Lean Misfires at 2700-2800 rpm

[DoctorDex]

This is more or less a double post from the my ISC troubleshooting thread, but I figured its relevant to this thread:

Well, I took my throttle body apart and installed my very own custom aluminum can FIAV blockoff. It did the EGR while I was at it too.

Anyways, after all that hard work. No change. The car runs how it always did. I still have a brutal hot start problem, my idle still drops 200 rpm when I turn on the AC. At idle my ISC count sits @ around 20. At idle with the AC turned on it jumps up to 100.

From what I can tell from looking at the FIAV, it looks to be pretty hardy. I have a hard time believing throttle cleaner (or methanol) could damage it...

To answer my own quesiton: the FIAV is not in contact with the coolant.

The FIAV blockoff did not help with the misfires or lean spot.

Interestingly enough, I'm seeing 1.16 psi more boost to redline. Guess I must've accidentally sealed up a boost leak.

[DoctorDex]

Came across a thread where someone disconnected their TPS and it fixed their problem. Tried this on my car, no effect.

[DoctorDex]

Does anybody else ever get random junk data in the logs? I've heard of this before with hybrids logging with the fuel pump resistor/relay still connected, but I haven't heard of this in 1st gens. Reason I'm asking is I get random junk data, at least 4-5x per day.

For example, my car will be idling @ 800 rpm. Then, for some strange reason the log will show one completely ridiculous data point. I had a one few minutes ago that said: rpm: 76, knock:34. All the while, the car continued idling normally.

Wondering if this could somehow be related? Perhaps a capacitor somewhere sending out random discharges or possibly a wire short?

[ProwlerGT]

Originally Posted by DoctorDex

This is more or less a double post from the my ISC troubleshooting thread, but I figured its relevant to this thread:

Well, I took my throttle body apart and installed my very own custom aluminum can FIAV blockoff. It did the EGR while I was at it too.

Anyways, after all that hard work. No change. The car runs how it always did. I still have a brutal hot start problem, my idle still drops 200 rpm when I turn on the AC. At idle my ISC count sits @ around 20. At idle with the AC turned on it jumps up to 100.

From what I can tell from looking at the FIAV, it looks to be pretty hardy. I have a hard time believing throttle cleaner (or methanol) could damage it...

To answer my own quesiton: the FIAV is not in contact with the coolant.

The FIAV blockoff did not help with the misfires or lean spot.

Interestingly enough, I'm seeing 1.16 psi more boost to redline. Guess I must've accidentally sealed up a boost leak.

Did you try your ECU in your friends car yet? Anxious to hear about that.

I wish there was some way you could DELETE the A/C compressor easily to take it out of the loop. I know its a pain and some work, but I'd be suspect of how freely your compressor pulley turns (IE: is it causing drag). I have always been suspect of this on my car cause I know my compressor needs to go.

I'm pretty disappointed about the FIAV thing. I am still banking that its my problem on my car though. I'm going to fork the money over and get my TB rebuilt and bored out in the process within the week.

[ProwlerGT]

Originally Posted by DoctorDex

Came across a thread where someone disconnected their TPS and it fixed their problem. Tried this on my car, no effect.

Well that is something EASY I can try although my TPS has passed its tests. At the same time when I press the throttle is usually when the car looses its idle stability and stalls.

[ProwlerGT]

Dex - what have you done as far as electrical testing? Have you multimetered the MFI components per the service manual? I'd say at this point you probably should instead of us babbling about whether or not the ECU is good/bad. I'd start with the usual culprits: IAC, MAF, TPS, Coolant temp sensor, etc.. and then check those component's voltage at the ECU as well. I have that Excel spreadsheet for doing the tests which helps if you have a laptop nearby you can just plug in the results for your records and it helps to have a checklist with instructions for each test to go down. I am not sure if the voltages are different for different years (I actually think they aren't different, but never confirmed it) or just the physical configuration of where the wires are - are whats different, but if you want it I have it. You could reverify my notes in the manual to make sure you are doing the tests right. I put short notes next to the cells in Excel so that I wouldn't have to look in the manual for how to perform the electrical tests.

[DoctorDex]

Once I get some time, I'll do those electrical tests.

At the moment, my priority is to re-do my FIAV block off. I think I have a poor seal, with my makeshift blockoff plate, inside the throttle body. Now when the car is cold, my car idles @ 1500 rpm. Once the car gets really warm (driving for 30 min), it idles where it should... annoying. I don't know why it is, but for some reason I have to do everything twice before I get it right.

[keithmac]

The ISC helps with fast cold idle as well, log a warmup from cold with the car just idling and you`ll see the isc counts gradually fall to hot idle settings. If the ECU`s commanded 100 from the ISC and it`s actually moved that much and the cars dropped RPM you have a problem with the ISC bypass passage in the TB, it should rev pretty high at 100 counts!.

[J-Ville VR-4]

Originally Posted by DoctorDex

Once I get some time, I'll do those electrical tests.

At the moment, my priority is to re-do my FIAV block off. I think I have a poor seal, with my makeshift blockoff plate, inside the throttle body. Now when the car is cold, my car idles @ 1500 rpm. Once the car gets really warm (driving for 30 min), it idles where it should... annoying. I don't know why it is, but for some reason I have to do everything twice before I get it right.

From what I remember when I did the fiav delete, is that the "coke can blockoff plate" can not block off only the fiav, you must block off the fiav and the isc, since I believe they share the same air passageway. I remember that I first considered that method since it was the easiest thing to do, and reversible, but I concluded that it wouldn't work that way. I honestly recommend doing it the way I and most others have done it, by filling the fiav and its passage with JB-weld. As I said in my how-to thread, the fiav is only there for emissions, to have a high cold idle to get the catalytic converters to warm up faster. My car still idles at ~1500rpms on a cold start even with the fiav filled in, which is plenty high IMO. Trust me, the car has great idle speed control without the fiav, it was hands down the best free mod I have done to my car.

[DoctorDex]

The FIAV bypass plate I made looks kinda like this (except out of a coke can):

http://www.slowboyracing.com/estore/...at=4673&page=1

It essentially only blocks of the FIAV output, so it should serve its purpose. Here is a pic of the part it blocks off:

http://www.ffwdconnection.com/fiav.gif

I'm going to try getting it to seal properly again, except this time I'm going to use real gaskets, on either side of my block off plate.

If blocking off the FIAV serves its purpose then I may consider going to a permanent block off.