Extremely hard backfire/bucking

[steeda763]

When I take my car into the high RPMs and under full boost, it often backfires once really, really hard.

It was misfiring a little before as I was climbing the RPMs so I replaced the plugs with BPR7ES (the store was out of BPR6ES) and the wires. I'm running at stock boost...I think. The car came with an adjustable wastegate actuator. It's not fast at all so I'm assuming stock boost. I have a vacuum hose run from the [16g] compressor housing directly to the wastegate actuator, and the stock solenoid is out of the vacuum/boost circuit. The vacuum lines between the turbo, solenoid, and wastegate were plumbed all weird, as one line ran to a nipple on the intake before the turbo. The car backfired one time and threw a P1103 code, "wastegate actuator" . I cleared the code, re-plumbed the lines to what I described, and the car still backfires hard, but hasn't thrown a code since.

There is a connector running down to the left of the ignition coils that was broken and the previous owner spliced in new wires and hot-glued them in place (no, really). Does this plug have anything to do with the coils, and, if not, any other ideas as to what might be causing this?

Maybe the attached picture will help you visualize the connector I'm talking about. Please ignore the neon green...the car came like that, unfortunately.

 

[slcorman91]

It looks like the connector to your coil. I would rewire it and make sure everything is connecting properly. This could be causing your bucking and backfires.

 

[steeda763]

BPR7ES isn't too cold for stock boost then?

 

[slcorman91]

Shouldn't be as long as you regap them. I have used them before to get my friends stock 1995gst home from the track. Just regap them.

 

[Mr Peepers]

I saw your thread on the BCS vacuum line question. With the way it was setup in your previous thread, it would overboost.
What you're describing sounds like fuel cut. The "wastegate actuator" code would also indicate this, since fuel cut is to prevent any damage from any malfunction with the wastegate leading to open boost.
Don't assume its just stock boost since it's slow, get an aftermarket boost gauge and know for sure.

You said an adjustable WGA, which tells me it's an eBay 16g. They have problems with the flapper arm sticking; keeping the wastegate from functioning. Take the WGA arm off of the flapper arm and work the lever until it moves freely.

Also, the adjustable WGA arm is notorious for not coming adjusted properly. You want it to be just pulling the flapper shut; most likely it's adjusted far too tight.

On top of that, the wastegate hole is the size of a penny, leading to boost creep at higher rpms, particularly with a larger exhaust. Porting will likely be required. Again, an aftermarket boost gauge is the only way to be sure.

Another big thing, check for boost leaks!

Good luck

 

[JohnnyT]

Can we say Fuel Cut?

 

[steeda763]

What gap would you recommend?

 

[Mr Peepers]

.028"

 

[steeda763]

I saw your thread on the BCS vacuum line question. With the way it was setup in your previous thread, it would overboost.
What you're describing sounds like fuel cut. The "wastegate actuator" code would also indicate this, since fuel cut is to prevent any damage from any malfunction with the wastegate leading to open boost.
Don't assume its just stock boost since it's slow, get an aftermarket boost gauge and know for sure.

You said an adjustable WGA, which tells me it's an eBay 16g. They have problems with the flapper arm sticking; keeping the wastegate from functioning. Take the WGA arm off of the flapper arm and work the lever until it moves freely.

Also, the adjustable WGA arm is notorious for not coming adjusted properly. You want it to be just pulling the flapper shut; most likely it's adjusted far too tight.

On top of that, the wastegate hole is the size of a penny, leading to boost creep at higher rpms, particularly with a larger exhaust. Porting will likely be required. Again, an aftermarket boost gauge is the only way to be sure.

Another big thing, check for boost leaks!

Good luck

I figured it was an eBay special, seeing as how it has a good amount of shaft play and there's no brand or logo ::cough:: SS Autochrome ::cough:: Haha, Jesus...

I'll give all of what you said a shot, and regap the plugs. Thanks for the quick reply!

 

[Mr Peepers]

I figured it was an eBay special, seeing as how it has a good amount of shaft play and there's no brand or logo ::cough:: SS Autochrome ::cough:: Haha, Jesus...

I'll give all of what you said a shot, and regap the plugs. Thanks for the quick reply!

Don't get me wrong, eBay 16g's aren't all bad. It's hit or miss as far as reliability goes, and for the creep, I got my friend's eBay 16g to hold 10 psi to redline with porting and a little modification. Keep in mind the car also had a full 3" exhaust with no cat. I've been pretty impressed so far with it actually, after all the initial issues were fixed.

I wouldn't get into boost before you check everything that was previously stated. You don't want to turn $1.5k into a bad deal The porting can wait, get a boost gauge to find out if it's creeping or not first.

 

[steeda763]

Haha well I'm still a little leery of those eBay turbos...maybe, just maybe, this one will change my mind.

 

[Mr Peepers]

No abnormal shaftplay on his, and it says TD05H on the compressor cover and has a nameplate on it as well. I don't know about the no-name ones, especially if you have a lot of shaftplay. *If* the turbo does go out, a 14b would be a cheap replacement and pretty easy to find in the classifieds.

 

[steeda763]

How does the 14b compare to the 16g, or the T-25?

 

[Rob10_99]

Sounds like computer issues like peepers was saying. Isnt there a fix(possibly a resistor to put in place) for the bcs?
1g's dont have a problem from what I've seen. But as for me runnin the ebay B16g for now and some heavy porting and a properly setup WGA I can hold 8psi at 7500rpm
Weaksauce I know, not enough injectors!
Get that coil pack wired up correctly, get some pigtails from a junkyard if you have to, thats just ghetto looking on top of the green imo.

 

[steeda763]

Sounds like computer issues like peepers was saying. Isnt there a fix(possibly a resistor to put in place) for the bcs?
1g's dont have a problem from what I've seen. But as for me runnin the ebay B16g for now and some heavy porting and a properly setup WGA I can hold 8psi at 7500rpm
Weaksauce I know, not enough injectors!
Get that coil pack wired up correctly, get some pigtails from a junkyard if you have to, thats just ghetto looking on top of the green imo.

That's not the only shady thing about the car, but definitely the star of the show.

I plan on using the BCS, I just didn't have enough usable vacuum hose this afternoon.

 

[Mr Peepers]

Not computer issues, but wastegate/boost control issues. Fuel cut is a safeguard against this.

One of many turbo comparisons: DSM: Top Ten FAQ

IMHO it would be a good idea to keep running a line directly to the wastegate (~8-10 psi if the flapper isn't sticking) until you do all the checks and get a boost gauge. I can't stress a boost gauge enough.

 

[steeda763]

I know...I'm just going to take the one out of my 240 to do some temporary monitoring. There's already a vacuum line run into the cabin and plugged, for my convenience.

 

[steeda763]

Going off on a tangent here, but if the computer cuts fuel at anything above stock boost, is it possible to add a boost controller without retuning the ECU?

And speaking of overboosting, my SR20DET had a hole in the WGA line and was overboosting like crazy, and there was no fuel cut. That was fun...until the turbo blew.

 

[Mr Peepers]

It cuts fuel after a certain airflow. You were likely much higher than stock boost, I'm going to guess in the 20 psi range.

As far as running a MBC, a logger would be a good idea to check for knock, or in your cause check the timing curve for any indication of knock (2g's don't show knock on a logger). You don't *need* to change the cars tune for upping the boost slightly past stock, but the key word is slightly. You won't get too much above stock power levels without tuning. 14-15 psi is generally considered a safe psi with the stock turbo and stock fuel system etc, but a 16g will flow more for the same amount of boost. You'll never really know for your particular setup, that's why a logger is important especially for safeties sake. It looks like that car has already seen hell, I wouldn't want to risk it any more.

 

[khartley]

Can we say Fuel Cut?

Not necessarily...my car has backfired like from running rich as well.

I also have a dreaded Ebay 16g, I got it ported with a bigger wastegate. No problems with it yet, but I haven't had too many opportunities to push it. It did hold 16psi very well though, but I was only running that for a couple days, because the car has other problems now.

 

[steeda763]

0mfg d00de I figured it out. Actually, I guess I should kick myself for assuming a proper setup, especially after "reverse-engineering the rice" thus far.

This eBay 16g, I suppose, was meant for an external wastegate. The wastegate exit is welded shut! Really, take a look at the picture. It's pretty sad that the previous owner was planning on racing this car.

But I digress... I guess I have two options: a) Buy an external wastegate, new exhaust manifold, and dump waste into the atmosphere, and b) Buy an O2 Housing meant for the 16g and try to grind open the wastegate port. Without the WGA arm attached, the wastegate does move freely, so I know that there isn't anything nasty under that weld. Does anybody have an option c?

And yes, the oil dipstick is short a very essential piece.

By the way, I'm not planning on owning this car for very long. I just want to make it as proper as possible without spending too much, and selling it to a more deserving person.

 

[steeda763]

I'm going with the O2 housing. Can somebody tell me exactly which O2 housing will fit the turbo in the pic above?

 

[Mr Peepers]

Can you get some more pics of the turbo? It's really hard (for me) to see what's what, it almost looks like there is a blank where the WG should be. I also can't tell if that single pipe coming from the turbine housing is the WG pipe or turbine outlet pipe. Are there 2 "pipes" coming from the turbine housing that merge together, one larger than the other?

 

[No Mo STi]

Well, I can't tell you what exact O2 you need for that but if your are wanting to just replace the whole thing, I've got a Buschur small 16g w/ internal wastegate, O2, & exhaust manifold. PM me if your interested.

 

[MrBoxx]

A: It looks like there is a broken stud/nut/bolt/whatever holding that "downpipe" on the turbine housing (bottom bolt). That needs to be replaced.

B: You're options here are to run an external gate off the mani, replace the turbine housing with one that's intact, or cutting open the welded shut part and using a new O2 housing with a provision for an external gate. I doubt the flapper door in that turbine housing is functional anymore. If it is, you may be able to get away with opening up the welded part again and just running a standard re-circ'ed O2 housing.

C: Dipsticks are available at Chrysler and Mitsu dealership for like... $14. Mine broke in about the same spot once.