2004 6 speed 124,000miles
Aem CAI, greddy cat back, gutted cat and resonator delete for mods

so I was driving home last night and right as I got off my freeway, my car decided to start stuttering and stalling, had to push it all the way out.

first I thought it was gas so I got gas but nope. Then I cleaned the Ess and reset the learing which after a while of holding the started got the engine running but super super poorly and making a really weird suction sound.
checked codes and have miss fire cylinder 2 and p0139.

i forced it home with the motor super unhappy and decided it might be an air leaks. So I took the whole upper intake mani off and looked for cracks as the sound sounded like it was coming from the back / top. But found no leaks. Decided to clean the fuel injectors. One injector on cylinder 2 was super gumped up so I cleaned everything I could. Got everything back together but Same problem.

today I’m going to see if maybe it’s a spark plug and see if maybe the throttle body is going haywire and opening and closing over and over again.

any ideas? After all that imma check compression.


https://youtube.com/shorts/2c-WGETQ83k?si=_TjOv3S9dZplfRE2

short video of air sound

 

1) Sounds like maybe something from your air injection pump delete might have come loose
2) Your motor does not sound happy at all. It kind of sounds like running on one rotor or one of the rotors has lost a seal and isn't having consistent combustion.

When was the last time you replaced spark plugs, ignition coils, and spark plug wires? Did you replace with factory replacements, and if so where did you source them from?

I fear your motor might have left the chat, but check those things I mentioned before moving forward to a compression test. I dont suspect the throttle body, and if your MAF is clean and the screens are in the AEM then I wouldnt think its your intake either.

 

Just started her up and I got a new code. 0
p0171 system too lean.

will check the air delete plate now. And coils and spark plug all ngk and replaced 2-3 months ago. Duralast wires, I like them better than ngk bc the ngk wires kept falling off. Compression check will be soon after

 

Looked at everything and decided to compression tested her.

shes cooked,
corrected psi @250 rpm
r1: 33 46 55
r2: 36 0 0

hopefully this isn’t the last of my eight. But it’s gonna be like that for a long time unfortunately. :/

 

Ouch, sorry to hear that news. Never a good thing when a motor calls it quits

 

With compression numbers that low, the engine wouldn't even start. How did you obtain those numbers?

Secondly, a P0171 code can be caused by a vacuum leak. you had stated that you hear a suction sound and that the engine is running poorly. These are indicative symptoms of a bad vacuum leak. I would diagnose the vacuum leak first and foremost and go from there.

 

I used the the leading spark plugs when the engine was to operating temps,
r1: 33 46 50
r2: 36 0 0

Im surprised it runs too, I can drive it down the block but it sounds like a v8. Maybe if you have another idea on how to check for no compression that more concrete I would love to prove me wrong

i mean where would i find a leak like that, it sounds like a massive leak and i took the entire upper intake off and inspected for cracks and worn gaskets. Nothing found, I’ve also check the air pump delete plate and it’s tight so I don’t think it’s that either.

the sound is like someone gulping water in a pool, just a lot of air, or like a plunger on the tub, I would imagine it’ll be easy to see at least a crack, any ideas on where to check next.

I was just gonna replace the motor with one that was imported from Japan for 1,800 with trans and ecu (don’t need either but oh well)

 

I would first ask what tool did you use to check compression? A rotary compression tester will give you an exact reading of each amount of compression per face of the rotor. There will be three sets of numbers per rotor. You did it correctly by performing the compression test with the engine at normal operating temperature. I always use the trailing spark plug holes because that what I was taught more than 20 years ago. This is what the reading should look like:



As for finding the vacuum leak, you can start the engine and carefully spray brake cleaner or starting fluid around the intake manifold. If there's a leak, the engine will increase its idle speed as it sucks in the spray. This will help you to narrow down where the leak is. If you hook the car up to a scan tool, you can also read the fuel trims in the lives data. I'd be curious to know where those are sitting at normal operating temperature and at idle. You'll want to look at the short term and long term fuel trims. If there's a vacuum leak, they will be high, as the engine ecu is compensating for the increase in air volume by adding more fuel.

 

I used the rotarytronics tester, it comes with two sensors so I can do both rotors at the same time
https://www.rotarytronics.com/produc...ression-tester

Spraying was the first thing I did. I drenched the entire engine with 4 cans of throttle body cleaner, nothing changed, I even sprayed degreaser to see if it’ll bog the engine and nothing happened, Idk if I just missed the crack somehow but yah I tried that before taking everything apart

Surprisingly it still drives and I’ll test the fuel trims soon and I’ll post the results here, never knew how to read them so I never checked them, but hopefully you guys can help👍

 

I resprayed the ENTIRE intake with 2 big cans of break clean, no change in RPM

i also recorded the fuel trims.
this one around 180-200

 

This is when the temps were 210

 

I can't see the two downloads of the fuel trims. Can you post what they were or upload a screenshot or picture of where they were sitting at idle? Strange that the engine is running that way with no vacuum leaks.

 

weird, let’s try YouTube like last time


so the chart of the 210 temps was a 60 second long graph

while the other chart was a 15-20 second long graph, that’s why they look so different, hopefully they help you guys understand my car🥲

Please let me know if you guys need me to show anything else or do differently 👍

 

I would guess dirty MAF or turbulent air across the MAF. The gulping air sound, does it increase in frequency with rpm? Can you localize it?
IT sounds like you might have a loose spark plug and are losing compression through there. Considering you read 0's in one rotor...

What units are those compression numbers? Psi? There's no way they're accurate and the car runs.

 

I cleaned the maf, I checked the metal wires for the CAI and their fine, I’ll recheck the spark plugs

so the sound is hard to locate as it’s coming from the top / back of the engine or round the lower intake mani and it sounds linear it doesn’t get faster as the rpm’s go up

what I can do is record my progress on getting the numbers and post it to YouTube for you guys to see.

 

Check the oil injector locations and the vacuum accumulator block that feeds them. They've been known to crack.

I wouldn't pay too much attention to STFT, especially if this was recorded while accelerating or slowing down. The ECU is doing its job. The LTFT being a bit high is a clue, but it's very within reasonable range of operation. What rpm is this last video recorded at?

I can't think of what mechanism would not be rpm-related in that area though. The sound could be unrelated to the driveability problem too? How recent is your last ignition change?

 

so I tighten the plugs and turned her on to bring her up to op temps, I tried listening for the sound by placing my extensions on different things, and no way to locate it

the test was done after the fans turned on to ensure she’s at op


now the number look correct bc this time I fully tighten everything, before I would put it hand tight, oops that’s on me. But still same results with 0 0 on rear rotor.

i ordered a replacement motor, hopefully gonna swap it in soon👍

 

I checked that block and found nothing, I could have missed it bc of all the cake on it but I also drenched everything in brake clean too, so I would imagine if the brake clean didn’t affect it there shouldn’t be any leaks

And the rpm’s were bouncing around 820-890 avg around 850

how would I accurately check the oil injector locations? Like I said I sprayed everything down, should I check differently?

as for the vacuum accumulator block, if it was cracked, wouldn’t it affect both rotors not just causing the one to show 0 0?

 

The vacuum block cracking wouldn't show as compression loss, but it would be a sizeable vacuum leak not on your intake, out of where you could spray it.
Injectors: Remove the UIM and visually inspect the injectors and vacuum connections to them. Odds are they don't hold vacuum any more, it's a factor of age but not a problem on this scale by itself. Obviously if the vacuum lines to have have cracked..

 

After the car started having problems I took off the UIM and I also inspected the injectors and took them off and cleaned them with new o rings, and no cracks in any hoses

 

Furl trims look pretty reasonable actually. I would have expected the long term feel trim to be well over 10% with a vacuum leak. With compression that low, I'm amazed it runs at all. Keep us updated on what you find as you remove the engine.

 

will do

 

Can you visually inspect the apex seals in the rotor with 0s through the spark plug holes? May need to rotate the engine by hand. We can argue about low compression numbers, but a complete 0 on 2 faces means the apex seal between those 2 faces is gone.

What's the history of the engine you ordered? It's good practice to ensure that whatever killed your current engine isn't still on the car when you put a new one on. Things like ignition coils, broken OMP wires, clogged cat, etc

 

It was imported from Japan 25-40k miles on it, or so their website says, it comes with all accessories, trans and ecu. I don’t plan on using much that was previously on my car but only some certain things obviously.

I can try but I doubt I’ll see anything and yah I’m pretty sure it’s an apex

 

So just yesterday I got the motor delivered to my house, spent the entire day swapping it in.

it came with everything and transmission.
the parts I swapped over to the new motor was
-ac compressor
​​​​​​-UIM
-belts
-spark plugs, coils, and wires
-coolant hoses
-thermostat ​​​​​​
(I had to swap some stuff as they were broken or missing, or cut)

after all the hard work, I finally got it started the same day but I have some issues

on start up current codes were

misfire in cyl 1
system too lean
HO2S voltage too high

i never figured out the misfire as it went away, system too lean was bc I left vacuum hoses off :/

but the HO2S code is always active I’ve cleared it many times but always comes back. I have a gutted cat, if that affects it

the last major problem is when I’m driving
at idle I can rev easily to redline but while I’m driving, around 4500 to 5000 rpm’s, the car starts to sputter and sound like I activate anti lag. Starts to loose power around that rpm’s so I’ve been driving under 4k.

I have not compression tested yet as I just put it in yesterday and I’m super tired, so I will soon and will get back with numbers.

for the sputter, I bought new plugs to swap in, but I’m sure I’ve had this problem before with my last motor and it turned out to be one of the air solenoids that controls the ssv and vdi. But I was getting codes when that happened.
i don’t have any codes related to them. If the spark plugs don’t help, what should i check next?