high idle plus backfiring

[THE REAL DEAL]

alright, this is from a post i put on a local forum about my problem to one of the previous owners of the car. i'm just gonna copy and paste so i don't have to type out my long explanation again.........

yeah it does pull good but that throttle body has to go. i think i screwed it up last night because i tried to clean out the FIAV with brake cleaner, water, and a compressor. there were calcium deposits from hell in there.

so basically it went like this........ first, when you started it up, it would idle high at around 3k and surge. gradually it would drop though but wouldn't usually go less than 1500 and still surged. so, i figured it might have been the ISC motor. swapped that out however, the ISC i swapped it out with looked older. instead of having the plug on the ISC itself, it had the plug on a few inches of wire. but when i took the ISC out, i noticed the inside of the FIAV was pretty nasty. thick layer of calcium deposit or some sh*t.

so, i thought that might have been the problem. i decided to clean it out. we had some brake cleaner so i figured that might work with somewhat the same effect as carb cleaner. so i sprayed it in there, carefully rinsed it out with water, and used the compressor to blow dry it. i think it was less than 10 psi. well, after that i put everything back together with the replacement ISC motor, filled the coolant, and started it up.

now, the idle still shot up to 3k but no more surge. it gradually went down to 1500 with very little surge. keep in mind this is with a broken BISS screw that seems to be screwed all the way in but it stripped to hell so i can't get it out. so i let it warm up, shut it off for a few, then started it up again. magically somehow the idle dropped to 1000 rpm but it was jumpy.

so i left chris' house and drove ~25 miles home and here's the best part......

still running open downpipe but since i did all that sh*t to the throttle body, it's backfiring and not pulling for sh*t. sometimes it won't go past 4-5 pounds of boost. no matter what gear i'm in or what, whenever i give it even the slightest bit of gas it backfires and bucks like crazy. pissed me off.

so i've got a few options here. i have a spare full throttle body (i gotta swap the spring though) and a spare coil pack. i'm gonna get rid of the cruise control and get a regular throttle cable because i think it's screwed up and causing the throttle to stick. i checked the ecu and it's in great condition. caps have been replaced recently. i'm gonna try to log it this week but it's hard driving it around here without pissing off the neighbors.

so, anybody got any ideas?

feel free to ask me some questions about something i might have missed.

 

[THE REAL DEAL]

update:
may have found the culprit. i used mmcd to disable the injectors to see if they were all spraying and when i disabled the #1 injector, it didn't seem to lower the rpms and come close to stalling like the others did. what steps should i take now?

 

[Talesin]

Uh, the FIAV has a wax pellet inside that melts when the car gets up to temp, and seals off the air passage. It's possible you may have cleaned that out. If so, blocking off the FIAV with JBWeld or RTV (can't remember what people tend to use to 'fix' it) is the way to fix the problem. The only problem is that after blocking the FIAV, on cold days the car will be hard to start.

If you suspect your injector, either grab a mechanic's stethoscope, or a screwdriver.. put the tip against the injector and your ear against the handle, and listen to make sure it's clicking properly.

As should be obvious, fix that BISS ASAP and do a boost leak test, you might have other vacuum leaks, but if the FIAV isn't working properly, that'd cause a whole lot of problems with your idle. A magnetic grabber (little magnet on a telescoping stick) could help you get the stripped BISS out, if the threads are completely toast.

 

[THE REAL DEAL]

so how does it click at idle? is it pretty noticeable with the screwdriver? is there a possibility that i'm not getting spark in that cylinder and that's why it didn't start to die when i disabled it?

 

[THE REAL DEAL]

oh i also noticed that my duty cycle would go from 1.5% to 0.7% at idle.

 

[THE REAL DEAL]

well i found out that i messed up the gap on the #1 spark plug and that's why it was backfiring. so that's fixed but today i noticed that BOTH the honeycombs in the MAS aren't there. so i'm gonna fix that this weekend and see how things go afterwards. thank god i have a logger.......

 

[Talesin]

I'm actually shocked that it really ran at all with both honeycombs out...

 

[THE REAL DEAL]

yeah it runs. like complete dog sh*t but it runs. i'm gonna replace the MAS tonight and see if that'll get rid of the surge and make it run better.

 

[tqmx1]

yeah it runs. like complete dog sh*t but it runs. i'm gonna replace the MAS tonight and see if that'll get rid of the surge and make it run better.

Get the BookTurbochargers by HP Books. A good backfire will tear the compessor all to hell. If you get the book look at Figure 17-7