Lean Misfires at 2700-2800 rpm

[DoctorDex]

Good news. I think I've _probably_ tracked down a scope through my parents neighbor. However, it'll be a few weeks before I can use it. I'll keep you guys posted.

Edit: What are the different sensors you guys would like me to test? Fuel injector harness, CAS. Anything else?

[DoctorDex]

Wow, now that its getting colder is this problem ever getting bad. I went to try and drive today, without letting the car fully warm up before driving (only let it run 30secs), and the car literally fell flat once it hit ~ 2600 rpm. It was almost like someone shut off the car. The rpms dropped to ~ 2500 rpm and then it tried again. Once it got close to 2600, it started to studder and then it dropped back down to 2500 rpm. Really annoying. Thankfully, I didn't have a passenger otherwise, they would have been like "WTF is wrong with your car?".

[ProwlerGT]

There's a list of sensors in my sig. I'd guess on testing the air intake temp sensor in the MAF first since this has changed when the temp turned cold. Then I'd look at the coolant temp sensor and if they are both good then go to the rest down the list.

[DoctorDex]

It turns out my ISC _does_ work. After doing numerous tests of the harness and ISC, I finally took the ISC out of the TB, left the harness connected, plugged the hole in the TB, started the car, turned the wheel side to side and turned the AC on/off. The ISC worked just fine. I really should have done this test first....

Therefore, the problem I thought was caused by the ISC, is probably caused by a bad FIAV (I think). Its been really cold out lately and when I start my car in the morning my idle hasn't been increasing to where it should be (1500+ rpm). It just sits @ 800 rpm.

Anyways, I'm going to proceed and do a FIAV block off using an aluminum can (yes, I know its ghetto). I'm also hoping/praying this might help with the hesitation/missing.

Prowler: Thanks for the suggestions. I think I'll try and go through them tomorrow. Aren't you tearing apart your TB right now? What are you doing to it exactly? Do you need a used (in good shape) ISC?

Edit: I doubt this will fix the missing problem, as last fall my FIAV worked just fine. I suppose I can still hope.

[ProwlerGT]

To be honest Dex, you have a wonderful flow going.... momentum extreme and I'm being lazy. I'm actually banking, gambling, HOPING FOR DEAR LIFE ON YOU, that it is your FIAV cause its one of the few things remaining that I think is the problem on my car but I don't feel like lifting a FINGER to try and fix my problem anymore until someone else comes up with something that seems like it'll work on mine too. If you do this FIAV block off thing and it works I'm going to be 100 times more eager and hopeful that it will fix my issue and then there will be a spark under my ass to go try it. I've been so frustrated with this on my car that I've just been reading and writing and letting the damn thing sit with disgust in the meantime. So..... FIAV BETTER BE IT ! LOL

[ProwlerGT]

After thinking about it for a lil bit it wouldn't make sense that the wax pellet would be mixed in with the coolant in the TB cause after all the FIAV must allow more AIR in to warm up the engine. In the diagram below you can see the FIAV looks (to me) like it shares a connected air chamber with the IAC. The parts program shows the FIAV as the whole bottom portion of the TB and looks like you could order it separately if you wanted (if they still are selling them) to know that you are using a clean lower TB and brand new FIAV. There is also this thing they call the FIAV O-Ring, but it doesn't look like an O-ring to me. Still maybe this FIAV O-ring thingy could be a leak zone too. I think the coolant temp affects the FIAV wax pellet thru the wall of the TB via temperature and thats why people say to disable the FIAV to disable the coolant flow thru the tb and then to block off airway cause its useless.





Aside from all that as I was looking at the diagram I noticed the VIC motor and I'm wondering now about that as it is not something I ever hear about. The manual says:
"Caution - Be sure to apply a voltage of not higher than DC 6V to the variable induction control motor connector terminals since application of high voltage may lock the servo gears." - I know at least in my car at least in one location (possibly 2) there were positive/negative wires arcing which caused my radiator fan motor to surge and spin the fan OFF the mount so fast that it melted/shredded the fan center mount and the fan spun into the radiator. Knowing a surge existed somewhere at some point could indicate there was a system wide surge and perhaps more than 6v got to the VIC motor locking it up. Its a stretch and I'm not even sure how it would apply other than its in the MFI section, but maybe this could be a culprit too. I don't feel like researching the VIC thingy at the moment. I'm still banking on the FIAV.

[DoctorDex]

I'm not sure about the wax pellet being in contact with coolant either. In this picture, it looks like it might be in contact with the coolant:

http://www.stealth316.com/images/isc_config.gif

However, according to the picture, I can't see how throttle body cleaner could get in to the area where the wax pellet it...

For the full write up see here: http://www.stealth316.com/2-3s-tb.htm

I'm going to try the blockoff first, using a piece of an aluminum can to make a blockoff plate. If it works, I'll need to consider replacing my FIAV. However, I might just keep it like this for good. I have a feeling maybe my methanol kit contributed to the loss of the FIAV. Its probably just a coincidence, but before installing my meth kit, the FIAV worked and now it doesn't. Maybe the meth acted in a similar way to throttle body cleaner and dissolved my wax pellet?

Edit: Took my TB apart and the FIAV pellet is definitely not in contact with the coolant.

[ProwlerGT]

Does the meth inject right into the air intake? If so maybe yer right.

From the pic that you showed on Jeff's site (thats the one I was looking for actually) though it kinda looks like the FIAV is in the AIR and in the COOLANT area of the TB with the coolant heating it up on one end in order to expand the wax pellet on the AIR end thereby closing the airway after the car has warmed up. In the picture I do believe the famous wax pellet has to be the triangular pointy thing in the FIAV diagram just in front of the air-hole for it. If you care about the IAC still being in the picture be careful when you make your blockoff plate to not block off the IAC area. This whole thing makes me realize that I don't think I'd ever want to shove anything "liquid" straight into the throttle body mouth while the car is running cause it'll obviously go thru the IAC and FIAV airway with who knows what kind of results. Seems the best thing to do is disassemble the bottom of the TB if you ever want to clean the air or coolant zones. HEY CHEF... I LEARNED SOMETHING TODAY !

[badass3000]

here is the FIAV delete that I did a few months ago.

[DoctorDex]

Originally Posted by ProwlerGT

Does the meth inject right into the air intake? If so maybe yer right.

I have two nozzles injecting into the intake about 3-4 inches before the TB.