High idle when setting Aux Air Control bypass screw.........

[Infinitiguy19]

I have yet to find out why my 1993 Infiniti Q45 has a every so slight idle issue when setting the bypass screw to 2.5 turns. When set ALL the way in (Closed) the idle stays at 650 RPM's (Laptop Consult). But when turned out the idle goes higher.

I set the bypass screw with a consult and I unplugged the connector wit no electrical load.

The car doesn't start up right away either, it takes 1-2 seconds. And sometimes when starting up the engine shakes really bad (But the injectors OHM fine) (I can get exact measurements if needed)

I cleaned the Throttle Body (TB) once last year, I cleaned the Auxiliary Air Control valve (AAC) twice in two years (This time its spotless to Q45techs standards) and I cleaned the EGR and the EGR port is not plugged up Doesn't make a difference in this case.

I replaced the spark plugs with the standard heat range OEM NGK's last year and I checked and the plenum is clean but not to Q45Techs standards.

The oil pan does have a small dent in it unfortunately so that maybe why the oil light stays on for a second after staring up.

Grounding the fuel pump help a little with the starting issue but not with the warm or cold idle issue.

A compression test was never done.

The "vacuum" pressure(I know Dennis I read enough to know you hate this phrase) is a steady 20 inches of mercury.

Oil is leaking on the #1 and #2 ignition coil packs, I have spares to replace them.

The fuel injectors, rails and harness were replaced with NEW.

I am not in a position to throw money at the car right now but I am trying the best I can. Funny thing is every penny i can afford goes to this car no joke whether its parts or tools to fix it.

I have at least 72 ECU talk (Laptop Consult) logs I can convert (to .ods form if needed so they can be readable).


I am willing to do what ever it takes for this car.

[qship96]

Is the rough idle condition only happen upon starting a hot engine? If so, it could be that the fuel is boiling in the rails-rev it up a few times to circulate cool fuel to the rail and see if it stops the rough idle

[Infinitiguy19]

The rough idle happens all the time from first crank to fully warm and then some. I wish it was the fuel boiling in the rails....

I really appreciate the response!!!

A few more things to add:

I have used Redline, BG44K, Techron and Lubro Moly fuel products but that has'nt helped.

I made sure the Fast Idle Cam (FIC) wasn't holding the throttle open when the car if fully warmed up (176*F). I also cleaned the Throttle Body (TB) till it was spotless and then some (If you going to do something do it right or go home).

I have tried a 1994 California model ECU and that hasn't made things better from the OEM NICO ECU.

I have a transmission cooler installed and I did a couple of drain and refills on the transmission a couple of months ago.

When disconnecting the MAF connector with the OEM (1993 Q45 with TCS) ECU the engine stalls but with the 1994 Q45 (California model with TCS) ECU the engine continues to run.

I have used several MAF sensors till I found one that I believe works correctly.

The TPS is set to .44 volts but sometimes moves to .42 volts without the throttle being touched so I will address that.

The ignition I assume is set to 15* Before Top Dead Center (BTDC).

But this all just started one cold morning in July two years ago, I remember it like it was yesterday. The car idled really low (~500 RPMs dash tachometer) and it idled rougher (Than the usual smooth as a rock not being able to tell its running). I called my father up because I was so scared that something was something wrong. I told him it must be a injector but he said its normal...To try and calm me down I suppose.

To this day I remember what "Norma" is for this car and its not there yet.

I remember clearly what the car was like before because my father and I tried to start the car when it was running because it was the most quiet we both have ever driven.
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I wasn't kidding when I said like 50 tabs open tabs open:


http://picasaweb.google.com/lh/photo/vs ... directlink

[Infinitiguy19]

I don't think I said what the idle was with the Auxiliary Air Control bypass screw turned out 2.5 turns from fully turned in (Closed). The vehicle idled at ~850 RPM's when warm and I have Laptop Consult logs to prove it.

C'mon Dennis, Guys should I do some 50-80 MPH runs or 0-60 MPH runs?

Do you want any logs or anymore information of any kind?

Right about now I think I might be happier with an answer as to why this is happening rather than a smooth idle.
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Now I have about 3 browser windows open with 20+ NICO tabs in each. I will put the best topics (All of them) in the document I made. I just hope NICO doesn't go under anytime soon.

[Infinitiguy19]

Well today after answering some person topic about his Q not starting mine gives me some trouble. After four days of sitting I go to start my Q and all I hear is the starter Relay clicking and all the lights on the dashboard light up and then die. After 2-3 times trying to start it turns over somewhat hard and starts up. When it started up the engine shook (All injectors OHM at 12-13 OHM's). At two thousand RPMs the engine shook the worst when cold.

The only good thing that came out of this is that the HVAC (A/C and Heater) controls actually lit up (Rare because he display is failing).

And here are the pictures of the Auxiliary Air Control valve/ Idle Air Control Valve (AAC/IACV) I promised:

http://picasaweb.google.com/lh/photo/nm ... directlink

http://picasaweb.google.com/lh/photo/ke ... directlink

http://picasaweb.google.com/lh/photo/2y ... directlink

http://picasaweb.google.com/lh/photo/ue ... directlink

http://picasaweb.google.com/lh/photo/Wh ... directlink

http://picasaweb.google.com/lh/photo/Vf ... directlink

http://picasaweb.google.com/lh/photo/as ... directlink

http://picasaweb.google.com/lh/photo/AE ... directlink

http://picasaweb.google.com/lh/photo/eR ... directlink

http://picasaweb.google.com/lh/photo/2S ... directlink

http://picasaweb.google.com/lh/photo/Rg ... directlink

http://picasaweb.google.com/lh/photo/uD ... directlink

http://picasaweb.google.com/lh/photo/2A ... directlink