Yo-Yo Idle

Nissan 300ZX technical discussion forum: Maintenance, performance, installations, modifications, how-to's and troubleshooting.
udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

I've seen the posts similar to mine with 0 responses, I've also seen pleasant people post "don't bring back an old thread post a new one" so here we go:

I have 90 NA That yo-yos back and forth between 1500 and 2000 rpm cold or warm engine does not change the condition. If you touch the gas it's like going WOT even though you BARELY touched it... rpms drop dramatically to a normal 600 and then pop back up to the 1500-2000 yo-yo

- I have replaced the IACV-Air Regulator
- I have replaced the IACV-FICD
- I did a smoke test and found no leaks (vacuum)

This is a project car my son and I sourced engine parts, etc and finally got put together


udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

I did just test all the injectors and they read between 15-17 ohms for resistance... so I'm assuming ALL the injectors are bad?

User avatar
NolimitZ32
Posts: 7112
Joined: Fri Jun 27, 2008 9:07 am
Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

Post

Where did you source parts?
What parts have been replaced?
Are all parts OEM?
Is the ECU producing any codes?
There are numerous issues that could be causing this type of behavior. You'll have to go down a couple rabbit holes before anyone will be able to really help you. Check the troubleshooting section in the FSM (see my sig).

udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

I've been getting responses like, set the TPS. So once I install the new injectors I'll set the TPS and su what results I get

User avatar
NolimitZ32
Posts: 7112
Joined: Fri Jun 27, 2008 9:07 am
Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

Post

The TPS being set incorrectly would cause high idle but it wouldn't make the engine rev as you describe. And if the injectors' resistance is too high it would cause the car to run leaner than mapped and would definitely have the opposite affect of overeager revving.

udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

Sounds like a good place to start esp if the injetors resistance is proving they are on their way out. If one causes over reving (TPS) and the injectors causing "the opposite affect of overeager revving" it sounds like both of those are ping ponging so to speak. Adapter kit will be here Wed and I will put it back together and see if there is a code.

User avatar
NolimitZ32
Posts: 7112
Joined: Fri Jun 27, 2008 9:07 am
Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

Post

You don't need the car running to pull the codes as long as you haven't disconnected the battery. And you should pull codes before you fix/replace anything to see if there is a correlation. Unless you've had the EFI harness and all electrical/electronic components replaced, often enough faulty connections cause weird issues which are usually easier to identify when you get the before and after effect of swapping parts. In theory what you're saying makes sense but I've never seen such behavior materialize in practice. Lots of other sensors have an effect on the idle such as the coolant temp sensor. After you get the injectors in and set the TPS take a good look at the FSM, swapping parts will get really expensive really fast.

udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

I agree, thats why I'm not looking to go that route. The new injectors were given to me from a buddy doing an LS swap. My injectors proved to be faulty regardless so I'm swapping them. The car was cleared as my was fooling with the side of the ecu to read the codes and put it in read mode, then instantly back... I explained to him he just cleared them... thats why I have to wait for the next start up to grab codes. Setting tps isn't swaping parts and more than likely needed to be done as the car was a barn yard find... the engine is from a local guy's car we grabbed so we have double of all the sensor's, etc to use and test. But yes I like real codes to have a good direction vs buying a ton and wasting a ton on things that aren't the problem.

User avatar
NolimitZ32
Posts: 7112
Joined: Fri Jun 27, 2008 9:07 am
Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

Post

Ok. Good to hear you're taking a pragmatic approach.

udfxrookie
Posts: 28
Joined: Wed Dec 16, 2015 9:09 pm
Car: 2008 Nissan Altima

Post

****FIXED****
TPS and injectors... Injectors were bad and TPS was waaaaaaaay off. She fired up and idled smooth (very low, but now it's easy to fix/adjust)


Return to “300ZX (Z32) Technical”