1993 Q45 engine runs better when ambient temperature is above 70*F

[bgerner12]

I could do that and getting some readings off my car for comparison toyours may tell you a whole lot more than any guessing at the cause Imight do. Mine seems to start and run quite well for the most part (knockon wood).

We'll have to figure out where and when. I'm in Pepperell and your inIpswich, if I remember correctly. I work in Burlington. Do you workanywhere near there? If not, we could pick a place and meet on theweekend. Sunday is probably the better day for me this weekend.

[Infinitiguy19]

You have mail!

[bgerner12]

Hmmm, not seeing it yet but I'll check again in the morning. Time to get tosleep for me.

[Infinitiguy19]

OK I recorded a log of a typical startup for my car: http://member.thinkfree.com/my...6a1bc

This one is where the ECU is at 675-725 RPM's: http://member.thinkfree.com/my...25045

This one is where the ECU tries is at 688-700 RPM's: http://member.thinkfree.com/my...ffb82

This one is where the ECU tries to maintain 750 RPM's: http://member.thinkfree.com/my...e9285

This one is where the ECU tries to maintain 650 RPM's: http://member.thinkfree.com/my...8d4b4

For the first one download it and open it with Open office (What I use) or Microsoft Office...

For the others you have to use Excel or Open Office...and space them out by comma's.

[Infinitiguy19]

OK I changed the fuel filter today (What a pain)...No change well maybe a tiny bit but that maybe a plesibo effect from working on the car.

So I am getting a AAC valve from Jeff* and I will be replacing the TB with one from a 1991 Q45 (Grey TCS** motor FTW) and cleaning out the EGR again soon hopefuly that will solve my stumble under idle and its inablilty to go past ~6750 RPM's. The only other thing i can think of is compression because the oil light stays on for 1-2 seconds maybe when first starting up. Sometimes it does it sometimes it does'nt.

So my last step would be to check oil pressure and compression, Would have done it when I was doing the plugs but the guy doing it said $70 and I was NO THANKS. I will be using BG Quick clean and BG MOA this oil change, hopefully I get something out of that.

*Jeff's 1995 Q45 part out: zer...450sx

**Traction Control System

[Infinitiguy19]

Here is a video that better shows the oil pressure light and how it stays on when starting the car up ONLY: http://www.youtube.com/watch?v=4PUaaxBR6s0

In slow motion on my computer using VLC media player. It looks like it stays on for a little more than 3 seconds possibly 4.

Also took some pictures of the oil fill hole:

Somebody got better with the camera.

Modified by Paul Wall at 4:37 PM 9/24/2009
Modified by Paul Wall at 4:41 PM 9/24/2009

[Infinitiguy19]

Yesterday I took off the throttle body to replace it with my 1991 one. I have to say it was much easier than I thought, Just four hoses!!! And the car runs a little better too but not perfect.

But on the TB:

The screws were unmolested.The Thottle Position Sensor is set to .44 volts.Grey throttle motor-best part.Clean as a whistle, seriously I bought four cans of throtle body cleaner for this mofo.

And for the non believers:

Now the sad news:

The original throttle body was fairly clean but I am unsure if the Fast Idle Can worked properly (the screws may have been molested).

And yes that is my trunk.

All in all I thnk I just have to clean or replace the AAC valve and set it to the correct idle. And the wierd part about this throttle body is that the throttle spring feel harder, meaning that the car may have not been redlined as offen or who knows.

Next is the Plenum!!!

O yea the only thing that separates my engine from a 1990-1992 VH is the sodium filled exhast valves but thats a little further down the road.

[Infinitiguy19]

I checked the EGR today against the ways said in these topics:

zerothread?id=44132http://forums.nicocl ... ?id=139192

And my EGR seems to be functioning fine.

For the lazy:

You can test it's operation by reving the engine slowly from idle up to about 3000RPM. Feel the bottom of the valve (that you pushed up). It will flutter for a while and then drop out at a higher RPM.

Then Push up on the EGR while the engine is running at idle...Do the RPM's lowwer or does the engine even stall?

If yes then the EGR is POSSIBLY OK.------------------------------------------------------------------------------------------------

So I am back to sqaure one by installing a working TB that closes completly when coolant is warmed up. Idle is a bit high at idle so I will adjust the IACV to where it should be (2-3 turns, Assuming Intake is clean as new).

But I still get a minor stumble at idle (15* BTDC) (less noticible in gear 20* BTDC), Not being able to reach 6900 RPM's, Stumble is gets worse at ~1700 RPM's

Would the oil light issue and I assume HLA's have anything at all to do with this?

I will also check the MAF ground to be sure.

[goody90q45]

Did you unbolt the EGR and clean out the port on the plenum? The hole is probably restricted with carbon buildup. Easy job as long as you have a new EGR gasket on hand.

[Infinitiguy19]

I "cleaned" the EGR today, Well there was'nt a whole ton to clean.

I can'nt belive I doubted the previous owner and thought he would miss something on this car, But I am wrong so far. As far as I can tell I couldnt get much out of the EGR hole.

And the idle did get a little better but still not (Rock solid?) As in not being able to tell the car is on or feelling the engine being on.

So went to the dealer and got a IACV/AAC gasket, Might clean that one out again.

Wish I had a Consult or someone near me who knows what a G50 is.

[Infinitiguy19]

OK I am having a bad day today (My dad want to sell my car AGAIN and I say NO!). So I am on my knees begging for help anything at all, tell me the truth which is I am not worthy of owning a Q45 but please help me.

Is the Q45 when maintained properly supposed to idle smooth enough to fool you into think its off? Is it also supposed to be quiet enough to fool you into thinking its off?

Could HLA's cause this?

I only hear HLA noise on one valve cover (Drivers Side, the one without the oil fill hole).

Any and I mean any help or comments are appreciated.

[bgerner12]

Well, you've heard and seen mine run and it's about the same as yours. I think mineis running as good as it can (averaging 20.6 mpg). I do believe your expectationsmay be too high regarding smoothness/quietness of this engine.

[Infinitiguy19]

Well pictures of your car don't do it Justice just to let everyone know.

But I would trade all of the modifications I have done to the car just to have it idle perfectly, In my opinion nothing is better than a perfectly idling Q45.

Before last summer I knew what a well respected/maintained Q45 felt, So that's why I will never give up on finding the problem with my Q45's idle.

Also this topic here might help some understand and hopefully motivate some Q45 owners: zerothread?id=5480

Most important post in that topic:

The only things that can cause a rough idle [standing still] are fuel or air or ignition related just like all cars...having too much or too little of each. They are one of the easiest to diagnose compared to a Lexus thanks to the Consult. It's just that there are so few QUALIFIED Technicians familiar with them [those that work on at least 1-2 a day [300-1,000 different ones per year].......not many techs at a dealer has that experience! Smooth stable idle is a badge of honor [and competance] on a 239,000 mile engine just proves its possible. Give me 4 hours and assuming it's not structurally damaged or has bad injectors or worn out rings and valves from ABUSE it will idle properly.

I'll do it for free if the owner agrees to EAT all the dirt that I remove. We could use biodegradable paper towel and let all the solvents evaporate see how you would idle with all that dirt inside you. In a machine world humans would be the slaves.

Second most important:

I have been in Q45techs car (230,000 miles then I think) and it idled perfect. Couldn't tell it was on.

My Q was almost as good as that for a while. I probably need to look at another TB cleaning.

Fred...

Right about now I might eat what ever tech finds dirty on my engine causing this annoyance.

[Infinitiguy19]

Wow this is starting to look like a one man show/conversation.

Well my idle started back up and went from smooth(er) to little more rough.

I sent the AAC/IACV valve at ONE turn because anything more results at a higher idle, So what can that possibly mean?

According to what I read (from Q45Tech) the AAC/IACV screw is supposed to be turned in all the way then back out 2.5-3.5 turns MAX when the AAC/IACV solinoid is uplugged at warm idle. Is that true?

I doubt its the injectors because I run the piss out of those things. I ran Redline S1 (Whole bottle) in less than a quater of a tank with the fuel pump grounded and thats pretty close to a BG flush in my opinion. So it has to be intake or air related.

[Haitian_King]

Well, you've heard and seen mine run and it's about the same as yours. I think mineis running as good as it can (averaging 20.6 mpg). I do believe your expectationsmay be too high regarding smoothness/quietness of this engine.

After I changed a bad injector and had some engine work done, the car tricked me at a red light. No vibrations, super smooth idle. So smooth, I thought I had stalled out. I had to turn off the radio, put the car in Neutral, and rev it, just to make sure I was good.

These engines can get pretty quiet. Well, for a V8.

[Q451990]

Get the $30 smoke machine test we talked about. If your car is idling that high, it's getting air somewhere it's not supposed to.

But I agree about your expectations being a little high... the Q is not the smoothest idling car ever. It's good, but you will always feel something...

Heath

[Infinitiguy19]

I did a vacuum pressure test using a analog gauge. My readings at warm idle were 21 Inches of mercury. So if Dennis says:

The idle plenum pressure should be 61 - 68 kilopascals. http://www.cleavebooks.co.uk/scol/ccpress.htm

That would mean my readings equal: 71.1 And that is much higher than the above.

I tee'd in the gauge between the fuel pressure regulator and started the car up. When I first started the car up I heard a hissing noise that went away within seconds ().

So what do those readings mean?

I actually thought this meant my injectors needed cleaning.

I can take readings again if needed, I can also take pictures or a video.

The car also stumbles sometimes when taking off from a dead stop. The MAF is resolder, transmission mount was replaced all the easy posiblities are done. I will check the fuel pressure tommorow just to be sure.

And ofcourse there is still the problem that if I set the IACV to 2.5 -3 turns the idle goes up to 1000+ RPMs. Right now (When I did the vacuum test) The IACV screw was turned all the way in and the is still ~650-750 dash tach.
Modified by Paul Wall at 12:35 AM 10/31/2009

[silkysmoothyjud]

I might be going out on a limb here, but I had the same prob last winter running Niqole around in stage III constantly.....Fouled spark plugs were to blame in my case. HLAs are always noisy right before an injector failure....Open circuit perhaps???

[Infinitiguy19]

OEM ECU with brand new OEM hot type plugs.

Thanks though.

[silkysmoothyjud]

Yeah, makes you not want to check em (those plugs). It took me a while to figure out it was a fouling spark plug due to an open injector. I replaced the plugs and it went away, only to come back again....The plugs are a PITA to pull so what I did was wait for the problem to reappear, then I grabbed a pair of long handled pliers, and I pulled each injector harness one at a time while the car was running until I found which one was doing it. There is only one injector that cannot be checked that way. I found out that it was was # four giving me the trouble. Soooo, I pulled the plenum, pulled the injector, switched the injector with #2 so I could isolate the prob without pulling the plenum again. I was glad to have finally figured it out. Even after I moved the failing injector (which ohmed perfectly) the plug was still foul. Said plug was dripping wet with gas when I pulled it and it would still cause a slight rough idle/HLA noise even with the new injector (rough idle). It was an intermittent problem and my commute is short. That injector fouled #2 plug before it was easily replaced w/o plenum removal...

By the way, adjusting the belts perfectly and setting the idle screw perfectly FREAKIN SUCKS!!! Also, a failing belt tension pulley will make it seem the car is idling rough. It took me a while to figure that one out too. I never would have found the tensioner issue. The tensioner failed and broke the belt....all fixed....

Niqole was a cluster when I rescued her....


Modified by silkysmoothyjud at 7:47 AM 10/31/2009

[Infinitiguy19]

I shut off each cylinder with OBD Scan Tech Nissan and I did'nt notice too much of a drop (Door shaking).

The first startup after plug change I noticed no differnce whats so ever, I tried hard to ignore any plesibo effect.

Motor and transmission mounts were replaced in 2005 (I think...Well it was somewhere around that time). 8 Injectors with rails and harness replaced in 2005 Injectors test goodKnock sensors test goodVacuum tests good (As shown in video below)Pulley bearings and belts were replaced in 2007

Let me know any other info I can provide and I will be happy to.

Could the transmission at all affect the idle?

1993 Q45 Vacuum test: http://www.youtube.com/watch?v=5x9dWhSLgJk

I am running out of idea's here I am think it maybe a clogged injector. But I swear that this problem started all the sudden overnight.

[silkysmoothyjud]

Just about every problem I have had was injector related. Make sure the coil packs are all the way plugged in (especially #7). Could be MAF related....I am running out of suggestions. I mean we are talking about a Q MF 45 already, there is really nothing else it could be for real....

[Infinitiguy19]

Well my valve covers are leaking internally not externally which is kind of weird. But thats because the seals for the spark plusg must have failed or were not installed.

Did you OHM the injectors so you know which to replace or did you do a power balance test?

I will try another MAF and see what that does.

[silkysmoothyjud]

I just pulled the wires right off the injectors while she was running one at a time to see if the misfire stayed the same. I used a long handled pliers to reach under the plenum. Better than ohming ever was for me.....

[qship96]

With all the problems you are having, why not just invest the $ in a troublefree 94Q, as it has all the major improvements you seem to want anyway?

[mtzgr777]

Or the best of them all....a '96!

[Infinitiguy19]

I just pulled the wires right off the injectors while she was running one at a time to see if the misfire stayed the same. I used a long handled pliers to reach under the plenum. Better than ohming ever was for me.....

I can't even imagine how to do that, How do you remove each connector on by one with the car on?

Pictures would help.

With all the problems you are having, why not just invest the $ in a troublefree 94Q, as it has all the major improvements you seem to want anyway?

There are two answers...the nice answer and the true answer. And since I don't want to "Start" yet another fight I will tell you the nice answer:

I want to fix what I have because who knows the condition of the next car and if I find one. Right now there are only FGY33 avalible.

And this is the biggest problem I have because I am a perfectionist when it comes to this car. And plus I want to have the best of the best with little to no sacrifices.

Or the best of them all....a '96!

No comment...Just kidding.

[silkysmoothyjud]

Be careful not to break plastic connectors, it does not take much to get it off the injector or to put it back on there. There is only one injector you cannot test that way. see if the misfire changes when you pull the wire. If it stays the same, you found it!! But then you have to narrow it down to plug, injector, coil pack, etc.....

[goody90q45]

I can't even imagine how to do that, How do you remove each connector on by one with the car on?......

The 90-93 has a 3 sided metal clip (same as EGR solenoids) that needs to be removed for the connector to pop off. On the 94-96 you just squeeze the connector clip as shown in the photos.

The metal injector clips on the 90-93 are easy to pull off with the plenum installed but near impossible to reinstall.

This is a moot point for those that have a consult program and can turn off one injector at a time through their laptops.

[silkysmoothyjud]

Interesting maybe I should just stick attempting to advise my year. Consult program? Is it free?