1990 Q with pre-detination at around 6000 RPMs.

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mattd1979
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Car: 1990 Pearl White Q45 plain Jane with 266,000 miles. 2015 moonlight white metallic Q70L with 20” wheels, sport brakes and a 5.6L at 58,000 miles.
Location: Jacksonville

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I really wish I could figure out this issue I have been having with pre-detonation in the upper RPMs when I get to 6000. The engine has 263,524 miles on it and the fuel filter is new, the plugs were changed a few months back with NGK Laser Iridium plugs part number IFR5E111 or stock number 7994. It has the later model fuel injector assembly in it, I run only premium 93 fuel in it. My buddy's 91 has 291K miles on it and hauls a**. His car has always had more power than mine. It was proven on a dyno when I put both cars on it a few years back. His was beating mine by 30 HP and his was stock and I was running the NICO ECU in level 3 mode. Since then the engine had been replaced in mine and I had also replaced the transmission do to losing 2nd,3rd,and 4th gear. I thought for sure that when I replaced the engine that the power would have been back to his level. But there was no change. Before I put the engine in my car, I made sure to swap the timing guides over to it because it had 199k miles with plastic broken guides. I have noticed at times that when accelerating at full throttle from a stop, the car kind of wants to surge and then when it hits 4000 RPMs it takes off like something is wrong with the VTC. Then it starts to pre-detonate at 6000 RPMs. The fuel pump is good because I checked the fuel pressure which measured 45 PSI with the vacuum line disconnected. I even bypassed the fuel pump controller and ran it at full speed to see if that made a difference which it didn't. Sorry for the long drawn out paragraph but I just wanted to get everything down that I could think of. I hopefully somebody here has some ideas that I can try that I haven't already tried to get power back that I have always lacked and also eliminate that pre-detonation. There is also something else I have noticed in the past that sometimes I here a hum from under the car in the rear passenger side after the car has been off for a little while. I found a relay or something like that and what looks like a valve. I looked through the FSM but couldn't find any mention of it.

Matt


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Brew Q
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Car: '92 Q45 91k miles, '05 FX35
past: '99 740i (r.i.p.), '92 Maxima SE, '89 Maxima SE, '04 FX35
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Here's my 1 cent, some others may chime in with 2!

What injectors does the new motor have?

I think the humming you hear is most likely the fuel pump. Even if it is putting out 45 psi, I wonder if it is not getting the job done at 6k rpms. Also the control unit for the pump? This is a replacement how to, but it has some other things to try that might help you - BUT a direct quote "Online mechanics say
the clearest sign of a bad pump is HUMMING."
http://www.nicoclub.com/archives/q45-fu ... ement.html

Personally, my Q is getting one of these and its Ethanol compatible and Deatschwerks will even sell you an install kit for our Q:
http://www.deatschwerks.com/products/fu ... 300-detail

Another thought, does it detonate on stage 1 and stage 2 or just 3?

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mattd1979
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Car: 1990 Pearl White Q45 plain Jane with 266,000 miles. 2015 moonlight white metallic Q70L with 20” wheels, sport brakes and a 5.6L at 58,000 miles.
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The hum occurs after the engine is off, key removed and it has been sitting a few minutes. I ended up climbing under the car one day as soon as I heard it to try and track where the sound was coming from and found a solenoid of some sort and a relay on the passenger side on the inner side of the frame rail at the highest point behind the wheel. The injector assembly is from a 1995 Q45. The engine seems to detonate regardless of which mode it is in.

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Q451990
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Did you have the problem before you put non-OEM spec plugs in? It might be worth playing with the timing a little...

Heath

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mattd1979
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I have had this same problem since I bought the car. I had just been driving it like it is until I drove my buddy's 91 that has been in the extended family since 2004. After driving his, I got the itch again to try and figure out (with help from here) what the deal is with mine. I thought I might try and step down the heat range to a colder plug. Unfortunately I just don't have the money right now to go by another set since I am between jobs and have been working here and there and fixing various things for people to keep the bills paid until a full time job comes along again.

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Brew Q
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My bet is gotta be fuel related... iridium plugs are great plugs and worth the money if you ask me. I ran them in a Maxima with bumped timing and never had problems, but of course that's a whole different motor.

How many miles were on the '90 when you bought it? Maybe the pump was not up to snuff then. Also check the controller for melted solder joints, connector melting, etc.... you'll have to pull the rear seat and shelf out to get there, but you may find your answer.

Hopefully others with much more experience than me will chime in.

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mattd1979
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The engine had 199K miles on it when I swapped it in. It had 4K miles more than the engine that came out of the car but seemed to be in better shape. It didn't smoke on start up and the oil pressure was where it was supposed to be and would increase when RPMs increased to 75PSI max. The other engine would clime close to 50 and then start falling off as RPMs would increase. I beefed up the ground terminal on the FPCU and ran an additional wire inside the controller to help in the event that another fuel pump were to go bad and put more of a load on the controller. I did this a couple of years ago and it still looks good.

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Brew Q
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So both motors did this...and FPCU is fixed. This is the 2nd fuel pump?

MAF is good and the connections are good? Put some dielectric grease on the connections and plug it back in. I've heard of oily MAFs (like behind an oiled K&N filter) that caused high RPM detonation - Dirty sensor or bad connections could do the same. If no dice there, try either your buddy's MAF or a junk yard one (never know with the junk yard MAFs though).

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mattd1979
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I replaced the MAF with a new one a few months back because it was stumbling and stalling and cleaning didn't help. I since swapped it with my buddy's a couple of months ago with no change. His hasn't changed either. I wired in a good replacement pigtail for the MAF yesterday and cleaned the connections to it along with the TPS primary and backup connection using De-Oxit cleaner. I unplugged both VTC controllers and drove it to see how it did. I noticed that obviously the lower end power wasn't there but the pinging went away on the top end.

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mattd1979
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I should add that when the temp is 60 or below, the engine feels almost as powerful and responsive as the 91 Q that we have which has 292K miles on it. It also doesn't ping win the temps are down in that range. The 1991 seems just as powerful in the summer as it is in the winter. I am beginning to wonder if maybe the outer ring of the crank pulley may be off slightly and when adjusting the timing to the 15 degrees it calls for, it may be off a few degrees. Is it possible for the outer ring of the pulley to shift and it still feel firm when you try to budge it to check for looseness?

Matt

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mattd1979
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I decided to check the timing yesterday after the car was warmed up. The idle was at 650rpm and the iacv was disconnected. I found that the timing was at 13 degrees. I was expecting it to be around 15 to 17 degrees or more by the way it has been pinging at around 6k. I decided to back it down further to around 10 degrees. I don't know how it was down to 13 degrees unless the outer ring has slipped slightly on the balancer causing it to show a lower reading then what it really is.

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mattd1979
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Location: Jacksonville

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I drove the car a few hours ago and noticed that the pinging so far is gone. At lower RPMs the torque isn't as strong as before but also I noticed that when at WOT the engine seems to take longer to accelerate but as soon as it hits 4000 RPM the engine takes off like I just sprayed a small amount of NOS.

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Brew Q
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Interesting... maybe before dropping the timing the knock sensors were killing the timing and hence power?

How clean do you think the inside of the motor is? carbon deposits can cause detonation too. Forgive me if you've already been down this road :crazy:

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mattd1979
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I replaced the o2 sensors a couple of years ago. According to qsiguy the o2 sensors are ignored with the ECU in level 3 mode and it was still pinging. I do not know how the engine looks internally since I haven't had the heads off or the valve covers off since I resealed the engine and put it in the car. At the time when the valve covers and the oil pan were off, everything had a golden yellow tint to it where the surfaces were machined and more of a dark gray appearance in the cast areas. I try to change the oil every 3000 miles though at times I have gone as much as 5000 miles before changing the oil. I run Mobil1 0W40 in it along with a PureOne oil filter. I try to change the air filter every 15000 miles. The plugs were changed more then a year ago and are NGK Iridium IFR5E11 plugs.

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mattd1979
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I was heading back from the store today and I needed to get around someone so I went WOT and when it got to 5500 it started pinging and so I backed off the throttle. I have it almost at 10 degrees btdc and it is pinging again. I don't know how it does fine one day and then it pings the next. This time at an even lower RPM. Before I backed down the timing the pinging didn't start until between 6 and 6500 RPM. The outside temp was 81 degrees. The other day it was 77 degrees and not a single ping after retarding the timing. I just can't seem to figure this thing out. :gotme

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mattd1979
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I did a compression test after I drove the car today and I took some pictures of the spark plugs. The plugs have around 17,600 miles on them. Here are the readings:

Driver side
Cyl 1: 195psi
Cyl 3: 193psi
Cyl 5: 193psi
Cyl 7: 195psi

Passenger side
Cyl 2: 200psi
Cyl 4: 195psi
Cyl 6: 195psi
Cyl 8: 195psi

The average compression according to the FSM is 185psi and the minimum is 142psi. The difference between highest and lowest cylinder is not to be more than 14 psi. Mine is at 7psi from the lowest at 193 to the highest at 200. So the engine looks to be pretty healthy in terms of compression.

Here are the pictures of the plugs:

The first two pictures are of both sides of the driver side from left to right 1, 3, 5, and 7.
Image

Image

The second two pictures are of the passenger side bank from left to right 2, 4, 6, 8.
Image

Image

The F that you see represents the front of the engine. Notice how the color of the tip of the plugs are different when you view them from the other side. I'm not really sure why that is. As mentioned above, the plugs have around 17,600 miles on them.

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Q-ZILLA
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FWIW, I'm running NGK BKR6EIX plugs. That motor has good compression.

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mattd1979
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What is the average compression on these engines usually with this many miles do you know? Also, do you think that a restriction in the exhaust could cause pre-ignition (pinging) in the upper RPM range? I mentioned earlier I think that when I go WOT I have also noticed that during the times when it isn't pinging which was only when it was down in the 60s is that when I noticed that the power was falling off towards the 6000 RPM range, I would begin to lift my foot off the pedal and the power would seem to return. It would feel strange. The exact opposite of what you would expect when lifting off from WOT gradually.

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Q-ZILLA
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FSM says 185 is standard, 142 minimum. 195 is good. IDK about the rest, my setup is completely different and I'm not a master mechanic...

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mattd1979
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I just wondered if you had done a compression test in the past on a N/A VH before and what the highest average out of all 8 was. I was a bit surprised that the readings were as high as they were. I was glad but just didn't expect it on an engine that is getting close to 300K. I did make sure to do the compression test after I drove the car so those are hot readings that I took.

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mattd1979
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I guess I better tell my brother the same. His 91 has close to 300k on it and it sees over 6000rpm half the time he drives it. He has his NICO ECU hard wired to level 3 at all times LOL...

rabsusa
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ya just realize you re running a 24 yr old car right upto its limits,,,,having had this car from 90k miles new n 4 yrs old (Q1) i can tell you i was not able to get what you were talking abt unless i used amoco ultimate clear gas - not sure what its called now. With everything else renewed, you ;ll prolly need flow matched injectors and new IAV to achieve what your aiming for. Mine seldom sees 4k rpm anymore, trans has too much slack in it now

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mattd1979
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rabsusa wrote:ya just realize you re running a 24 yr old car right upto its limits,,,,having had this car from 90k miles new n 4 yrs old (Q1) i can tell you i was not able to get what you were talking abt unless i used amoco ultimate clear gas - not sure what its called now. With everything else renewed, you ;ll prolly need flow matched injectors and new IAV to achieve what your aiming for. Mine seldom sees 4k rpm anymore, trans has too much slack in it now
They call Amoco 93 white BP 93 now. BP bought out Amoco and phased out their fuel. If everything you said was true in the above quote then my brother's '91 would be experiencing the same problems. He isn't. The car seems to have as much power now at close to 300k as it did when my mom bought it back in December of '04 with 199k on the clock. Sadly it hasn't seen the maintenance that it use to get and it still out performs. The power is right on tap with the throttle. It seems linear. The more you give it throttle, the more power it puts out. And it doesn't have to downshift to go up the same bridge as mine to maintain the same speed. I was sold on the car for sure after driving her's. I had to get one and I finally was able too but I have never seemed to be able to get it to the same power as her's as proven on a dyno. I'm beginning to think that the problem lies in the catalytic converters and they may be partially clogged and not operating fully. I measured the temp before and at the cats and found that there was only a 50 degree difference. I believe it was 350 degrees before and just over 400 degrees at the cats. That is the only thing I haven't replaced on the car yet. I also believe that as long as you keep regular maintenance changing your oil, oil filter, and air filter you should be gold. The weakest link I have seen is in the transmission. The only other thing I would do to help keep the engine together is use a good set of ARP fasteners to the bottom end for good insurance.

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Infinitiguy19
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I can only add that when redlining a engine you must be sure everything is properly balanced and oiling is not an issue. If you know how to fix it, you can afford to break it.

OwnerCS
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Matt - If I had this issue, I think I would use the ECUTalk handheld diagnostic unit while driving recreating the issue to display vital ECU readings. If I didn't have the handheld unit, I would use a laptop and get someone to ride with me and snap record the vitals into a comma separated file for later importing into a spreadsheet to analyze the readings. I wish you were closer. I have the handheld unit. I've used the ECUTalk USB cable and software with success several times in the past.

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Brew Q
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I still think it's carbon build-up on top of the pistons or piston pre-igniting fuel causing detonation. He seems to have checked everything, compression, power balance test, injectors, fuel pump... but it is a higher mile motor, that's why I think it has some build-up. He's run cleaners through it, but still does it...

Matt, if you want to borrow my ECU talk, I'll mail it to you. You can download the software for free to a laptop and the rest is plug n play. PM me if you want to try this

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elwesso
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First off, I cleaned this thread up with all the useless posts. There will not be any more "sorority house" type banter any more.. Try me if you'd like to find out what happens next. Not only do you make yourself stupid, but you also make our community look bad, which our Q resource is as good as any other resource on the internet for anything.

Looking thru the thread again, everything looks good on paper Matt.. My engine at 180k had basically the same compression numbers as yours (and I drive my car hard). What I find interesting is that the 2nd cylinder in on both banks looks to be running the leanest. They all look a little lean though.

Carbon build up is possible, however it's odd that it would happen at such high RPM and no where else.. Most times you see detonation at low speeds under load.. SO normally you'd see it say at 40MPH in 4th gear during lockup, or climbing a hill in 4th gear, or something like that....

What I find interesting is that the same thing happened on 2 different engines in the same car, which means it has to be something specific to the vehicle. Carbon buildup isn't really that big of a problem on the Q engine, especially to the point where it would cause detonation. I've never heard of that, even on cars that are babied. The cats could be another issue, you can always gut them out to see if that does anything, and then replace as necessary. You also have a set of cats in the exhaust manifolds that would probably be worth looking at too. It won't cost anything to gut the cats.

I think the next route would be to inspect the cats. If you ever had a bad injector or continual misfiring, that would destroy the cats. If it were me, I'd probably start with the cats in the exhaust manifolds.

OwnerCS
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elwesso wrote: Looking thru the thread again, everything looks good on paper Matt.. My engine at 180k had basically the same compression numbers as yours (and I drive my car hard). What I find interesting is that the 2nd cylinder in on both banks looks to be running the leanest. They all look a little lean though.

Carbon build up is possible, however it's odd that it would happen at such high RPM and no where else.. Most times you see detonation at low speeds under load.. SO normally you'd see it say at 40MPH in 4th gear during lockup, or climbing a hill in 4th gear, or something like that....

What I find interesting is that the same thing happened on 2 different engines in the same car, which means it has to be something specific to the vehicle. Carbon buildup isn't really that big of a problem on the Q engine, especially to the point where it would cause detonation. I've never heard of that, even on cars that are babied. The cats could be another issue, you can always gut them out to see if that does anything, and then replace as necessary. You also have a set of cats in the exhaust manifolds that would probably be worth looking at too. It won't cost anything to gut the cats.

I think the next route would be to inspect the cats. If you ever had a bad injector or continual misfiring, that would destroy the cats. If it were me, I'd probably start with the cats in the exhaust manifolds.
+1 - I recently had an ordeal with my 99 Maxima where I had a series of strange (hard to start from flooding, engine wouldn't idle, engine wouldn't start, you name it across the board issues) on the 2nd engine that the dealer couldn't find that were caused by the following problems. In my case one problem helped cause the next.

1) Broken injector pintle caps on two injectors (Phase II type) resulting in way too much fuel on cylinders 2 and 5 (yep both banks). Since the original injector rails were moved to the newer engine, it inherited the problems from the old engine.

2) Cooked/plugged up cats. After I had the car towed home from the dealer and paying $750 (ouch) for another misdiagnosis, I removed the upstream O2 sensors so the engine it could breath and it started up. Once I got it running with the O2 sensor holes open, the excessive carbon build up started burning off and it would start and run without issue. Again, the newer engine inherited cooked/plugged up cats, bad injectors, and all of problems that plagued the original engine.

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Brew Q
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good points... He said it would ping with the original injectors as well. Even if the fuel pump is putting out good pressure, could it not be flowing enough at 6k?

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mattd1979
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Car: 1990 Pearl White Q45 plain Jane with 266,000 miles. 2015 moonlight white metallic Q70L with 20” wheels, sport brakes and a 5.6L at 58,000 miles.
Location: Jacksonville

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I know that some of the pintle plastic rings were broken on a couple of the injectors but didn't see any way they would affect the spray pattern as they never sat in the path of the nozzles from what I could tell. The engine runs smooth with a slight erratic stumble at idle if left idling more then a couple of minutes.

I have noticed that during moderate acceleration that the engine seems to have the same amount of torque and power as compared to the '91 until you get to 1500 RPM and then it feels like it starts to drop off in power until it climbs to 2000 RPM and then it starts to come back. It is strange the way it acts. If you were riding with me you would think that I was easing in and out of the throttle even though I am holding the throttle at a fixed point. I have also noticed that if I hold the pedal to the floor when accelerating to enter the freeway that as I am lifting my foot off of the pedal gradually the power seems to increase.

I have ECUtalk installed on my laptop and the cable. I will try to rig up a fuel pressure gauge that is long enough that I can have it in the car to read more easily as I am accelerating and I will also record with ECUTalk and I will attach it to a post for OwnerCS to decipher and review and maybe someone can make heads or tails of it.


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