mcx apex help.

julio · Apr 5, 2009

I am completely stumped. I put a mcx turbo on my 06 apex, with head shim.
it runs great till it hits 10lbs of boost then it sounds like it detonates.
I have checked the cam timeing, all the wires are connected and check with ohm gauge, checked the fuel presure 45lbs and goes up with boost. tried a different controller. checked the key in the mag. the mcx injectors throw fuel.
any ideas are welcome. thanks in advance julio

hobbes · Apr 6, 2009

Sure you aren't hitting the rev limiter??

Wheel House Motorsports · Apr 6, 2009

yeah, this sounds just like what woddies was having happen to his nytro. said it sounded like a lean pop up high, it was his clutching and he was hitting the rev limiter even though his tach looked otherwise, read back a few pages and try to find it, was a good read.

julio · Apr 6, 2009

rev limiter

I dont think its the rev limiter. I know what that sounds like not it. this sounds like det. pinging/ clatter. if anything I think my clutching may be too heavy.

just did a comp. test and it has quite the spread. 130,140,145. it feels like the rubber plug catcher from the wrench is stuck on the last plug so I am working on getting that one out.
next is a leak down then pull the head.

julio · Apr 6, 2009

so the big ?

is it possible that I have some valves that are on the edge. they seal ok till boost is over 10 then they leak. if so would the engine clatter like its detonateing ?

julio · Apr 8, 2009

lots of help

I cant believe almost a hundred people have looked at this and two coments.

for those looking out of curiousity I didnt pull the head, comp. test and leak down lead me to think its fine. I did find a leak in the intercooler. I am hopeing the gromet left on the plug (may have held the coil back a little) or the leak are the cause of my woes. julio

noob · Apr 8, 2009

you checked for leaks?? I took my throttle body off to put a lefty throttle on, and thought it was on but it wasn't. sounds exactly what i had happen then, and another time as well. when it hit aroudn 9-10 pds boost, it would fall flat on it's face. make sure everything it tight.

tntm7 · Apr 8, 2009

try gapping your plugs to .018 and your problem should go away. any of the boosted CDI ignitions shouldnt have max gap of .022

julio · Apr 9, 2009

plug gap

I read your post on another thread, thanks for the info, curious what makes you say this. its the first I have heard of it. I did close the gap on them a little but not as much as you are adviseing. I also have run my other sled for the past 3 seasons with stock plugs and gap. Have I just been lucky not to have a problem with this. julio

zebiraross · Apr 9, 2009

noob said:
you checked for leaks?? I took my throttle body off to put a lefty throttle on, and thought it was on but it wasn't. sounds exactly what i had happen then, and another time as well. when it hit aroudn 9-10 pds boost, it would fall flat on it's face. make sure everything it tight.

X2. This is extremely important that you do a proper boost leak test. Have you done this? With the rear mount there are so many places a leak can spring up. And 90% of the time you can't find it with the naked eye, you have to be a boost leak test. Make a tester to clamp on to the inlet of your turbo and pressurize with compressed air up to 25-30 psi. If you need to see what I am talking about let me know and I can send you a picture of what I use to give you a idea.

julio · Apr 9, 2009

leak test

yep, pluged the intake and used a leak down tester, thats how I found the leak in the intercooler. I am hopeing to sneek away and run it this afternoon.
mcx said it should be under 30% loss. I was at 24 with the leak in the cooler after fixing it I am at 6-7%. granted my leak down probably doesnt read the same as the official yammy one. The way the yami one reads they couldnt tell me what presure they use mine uses 14-15lbs as a set point. also told me my boost gauge was on as well.. julio

tntm7 · Apr 9, 2009

julio said:
I read your post on another thread, thanks for the info, curious what makes you say this. its the first I have heard of it. I did close the gap on them a little but not as much as you are adviseing. I also have run my other sled for the past 3 seasons with stock plugs and gap. Have I just been lucky not to have a problem with this. julio

you may be running more boost now, there are many variables, some have better noise amunity then others.
but its only a matter of time before the ecu will eventually crash with .030 plug gaps and boosted.

julio · Apr 12, 2009

still pings on boost

At this time I am going with the head gasket must not have sealed. Its the only thing I didnt do on the install.
this last run I had an af guage and it never read over 13 and that was when I let up. most of the time it was right between 12-12.5. The other thing it did was dump the coolant out of the bottle, first time it has done that and it didnt pull the coolant back from the overflow either.
still not sure why this would cause the noise I am hearing. julio

julio · Apr 27, 2009

update

so it was the head. head bolts were not torqued correctly or he didnt back off the bolts and retorque.
now I am back to trouble shooting. no more det. noise, just has something wrong in the electrical. took it up and ran it ,it was intermitent would run then loose fuel. found the rpm wire literally on its last thread.
fixed that and all the other wires on the connector. epoxied them in so they couldnt push out. took it up she screemed for 5 pulls and then went back to not fueling with boost. cant find any broken wires and an ohm meter says all wires are good.
I am checking all sensors even tho there are no codes. Waiting for the dealer to be open tomorrow.

any ideas what to check.

julio · Apr 27, 2009

sensors

so far tps checks, air temp checks, both map and barro read low for voltage but they are only being fed 5 volts is that normal?

julio · Apr 29, 2009

answer

found the problem, it seems to have been a pluged fuel filter. I presure tested and it made presure, checked flow and it seemed good, just wasnt good enuff. I bypassed the filter on the hill today and fixed the problem, put the filter back and problem returned. replaced filter.

Thanks to Mark Liepheimer for all his help, I never would have looked at the fuel filter, its only had a half tank of fuel threw it. julio

zebiraross · Apr 29, 2009

Glad you found it man! What a headache for something so easy, but that usually is the case.

Yamamauler · Apr 29, 2009

Gremlin's suck, glad you found the problem.
I chased a a bad AS for 5 weeks. I should have chimed in but your symptom's were not the same that I experienced.

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mcx apex help.

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