6

Background:

I had my 2003 Infiniti g35 at the mechanic to fix an electrical problem (turns out remote starter wires were rubbing and causing a short) and to fix an oil leak. All in all they changed the ignition fuse and a couple relays, and the oil cooler seal.

Problem: Ever since I got it back from them the car turns off most of the time immediately after starting it. It looks like it's due to the RPM dropping very low, and if I give it gas in the first second it is able to overcome that initial drop and go on to maintain 200-1000 idle RPM and doesn't turn off. Basically this video is exactly what I experience: https://www.youtube.com/watch?v=RKFe76479ws

The mechanic suggested seafoam with premium gas, which I tried but it did not fix this problem.

Based on my research it seems like this would be caused by a dirty throttle body. This car never had these issues before I took it to this mechanic.

My questions are:

1) Does that diagnosis sound correct?

2) Is it possible that the mechanic unintentionally caused this? (Maybe they got some dust on the throttle body or something?)

3) Is it true that Nissan and Infiniti throttle bodies should not be cleaned by someone who is not an expert (i.e. dealer) due to it being a delicate operation and easy to mess up and require some sort of electrical reprogramming?

Thanks!

  • Did you ever get this issue resolved? What was the fix? – DucatiKiller May 3 '16 at 0:58
  • In case you weren't aready: The VQ35DE engine in the G35 has a high compression ratio (11,9:1 IIRC) and should always be run with premium gas. As for the TB, you can definitely do it yourself. I read the same thing about having to do a throttle control reset, but I disconnected the battery, took of the TB, cleaned it with carb cleaner, reinstalled it, and started back up with not issues or reprogramming. – MooseLucifer May 18 '16 at 23:30
  • @DucatiKiller Not yet, been taking my time since RPM was only dipping on startup and this can be worked around by giving a bit of gas every time I start the car i.e it is not a critical problem. Current suspect is MAF sensor and I hope to update soon. – user453441 Jun 24 '16 at 14:14
3

1) Does that diagnosis sound correct?

Seafoam sounds like a good way to go, but in this case it isn't going to cure the ill. The throttle body itself needs to be cleaned. I found this video which should show you pretty much how to clean it (as long as your engine is the same as the G35 in the video). Since the engine has reusable gaskets, as long as you are careful with the removal and installation of the throttle body (TB) you won't have any issues. You are just trying not to damage it, which in actuality shouldn't happen with the TB removal. If the TB to manifold gasket is dried out and cracked, it will need replacement, though.

The reason I said Seafoam isn't going to do much for you as the mechanic suggested, it's because adding it to the gas tank will not clean the TB. It will clean the fuel system and injectors, but won't make it to the TB because the top end of the intake tract is dry (meaning gas is not found there). You could possibly use Seafoam using this method, which may help some, but even in this case, it wouldn't get to the TB, so you'll need to use the carb cleaner method to accomplish.

2) Is it possible that the mechanic unintentionally caused this? (Maybe they got some dust on the throttle body or something?)

You never know about this as who knows what goes through the mind of a mechanic, but for the most part, mechanics are not going to do something to your vehicle, especially if this is a mechanic which you've known for a while. The reason I say this is because, while they want business, repeat business is where the money is at. If they start screwing their patrons over by doing things to their customers, they will soon find that through word of mouth they will run out of customers and business. I'm not saying there aren't shady mechs out there, I'm saying that they are usually few and far between. I would personally stay away from shops which have the moniker of "The Honest Mechanic" or some such, but that's just me ;-)

3) Is it true that Nissan and Infiniti throttle bodies should not be cleaned by someone who is not an expert (i.e. dealer) due to it being a delicate operation and easy to mess up and require some sort of electrical reprogramming?

I personally have not done a TB cleaning on Nissan/Infiniti vehicles, but looking at the video I posted above, it doesn't look any more awkward than any other TB I've seen. As long as a person is careful (as in not banging the TB around), there should not be any problem with a layman cleaning the TB. You do want to be careful with not over tightening the four Allen head screws which attach the TB to the intake. Other than that, ensure you are using a good brand of carb cleaner, such as CRC and you should be golden. The only things I'd do differently is to wear some nitrile gloves to keep the cleaner off of your hands and don't use a rag to clean out inside of the TB. Instead, utilize enough of the cleaner to flush the residue off of the TB. Just be ready with a couple of cans of the stuff and there shouldn't be an issue. The carb cleaner will completely evaporate, so it won't leave any residue behind on the engine and such, but put a rag under the TB while you are at it if you like to catch the cleaner and gunk as you clean.

  • Thanks, to clarify I was asking if the mechanic could have accidentally caused that issue. It's strange to me that it never happened before but started happening right after I got it back. – user453441 Mar 13 '15 at 14:51
  • @user453441 ... Sure, the mechanic could have inadvertently done something to it, but it's doubtful. Anything is possible. – Pᴀᴜʟsᴛᴇʀ2 Mar 13 '15 at 15:51
  • do not use carb cleaner on throttle body. use throttle body cleaner. I am not sure if your car/model has any kind of coating, but i think a lot do. – Zero Jun 3 '16 at 1:42
1

Your issue could be a camshaft position sensor going bad. My G35 wouldnt start right away unless I gave it some gas. After 8 months..car stop accelerating while driving. Issue was camshaft position sensor bank 2. It was an easy fix, I just youtubed it. Part was $100 at AutoParts store.

0

It's very possible that the TPS sensor pigtail was not fully locked in when reconnected. I've had this issue before when I failed to push the connector in far enough.

Since this question was posted in March, I assume you have resolved it. Please share what the outcome was.

Additionally, seafoam + premium gas was a horrible suggestion for this issue. If it didn't do it before the repairs, then it was most likely something the mechanic did or didn't do or didn't do correctly, such as not plugging in connectors which is easy to miss or do incorrectly.

0

I just fixed the same problem on my 2003 Infiniti G35. It's an easy fix. Clean the throttle body. All you need is some WD40, tooth brush, and electric motor spray. All you do is hold the throttle open and spray WD40 on the tooth brush. Brush around the throttle body's inside, then wipe out with a cloth. Spray it out with electric motor spray. Repeat until clean. Use a cloth to hold throttle open and do the top and bottom both.

0

The problem was caused by a tear in the air intake boot. I think the other reasons mentioned in other answers could also cause the same symptom. I have no way of determining whether or not my previous mechanic had inadvertently caused the issue.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.