Boost Spike

[NEW 2 DSM]

So I'm looking into a 1990 Eclipse Gs-T and it seems to be decent condition, just little body stuff here and there. The guy has only had the car for 2 months and he says he was told, only the block was stock. I'm going to call the previous owner.

So here's the problem, when my dad came with me the 2nd time to test the car again, we experienced a bad boost spike and the guy said that there was something going on.

Here's what happens: He was pulling onto the highway in 2nd gear and gave her the cherries, not all the way to the floor. Reved and spooled up find but all of a sudden the boost began jumping between 9-15psi back and forth until he let off. Cruised the rest of the way to 65 and everything was fine. Tried it again later and the same thing happened. It has a MBC and but the guy I'm buying from knows nothing about turbos. Please help with cause and fix.

Looks like a stock turbo to me. I know a decent amount about cars, very little about turbos and even less about DSMs. Please help, I like the car just want to know how hard/ how much to fix it?

 

[LKWTSI]

Update your profile with what mod's have been done. It'll help out a lot

As for the spike, I can only assume because you don't mention it, that you are still using the stock dashboard boost gauge and not an aftermarket one. This alone is going to be half the problem. The stock boost gauge is pretty much useless once you start to add toys to your DSM. You say it has an MBC. BE VERY careful using one of these and not coupling it with a reliable aftermarket boost gauge as you could very well be way over boosting and doing some damage.

The stock gauge measures boost based upon a lot of different parameters from the ECU and it converts the signals into what it thinks the boost is approximately. An after market boost gauge you get actual readings (depending if it's mechanical or electronic) the boost reading though is the actual amount not some derived number the ECU comes up with.

Once you have done the gauge conversion, see if you're still getting spikes and re-post.

 

[NEW 2 DSM]

Sorry, i forgot to mention that it does have a aftermarket boost gauge, and it seems like a pretty good one. I can clearly see the boost jumping between 9-15psi back and forth until you let the throttle back off. You can hear and feel the jumping as well.

 

[talondave]

Sound like a boost leak! It also could be blowing out the spark, might need a new set of spark plug wires and plugs a basic tune up might fix the problem..

 

[gusu]

No one here wants to give you a solution.

Spray any flammable aerosol into it as long as it isn't highly flammable like hair spray. I would suggest WD40 or especially break cleaner that works the best in my experience.

You should spray anywhere you can get a vacuum leak. I'd start around the intake manifold then go through all of your vacuum lines. If the car revs up it has a vacuum leak and you have just found it. Once you find it, it is really easy to fix but that will be for a later time.

As for the spark plugs/wires maybe being bad I would usually do spark plugs first because they are only a few bucks and are easy to change and if that does not fix it then move onto the wires.

DO THE VACUUM LEAK TEST FIRST!

As always Let me google that for you incase you need additional information.

 

[97gst_spyder]

My 2g was doing the same thing. I put all new claps on the factory piping, after-market bov, and mbc. Now it holds 15-16psi all day.

 

[NEW 2 DSM]

Ok, well I'll try all of those things. Hopefully the guy will still have the car when I have the cash to buy it again.

 

[tvscream]

yeup, definitely sounds like a vacuum leak.