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.

 

[steeda763]

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, there is only one pipe coming from the turbine. The wastegate outlet is blocked off with a piece of metal cut and welded in.

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.

A: Yeah...I know. It's a shame what condition this car is in

B: The flapper door does seem functional! I took the WGA arm off and it moves freely. Thank God for that

C: The Mitsubishi dealership was replaced with Mazda in this town. We're better off -- those people were scumbags anyway.

I'm going to look for a 16g O2 housing and open up the wastegate outlet. That seems like my best bet for now...wish me luck!

 

[steeda763]

In case anybody was wondering at some point what happened here I finally got around to fixing this problem.

Get ready.

A vacuum leak was causing the trouble. There was a small vacuum line run into the cabin where a boost gauge might have been, and it wasn't plugged. I took this out along with the T it was connected to and the car hasn't backfired since.

As for the blocked-off internal wastegate...well I found the same kind of eBay turbo that I have from a vendor on eBay. It's evidently not an imitation 16g at all...it's a full-fledged imitation 20g! I contacted the vendor asking about the blocked wastegate (and why the actuator is even included). I got a response similar to:

"You should use turbo like this. We install many car no problem. Dyno good."

Whatever. The car accelerates hard to redline now, and haven't pulled any CEL codes since.



Edit: This eBay turbo actually has a very quick spool, even after I believe 10k miles. I'd still never chance knock-off parts on a car I really cared about though.

 

[Mr Peepers]

...So you're running with no wastegate? Where's that boost gauge I was heckling you about 2 months ago

 

[steeda763]

...So you're running with no wastegate? Where's that boost gauge I was heckling you about 2 months ago

Boost gauge will come, granted I find a used non-eBay one on the cheap.

As for running with no wastegate...well yeah, I guess. Lmao

For some reason it's been uber cold here up until about yesterday, and there's nothing that I hate more than working on a car in the cold. I'll get more into it as it warms up (and when I finish painting my 240!).