Stumbling Trouble

[wishihadatalon]

Alright, I have been recently putting together a 1990 GSX that sat in a field for 6 years rotting away and getting chewed up by field mice. I had a motor built, addressed the harness issues, and have replaced pretty much every bad thing that I can find on the car. Now that I have it running and driving, I am having an issue accelerating.

The issue: Idle surge and I can't rev the car past 3k. If I approach boost, it falls flat on its face and begins decelerating. I can't even tell if its a fuel, spark, or mechanical issue, because its nothing I have experienced before. To add to that, I took it to work today and on the drive home after the car was very hot, I wasn't able to accelerate in vacuum. Anything over 20% throttle would cause a similar stumble.

Whats done to the car?: New motor, 550cc injectors, 255 pump, 2g MAS, SAFC, mostly all 91+ components (PTU, ECU, and CAS). These are the items that I think are relevant to this issue. Also, the knock sensor is currently not hooked up due to a field mouse chewing the shielded wire. I will fix this when the issue here is fixed, unless this could be a contributing factor. Currently there are no check engine lights.

What have I done?: I have swapped the CAS, check resistance on coil packs, closed spark plug gap (from .029" down to .024"), and did a boost leak test. The plugs and wires are brand new NGK units. The boost leak test showed a significant boost leak at the throttle shaft seals (sat for 6 years) so I currently have those being shipped to my house and will fix asap.

At first I thought it was the large boost leak, but now with how consistent the issue is in vacuum as well as when the car transitions to boost, I am thinking there is something else that I am missing. I have searched and search for threads outlining similar issues, but none really match the exact issue that I am having. If anyone has some insight, I would greatly appreciate the help.

Thanks,

TJ

 

[lasershark]

with no knock sensor the check engine light should be on, I would get a new knock sensor or get it wired asap it's pretty vital to your engine health that alone won't cause the issue though previous owner of my gsx unhooked mine and it drove fine from his house to mine. It did throw a CEL though

have you checked the ignition timing?

 

[wishihadatalon]

Ignition timing is set at 5 degrees I believe. I have a fluidamper on it which didn't have timing marks on it. Through a series of swapping on a stock pulley and using a screw driver to find tdc on #1, I am pretty confident I have it set properly.

 

[lasershark]

did you mean 5* btdc right?

do you have a wideband? depending on how significant the boost leak is and with larger injectors and such you might be running rich at mid thottle+

 

[wishihadatalon]

5 degrees btdc is correct. I do have a wideband, but I haven't watched it too much because the problem was progressively getting worse.

 

[o0GuitarKid0o]

This may be a long shot but check the cars gas tank and clean It since it sat for a while who knows what's in there

 

[wishihadatalon]

So last night I worked on replacing the throttle body shaft seals. After pulling out the old ones, I found a significant reason for the idle surge. the seals were so bad that chucks of them were missing. After replacing them, the car no longer idle surges but still does the stumbling thing. I took it out today and checked to see if it stumbled which it did, but what I was was as soon as the car reached positive pressure, my o2 voltage went to 0.00v. It cycles fine when idling and cruising, but not in boost. Also I decided to test the injectors on my logger and my #4 injector didn't cause the engine to stumble like the other 3 injectors. I'm going to try to find either a set of evo 560cc injectors or another set of RC550 injectors and maybe, hopefully, that will fix the issue.

Thanks for the help guys.

 

[wishihadatalon]

A little update. I tried evo 560s and there was no change. I could get the engine to stumble on all 4 cylinders but nothing after that. I discovered that the car is running a non turbo ecu but that should just mean that it would run rich, which is different than what I am experiencing. I have no way to verify my fuel pressure, but I know I have good spark, good compression, some level of fuel, etc. Anyone have any ideas on this? I am completely at a loss on which direction to turn to next.

 

[Rsawd95dsm]

What about your TPS? Is it new or used? Your bad alt problem earlier may have fried that.

 

[wishihadatalon]

Its used, but appears to be working fine via logger.

 

[lasershark]

the non-turbo ecu's use a different o2 wire, or at least the car does itself. Every non-turbo n/t 4g63 I have seen run I believe a 2 wire o2 and our turbo's run a 4 wire that could possibly be an issue

https://www.ecmtuning.com/wiki/using1gntecu

I found a site a few days ago about the pin-out difference between the two and how to covert it but the thread got deleted for some reason

 

[wishihadatalon]

I will try to procure a turbo ecu. I have many spares and none of them seem to start the car. Some acid damage to the board on a few. Then I had one eprom that stared the car, had a socket soldered on the board by a very capable person, and then had an eprom chip added. Once the work was done, the car wouldn't start with that chip.

 

[wishihadatalon]

Little update: Found a turbo ecu locally and tried that out today. No change to the driveability. I verified that the TPS is working through its full range while running. I also, turned the car off, opened the hood, and could hear a leak from the fpr solenoid/brake booster area. That could be the culprit for the high idle, perhaps a bad FPR solenoid causing a fueling issue? I'll try to bypass it later to see if it helps. I'm open to any other opinions/ideas guys.

Thanks

:Edit:
Well, I tried a new ptu and a new coil pack with no change. I decided to pull the fuel pump just to check. The pump is brand new with probably around 50miles on it. I'm not sure if this is a problem or not.

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what do you guys think?