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idle issue...halp

desant78

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Jun 23, 2010
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Clarksboro, NJ
Black magic? It seems you have almost done everything associated with fuel. Good luck!
 

Terry Posten

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Dec 16, 2003
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Davenport, Iowa USA
I have my FIAV Off the TB that Throttlebodys.com rebiult for me. I took it off and did a block off. I dont think I even ran coolant through it. Wanna try it?

Looks like brand new.

PM me if you are interested.
 

turbowop

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I'm absolutely sure that it's not the FIAV. I blocked it off using JBweld. There is no way in hell that air is getting through the FIAV passage. Even in the cold weather, the car starts just fine without it, and doesn't require any extra throttle input. All winter, ski trips every weekend, zero issues. I prefer to leave it off as it makes removal of the TB way easier when there isn't coolant running through it. But thanks for the offer.
 

Terry Posten

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I did the exact same thing but used an old core to "weld" up.

And since the coldest my car sees is 45deg, I was not worried about cold running.
 

gramkrakr89

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Jan 25, 2010
Messages
308
Location
Bunker Hill, WV
689 came with a 2G MAF, and no matter what I did, (besides playing with DSMLink) the idle never recovered just right from a clutch-in... I had new IC piping fabbed, new gaskets and seals, nothing completely solved it. I never found out what caused it, because the blow-through GM MAF that I installed w/ V3 eliminated the issue. /ubbthreads/images/graemlins/grin.gif

Quoting DR1665:
...Have you been logging things when the car is actively shitting the bed? ...



^this...

Maybe taking a look at metered airflow just as the clutch is disengaged or just as the idle slips will offer a clue?

Perhaps recirculated air creating disturbances near the MAF is registering as airflow... causing a rich spike /ubbthreads/images/graemlins/dunno.gif

How close (physically) is the recirculation fitting to the rear of the MAF? Does it stumble worse when there is more air recirculating? (like coming off of different loads) You mentioned that it acts as if the BOV is vented, so maybe the turbulence from recirculated air in the inlet is causing some Karman vortex woes...

Just trying to offer some food for thought since you've already tackled all of the possible causes... good luck!
 

turbowop

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I talked with Andre on the phone today and some of that came up.

The recirc enters the intake pipe right before the turbo. It is a Dejon "2gMaf in a 1g car" intake. It's been on there for years. Way longer than this problem. Maybe I just need to borrow a Maf from somebody local and see if anything changes. That's one thing I don't have a spare of...

This issue came on fast. It wasn't the type of thing that got worse over time. It never stumbled coming to stops ever. Then the day I installed the first custom eprom chip the car has ever used, it started doing this. At first I thought maybe the ECU or chip caused it, but after trying the stock chip and other chips along with other ECU's, I know now that's not the problem. The day I installed that chip though, I was actually able to go out and romp on the car. So that's what I did. A lot. Before that, I never really did that because the car would hit fuel cut on the stock chip. After romping on it, I noticed the shitty rough idle. Boost leak test confirmed bad injector isolators at the head. All that boost pressure and acceleration made those crusty fuckers give up. /ubbthreads/images/graemlins/rofl.gif New isolators fixed that, so idle was back to normal, but the car would still stumble coming to stops. That's where I am now, after a ridiculous amount of troubleshooting. /ubbthreads/images/graemlins/dunno.gif
 

grocery_getter

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Jun 20, 2004
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Kent - industrial suburbs of Seattle, WA
Quoting turbowop:
I'm absolutely sure that it's not the FIAV. I blocked it off using JBweld. There is no way in hell that air is getting through the FIAV passage. Even in the cold weather, the car starts just fine without it, and doesn't require any extra throttle input. All winter, ski trips every weekend, zero issues. I prefer to leave it off as it makes removal of the TB way easier when there isn't coolant running through it. But thanks for the offer.



So this morning when we talked, I told you that I had a reasoning on why I said that you must be bypassing air internally but I can't recall why I wrote that initially because I wasn't focused on our conversation topic - was at work and my mind is full of other things.

So...

I reread your thread and reread it and reread it and reread it. And reread it... the *whole* thread over and over again. That highlighted sentence above is the only thing that sticks out to me. Then I remember. The question is, in my mind, why *WHY* with a blocked off FIAV that you never need to apply any extra throttle input when starting the engine from cold. FIAV in our car is a pure mechanical device. The ECU doesn't know if its not functioning anymore, and it can't account for the removal of it. Coolant pass thru it and when coolant is warm, a mechanical process pushes the middle pintle on fiav to close the hole in the middle of the round plastic ring. The hole allows for bypass of air. Once that is shut, your idle goes down to the normal set warm idle. The reason that you need the high idle is because the ecu injects extra fuel (per the coolant warm up temperature compensation) when temp is below 176deg and all this extra fuel needs extra air to burn properly. So thats why FIAV is there, to give us that extra air when coolant temp is "cold". Now without FIAV, all that extra fuel will have no matching pair of air molecules to burn, which will cause heavy sluggish running to the point of engine stalling. On all FIAV removal/ block off cars that I've done, you will not be able to maintain an idle on a cold car. Therefore it is the common exercise if you have a car with blocked off FIAV, that you have to put your foot on the throttle pedal to open the plate to allow for air to bypass the throttle plate till the the coolant temp is warm enough for the ecu to ease up on your fuel enrichment.

Sorry for the ramblings but that is how I think, when dealing with an unknown, I have to follow my logic of known facts.

Now you said that you never have to help your car to cold idle with a bypassed FIAV by pressing on the throttle and I find that strange.That is the only single singular fact that sticks out to me and why I am still stuck on the "you must be bypassing air internally" answer. I've done so many blocked off FIAV and on every one of the cases, you have to apply throttle input to maintain a high cold idle since the FIAV is not there anymore, either physically (by complete removal) or functionally (by chamber blocking - like what you did).

The connection between this and your warm idle problem? I am not quite sure at the moment, this is still a process of thought. I just found an anomaly that I had to point out.

So if your egr is blocked off (per your list), can I ask what did you do to the 4 vacumm nipples on top of the tb? Do you still have those vacumm lines? Remove all the emmision related vacumm lines or stil have some of them? What was removed? What remained?

Is it possible to have perfect boost leak result (with the engine not running) and yet somehow air bypass the TB when the car is in a running state? What change with the existance of engine vacumm? Sorry the brain still doddling away. I am too tired to think about the problem but my brain is still going and going and going.
 

turbowop

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You bring up a good point, Andre. I have to input some throttle on 1051 during cold starts, but I thought that was more due to the light twin-disk and 272 cams in conjunction with a blocked off FIAV.

Although, this car idled perfect for months after the initial FIAV block off. It started up just fine as well, without throttle input.

Does the ECU use the ISC to bump up the idle during cold starts if the FIAV is not present? It may not know the FIAV is gone, but it knows what the engine RPM is, so perhaps it bumps up warm-up RPM via ISC?

I removed all emissions equipment on this car. The four vacuum nipples on the throttle body are capped off with nice vinyl caps and zip-tied tight. I just have the basic vacuum hoses: BOV, FPR, and boost gauge. And the boost controller is fed pressure from a nipple on the compressor outlet.
 

jepherz

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Aug 8, 2004
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KC, Missouri
The operation of the FIAV and ISC is fairly simple. The FIAV allows in extra air when cold as the wax pellet isn't melted yet. The ECU uses a warmup table to determine ideal RPM. There is no feedback from one to the other so while the ECU would still shoot for 850 RPM by adjusting the ISC when the car is fully warm and the idle switch is triggered, it has limited adjustment.

Does that answer your question?
 

turbowop

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During warm up with the FIAV blocked off, my car will idle at around 1400rpm. I figured that was the ECU using the ISC to bump up the idle until it was to operating temp. Once it gets to that point, it idles at normal RPM. When the FIAV was still functional and worked properly, warm up RPM was around 2000. A couple years later it started warming up at much higher RPM and would also surge until warm, so I blocked it off.

The car did not have this stumbling issue for months after I blocked off the FIAV though, so I don't believe that it's related.
 

beaner

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I should probably reread this thread before posting, but whatever.

Last summer I kept pulling my car apart and ended up looping the coolant lines going to the throttle body so it was easy to yank out. Didn't think a thing of it and the car idled perfect. Then fall crept in and the temperature started to change. It would surge randomly, idle way low, act like the bov was venting, etc etc. Very inconsistent. I figured the ISC was going bad, but it tested fine and the ecu was fine. So I pulled the TB and blocked off the fiav. Problem persisted. Then I blocked off the ISC. Even worse. I was pulling my hair out checking everything. I had a moment of clarity and realized this was all ridiculous.

The bottom of my tb was irreversible with the blocking off, so I had to raid a mystery junk tb in the garage. Bolted on the stock bottom of the tb and voila! Back to perfect idle. I think some cars just want the FIAV. I was 1000% sure I blocked it off correctly and everything else on the car was as it should be, but the car was hating life without it.

If I were you, I would get a fiav back on there. An overlooked idle issue is the tb not getting coolant or enough of it. Had I just hooked the coolant lines like stock and burped the air out of the system, the fiav would have seen coolant and everything would have been fine.

Keep it simple.

Quote:
with the FIAV blocked off, my car will idle at around 1400rpm. I figured that was the ECU using the ISC to bump up the idle until it was to operating temp. Once it gets to that point, it idles at normal RPM. When the FIAV was still functional and worked properly, warm up RPM was around 2000



You can keep the fiav hooked up as stock and adjust the rpm (2000 vs 1400) by turning the valve behind the freeze plug. The free fiav block off is to pop that plug off and turn the valve in all the way, but if you thread it most the way instead of all the way you will reduce that warmup rpm.
 

turbowop

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Then riddle me this...

How is a fully warmed up and closed FIAV any different from one that's blocked off? /ubbthreads/images/graemlins/dunno.gif
 

beaner

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b'ham, mi
No clue. All I know about the fiav other than what I typed above is there's no mysterious wax pellet.

Did you zero out or remove the safc?

All honeycombs in the MAS?

Are you sure the idle switch is being grounded when you let off? I had to adjust mine so the throttle really closes on it to ground _every_ time. I could have a jalopy switch though.
 

pot

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Oct 28, 2003
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Fayetteville, NC
Just chiming in my two cents Mark, but have you considered/inspected for a leaky fuel injector(s) or possibly a faulty Coolant Temp Sensor? In your first post you cited that you had purchase a new OE unit. Was it a Vatozone or Mitsubishi one? Just two things to consider....
 

turbowop

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Quoting beaner:
No clue. All I know about the fiav other than what I typed above is there's no mysterious wax pellet.

Did you zero out or remove the safc?

All honeycombs in the MAS?

Are you sure the idle switch is being grounded when you let off? I had to adjust mine so the throttle really closes on it to ground _every_ time. I could have a jalopy switch though.




SAFC isn't zeroed, but I just took a three hour trip in the car and my fuel trims look great. All three are between 100-110%. I'm only having to add about 8% on the low settings to get the trims where they are.

All honeycombs are in the Maf.

Idle switch works perfect on every close of the throttle. I used my logger to verify.

And for what it's worth, the TPS goes to 10% every time I let off the throttle, just like it should.
 

turbowop

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Quoting Pot:
Just chiming in my two cents Mark, but have you considered/inspected for a leaky fuel injector(s) or possibly a faulty Coolant Temp Sensor? In your first post you cited that you had purchase a new OE unit. Was it a Vatozone or Mitsubishi one? Just two things to consider....



I have brand new RC750's in the car. It did this with the older RC550's that were in the car previously as well though.

The coolant temp sensor is a new OE factory one from Mitsu. The old coolant sensor was actually okay. The problem was with one of the wires leading to it hanging by like one strand of copper. Enough to get a signal and a reading that was 20 degrees colder than it should have been. I repaired that and the coolant temp sensor works great now. I'm using a factory 190 degree thermostat and the coolant temps are always right where they should be.
 

beaner

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Quoting turbowop:
the TPS goes to 10% every time I let off the throttle, just like it should.


Explain.
 

89Mirageman

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Jul 5, 2006
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Stantonsburg, NC
On the 94 Mighty Max that I picked up a few months back I had some stumbling problems under load. Did basically everything that you have done plus a tune-up and nothing helped. After a ton of searching someone on Tuners reported similar symptoms and a new alternator fixed their issue. I checked mine under load and even removed it and took it to O'reillys for testing and it came out fine. I brought it home and put it back on and changed more stuff and still had issues. Then one day while at the junkyard I decided to buy a used alternator from another MM just for the heck of it, never can have too many spares right? Came home and slapped it on and all of the issues went away and its been running great ever since.

My guess is that it was slowly dying because it always had enough power to keep my battery charged and start the truck but it wasn't 100 percent. Can't say that this is your problem and it very well may not be. I would have bet anyone that the alternator wasn't my problem either but it was. It may just be worth the hour or so that it would take to swap out the known good one from 1051. At the very least it would be one more thing to eliminate for sure.
 
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