B230FT backfire under boost

[superveggie12]

I don't have any soft intake hoses, no boost leaks, afr's go down to 11-12 before backfiring starts at about 4psi of boost. I installed a boost controller, boost gauge and afr gauge. I had the boost at 12 psi, car was running great, then I turned it up to 14psi, didn't go lean, but it barely did that backfire thing, so I turned down the boost and it just got worse and worse. Now it hits 4psi and backfires/ missfires / bogs. I have a video of it that I'll post soon, and I'll gap the plugs to 0.026 when I get home from school. Thanks for the help!

[2barxr]

I had one do that

I changed out cap and rotor the old cap and rotor had less then 6K miles on it

[Dirty Rick]

Head gasket leaking fire between cylinders?


Start with plug gap then fuel pressure (under load) to make sure fuel pressure raises with boost).
Then look at ignition secondary, measure plug wires, check cap & rotor.
Maybe a new set of standard cheap plugs OEM heat range?

[superveggie12]

I just got a new cap and rotor and plugs from IPD for the turbo models. Replaced intake manifold and throttle body gasket, cleaned throttle body, did a hot compression test with 138-145 psi on all cylinders. I have a coolant leak between back of motor and firewall if that does anything.

[culberro]

Could also add to the list of possible failure points: Failing fuel pumps, bad MAF, dying ECU, weak coil.

How did you check for boost leaks?

[superveggie12]

Originally Posted by culberro

How did you check for boost leaks?

I pressurized the system before the maf and listened for air leaks. That's how I found the intake manifold and throttle body leak that I fixed.
Here's the link to the video of my car backfiring : https://youtu.be/eHWMe0t9gIo

[Dirty Rick]

Originally Posted by superveggie12

I have a coolant leak between back of motor and firewall if that does anything.

No coolant leak is acceptable, more so if it is coming from between the block & head.
Even more so on a boosted motor!
That's the clue bus stopping and giving away day passes.

Is it rolling coal or is the rear bumper sooty?

Did gapping the plugs cause a change?

[superveggie12]

Originally Posted by Dirty Rick

No coolant leak is acceptable, more so if it is coming from between the block & head.

Is it rolling coal or is the rear bumper sooty?

Did gapping the plugs cause a change?

I don't think that it is rolling coal, doesn't appear to be. I have an open downpipe so the rear bumper isn't sooty. The coolant leak seems to be coming from the heater hoses between the engine and the firewall but I'm not 100% sure. Give me tips to try to pinpoint the leak please. Yes, gapping the plugs caused a change!... for about 10 minutes. I let the car idle and warm up and I was happy when the car ran ok, and pulled hard at 7psi with only a couple misfires. I turned up the boost to 12psi and the car continued to run with only a misfire or two per pull with AFR's around 12. 5 minutes later, the car started to do the same bog/ backfire at 12psi, then 11, then 9, 7, 5, and now it only goes to 4 psi before completely misfiring. I'm racking my brain trying to figure out what the problem is. I really hope it isn't head gasket related. This whole time I only lost about a quart or two of coolant, I know that isn't good, but I also don't feel like it is too bad. Please post some more ideas

[thelostartof]

Sounds like you have a large boost leak, I had something similar and it was the IAC hose was torn under boost, it would whistle over a certian PSI but at lower psi's it would just leak can cause misfires. Next time you pressure test it use a spray bottle with soapy water and spray it on every place there is a connection for pressurized air.

[cmanns]

Originally Posted by superveggie12

I pressurized the system before the maf and listened for air leaks. That's how I found the intake manifold and throttle body leak that I fixed.
Here's the link to the video of my car backfiring : https://youtu.be/eHWMe0t9gIo

Try cleaning / fixing the MAF/AMM connction...

Mine did similar

[maxitoman007]

Having a similar issue. Was this ever solved?

[Magnum TE]

Originally Posted by maxitoman007

Having a similar issue. Was this ever solved?

yeah it got solved, I think he crushed the car in 2013

[Moike]

The progressive drop in boost where this issue is occurring might point to insufficient fuel supply. Does it happen more with the tank 1/4 full or less than with it 3/4 full or above?

[Dirty Rick]

Put an ohmmeter on your plug wires?

[nibroc]

crushed the car???????..............what a waste

.....................

[Sliding242]

+1 on checking to see if the intake hose is collapsing, happened with mine. The car would buck with the throttle pinned running 12#'s

[dalek]

Originally Posted by Magnum TE

yeah it got solved, I think he crushed the car in 2013

Did he replace it with a Smart car?