Backfiring? under boost

[chet1185]

I don't know anything about this car yet. bought it as a fixer upper. 6 bolt swap, kiggly kit with 2g trans.

Just got it up and running. front and rear motor mounts are bad, motor flexes to firewall and ac pulley rubs frame. Just changed the front and it fixed it halfway, so I'm ordering the rear now. But to the issue here.....I'm assuming as the boost builds, the car backfires. If I slowly raise the rpm's while cruising it just takes a little longer to do it. It is the stock exhaust so it kinda sounds like a pop and the car jerks a little. Feels like the bakes are being hit on and off. Sometimes if I'm WOT, the rpm's go up smooth but other times its rough.

Only thing I did to the car was the stock boost controller mod. Don't know if it has a boost leak or anything which I'm sure I'll have to do before anything else. Spark plugs look brand new but I didn't check the gap on them. Read about fuel cut off but I don't know what that is exactly.

 

[chet1185]

Just pulled the plugs. They are the ones recommended. They were gapped at like .040. I gapped them to .028. Seemed to clear up a bit but not much.

The electrode on all plugs looks like a needle not like the 1 in this pic.

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[chet1185]

Is that how they are supposed to be or should they look like the electrode pictures?

For the 6 bolt swap should I be using the 1g plug wires? Like the Ngk 9634

 

[Jermoturbo]

The plugs with a needle like electrode are the iridium plugs. Many people don't like using them for multiple reasons. I haven't had any experience with them in a 4g motor. I've always used the standard copper plugs with the electrode like you have in the pic, and haven't had any problems( besides spark blowout on the es's).
You stated in a previous post that you are using a used tps and iac. I would look to make sure both of those are functioning properly in order to get your idle in check.
Are you recirculating the bypass valve(BOV)?

 

[chet1185]

The BOV is recirculated. I got a used 1g BOV and installed it.

I am in the process of making a boost leak tester. Is the BOV suppose to be releasing air into the recirc tube while idling? Also just installed the standard copper NGK plugs and just ordered the NGK wires. I still haven't installed the tps and iac. Will a boost leak cause the car to backfire? If i drive it "normal" it won't backfire.

 

[jada64]

It could be idling weird due to the boost leak also, if it isnt a bad leak, and your staying out of boost issues wont be apparent. But when your really on it and building boost, the more it builds, the larger the leak is gonna get. A BLT is a good tool to have if you own a turbo car, so I would check this first, and its cheap.

 

[Jermoturbo]

From my experience, a boost leak never caused a backfire, it only makes the car run and idle like crap. A backfire is caused by an excess of raw fuel in the exhaust and when it ignites.... BOOM! This is usually from being too rich.

 

[chet1185]

And a boost leak wont cause that? If I'm loosing air?

 

[codym]

From my experience, a boost leak never caused a backfire, it only makes the car run and idle like crap. A backfire is caused by an excess of raw fuel in the exhaust and when it ignites.... BOOM! This is usually from being too rich.

What do you think is happening when you have a boost leak? Depending on the location of the leak , air that is already measured by the MAF leaks out , meaning less air gets in the combustion chamber than what was read to the ECU, causing an excess in fuel to be in the chamber.

A boost leak WILL cause backfiring during boost , idle issues and normal driving issues.

A boost leak tester isn't just a good idea , it's absolutely needed. Even if you visually inspect every single coupler and connection , things get overlooked.

 

[chet1185]

I've made a tester but my only worry is about a gauge. Do i need a boost gauge hooked up?

 

[codym]

You need a pressure gauge threaded into the end of the tester, right beside the Air hose fitting.

 

[chet1185]

Just an air pressure gauge?

 

[codym]

Yes, with a threaded fitting.

 

[chet1185]

Ok. Thank you

What psi do you suggest? Stock t25 with restrictor in stock boost controller removed.

 

[codym]

If you're running stock boost levels, 8-12lbs, it isn't a bad idea to ensure the system will hold a few more lbs of pressure than what it will see during operation. If your system is leak-free at 20lbs, than it will be more likely to stay leak free at 8-12lbs.

20 lbs is good insurance.

 

[Breezio69]

Sounds like a textbook boost leak. Its one of those things where you poke your head around, visually check everywhere, but in the end, there could be a massive leak right in front of your face. Case in point, I had a slit in a coupler that I couldn't see. Swore up and down no boost leak because of a test a month prior.... in the end, it was a large enough crack in a coupler to stick my pinkey through.

Get your boost leak tester made asap before you buy anything else and boost test it... you could spend $200 on parts and sensors that are already working to begi with, when its a simple boost leak and the tester costs $20.

 

[mitsubishikid]

in addition to the boost leak test, also do a compression test
[you can rent the tool from an auto zone for free]

you might want to clean your intercooler, take it off the car, fill it with fresh gasoline mix it around, then pour it out, repeat until the gas comes out looking clean.
check your fuel injector seals.
also check coolant temp sensor, and your o2 sensor, i.s.c.
good luck.

 

[chet1185]

Thanks for all the great info! Ill get my test done asap.

 

[chet1185]

Well, got around to testing boost leak today. Didn't get very far because the smic has a big hole in it. Hopefully this is my problem.

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Sorry its a little blurry. Would JB weld seal it or just get a used one?

 

[dakang]

JB weld may work but i would not reccomend it for a long period of time. Just remove it and take it to get welded. if you have a "mom and pop shop" near you, i wouldn't see that repair costing more than 30 bucks for confidence in your car.

BTW
That is definitely a leak that would cause problems you are having.

 

[chet1185]

Yeah, . The way it leaked with the compressor hooked up, i bet there isn't much boost getting to the engine. Is that why the car is sluggish also?

 

[dakang]

I wont say you dont have any other issues per say, but i will say that just that problem can cause all the issues you are having including sluggishness. if you can get to the hole while the car is running, then you can take a piece of plastic, fold it over a couple of times and put it on the hole. your RPMs should go up while you hold that piece there. Take that as you will. i just come up with creative solutions that have worked for me in the past. you should be able to hear the difference if that was a major leak(cant really tell the size of the hole). good luck

 

[chet1185]

Its a 1/4x1/4 hole. You could hear it instantly. It was pretty loud. I pulled the intercooler and I'm going to throw some jb weld on it to test the rest of the system.

 

[Breezio69]

There's a high chance that you will find more leaks. Make sure you have a spray bottle with soapy water in it, spray down the couplers and tb, manifold, injectors. At the end of it if you didnt find anything else, at least your intake piping will be all shiny clean

 

[chet1185]

Thanks, i will do the soapy water trick.

Think i got the intercooler sealed up. The throttle body is leaking everywhere. What gaskets should i get? I believe its a 2g TB and a 1g manifold. Here is a pic.

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There was also 1 bolt that wasn't tight because its too short.

 

[chet1185]

Also, the screw right above the tps is leaking. I think i may have f'd it up. I just thought it was loose and turned it, come to find out its the biss screw? What do i do now? I dont have link or a scan tool to reset it.