Why is my car insane

[Dansmaxima]

I'm busy working to afford gasoline; but when I get the time; I was told by another mechanic that my erratic high and surging idle problems must be a vacuum leak. I've had the intake parts off including the throttle body, new iacv valve, new mafs sensor, new O2 sensors. I should be doing more tests such as voltage readings and continuity tests as per the factory manual. This mechanic thought I might want to take off the intake manifold, which I don't mind doing at all. Are these cars prone to vacuum leaks at the manifold or injector seals? All this because I can't seem to find anybody to diagnose this tough problem. The service manager at Somerset Nissan gave me a bunch of BS- he looked like they got him from a prison work release program. Dishonest people there. Wasted my money at that place.

[allensteiner]

http://www.motorvate.ca/mvp.php/517

check it out, maybe it's the same problem

[Dansmaxima]

Thanks-- throttle body is so simple- it's completely clean. Everything is coming apart one more time, gonna look from underneath. Then I have one more garage that I'm going to try. Then I'm looking for an antique car with no computer in it.

[Sentientbydesign]

I thought your Max was fixed

Could you go through the exact symptoms again and include what you've done and what effect it's had on your car.

I wanna take another stab at it.

[Dansmaxima]

Sure , thanks very much. I got the car 2 years ago with 94k on it. I knew the sec light had been coming on, the lady was told it was fixed. It was ok for a few hundred miles, then the light came on again, I think it was pulling a catalyst code. It then started coming on every 40-250 miles. I wasn't using the car much, so I would just disconnect the battery overnight. This is how I got it through NJ State inspection just a few months ago. That's clue 1. One time the car stalled, wouldn't idle. I poked around the TPS and other connectors and it stopped stalling. I got hundreds of miles more without a problem. I had just let the sec light stay on with no driveability problems at that point. I had universal Bosch O2 sensors but hadn't felt a need to try that fix. A few weeks ago, it stalled again. I put the universals in carefully, all 4 of them. 2 are 3 wire, 2 are 4 wire. I matched the 2 white to white, and grey to grey and black to black. Then it started idling high and surging. I replaced the iacv and the maf sensor. I tried the idle learning by briefly disconnecting the brown tps connector as instructed by the factory manual. I tried the tps idle reset by turning the ignition on 5 secs and off 10 secs-20 times as described in the factory manual. I had the intake system off including the throttle body. It's clean and reassembled. It idles very high now over 2000rpm, until it warms up, then it starts surging. That's where it is now. No sec light. I need to get much more focused and study the manual, and systematically do every test I can without Consult II and record it. Such as voltage and continuity tests at the ECU terminals where indicated. Haven't seen any vacuum hose leaks, but I will get under the car and see what I can see from the bottom. I did previously put the battery on a 10amp charger for a while. Could I have hurt something in the ECU?Please- this is unbearable hope you can help lol!!!

[Sentientbydesign]

Here's what I would have done.

When the CEL came on, I'd pull the code and figured out which system triggers that code. Some times that narrows it down exactly, sometimes it's 1 of 5 or 6 possible culprits. I would kill the code and run it to see if it would come on again. If it did, then there's obviously a problem.

I would have also installed Nissan O2 sensors, NOT generic. Why? Sensors are very tempermental. Your O2 sensors monitor the amount of oxygen in the exhaust at 2 or 3 locations and the ECU adjusts the Air/Fuel ratio to get it back into favorable specs.

It's kind of like checking your pet's poop to see what nutrients they're missing (excuse the weird simile).

I probably would have not had anymore idle issues after that point. If I did, I'd go on a wild goose chase through the intake step by step trying to fix the problem (as you did).

Idle problems are almost always an intake/sensor problem. I don't just say intake, because some of the sensors are past the TB.

My next suggestions (choose one):

Take it to an exhaust shop and have them inspect your O2 job to make sure it looks right.

Go to a junk yard or the dealer and get new Nissan O2 sensors. If you go to the junk yard, you may or may not solve the problem (isolating the O2 sensors). If you go to the dealer, you solve the problem (hopefully that problem is the same as the one causing your erratic idle).

To all those reading this. I've seen very few people who have this problem really NEED to replace their MAF. It's an expensive piece and there are ways to test it, including borrowing one from another car. Leave the MAF for last!!!

[Dansmaxima]

Thanks for taking the time to help! Very much appreciated. OK- somebody told me here that Nissan O2 sensors are Bosch. It's a $$ factor; if I was wealthy like my employers ( they are worth hundreds of millions literally- mortgage industry moguls) then I would be driving a new car. ( I maintain the exteriors of their mansions.) Point being, dealer O2 sensors would probably be $250 apiece. Very many guys have told me to avoid universal O2 sensors. So....Scientifically, my next move is to do the voltage test on the O2 sensors. At 2000 rpm, at ECM terminal 63 (right bank) or 62 (left bank) the voltage reading should be 0 - .3v ~ .6 - 1.0v more than 5 times in 10 seconds.I don't know why a code isn't coming up if my new O2 sensors are incorrect, maybe it only works if there's an open. Manual says it could also be fuel pressure, pcv valve, etc. I also wonder about the pre cats and the cat-- if it's shot or clogged with carbon from running rich or just worn out could that be screwing everything up.Maybe I should consider a horse and buggy with nothing more complicated than putting bear grease on the axles and a wooden brake lever---

[Sentientbydesign]

The Nissan O2 sensors are between $145-$175 at Riverside Infiniti (Ask for Tony if you order anything from them).

Or call Infiniti of Scottsdale and ask for Joe, he takes care of all of the G35 guys.

Does your car have a clean title?

Also, are you sure your ECU isn't throwing a code, but not illuminating the CEL? I think it's time for you to invest in an OBDII scanner if you haven't already. $60-$70 bucks isn't a large investment, plus it will help you avoid having to disconnect the battery to clear the codes.

[Dansmaxima]

Thanks again! I have a Memoscan scanner- no codes showing! Is there any such thing as a Consult II equivalent scanner?! I could really troubleshoot with something like that! I think it is worth it to do a little more pouring money into my engine compartment. And you put it perfectly, I go on wild goose chases with this problem and need to approach it rationally.

Yes, the title is clean, I keep it in a file folder in my desk......lol

[Sentientbydesign]

There is, but I'm having trouble finding it. There's a company that makes a consumer version.

[Dansmaxima]

That would be fantastic. I'm back to square 1. If it's idling at 2500rpm the iacv must be wide open. something is telling it to do this.

[Sentientbydesign]

Throttle Position Sensor?