'86 3.2 won't rev past 4000rpm

[TimK]

I've an 1986 3.2 Carrera Targa who until this problem has behaved very well and was in regular use.

Symptoms are as follows.

Starts and runs fine upto ~ 4000rpm.

She will not rev above 4000rpm without backfiring/stuttering very badly.

Many of the common solutions have been tried:-.

1. New plugs,leads
2. Replaced common problem relays (fuel pump relay etc)
3. Main ECU/DME module has been tested
4. Extensive testing of all engine/ignition related wiring
5. Airflow meter has been rebuilt
6. Rear exhaust has been removed and tested for blockages

My mechanic and electrics specialist have spent a long time on her already and are fast running out of ideas (and hair).

We're open to suggestions!!

thanks

TJK

[zippy_gg]

Could it be bad gas? Or moisture in the fuel system?

[john walker's workshop]

too much gap between crank sensors and flywheel teeth? that'll do it.

[rick-l]

Would a rusty advance in the distributor do this?

Edit: not an advance a positioner.

[Imcoz]

Sounds like classic ref / speed sensoritis.

[djcdmv]

Check out this thread. I'm still having the same problem. A few posts down, I list a few possibilities that the PCA tech thought might cause the problem if it isn't the sensor. Plus, there are a bunch of different suggestions from other Pelicans

Help! 3.2 looses power at 5500 rpm while accelerating,

[Flat Six]

Originally Posted by Imcoz

Sounds like classic ref / speed sensoritis.

+1 John Walker & Imcoz

Also fuel filter (tank filter too) and FPR

[911pcars]

Originally Posted by Flat Six

+1 John Walker & Imcoz

Also fuel filter (tank filter too) and FPR

... and/or FP.

[Scott R]

Blocked cat?

[techman1]

Mechanical advance in distributor?
I know the DME controls spark, but the mechanical advance puts the rotor near the proper post at higher speed.

[vwporschegt]

Intake leak...big one, running uber lean. possible fuel delivery problem i.e. not enough

[Quicksilver]

Originally Posted by vwporschegt

Intake leak...big one, running uber lean. possible fuel delivery problem i.e. not enough

Intake leak would cause the bigger problem at high vacuum not WOT.

Originally Posted by techman1

Mechanical advance in distributor?
I know the DME controls spark, but the mechanical advance puts the rotor near the proper post at higher speed.

Interesting idea. Not sure where the springs are set to move the rotor but I'd expect the "advance" to be all in before 4K. Also if it failed I would expect it to fail in the direction of being stuck in the high RPM "advanced" position. I would put this idea after the first two following ideas:

- The sensors are an obvious one. Hook up the oscilloscope and see how good a signal you are getting.
- Too much spark gap so coil isn't able to saturate enough to fire them.
- Restricted fuel flow might effect it past a certain power level. At light throttle it should rev higher. How old is the filter?
- Degraded cap, wires, plugs but it would be more of a "power level" problem as lower cylinder pressures make it easier for the spark to jump.

[janz]

Sounds like fuel delivery, change filters if that doesn't do it check fuel pressure from pump. Sounds like the race cars with restrictors in them they sorta backfire when they can't go any faster due only to fuel restriction.
Providing all else is OK up until 5K.

[Lorenfb]

"Would a rusty advance in the distributor do this?"

Actually, not that exact situation, but one where the distributor
was mis-aligned/installed that caused a basic rev limit/misfiring
at about the mid RPM range. This usually occurs where the distributor
was R/R'd at some point. If the mechanical advance was sticking and
the rotor was initially mis-aligned, then a higher RPM mis-fire could
result.

[TimK]

Many thanks for all of the suggestions.

I turned out to be the spacing of the sensor.

The solution was to remove the mounting bracket and elongate one of the mounting holes.

The enabled some adjustment on the bracket so as to move the sensor in slightly.

[djcdmv]

Tim, do you have any more info or photos of the spacing you are talking about and the mounting bracket you altered. I'm having this problem and I am getting the car out of storage in the next few weeks and want to determine if it is the sensor. Thanks in advance!