EGR System Check

[My_Q45]

Hey

I have a 94 Q45 & are almost finished with all the forgotten maintenance by the previous owner. The drivability is finally good with LOTS of power:ylsuper !

The final problem is a bumpy idle. I changed the plugs to OEM & that was the final step in the power search, but not the Idle. I think it's the EGR system. I first I tested the solenoid's in the front of the car & the black one is bad. I don't know which one is the carbon canister & the egr solenoid. I took the egr valve off & cleaned it. I also checked the PVC valve but it was pretty clean. When I first got this car I had an independent shop do some work. One of the things they worked on was the egr system. So I took a pic of my egr valve section so you guys can let me know if it's properly connected. Also if anyone has a diagram or a couple of pics for the hoses around the solenoids, please post them.

PSSorry the pic is not the best. It's from my camera phone.

[Q451990]

EGR shouldn't have an impact on your idle quality. It only comes on in the medium (cruise) RPM range, not at idle or above about 4K RPM.

I checked your picture with mine and that looks right except yours has an extra hose (probably a difference between 1990 and 1994).

The front solenoid controls the purge canister, while the rear has the EGR. You might check for corrosion on the electrical contacts - had that problem once.

Does the bottom of the valve lift up and flutter between about 1500 and 4000 RPM? Does the engine die or almost die at idle when you push up on the bottom of the valve? If so the EGR system is fine.

I'd suspect dirty injectors (needs a pressurized flush, not fuel additive) for your idle problem. Also dirty plenum and runners, throttle body, etc. if you haven't addressed those yet.

Good luck!

Heath

[sijoko]

The EGR doesn't come into the picture at idle as long as the valve is not stuck open.

If you want to check its operation, put your finger under the diaphragm while you rev the engine. You can also put a vacuum on the EGR valve and the engine should stumble and cut off.

[natsoundup]

Do you use BG44k for a pressurized injector flush?

[Q45tech]

BG has a special injector cleaner that contains more burnable fuel than BG44k [so the car will run at least at fast idle during the pressurized flush]...............44k is mostly detergents and solvents!

Sometimes I mix the 44k in with the injector cleaner ......say add 2-4 ounces to 11 ounces of cleaner...............depends on how severe the power balance numbers are.

In a conversation with the engineers at Bosch/Japan, I was informed that if the injectors last 258,000 miles like mine have, that there is microscopic wear of the pintle shape and the injectors may run rich at idle [instead of the normal lean].

I have wondered why mine were 8-10-12% rich [as shown on block learn test] at idle with the same opening time and fuel pressure [thought I had other problems]. The O2 corrects this at cruise by lowering the open time 0.1-0.2 millisecs. At WOT the few tenths is insignificant in a 10-11 millisecond opening time.

Just wearing out after 10-11,000 hours of use........they only test them for 5,000 hours.

[My_Q45]

I checked the egr valve & it doesn't move when revved. I cleaned off the solenoid connections & I heard it open/close. If I push on the valve while at idle the idle goes low & almost dies. So I determined the solenoid & valve is good. I also checked a bunch of vacuum hoses & they are clean. Where should I go from here?

As far as the rail flush I haven't done one yet. The car has been sitting for quite a while. Today is the first day in 2 years I have gotten a code 55 - which means all looks good for those who don't know. My last question is when starting up the car I'm getting some dark smoke. The fuel in the tank has been in there for quite some time! Is this most likely the cause? I have a 5 gallon fuel carrier which I'm going to fill up today & put in the tank. The tank is almost empty. Do you think it is necessary to get the old fuel out of there first? If so do you have any suggestions?

Thanks for the help. If it wasn't for this board I wouldn't have gotten this far!

[VenCountyQ]

For those members experiencing rough idle problems there is a TSB relating them to a certain faulty ECUs.

Reference: ITB95-040

Date: June 21, 1995

1994-95 Q45 LOW OR ROUGH IDLE

APPLIED VEHICLE: 1994-95 Q45 (G50)

APPLIED V.I.N.:JNKGO1D*SM306154 (w/o ACT)JNKGO1D*SM306156 (w/o ACT)

APPLIED DATE: January 26, 1995

[maxnix]

Hmmm......does that only apply to 3 cars? You quoted the bulletin correctly.

[My_Q45]

Thanks for the TSB, but it doesn't apply to my car.

Manix, if i'm thinking of the vin's right the * is the unknown character. So if it's a number it could be 30 cars or a letter 81 cars.

If anyone has other suggestions, let me know.

Thanks

[Q451990]

I checked the egr valve & it doesn't move when revved. I cleaned off the solenoid connections & I heard it open/close. If I push on the valve while at idle the idle goes low & almost dies.

It never moves? You should feel the bottom lift and flutter in about the 2000-4000 RPM range. Make sure the car is fully warmed up before testing - the ECU blocks out EGR function during warm-up.

Black smoke sounds like flooding (bad injector or lower o-ring) or bad MAF connection. I'd get fresh gas to eliminate that as a cause, but I doubt that's it. Is the car hard to start, especially after a hot soak (e.g. drive for 30 minutes, park for one hour, then restart)? When you mentioned a bumpy idle, does it really feel like the car is "bouncing" or just a bit irregular. I should have been reading more carefully, but it sure sounds like you have a dead miss on one cylinder (usually a bad injector).

If you have a non-contact IR thermometer you can isolate the bad cylinder during warm-up by checking each leg of the exhaust manifold. The bad one won't heat up much. A Consult power balance test would tell you a lot as well and is really the best way to check it. Also, search here for the "ohm test" method to check resistance.

If you don't have any of the above, you can typically find the bad cylinder by removing the spark plugs and finding the one that looks different. Mine were always black and typically wouldn't spark w/o cleaning after an injector failure.

Other things to check. Does the idle speed change at all when tapping the MAF connector, CAS connector, etc? Any change is bad and needs to be repaired by cleaning corrosion, tightening connectiors, etc.

Good luck!

Heath

[My_Q45]

Thanks Q451990 for the long detailed post.

I may not have waited long enough to check the egr valve. I'll try that today hopefully.

I recently did the plenum job due to bad knock sensors. Before I did this I ohm tested the injectors & found 2 bad injectors. Since then I replaced them. Just this week I also replaced the spark plugs & they all looked the same. I don't have a IR thermometer so that's out.

The idle speed doesn't change but the engine is bouncing enough that you can feel it in the cabin. A couple of years ago I had the engine mounts changed. As far as starting it starts right up. I'm currently not using this car since it's been sitting in my garage & the registration has expired. I have to get emissions testing done on it so I want to make sure I past the first time. So I really can't drive it around for an hour. It has idled for 30+ minutes & went back to it about an hour later with no problem starting.

The MAF & CAS are good. They do not affect the idle when wiggled. I've read about adding a grounding wire to the maf. Would this help my situation. What wire would it go from and where should it connect?

Thanks for the suggestions...

[maxnix]

Usually, there are no grounding problems with the later MAFS (as Infiniti refers to them) connectors. Probably is worthwhile to trace the ground to verify it is functioning correctly.__________________Brian1995 Q45 & Q45t & 2000 Q45

Discover the power of the button!

[Q45tech]

The ground corrosion affected the idle as 1.200 volts might have been off by +-0.05/maybe 0.09 volts.........other than that you would never notice the variation.

[My_Q45]

It's possible the maf is failing in which case what are the test procedures for the maf? Which wires do I probe & what should the readings be?

[Q451990]

Remember that just because the injectors ohm out correclty, they can still be physically clogged. The bouncing you describe is definately a symptom of a dead miss. I think your best bet is to get it to a dealership and have a power balance test done. That and a quick scan of the other systems will tell you a lot! Have them give you print-outs of the results and post them here.

The power balance test cuts each injector off one at a time while monitoring the overall RPM level. It then computes the contribution that each cylinder is making to the overall total RPM. If one is significantly lower than the others, there's your problem. Often, a pressurized flush will clear out the screens and injector mechanical parts and solve these problems.

Heath

[Q45tech]

A cylinder that is not firing is a drag on the motor because of the horespower loss to compress the air is still there without the corresponding gain later.

During the power balance test the IAC is held wide open allowing enough air to run 1000-1100-1200 rpm...............the higher the test rpm to a point the more sensitive the test is.

If the TB is dirty the IAC may not supply enough air to reach these higher rpms............so the enhanced base [test idle] is another thing to analyze.

Important that the IAC only have a 10-15% duty cycle [when you adjust speed screw out 2-3 turns from bottom] at the stated [non testing] idle rpm so that it has enough dynamic range to handle throttle lifts at 60-70 mph and reserve for AC, power steering, alternator loads.

In winter the preciseness of the hot/cold wax/spring warm up TB cam is important as this force opens the TB minutely to add the extra air needed that the IAC cannot provide to get 1500-1750 rpm. It progressively closes the TB as the circulating coolant warms the wax until around 100F then the IAC has enough reserve to begin to maintain the idle and still correct for sudden steering loads.

Remember at idle there is no excess power every thing is in balance to maintain the idle speed. A steering manuever can demand a sudden 3-4 HP.........either the idle speed drops or the IAC adds air and the ecu adds fuel to maintain..........the quickness of response and overshoot is a clue!