Does this problem sound like a boost leak to you?

[Grendel]

Hi all,

So I just got to Alabama, and finally got my car shipped here. About a week ago the car started acting funny.

First the idle would bounce all over the place, it would go from about 200rpm and on the verge of stalling to about 1000rpm. I searched, and one of the fixes people were suggesting was to clean the IACV. I did that, and it didn't seem to fix the problem.

Now the other day I was on base, driving around in 2nd gear around 25mph and the car started bucking. It was putting out black smoke. I called my dad, he said black smoke is normally running rich. I gave the motor some gas, and it struggled to rev, but after a few secs a big black smoke cloud came out the exhaust and it seemed to run ok.

Everytime I get into boost, the car sounds funny. With my old 280zxt when it would hit boost, I would just hear the turbo whistle. With my 240, I hear a kind of whistling sound. I'm thinking I might have a leak somewhere. Going to check out what I can today, but I dont have access to any jack or lift today.

Does this problem sound like a boost leak to you guys? I was thinking of buying a FMIC anyways, if I got one, that would eliminate a ton of piping to check for leaks eh?

I found a few threads with similar symptoms, and people suggested the MAF was going bad. Is that a possible cause too?

Thanks a bunch :)

[nicku]

my car had this same problem, and we didnt think it was timing, but it turned out to be the timing was WAY OFF.....check the timing, it sounds like the timing is off. and also maybe you have a boost leak, too. but im pretty sure the timing's off

[khilgers]

build a boost leak tester, pressurize the system and check for leaks. it also helps to spray some soapy water on the fittings to make finding a leak easier.

http://www.vfaq.com/mods/ICtester.html

[Pepperoni]

It does sound like a boost leak, and if u want to buy a boost leak tester instead (aluminum) let me know. Good to have one whether you're using a SMIC or FMIC

[Grendel]

Thanks for the replies. Pepperoni, I sent ya a PM about that tester, I have no tools to make my own at the moment :)

Nicku, if it was a timing issue, would the problem still come and go randomly?

It's so wierd I just drove to get lunch, and it idled fine at every stoplight. Sometimes it will try to die every time I stop. So wierd...

[nicku]

if you dont re-adjust the timing of course it would not go away. My car had this issue before. The rpm keeps jumping up and down while idling and sometimes i could get it start but it died by itself after couple seconds. but when it started, the rpm just kept jumping like crazy. It also sounded like misfiring somehow. But then we found out the timing was way off.

[Tenchuu]

it is easy to test for a larger boost leak if you have a boost gauge. just look at it and if you know how much vac you should be having at idle, and you are not getting it, then you do have a boost leak.

[Leo'S13]

I think it's your MAF, because with a failing MAF you'll get lot's of black smoke coming out the exhaust when reving. But checking the silicon hoses and inter-cooler piping would be good too. You might find unconnected hoses, leaks and loose joints in the system.

[KA-T_240]

If it didnt do this before, its not the timing. Your timing doesnt just up and change randomly, unless the ecu is telling to.

Start by checking for Boost leaks. If you have a wideband, monitor your AFR. From there I would test the MAF and coolant sensors

[Koopa Troopa]

Vacuum leak, check your lines and grommets.. Something is probably all brittle and cracked.

[DanDriftS13]

Easy way to rule out the maf is to unplug it and see if the car runs any different. If it doesn't than it is more than likely a boost leak somewhere. If the timing was off the problem would always be there and wouldn't come and go like you're describing.

[Grendel]

Thanks again for all the replies guys :)

Easy way to rule out the maf is to unplug it and see if the car runs any different. If it doesn't than it is more than likely a boost leak somewhere. If the timing was off the problem would always be there and wouldn't come and go like you're describing.

I'll try that today. I bought a leak tester from pepperoni, so I'll check that in a few days when the tester arrives.

*edit* After checking the hoses earlier, I unplugged the MAF. The car kept idling fine. When I would plug the MAF back in the car would stumble for about a half second, then idle fine again.

When I'm driving around and the idle starts jumping around, I'll pull over and unplug the MAF to see what happens.

Is it safe to unplug the MAF and drive around?

it is easy to test for a larger boost leak if you have a boost gauge. just look at it and if you know how much vac you should be having at idle, and you are not getting it, then you do have a boost leak.

I don't have a boost gauge, I'm looking into getting one. Not sure if I want to spend the money for a defi or just go with a greddy or other less expensive gauge.

Vacuum leak, check your lines and grommets.. Something is probably all brittle and cracked.

By vacuum leak, you mean a leak from somewhere other than the piping from the turbo to the manifold? From one of the little hoses? I'll check those too.

Thanks again for the help guys, I'll post anything I find out :)

*edit*

Pretty much every hose from the turbo to the intake manifold is hard and stiff. Last night I noticed the recirculating valve was really loud... like as loud as a regular BOV. When I looked at the hoses down there this morning, one of them looked kind of like this:

http://img253.imageshack.us/img253/3140/valvehv3.jpg

It's kind of hard to see, but the black line is the pipe, red line is the hose connecting to that pipe, and blue line is the clamp. I'd take a picture but I can't find my camera at the moment.

The hose was on the pipe, but on one side of the pipe I could feel the little lip that the hose slips over. Think that could be causing a leak? I undid the clamp, but the hose was too stiff to move.

If I just buy the Greddy intercooler kit, I'll get rid of all this junk plastic and rubber tubing. Might fix my problem right?

[nicku]

vaccum leak could happen on any vaccum hose in your engine bay. basically, look for all the rubber hoses. those are vaccum hoses. as for the boost gauge, i was recommanded by a guy on the forum. Try find STRI gauges on phase2motortrend. those are cheap and very nice quality.

[nicku]

http://phase2motorsports.stores.yahoo.net/stxslmbogaba.html
here...its 55 dollars and this is slim version. They have normal version which is 52 dollars