2G Help Diagnosing Power loss. 1995 GSX

[FirstTimeDSM]

1995 GSX


Hey guys. So here's the deal. new head, new valves/seals/timing done fresh.

When i first bought this car 2 years ago it was an absolute monster. boosted great and was insane. Been a lot of learning and now i know the car inside and out. Except for this.

So, here's my problem.

After i redid the headgasket and head everything seemed super cool and the power was back.

Then i started getting random missfire codes. Chalked that up to a 1g cas on a 2g so i disabled the missfire in v3 as i seen in a few threads here but power was still low. Okay, must be a timing mishap? Not sure.

Here's where it gets weird. in WOT at around 4k-5k i get a CEL, but no DTC's in v3 at all, even tried searching for codes while it was wot and the cel was on with passenger. Nothing. So i assume based on other threads it's a knock sensor or i have my knock detection too early.

Anyways, this is where i get lost. Earlier yesterday immediately after timing, cleaned plugs and decided to give it a test, on my way to driving to work i was in first gear and seen a mustang. He got up next to me and i let it rip. The power BLEW ME AWAY, so much so that it scared me because it'd been so long since i had it in prime running condition, so i let it chill out, didn't go hard and relaxed a little bit. fast forward like 8 hours. Went to give my buddy a ride after bragging about how it was back to insane mode. CEL at 4-5k rpms again, but it didn't cel or lose ANY power earlier that day in first or second. So i adjusted the CAS(1g) to retard mechanical timing a little bit. No CEL but power is not even close to the same.

UPDATED, IDLE: It's MUCH better after isc issues fixed and doesn't bog under idle or die after throttle is released when BISS was adjusted.
Here's somethings i KNOW are wrong that may or may not be relevant or that have changed since it was last at peak performance

Wideband (Powerdex aem) isn't displaying and there's two wires disconnected form the back(single wire, yellow, 1 strand) A brown wire with a clamp on it looks like there's a wire that's supposed to go into the clamp area. Could a disconnected wideband cause this whole thing?

(UPDATE: FIXED THROTTLE BODY no more coolant lines to TB/ISC hooked up) Still have to block off FAIV

oil cooler disconnected again because it was winter but the temps here peak at about 81 so not sure if i need to hook that back up or not.

Boost holds fine at 14lbs, as in i can reach 14 lbs at around 4-5k rpms(Turbo is a evo 3 16g) but it's possible boost leak is there. Would this cause these issues?

I'm so lost on what to even try. Seems like when i replace plugs and make sure headbolts are correct torque(arp 120lbs motor oil) everything's cool for about 1-2 pulls, then no more power. I just want this thing back to normal performance.

I live in missoula montana so if anyone has any ideas or is even remotely close i'd be willing to make the drive and try to figure out anything on my dime of course. Please dsm community. You're my only hope.

 

[rEclipserGST]

Your knock sensor activation. Move it in the range of 4700 rpm.

Do you have solid mounts?
Boost leak test performed?

Does your knock sensor activate CEL?

What voltage is your battery at?
Alternator putting out correct voltage?

 

[FirstTimeDSM]

Your knock sensor activation. Move it in the range of 4700 rpm.

Do you have solid mounts?
Boost leak test performed?

Does your knock sensor activate CEL?

What voltage is your battery at?
Alternator putting out correct voltage?

The mounts are fairly solid i'd say. all torqued down to what they should be rubber seems to be in good shape.
Boost leak test not performed recently but, last time it was the seals int he TB so i replaced that and INSTANTLY got 100% of my boost back. so i assume it's still good.
Unsure on if knock sensor actually activates the CEL, it's just my best guess and a seen a few threads that seemed to line up exactly with my issues

Voltage of the battery is at 14, i had the alternator tested and they said it was putting out 14 volts to the battery, but, one time i f***ed up and hooked a battery up backwards and blew the alternator fuse. It was after that i had it tested. they said it was good and it was outputting the correct voltages.

I'm going to set knock sensor activation to 4700 today and see what comes of it. I've read that 10 counts is a decent number to be safe with and at .35 per 1 knock should mean that my sensitivity or activation of cel should be at 3.5 right?

 

[Vegas Smith]

I can tell you with absolute certainty that part of your problem is the disconnected isc. My strong suggestion to you is to remove the throttle body and close your fiav then loop your coolant lines so that they don't run to your throttle body. After that, reconnect your isc and go through the full process of setting your throttle cable and biss screw. Obvisouly make sure all the gaskets are replaced or replaced with quality sealant.

Basically go through this entire page then report back:

https://www.sixsigmatuning.com/pages/dsm-idle-control

 

[FirstTimeDSM]

I can tell you with absolute certainty that part of your problem is the disconnected isc. My strong suggestion to you is to remove the throttle body and close your fiav then loop your coolant lines so that they don't run to your throttle body. After that, reconnect your isc and go through the full process of setting your throttle cable and biss screw. Obvisouly make sure all the gaskets are replaced or replaced with quality sealant.

Basically go through this entire page then report back:

https://www.sixsigmatuning.com/pages/dsm-idle-control

I will go do this right now and report back later on today. I really appreciate the quick replies guys.

 

[Cherry]

I like having the fiav, then you dont have to sit there and warm your car up yourself. But im having a hell of a time setting my idle for some reason which for me seems to link back to the ISC every time. I dont even have the cable on it and when going through the procedure to set my idle I can get it to idle at 750rpm with grounding all the right stuff and it will idle perfectly fine, shut the car off, remove the grounding wires, fire it back up and its all over the place with surges and then the idle creeps up.

I dont know if blocking off the isc would really hurt anything other than when fans or the AC comes on you would have to give it more throttle to keep it running. I have a new ISC as well and I cant find my old one. Ill post all this on my thread but at the moment im taking my JM Fab intake manifold off to see if that gets rid of this whistle I keep hearing between 1-2k rpm when at idle and the isc is trying all over the place. Maybe I didnt have it seated right and that extra air is making the ISC go crazy or something.

All I know is whenever I blocked off the ISC is when I could get the car to have a stable idle. Unplugging the ISC though makes it just run like crap.

 

[FirstTimeDSM]

Update!: Disconnected throttle body coolant lines. and reinstalled ISC and adjusted BISS. Idles still a little boggy sounding even though it holds at 900-950 rpms while "warming up" still a noticeable difference in audio/overall engine smoothness after 30-45 seconds but, it gets to that point a lot smoother now.

Power still gone, will update again when i have set the knock sensor to 4700rpm and the sensitivity to 3.5 for a 10 knock count.

Any other ideas on why the power would be so low compared to how it used to be?

Could the wideband disconnected be an issue?

 

[Vegas Smith]

Did you make sure you did the fiav mod or do you have the bypass plate on there? When you do this mod, the car will idle weird until the car warms up.

 

[Cherry]

The fiav has a small thermostat in it that is open when cold allowing more air in on start up so you don't have to sit there and warm your car up. When the engine gets to operating temps the thermostat closes. If you remove the lines then the thermostat stays open unless you do the mod which closes it permanently or you get the block off plate.