial?

[USDM_OneVia]

vacuum leak!!!

Joe

[boost_boy]

Look at the harness's plug just above the blue ecu connector and verify tat there isn't a white wire cut. Sometimes, people add those little black boxes such as an S-AFC, VPC, etc,etc. and remove them when the car is scrapped.

Dee

[XtremeHKS]

Look at the harness's plug just above the blue ecu connector and verify tat there isn't a white wire cut. Sometimes, people add those little black boxes such as an S-AFC, VPC, etc,etc. and remove them when the car is scrapped.

Dee

Is it going to be in the main Connector on the back of the ECU?

it cannot go past 2500RPMs, it is a bone stock conversion minus an air filter / downpipe, my boost gauge reads .5KPA vacuum, and also today when I was test driving it, I came back and started tinkering around and found that unplugging my #1 injector had no effect. So what I did was pull the harness and check for injector pulse (which there was) but for some reason the injector wouldn't fire, so for hours i struggled getting them out of there (breaking 1) and then I took them to an injector shop to have them cleaned and blueprinted. When I got back from the injector shop I pulled my plugs, the car is running pig rich as #2, 3, and 4, are extremely black (and have been installed for a day) where as #1 isn't nearly as bad.

Do you guys think the issue is solely fuel supply or is it aided from a malfunctioning sensor, connection etc. (I did some testing on the maf sensor and I found that there is continuity on all four wires, there is a good ground and good power)

[boost_boy]

Judging from what you're telling me, it's sounds like a clssic case of what I've desribed above. What you're looking for is a whte wire with possibly a butt connector on it, but no connection at the other end. You AFM signal is not sending the signal to the ecu, so the ecu gives your test range and kicks into limp mode after 2500rpm.

Dee

[XtremeHKS]

Judging from what you're telling me, it's sounds like a clssic case of what I've desribed above. What you're looking for is a whte wire with possibly a butt connector on it, but no connection at the other end. You AFM signal is not sending the signal to the ecu, so the ecu gives your test range and kicks into limp mode after 2500rpm.

Dee

Ok I'll check that, but if it's uncut where should I go from there?

Also how can i check if the ECU is getting a signal from the MAF?

[USDM_OneVia]

Easiest way is to download the FSM from this site, pull out your ecu, and put your ecu into the fault code mode.

That will tell you right away if your AFM is disconnected. Then you can go into the real-tim diagnostics mode and check the code in real time.

Joe

[XtremeHKS]

And as far as the swap, it's making a noise like a KA makes when the timing chain guide is lose, except this motor doesen't have a timing guide

[slw240sx]

Look at the harness's plug just above the blue ecu connector and verify tat there isn't a white wire cut. Sometimes, people add those little black boxes such as an S-AFC, VPC, etc,etc. and remove them when the car is scrapped.

Dee

he is very very very correct !!!! this is why i couldnt get a maf to work on a swap i did. i had been previously installed and had a emanage on it, they just cut the maf wire there, so it was all wired up under the hood correctly , but it wasnt connected at the ECU , took me hours of trouble shooting to realize it.

[boost_boy]

Quote »Also how can i check if the ECU is getting a signal from the MAF?[/quote] Run a diagnostic test on the ecu and let it tell you what's wrong. These old school nissan computers are the best for determining major problems with driveability. If you don't know how to do, follow these simple instructions:

1. Turn ignition on (meaning have all the dash lights fired up and ready for the car to start) and leave it on.

2. Go to your ecu, locate the little diagnostic screw which should be next to the little red and green lights which are on the opposite side of the ecu connector.

3. Turn the screw clockwise and watch the lights flash in unison.

4. They will flash a couple of times, but when you see them flash three consecutive times together, immediately turn the screw counter clockwise before the computer moves on to the next sequence.

5. Observe how many times the red light flash first, the n observe how many times the green light flashes. These individual flashes will make up a code such as : 1 red flash and 2 green flashes will be the air flow meter circuitry and that's basically the one you would see if something was wrong with your AFM circuitry. It's usually accompanied by 3 flashes on the red light and 4 flashes on the green light which would be the detonation sensor which is a slave system. In the event that any part of your computer system defaults, the system will automatically prompt the detonation circuit to to retard the timing which will prevent further damage from happening to the engine. This sequence is also call "Limp-home mode" .

Let us know how your results come back so that we can further assist you!

Dee

[XtremeHKS]

he is very very very correct !!!! this is why i couldnt get a maf to work on a swap i did. i had been previously installed and had a emanage on it, they just cut the maf wire there, so it was all wired up under the hood correctly , but it wasnt connected at the ECU , took me hours of trouble shooting to realize it.

The only white wire that I could find that was cut was the white wire off of the check connector (or the dash instruments)

[slw240sx]

i think my wire was actually green, but inspect it carefully, also could just be a bad MAF sensor. happend to me more then once, plagued me for weeks cause it would goway and come right back

[XtremeHKS]

i think my wire was actually green, but inspect it carefully, also could just be a bad MAF sensor. happend to me more then once, plagued me for weeks cause it would goway and come right back

Why is my #1 and #4 coil pack not firing? When I pull it out and test it for spark it's sparking but when i have them installed and if i pull the clip the heavy misfire doesn't change wether they are plugged in or not

[float_6969]

Then maybe you aren't getting fuel to those cylinders instead of not getting spark....

[biosehnsucht]

Why is my #1 and #4 coil pack not firing? When I pull it out and test it for spark it's sparking but when i have them installed and if i pull the clip the heavy misfire doesn't change wether they are plugged in or not

Have you tried moving the coilpacks around, to be sure if its the coilpacks themselves or something else?

[boost_boy]

Quote »Why is my #1 and #4 coil pack not firing? When I pull it out and test it for spark it's sparking but when i have them installed and if i pull the clip the heavy misfire doesn't change wether they are plugged in or not[/quote] Crank Angle Sensor, Igniter or possibly a bad ground (I think it's one of the 1st two).

Dee

[XtremeHKS]

Crank Angle Sensor, Igniter or possibly a bad ground (I think it's one of the 1st two).

Dee

So does that mean it can either be a bad CAS or bad Ignitor or just something that needs to be adjusted?

[boost_boy]

They could very well be bad. Once again, you should do what I told you to do in my previous post. You really need to run a diagnostic check on your computer. Guess-timation is not a good thing.

Dee

[XtremeHKS]

1 red 2 green3 red 4 green 4 red 3 green1 red 1 green

[biosehnsucht]

12 = Air Flow Meter34 = Detonation Sensor43 = Throttle Sensor11 = Crank Angle Sensor

Go read the FSM! look at EF&EC 71-72, pages 193-194 of the PDF, it'll tell which pages to find the diagnostics for those on.

[XtremeHKS]

12 = Air Flow Meter34 = Detonation Sensor43 = Throttle Sensor11 = Crank Angle Sensor

Go read the FSM! look at EF&EC 71-72, pages 193-194 of the PDF, it'll tell which pages to find the diagnostics for those on.

Hey guys, what does it mean when my car runs the same if my TPS is hooked up or not.

[boost_boy]

Quote »Hey guys, what does it mean when my car runs the same if my TPS is hooked up or not.[/quote] Your computer is stuck in stupid mode and until you correct whatever issue you're having, it's going to give you drama. Your AFM is screwed or you've burned the curcuitry for AFM in your computer causing a fault that needs to be electrically repaired.

Dee

[XtremeHKS]

Your computer is stuck in stupid mode and until you correct whatever issue you're having, it's going to give you drama. Your AFM is screwed or you've burned the curcuitry for AFM in your computer causing a fault that needs to be electrically repaired.

Dee

How do i fix that?

[boost_boy]

Quote »How do i fix that?[/quote] Find out which component is screwed-up, replace it, crank the car dry-rev and then take it for a drive and see if you notice a difference. If you put a new AFM, CAS, and adjust or replace your TPS and it still won't run right, then safely assume your ecu is garbage.

Dee

[XtremeHKS]

12 = Air Flow Meter34 = Detonation Sensor43 = Throttle Sensor11 = Crank Angle Sensor

Go read the FSM! look at EF&EC 71-72, pages 193-194 of the PDF, it'll tell which pages to find the diagnostics for those on.

Can someone give me an idiots guide to diagnosing this? I have all the tools but I'm not to sure on where to start..

[biosehnsucht]

Go read the FSM

You can find it on zilvia net (PDF pages I gave won't match, they have the old one w/ missing pages in the EM section, so you'll have to jump around and find the EF&EC page #'s I gave), or someone posted a ftp link awhile back and a web link awhile back for the update one w/ all the pages...

[XtremeHKS]

Go read the FSM

You can find it on zilvia net (PDF pages I gave won't match, they have the old one w/ missing pages in the EM section, so you'll have to jump around and find the EF&EC page #'s I gave), or someone posted a ftp link awhile back and a web link awhile back for the update one w/ all the pages...

[XtremeHKS]