'84 3.2 Wont Go Over 1600rpms

[X JBM X]

Hi folks,

A couple years ago i had an issue, brought to the mechanic, replaced a few things, and was all good...

fast forward to last weekend... i experienced the same issue.

i was pulling out of a car show going in 1st slowly for about a mile. once onto the streets, i hit the gas, and the car responds, but as soon as the engine hits 1600rpms, it dies... not as in stalls, but no more response from the throttle. once engine speed comes back down, i can accelerate again, but only until the engine hits 1600rpms.

this behavior occurs in all gears, so i was limited in my limp home to 40mph in 5th gear.

anyone have suggestions on where to start? my gut makes me think it's a sensor, but i'm turning to you fine folks for some ideas...

thanks in advance.

[Dpmulvan]

Speed sensor and or gap would be a good place to start.

[Dpmulvan]

http://forums.pelicanparts.com/porsche-911-technical-forum/638646-carrera-3-2l-rev-limiter-problem-speed-sensor-solution.html

[X JBM X]

thanks. i'll definitely keep that one in mind, although my issue feels a bit different from others in the thread.

mine doesn't give me a feeling like the car is misfiring... it feels as if fuel is cutoff from going to the engine despite pushing the throttle. i don't notice any rough running (save for the bucking from my foot bouncing on the throttle while dealing with trying to shift under 1600rpms)

otherwise, it starts fine and idles fine. when sitting still though, i do see the same behavior to a degree... when i blip the throttle i can get the rpms up, but it's only momentary and then drops back down... i don't think i could redline it at idle if i tried (i haven't).

[jlex]

Have you pulled the distributor cap to see if anything is looking weird? Maybe your ignition rotor is burned out & not making good spark for you at higher RPMS.

[X JBM X]

Originally Posted by jlex

Have you pulled the distributor cap to see if anything is looking weird? Maybe your ignition rotor is burned out & not making good spark for you at higher RPMS.

I honestly haven't done anything beyond some searching on Pelican so far...

The reason I'm pretty convinced it's a sensor and not anything else is just because of the abruptness with which it stops responding. 1600rpms. 1st gear, 2nd gear, 3rd gear, 4th gear, 5th gear, and in neutral.

I tried getting up to 40 using 5th gear, and then dropped back into 2nd to bring the RPMs up artificially, but even when doing that I get no throttle response.

I'll also add that on my way to the car show yesterday, I did drive her a little harder (kept the tach around 4k) for a few miles, but nothing crazy... was just giving an old Italian tune-up to break up some carbon.

[proporsche]

also it would help to help you if you would say what was done last time to your engine to solve the problem
"brought to the mechanic, replaced a few things, and was all good...
:......for the future onlookers..

Ivan

[X JBM X]

According to the paperwork, they replaced the crankshaft speed and position reference sensors, and adjusted the gap to the flywheel on 8/26/2019. Additionally, they replaced the DME relay.

[john walker's workshop]

Toasted cat?

[grb008]

I will throw this out for john or ivan to answer but what about if the idle switch was stuck.

[porschyard]

Unplug the closed throttle micro switch connector and see what happens.

[wazzz]

Originally Posted by john walker's workshop

Toasted cat?

Was about to suggest that.
Exact same behavior as my BMW E36 when the cat died and blocked the exhaust gas out. Car was running ok in lower RPM, but couldn't breathe or fart at higher RPM.

[X JBM X]

Originally Posted by john walker's workshop

Toasted cat?

I've got a fabspeed cat bypass on the car, so I don't think it's the cat...

Originally Posted by porschyard

Unplug the closed throttle micro switch connector and see what happens.

Hmm... haven't tried this one yet...

[proporsche]

hmm ,the micro switch is a possibility..but if it is bad the idle would not go down it would stay high......just a hint ,how old is the fuel filter??

Ivan
btw are you able to check your fuel pressure with gauges?

[wazzz]

Ivan, I agree that when you disconnect the microswitch the idle rpm goes up to 1200-1500, but the microswitch could be faulty by being stuck in closed position or shorted somewhere.

In this case, idle rpm would be normal (not high) but the faulty shorted switch would prevent reaching higher rpm because the ECU keeps thinking throttle is closed.

[proporsche]

In this case, idle rpm would be normal (not high) but the faulty shorted switch would prevent reaching higher rpm because the ECU keeps thinking throttle is closed.[/QUOTE]


yup let`s hope so...

still .would be nice if the op double checked the sensor gap?

ivan

[X JBM X]

Originally Posted by proporsche

In this case, idle rpm would be normal (not high) but the faulty shorted switch would prevent reaching higher rpm because the ECU keeps thinking throttle is closed.


yup let`s hope so...

still .would be nice if the op double checked the sensor gap?

ivan

More than likely the car is going into the shop this week, but trying to get ideas before bringing it in.

From my records, the last time the fuel filter was changed was in 2008, but the hard & fast cutoff at 1600rpms consistently throughout the gears makes me lean toward something electrical.

[pmax]

Pop the dizzy cap and have a look see.

Show pics.

[proporsche]

Originally Posted by X JBM X

More than likely the car is going into the shop this week, but trying to get ideas before bringing it in.

From my records, the last time the fuel filter was changed was in 2008, but the hard & fast cutoff at 1600rpms consistently throughout the gears makes me lean toward something electrical.

2008 way too long i`d say- i wonder what is inside....??

Ivan

[pmax]

No special tools needed.