Stupid CEL.

[twadman]

I recently bought a 98 gst eclipse and I think the guy I bought it from did the pull off the battery cable to reset the CEL light for 20 minutes trick and so I bought it, not knowing the light was on. But anyway now its throwing a fuel trim malfunction code. I took it to a local auto shop that my family and i have taken many vehicles to, and they looked at it for three days and said it was either the MAF sensor or the ECM. I know the car is running pretty rich as I am getting like 10mpg, and tonight I replaced the MAF, my self, with a used stock one, and gave it a new air filter as well. I'm new to DSM and don't really know what else to do, and before I go and replace the ECM I just wanted anyone elses opinion on what it could be. It's all pretty much stock, its got a Greddy blow-off valve and Auto Meter boost gauge and thats pretty much it as far as after market goes. Does anyone have any suggestions? Would an ECM from an AWD car, i.e. a GXS or TSI work for my GST? I read somewhere else that the O2 sensors that get messed up with after market exhaust can sometimes throw this code, but i thought that was a separate code? Would it still throw it even if I have the stock exhaust on it? I read some where else that most of the time the O2 sensor near the turbo goes bad first and that can cause this? What would my next best route, next to the MAF, be? Should i get an ECM off a pull-a-part, because thats what the shop said? Or should I change out the O2 sensors? Is there like an order of things that is the most likely culprit of this problem?

 

[silver bullit]

What fuel mods are done to the car?

 

[twadman]

None to my knowledge.

 

[2point3Tsi]

recirculated bov right?

 

[blownturbotsi]

recirculated bov right?

Exactly what I was thinking.

 

[DanThMan1983]

Exactly what I was thinking.

whats that matter? asking because i have no idea

 

[twadman]

Yes, it is recirculated.

 

[blownturbotsi]

whats that matter? asking because i have no idea

It's metered air that the computer is expecting to go into the motor. When it doesn't get to the motor (venting to the atmosphere), there's more fuel than is needed (missing air left through the bov) so the o2 sensor sense's rich, leans out the fuel and almost kills the motor or makes it run crappy. For regular driving, the 1g/2g bov's mostly leak creating the same problem as when shifting.

This is of course, my understanding of the way it works. It could be completely wrong.

 

[twadman]

So from what you are saying ^ it sounds like if i had my blow off valve not recirculate the air it would be reading right and fix the problem? Has any one else thrown this code when they have added a BOV and had it recirculating?

 

[98GSXtreme07]

No, no, no! Have it recirculated! He was just explaining how the MAF works and why it is bad to have a non-recirculating BOV. Always make sure you have your BOV recirculated.

Note* Non-recirculating BOV is the same as saying "venting to the atmosphere".

 

[twadman]

Ha ok, I tought he was saying thats what mine was doing? Lol, my bad. So any other ideas on what my problem could be? I have read bad things about autometer boost gauges, and how they can affect idling and stuff like that when they are hooked up. Could this be my problem?

 

[crimsondragon]

Bad gas mileage you say? Could be your O2 sensor walking out the door. Doesn't necessarily have to throw a code. Or maybe it's your fuel filter. Or it could just be a major boost leak you're not seeing. How does she run? Shitty?

 

[twadman]

Yeah like 10 miles to the gallon bad. Well I was not sure about the 02 sensor, I thought that was a separate code from the Fuel Trim Malfunction. Would the fuel filter do this? I took it to the shop and they said I had a hole in some hoses and they replaced them, so I am pretty sure they would have seen a boost leak. She runs alright. Like I got her like this, so she is running normal for me. The other day after I changed out the MAF, she ran shitty and stalled out on me like twice, but thats the only time she has done that, and now she runs fine. She idles a little rough and uneven though.

 

[crimsondragon]

Yep sounds like a boost leak to me if it's a bit rough. Don't think shops will always catch them. if they don't do a boost leak test, they're not bound to find the itty bitty leaks like around the TB area maybe.

 

[twadman]

Hmm, doesn't sound good. Is there a tool or something I can rent from AutoZone or Advance Auto Parts to do a boost check my self? Can someone walk me through this?

 

[Jetrosr]

Articles: Turbo System & Intercooler - DSM Forums Found a few ideas here

 

[syrushcw]

Hmmmm when I got my car I was getting 8 miles to gallon never looked into it though just thought it was the way I was driving.

 

[pdc]

20 - 26 is more usual gas mileage.

 

[crimsondragon]

You be lucky to get 25. You gotta drive like a conversative old lady.

 

[madmike]

yeah someone on here has a boost leak tester post, how to make one, how to install it and how to test with it the right way, do a search

 

[EclipseTical]

http://www.dsmtuners.com/forums/search.php?searchid=4513185

that should get you started. Boost Leak Tests are easy but time consuming.

Good luck.

 

[knochgoon24]

Here's what my tester looks like.

I went to the hardware store and found the rubber coupler in the plumbing section. It's a 2" inlet on the turbo. They had 2" straight couplers, but they also had this 1.5" to 2" coupler that was 30 cents cheaper It was also cheaper to get a 1.5" end cap instead of a 2". The white PVC was cheaper than the black stuff.

From there, all I did was drill a hole in the end cap, then use some random fittings that I had around the house to make it connect to my air compressor.

Total cost... less than $7

 

[twadman]

Thanks guys. You guys are a whole lot more helpful then the people at dsmtalk.com. They were no help at all.

And, knochgoon24, did you not need a pressure gauge on there?

I think if cleaning the O2 sensors does not work tonight I will get the stuff to do the boost test tomorrow. But can any one tell me where my O2 sensors are so I can get at them and clean them. I bought some CRC to clean them.

 

[knochgoon24]

I have a regulator right on my air tank. I set it at 20psi and then hook it up. I also have my little bro watch the boost gauge, just to be double sure. I didn't want to make the boost tester any bigger than it had to be, because it's a very tight fit down in there.

 

[98GSXtreme07]

There's one on the o2 sensor housing. Right here:

<a href="http://imageshack.us"><img src="http://img206.imageshack.us/img206/2719/1000782o2pd6.jpg" border="0" alt="Image Hosted by ImageShack.us"/></a><br/>

And one right after your catalytic converter. Sorry I don't have a picture of that one.