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AZTechBrian
AZTechBrian, ASE Certified Technician
Category: Nissan
Satisfied Customers: 708
Experience:  Owner
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1994 Nissan Hardbody RPMs drop to 300-500 while at red light

Customer Question

1994 Nissan Hardbody RPMs drop to 300-500 while at red light
Submitted: 1 year ago.
Category: Nissan
Expert:  AZTechBrian replied 1 year ago.

Hello. Is this an intermittent problem or is it constant? If it's an intermittent problem, there is a TSB that pertains to it. If it's constant, try first cleaning the throttle body with brake cleaner and a rag and a tooth brush.

Finally, have you checked for diagnostic codes?

Customer: replied 1 year ago.
It happens about 80% of the time. What is a TSB. And I'll try the throttle body cleaning tomorrow. Can I use carb cleaner since I have that already. I have not checked for codes because the heck engine light is not on. Thanks
Expert:  AZTechBrian replied 1 year ago.

Yes you can use carb cleaner. The TSB is a technical service bulletin. It helps us quickly identify common problems. When a problem is rather common on a particular vehicle, a tsb is often submitted. If the cleaning of the throttle body doesn't work, I can email you the TSB

Customer: replied 1 year ago.
Ok I'll clean the throttle body today when I wake up and I'll let you know if that fixes it.
Expert:  AZTechBrian replied 1 year ago.

While your at it, apply power to the IAC located on the side of the throttle body. See if it clicks.

Customer: replied 1 year ago.
What is a IAC and apply power how. Alligator clip from battery?
Expert:  AZTechBrian replied 1 year ago.

Yes. That will work fine. IAC is the idle air control valve. It has a lead on it with a connector with a couple wires. It should click with power applied if it's not sticky. If it's sticky, it would cause this issue as well. Clean the throttle body first though. See if it fixes the problem.

Expert:  AZTechBrian replied 1 year ago.

here is an illustration.

Customer: replied 1 year ago.
Ok I let u know
Expert:  AZTechBrian replied 1 year ago.

sounds good. Thanks.

Customer: replied 1 year ago.
Just making sure. Is throttle body located directly under the air filter?
Expert:  AZTechBrian replied 1 year ago.

yes.

Customer: replied 1 year ago.
I cleaned the throttle body the best I could and that helped a little. I didn't have any wire to check the other thing. As soon as I get wire I'll check it.
Expert:  AZTechBrian replied 1 year ago.

Sounds good. Here is a picture of it. Since you have carb cleaner, you can remove it and clean the carbon out through the holes on the mating surface. After a while, they get sticky and don't function nearly as well as they should.

Customer: replied 1 year ago.
Can you email me the TSB just so I can read it
Expert:  AZTechBrian replied 1 year ago.

The TSB is directed toward intermittent idle fluctuation, or surging. It indicates a bad connection at the splice on a black and grey wire coming from the computer and branching 3 ways going to the throttle position sensor, engine temp sensor and exhaust temp sensor. the splice is located on the top of the engine toward the back of the valve cover. If you would like me to email you the TSB, I will gladly do so. I would send you an additional service offer and you would provide your email address there.

Customer: replied 1 year ago.
Ok that's too advanced for me lol. I'll work on the wire thing later
Expert:  AZTechBrian replied 1 year ago.

It's not too bad. You would just have to either Re solder that splice, or check continuity at the splice. I'm sure once you saw it you would realize that you could easily handle it. Look for it when your checking out the idle air control.

Customer: replied 1 year ago.
I didn't forget about you. I'm working nights and can't get a lot done during the day
Expert:  AZTechBrian replied 1 year ago.

Not a problem. I'm here when your ready. No rush.

Customer: replied 1 year ago.
I'll prolly work on truck tomorrow and let you know
Expert:  AZTechBrian replied 1 year ago.

OK. I'll be here. If I don't reply right away I'll reply asap. Thanks!

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