911 3.2L Motor Strain / High RPMs

[lkk@ksglaw.com]

I have a 1989 3.2L Carrera coupe (stock) and my mother-in-law has a 1987 3.2L Carrera coupe (stock). After driving both cars, I noticed that her '87 has more rapid acceleration and HP. With the comparison, I noticed that in my '89 when accelerating pass 3500 or 4000 rpm in any gear, the motor seems to strain and somewhat vibrate not to mention gets louder. I've taken it to my mechanic who has suggested a number of things such as an adjustable fuel pressure regulator, bored out throttle body, temp sensor, air sensor meter and ajusting the cam timing. I have already changed the temp sensor and added an adjustable fuel pressure regulator and the problem still persists. Any suggestions as to what could be wrong and what is the solution? Thanks.

[stlrj]

the motor seems to strain and somewhat vibrate

Based on this clue I would concentrate on my ignition, replace my ignition cables, new plugs, and then move on to my injectors which may need a good injector cleaning.

One thing I would try avoiding no matter how tempting it may appear is adding anything aftermarket to my engine that would complicate the problem but put my energy into getting it to run well in stock configuration, using the 87 Carrera as your baseline.

After taking care of your ignition and injectors, I would try swapping air flow meters, not all are created equal.

Joe

[Tim Polzin]

Wow, I'm impressed

"my mother-in-law has a 1987 3.2L Carrera coupe".

Mine had a 78 Plymouth Horizon.

Tim

[Superman]

Agreed. First, put all your energies into ensuring that the engine is performing optimally in stock configuration. I continue to feel that ignition systems, including ignition wires, cap and rotor, etc. are commonly not working as well as owners think they are. Next step is fuel. This is where Motronic gets complicated, with DME relays, air flow meters and such, but clean injectors is an excellent place to start. After all that, compression test.

I'm with you, dude. No way should a man's mother-in-law's car outperform his Porsche.

[stlrj]

You also might want to check if your intakes are loose and tighten them down.

Joe

[ChrisBennet]

Forgive me if something was lost in the translation but suggesting "performance mods" (of very dubious effectiveness BTW) in order to fix a running problem would not inspire my confidence in that "mechanic". You really need to find a new mechanic IMO.
-Chris

[stlrj]

Ditto

Joe

[john walker's workshop]

being that you have two basically identical cars to work with, try swapping the computers and the airflow meters between the cars to see if one works better than the other. compression and leakdown tests may also show something. maybe you have a low hole. the oxygen sensor signals may not be equal between the two cars. try unplugging them temporarily for test purposes.

[lkk@ksglaw.com]

Wow! Thanks for all the support and great information. I'll start with the ignition and work my way to the air flow meter. Will let you know how it turns out. Any thoughts on this cam timing suggestion?

And yes, it's quite humbling that my mother-in-law's Carrera out performs mine but hopefully not for long.

[ChrisBennet]

Originally posted by lkk@ksglaw.com
Wow! Thanks for all the support and great information. I'll start with the ignition and work my way to the air flow meter. Will let you know how it turns out. Any thoughts on this cam timing suggestion?

And yes, it's quite humbling that my mother-in-law's Carrera out performs mine but hopefully not for long.

With the stock cams you have 2 or 3 positions you can time the cams at within the spec. By changing the cam timing you can move the torque up or down in the RPM range a little. I've played with this some but I never dynoed it to see if it made a difference. Unless you can see from the records that someone has changed (and possibly screwed up) the cam timing I would leave the cams alone.
-Chris

[lkk@ksglaw.com]

Thanks Chris. My goal is to get my car running at optimal performance in stock condition without paying a lot for hits or misses. The information from this board will definitely help. Thanks.

[silverc4s]

Just a thought, you might check to be sure that your throttle is opening completely when the pedal is floored. This seems to be not all that unusual, and fits your description of the problem, IMO

Good Luck!!

ps. The times I have been in Hawaii, I have always thought that it would be the worst place to have a P-Car, as everyone clogs every road all the time, (admittedly, that was Maui, so may not be the case everywhere).

[don911]

My 87 seemed to go flat on the straights at the track. I thought it was old and tired until I put it on the dyno and found out my fuel mixture was way too lean.
I had my fuel pressure and injectors tested but they were all found to be normal. During the injector rem/installation, the mech. found a vacuum line off that is on the back of the intake.
My cars now idles smoother and most importantly, pulls down the straight in 4th and 5th. Feels like a new car.

I would suggest getting your car on a dyno to see what's happening through the RPM range under a load.

Also, any chance the clutch is slipping under hard accel.?

[jpachard]

Don, Where is this vacuum line you speak of. My '87 seems to be doing the same thing. When I'm at Watkins Glen I shift into 5th at 6100rpm and my car barely gains any speed by the end of the straight. Sounds like I have a leaky vacuum line somewhere too. I just noticed that my cruise control does not stay put when I set it, could this be related??

Cheers, James