Buying a car with a rough idle

[RawrImAMonster]

There is a 98 GSX for sell at my local dealer's auction. My uncle is a car dealer so this usually ends up being where my family gets most of their cars. Since this car is at an auction, I wont be able to drive it, but i did get to start it up and let it run a little.

First off there is some sort of exhaust leak, it was loud as hell.

Second, it idled really rough and would die out if you didn't give it gas to keep it running. This is mostly what I'm worried about. From searching I have gathered that rough idle usually isn't a big deal, but I want to make sure before I go buying this car. Are there any major problems that can cause a really rough idle?

I'm asking all this now because I don't want to get stuck with something thats going to fall apart as soon as I get it off the auction lot. Because with a car that has over 100k miles, there are absolutely no refunds.

That being said, I think I could pick this car up for around 2500. 98 with 133k body is in decent shape.

Thanks in advance for any help.

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What do you all think, is it worth it?

 

[webconnect]

Great buy man. Yes it is a non t-25 turbo.

 

[toojung2die]

Any ideas on that rough idle would be appreciated.

Leaks. Looks for leaks in the intake from the air filter to the intake manifold. Leaks from the head to the o2 sensor. Check everything from injector seals to all the vacuum tubing. Improvement after warming up indicates something is sealing up better as it heats up and expands. It could be leaking in the exhaust manifold/turbo area. Verify all vacuum hoses are connected where they belong and tight. You're first goal will be to catch up on routine maintenance. Make a boost leak tester and use it. Verify the timing belt is installed right. It can idle okay with a tooth off because the ECU will try to compensate but you'll notice the difference when it's timed right.

It looks like you bought a lot of potential for for a reasonable price. Do whatever is needed to get what you have running right before you start adding more to the equation.

 

[RawrImAMonster]

Yeah, I'm definitely not modding it until I have it running perfect. I will look into the leaks later today.

Another problem I forgot to mention. It's really hard to unlatch the hood. I'm guessing the cable that controls the unlatching mechanism has just gotten stretched or slipped out of adjustment. What is the best way to go about fixing this?

 

[Jeff99GS]

Yeah, I'm definitely not modding it until I have it running perfect. I will look into the leaks later today.

Another problem I forgot to mention. It's really hard to unlatch the hood. I'm guessing the cable that controls the unlatching mechanism has just gotten stretched or slipped out of adjustment. What is the best way to go about fixing this?

Try some Wd-40 on the mechanism...then some white lithium grease! If that doesn't work you may need a new latch

 

[RawrImAMonster]

Another update:

I found the exhaust leak, its just the flex portion of the down pipe, no big deal.

I also found a mbc. Its t-ed into the line that goes to the bov. Is this a good place for it or not? Also, would I be safe turning this all the way down and getting into boost? I haven't really hit boost yet since I didn't have a boost gauge.

I also did a compression test yesterday before I waste money on a water pump and alternator. The compression was 170's across the board. The car has 130k on it, so does this mean that the engine was either rebuilt or replaced with a low mileage one recently? Are there any ways for compression tests to give false high readings?

Also here are some new pictures since I've cleaned the car up:

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[toojung2die]

I found the exhaust leak, its just the flex portion of the down pipe, no big deal.

I also found a mbc. Its t-ed into the line that goes to the bov. Is this a good place for it or not? Also, would I be safe turning this all the way down and getting into boost? I haven't really hit boost yet since I didn't have a boost gauge.

I also did a compression test yesterday before I waste money on a water pump and alternator. The compression was 170's across the board. The car has 130k on it, so does this mean that the engine was either rebuilt or replaced with a low mileage one recently? Are there any ways for compression tests to give false high readings?

I replaced a leaking 2.5" flex section on my downpipe with a 3" ID flex. Clearance is tighter but it'll fit.
The best place to get the boost signal for the MBC is off the turbo compressor or j-pipe. You don't want it tapped into the BOV line. http://www.dsmtuners.com/forums/art...-proper-mbc-hookup-diagram.html#post151142642, http://www.dsmtuners.com/forums/articles-turbo-system-intercooler/237982-best-way-install-mbc.html
Don't increase boost without a boost gauge. Some MBC's can go from safe to dangerous boost pressure with only a quarter turn increase. It's incredible the previous owner installed a MBC without a boost gauge.
I would trust the compression readings and breathe a sigh of relief. Those numbers are good. It's likely the engine was rebuilt or replaced.

 

[RawrImAMonster]

I wasn't talking about increasing boost. I was talking about turning it all the way down. What would that be on a 16g or something similar? I have not hit boost yet since I don't have a gauge and don't know what its currently set at. I'm just asking if I would be safe hitting boost if i turned it as far down as it would go with the mbc.

About the flex piece, my neighbor owns an exhaust shop so I'll get him to do it cheaply.

 

[Ravenous]

I hate you .


Naw man, that is great. The car looks fantastic. It makes me want to cry that I spent more on my 90 with a lot more problems ... I wouldn't be boosting until you know what type of turbo you are running.

 

[toojung2die]

To be completely safe you can eliminate the MBC and connect the boost signal hose directly to the wastegate actuator. You'll get very little boost this way but you will also be sure not to damage anything until you have a boost gauge installed. When you said, "Turn it down" I thought you were talking about turning the MBC adjuster all the way in. Backing the MBC adjuster all the way out would effectively be the same as eliminating it as I just described.

 

[bluegs03]

Omg i hate you, i mean seriously come on you just got my dream car and in wonderful condition. That is an absolute STEAL, plus the problems that you are describing dont sound that bad! Omg wanna trade i got a pos 90 black eclipse with a broken motor and an iffy tranny for 1k ! hows that deal sound.

But on a serious note great job on finding the car and i hope you fix all of the problems then boost the crap outta that thing!

 

[1983gsp]

Great buy.

 

[two4x4s]

Looks like you got a pretty good deal. I bought a 94 TSI AWD six months ago and it idled rough and smoked a little. Thirty miles later it overheated and spun a rod bearing... Needless to say i wasnt happy at all, but I finally got my motor pulled today and have a rebuilt motor out of a 91 TSI waiting to go in it. Good luck with your car man

 

[dsm_Prince]

Wow nice man. Can we get pictures of the engine bay to see whats going on in there?

 

[RawrImAMonster]

Yeah I'll get a few really high res ones up tomorrow. I have a few questions about certain lines and such i wanted to ask.

 

[Bubbs Malone]

Clean up the fuel injectors, might help the rough idle.

 

[RawrImAMonster]

Sorry for the slow updates had to fix the computer that my brother screwed up. Anyways here are the engine bay shots. The line right below the air filter in the first picture isn't connected to anything... its just setting there. Is this normal? I asked two other questions in my second picture.

Tell me if anything looks out of the ordinary on either of the pics.

Click the pictures for a much bigger version

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[Jeff99GS]

The thing you circled is the Fuel Pressure Solenoid.

The tee looks like its used for a Boost Gauge that somone probably stole

you should block the Open end on your drivers floor so you dont have a vacuum leak.

Or get a boost gauge and hook it up to that line

 

[toojung2die]

Sorry for the slow updates had to fix the computer that my brother screwed up. Anyways here are the engine bay shots. The line right below the air filter in the first picture isn't connected to anything... its just setting there. Is this normal?

By "line" do you mean hose or wire? I don't see any wires below the air filter so you must be talking about the hose that comes out of the white bottle? It's the coolant overflow hose. If coolant fills the bottle it goes out that hose to the ground. It's not connected to anything other than the bottle cap.

 

[RawrImAMonster]

Wow, sorry for the slow updates guys. I've had a busy month.

Anyways, the rough idle is no longer rough. Turns out the timing was off a tooth. The alternator and the water pump have also been replaced since both weren't working so great. The bs belt and all the pulleys and such have also been replaced since everything was already off.

Anyways, the car is running really great, except one thing. The turbo is blown. Loads of in/out shaft play. It smokes sometimes under boost. So yeah, thats the next thing on the list of things that need to be replaced.

Will it hurt anything driving the car with a blown turbo for a while? Obviously its burning oil so ill watch the oil level and such, but I would like to be able to drive it a little until the turbo is replaced.

Also while I'm at it I took another picture earlier today so I'll go ahead and post that up.

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