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Discussion Starter #1
Still having stalling problems with my '91 3-5FS franken motor. PO had put misc parts of two motors to make one.
Today I pulled off the NSS and after cleaning and refurbishing it found that one of the male prongs on the wire connector was corroded off.....GONE! No way to fix it so had to order a new NSS. Those honeys are not cheap! :devilish:
Took the TPS apart and found that one of the contacts was burned and not making connection, just had to sand the contacts and tested ok.
Question for you gurus,, would a non functioning TPS cause stalling after a few minutes of idle?
Would a missing wire contact on the NSS cause stalling or stuttering during up shifts of the auto transmission?
 

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The NSS controls the starter circuit. Once started, the circuit is deenergized by the ignition switch.

The TPS provides throttle angle info to the ecu for
  • timing of egr opening
  • timing of the gear change
  • initial adjustment of fuel trim changes

The TPS provides a variable resistor type change to a std voltage (potentiometer). When heated up, the resistance can increase.

YES, the TPS is possibly contributing to your problems.
 

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Discussion Starter #3
After looking at other info the tps on this intake has just three contacts. It is not a pot. Two contacts inside. When the throttle is closed one set of contacts is closed than open when the throttle opens, about 3/4 throttle the other set of contacts close to complete another input to the ecu. Everything I've seen on the net is a pot with four contacts. That's what makes another conundrum with this franken 3s-5s motor. Weird. Anyway, I cleaned all the contacts and set it up according to specs. .026 gap. Installed a new NSS today. I've had lots of experience with these when I had my Jeep XJ. Good thing is I now have back-up lights :)
Engine started right up and ran smooth and quite responsive but after a few minutes it stalled again. Problem seems to narrow down to fuel. Got spark, air, timing is spot on. I'm going through the complete Celica repair manual FI section for step by step trouble shooting. Two steps forward, one step back. Others have/had this same problem but no one has posted a solution. It will get fixed and then I'll post.
 

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Discussion Starter #4
On a cold start do the main injectors function or is it just the cold start injector. Almost like the cold start is working as it should but the mains are not turning on?
Thoughts.
 

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Oops, my bad on the TPS. Made the bad assumpTion that Toyota TPS are like GM TPS.

The cold start injector operation is tied to coolant sensor as well as the IAC/ aux air valve under the throttle body. The aux air closes up and the injector is cut back as the coolant temp climbs.

Cold start injector. It provides enough fuel to provide AFM ratio for air coming in thru open IAC
  • Remove from manifold, check if leaks when car is on (not running).
  • plug hole on manifold, hold injector over container, start car and monitor output. It should decrease with temp.

IAC/Aux Air. This allows air to be routed around a closed throttle. You can see the opening to aux air in front of the throttle.
  • on cold start, you can plug the hole and see a significant drop in rpm.
  • once warm, little to no drop in rpm should be evident when pLugged.

Sounds like
- aux air is stuck open and no additional fuel is provided on warm-up
E.g., car is Running lean and needs extra fuel
- cold start injector is stuck on and when the aux air shuts off, the result is a rich condition.

If both are working, then I would focus on minimum idle setting tuneup. Also, you can check the o2 sensor pulse count too verify if a) operating correctly and b) running lean or rich
 

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Discussion Starter #6
Did the cold start removal and test yesterday, Resistance was 3.5 ohm right on the money. Nice "V" pattern spray. Everything worked as it should. Aux air was cleaned and free when the throttle body was removed, same time the egr was cleaned. Good procedure though. One tip I learned years back with adjusting those nss(s) is to turn the key on, put the trans in reverse and just adjust the nss until the backup lights come on. Works everytime.
The problem is getting narrowed down somewhat. Got spark, fuel, air, so it might be electrical. When it stalls it's like the key was just turned off. Today I'm removing the ignition key switch module. 268k miles is a lot of start/stop/acc. motion. Might have some worn or corroded contacts. Indications are some clicking and weak start like a dead battery but the battery is brand new and starter lugs/solenoid are clean. Needs to be replaced anyway.
Should end this labeled nss thread and maybe begin a new one on ignition switches. Too easy to get off subject.
Always good to share info to help others.
 

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Btw, you can rule out starter circuit vs battery issues by jumping the starter. Use a 2-4" wire, bare ends, to jump from large wire lug connection on the starter to the small wire connection near it. This will engage the starter. Key on and jumped starter gets the car running. If the starter does not engage, then battery is dead or starter solenoid is shot.
 

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Discussion Starter #8
Yah, I have a remote starter button that I used back in the early 70's. Also an induction tach and timing light. Those oldies are coming in handy now.
PS, I was in my mid 20's then :rolleyes:
Thanks for all the help you've thrown my way since I joined this group.
 
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