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Added load during idle can also be caused by failing bearings in the timing system, alternator, water pump, power steering pump, and AC compressor. Also if your throttle and cruise cables don't have enough slack they can keep the throttle plate open too much causing the IAC to work too hard. Same goes if the throttle plate closes too much. Also if you happen to be using any kind of IAC port opening restrictor that can cause issues as well.
 

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Discussion Starter #322
I had a whole giant paragraph typed up as a response and then the site timed out so it didn't post. You know how annoying it is to have to retype everything all over again.

Charlie I know what you mean man. I was helping a friend of mine with a 67 Impala and it was ridiculously easy to tune it with a screwdriver. But I think I'd still take my EFI car, especially for a daily.

Wow guys.... that is quite a bit of potential problems to look into. dmdicks I'm not using any kind of IAC restriction, so I guess that's one thing off the list.

A few codes have popped up in the recent days, which is usually not ideal:
P0102 - Mass or Volume Air Flow A Circuit Low Input
P0170 - Fuel Trim Bank 1
P0101 - Mass or Volume Air Flow A Circuit Range/Performance
P0507 - Idle Air Control System Revolutions Per Minute Higher Than Expected

All of that is definitely not ideal...
 

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Discussion Starter #324
Long time no update, but unfortunately no good news to report. The car is still not idling correctly.

dmdicks, I'm not messing with the voltage for the MAF except for capping it at 4.41.

At this point I'm wondering if it's not a vacuum issue. I remember before this started, a normal vacuum at idle was -22 or so. Now, it's at about -15. It feels like the ecu is trying to keep the RPMs slow, but it can't because vacuum is not where it should be. So I either have an incredibly bad leak (like an open hose) somewhere, or the engine is not creating vacuum as it should. We did a compression test, and here are the results from left cylinder to right:








I vaguely remember last time we did this, years ago, all cylinders were over 200. But I'm not sure of that. Should probably have written it down...

Also worryingly, the spark plug from cylinder 2 looked like this:


Hopefully it's from the water getting in through the cover over the spark plug, and not something wrong with the engine internals. I checked the dip stick and the oil looks good, no milky coolant in there.

At this point, I'm not sure what else to try....
 

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Were those engine cold numbers? If so then they look ok to me. That oxidation on the plug is from a poor plug wire boot seal. Nothing major to worry about.

Its been so long between updates I forget all that's been suggested and tried and I don't feel like digging through the whole thread again. Have you posted what your short term fuel trims are while the problem is happening?
 

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Were those engine cold numbers? If so then they look ok to me. That oxidation on the plug is from a poor plug wire boot seal. Nothing major to worry about.

Its been so long between updates I forget all that's been suggested and tried and I don't feel like digging through the whole thread again. Have you posted what your short term fuel trims are while the problem is happening?
Agreed other than.....look at LTFT's NOT STFT's since they bounce around a lot.
That plug, I agree with dmdicks, looks like water got past the plug seal and rusted the steel on the plug. Unless a lot of water in the plug well (which may short the plug and create a misfire on that cylinder, I wouldn't worry about i).

Cold engine compression numbers will yield a lower pressure, look for spread from high to low. Yours look OK.

As to vacuum leaks, this is over a decade old, rubber bits have a miles limit as well as a calendar limit, may be worth buying new rubber bits related to the intake side.

Dirty IAC valve may be an issue.
Vacuum leaks post MAF may be an issue.
Need for new plugs may be an issue.

Start simple, go from there......
 

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Discussion Starter #327
Hi everyone. Sorry it takes so long between updates. I travel five days a week for work, which makes working on the car difficult. I miss my car, to be honest.
Glad to hear that the compression numbers look ok. As far as fuel trims, the LTFT are all over the place. Between -30 and -50 within days of resetting the ecu. But then again, sometimes it sits crazy rich at 10, other ties it jumps to 17 during cruising. They haven't been stable since the idling issues have started. I did a check for vacuum leaks a while ago and didn't find anything, but will check again. Starting from the intake manifold and going from there. A few of the rubber lines look old, but no obvious cracks. I don't remember if I mentioned this, but now it's idling at -15 psi and when hitting boost, it only goes up to 6 psi, even though the boost controller is set for 10. So I'm losing air on both sides.

New spark plugs, new IAC, so those are not an issue.
 

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Discussion Starter #329
How is the IAC sealed? Those OEM paper gaskets tend to blow out under boost. I recommend using something like like honda bond or permatex ultra gray for the seal.
I'm using the OEM gasket but it's a new one that came with the new IAC. I checked around it when the motor was running and there were no leaks.

Oh, there's a cylindrical object right under the intake manifold and that's the first thing vacuum goes to. Out of curiosity, what is it?
Right now I'm thinking about doing basic vacuum lines only going to the original stuff on the car and my boost gauge to see if I can eliminate the problem assuming it's a giant vacuum leak.
 

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Hi everyone. Sorry it takes so long between updates. I travel five days a week for work, which makes working on the car difficult. I miss my car, to be honest.
Glad to hear that the compression numbers look ok. As far as fuel trims, the LTFT are all over the place. Between -30 and -50 within days of resetting the ecu. But then again, sometimes it sits crazy rich at 10, other ties it jumps to 17 during cruising. They haven't been stable since the idling issues have started. I did a check for vacuum leaks a while ago and didn't find anything, but will check again. Starting from the intake manifold and going from there. A few of the rubber lines look old, but no obvious cracks. I don't remember if I mentioned this, but now it's idling at -15 psi and when hitting boost, it only goes up to 6 psi, even though the boost controller is set for 10. So I'm losing air on both sides.

New spark plugs, new IAC, so those are not an issue.
OK.....let's clarify about LTFT's.......
The number shown is what the ECU is doing with fuel.......
Negative numbers....the ECU is pulling fuel.
Positive numbers....the ECU is adding fuel.

LTFT's within +/-10% is sorta OK, within +/-8% is reasonably good.
Usually outside 25% trips a trim code.
 

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Discussion Starter #332
Random question: if you remove the oil cap on our cars, what's it supposed to do? Most of the cars I've messed with usually suck in air. I tried it earlier today and it was slightly pushing air out. Is that unusual?

Charlie last time I checked the LTFT were over -30%, which in itself is not good. But it's running the exact same tune it was running before the idle issues started, and at that point the LTFT were around -5%, which makes me think it's not the tune.

Just now I reset the ECU and removed all of the after market vacuum related things (boost gauge, BOV, boost controller), to see if any of them were causing the issue. But no, the car behaved exactly the same way.
 

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See some of my comments above. Check for any pre O2 sensor leaks. Any time gasses leak before getting to the O2 sensor it will cause rich/lean issues as the ECU is not seeing the true combustion gasses. Also having the O2 sensor too far away from an exhaust port will do the same thing.

A smoke test is a good thing to do because it will let you easily see any place air is escaping on the intake or exhaust side.

If your getting air pushed out your oil fill location then a couple things could be happening.

1) You'r PCV system is not working or set up correctly. It MUST be a closed system with the PCV valve drawing intake manifold vacuum. If you want to use a catch can use an air tight one that can go in between the PCV valve and intake manifold. The breather port on the valve cover should go to the turbo inlet pipe.

2) You have leaky valve stem seals allowing combustion gasses into the valvetrain area

3) You have poor piston ring seals causing blow by and pressurizing your whole block

I'm guessing its #1
 

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Discussion Starter #334 (Edited)
I'm still trying to find a smoke machine to do a smoke test, to make sure there are no leaks I'm missing.

In the meantime, I took out the catch can just to make sure, and checked the PCV system. Everything looks good, and the breather port goes to the inlet pipe.

A friend of mine used a scope to look in the engine, and the valves and pistons look good. So I feel much better about that.

PS Where is our speed sensor located? I have a code saying it's not sending good data.
 

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Discussion Starter #336
It's really sad how rare updates happen these days, but I took apart the exhaust side of things yesterday and the exhaust manifold gasket was not looking too good on one side.



Obviously I'll be replacing all the gaskets when I put it back together, but this is a worrisome development.
 

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How did you have the EVO manifold bolted down on the driver's side? Some people cut off that right most hole and bolt it down with a washer. That can cause leaks if not done right. I suggest actually drilling and tapping and installing a stud in that location so it can be bolted down properly. Also check the flatness of the EVO flange. Those can warp over time.
 

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Discussion Starter #338
Mine is the not so nice option one, with a notch cut into the manifold to allow the stud to sit there. I know it's not the nicest way, but it's been working well for 2 years before current problems started. The evo flange looked pretty good. I cleaned everything and changed out the gaskets just to be safe. To my great dismay, the car is behaving exactly like before. Even though the exhaust manifold gasket had gone bad, it wasn't the cause of the original problem.
 
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