Lean under boost!!!!

[laracroft]

I have a Spool CAI, 3" DP, Forge BOV, MBC. I had the first original flash before Mazda came out with the second version. I have backfires at least every other few stop and go's from a stand still. It's about 65-70 in the morning and 80 degrees by the afternoon. After I hit about 3500 rpm, my boost drops to about 2 psi from 10, barely increasing speed. Usually this happens after I get to 3rd gear on up. It feels like there is back pressure or soomething. Before I modded, I didnt have this problem and the boost would hold at 5-6 psi until I let off the gas. Now, it lets off on it's own after it gets to 10 and drops dramatically down to about 2 or so. Not sure if this is normal or something is going on that I don't know about. I checked my hoses and wiring, everything seems kosher.

 

[K-S-W]

Sounds like the plastic pipes aren't holding boost to me. The thing is when the pipes get hot they expand. Just imagine how the plastic pipes expand under more boost. They cause major pressure lost at higher rpm's.

 

[jeffmsp]

i dont know what your problem is, but to stay on the safe side you may want to consider relocating the intake temperature sensor in you airbox to near you bov so that it reads hot air and retards the timing a bit. May help save the engine before you can afford a wideband....

 

[Mx6GT91]

The ECU is flashed, its a 03.5 and its actually been flashed a couple of times I think.
That little sensor is just before the MAS.

I know its not boost cut because thats a jolt more than a studder.

The car does pop/backfire and then the CEL comes on but it doesnt read rich. Once it pops and goes lean.

Do you think its the plug gap?? Why would it start doing this a while after the plugs were put in??

A crack in the intake pipeing?? I never looked at that. Wouldnt that cause the car to run rich though?? One of my couplings ripped and my car would run rich as hell?? I have an AFM though.

 

[jeffmsp]

did you check what the code for the check engine light, im sure that will give you the answers you are looking for.

 

[changedman]

(rlaugh) some people... (not refferring to anyone specifically)

 

[Yay-Boost]

Fuel cut can feel like a studder. It all depends how far over the limit you go. But, it's not going to throw a CEL on you for hitting fuel cut.

 

[Mx6GT91]

Im pretty sure the CEL light is because of the exhaust. It does have the O2 still in it but it would come off and on after the exhaust was done.

We did find a crack right where the bypass vented into the intake. Its on the intercooler pipeing. A crack in the intercooler pipes would make the car run rich though. Not lean.

We also changed the spark plugs. Once they were changed and we started the car the CEL turned off. Its not really a time to test the car because its raining. I'll let you know if it turns back on and the car is studdering.

Fuel cut can feel like a studder. It all depends how far over the limit you go. But, it's not going to throw a CEL on you for hitting fuel cut.

His car has never studdered before. When boost cut hits its a huge jolt. Im sure you know what it feels like. My car did the same thing untill I bought a chip, except my car beeped as the car lunged forward. I kinda wish his did that. Then we would know if its boost cut.

 

[kingpin7666]

hmmmmmmm i think i just might follow your lead and change my spark plugs. ive had copper plugs in my car since jun 03

 

[turbo speedy]

i guys it is my car that he is talking about and i no what fuel cut is and its not that its sum thing else it pops then go lean real fast and stays there

 

[Mx6GT91]

He called me a little while ago and he said the car runs fine now.

I guess it was the plugs. He still does have a leak in the intercooler pipes. Its a good reason for hardpipes.

 

[kwiktsi]

If you have a boost leak, you will fuel cut sooner- making it buck, run uber rich making it pop and possibly backfire- AND it will read lean on the AF gauge if it is extremely rich. Also, the CEL can be the exhuast, or if it happens after the break up- it can be a MAF code for excessive airflow/maf voltage high (if the MSP throws a CEL for that- don't remember) or a misfire code from it breaking up. My first response was going to be look for boost leaks before I saw this reply- sounds like you found your problem- now fix it .

Joe

Im pretty sure the CEL light is because of the exhaust. It does have the O2 still in it but it would come off and on after the exhaust was done.

We did find a crack right where the bypass vented into the intake. Its on the intercooler pipeing. A crack in the intercooler pipes would make the car run rich though. Not lean.

We also changed the spark plugs. Once they were changed and we started the car the CEL turned off. Its not really a time to test the car because its raining. I'll let you know if it turns back on and the car is studdering.


His car has never studdered before. When boost cut hits its a huge jolt. Im sure you know what it feels like. My car did the same thing untill I bought a chip, except my car beeped as the car lunged forward. I kinda wish his did that. Then we would know if its boost cut.

 

[kwiktsi]

Good deal that the plugs fixed it. Still need to do the IC pipes though- not only will the car not run properly with a boost leak, it can also lead to turbo failure sicne you are overspinning the turbo trying to maintain boost with a leak.
Joe

 

[Mx6GT91]

He says sometimes it breaks up and sometimes it doesnt. Mostly in 1st gear.

He just ran my friend and the car ran fine. He doesnt hit boost cut either, well no more than before. He usually hits it when the intercooler gets really hot. Which is after 1 run.

He's going to order some hardpipes.