mystery 3.2 problem - please help if you have 3.2 knowledge

[mjshira]

Thanks for reading.

I have a 3.2 with 70K on it. The engine runs very well and with the exception of the condition I am going to discribe is strong.

From time to time the engine will lose power. The best way I can communicate what it is like is to give the example of running out of fuel to illustrate. Then in a matter of seconds it goes away.

Here are the conditions I have been able to learn must be in place for this to happen:

1. the engine must be at normal op. temp (the first line on the gauge)
2. the car must have been running for about and hour.
3. it must be atleast 65-70 degrees outside

The condition can range from being mild to quite extreme but it always is sporatic and only when the above conditions are in place. For example in the winter I took a long trip to ski. The problem never happened. However last year when I drove from NYC to Indy for the F1 race it happened on the way back.

Here is what I have done:

1. changed DME relay
2. changed cly. head temp sensor
3. changed the two rpm sensors
4. total tune-up and valve adjust
5. checked all grounds
6. changed all filters (fuel and oil)

I would really appreciate anyones help. My shop had the car for a month and it never (murphy's law!) happened for them. We are not sure what to do.

Regards,

James

[RickM]

This sounds like a fuel pump on it's way out. Unfortunately, there is no way to test (that I know of) as it fails sporatically.

Others will chime in shortly, I'm sure.

[bento]

what kind of plugs are you using? your wires are all good?

db

[Don Plumley]

I've had a similar sounding problem with my 87. When you said total tune up, did they replace the spark plugs? What condition are your plug wires?

Another potential culprit is the Air Flow Meter. I broke mine trying to fix it. Ultimately, my problem which was a very slight hesitation or loss of power under accelleration and load, was traced to a faulty spark plug by an ignition analyzer.

Good Luck!

[mjshira]

I am running new plugs from Bosch and new wires. Could a fuel pump only fail sporatically when it is about a certain temp outside?

[scottb]

70k...have you replaced the 02 sensor yet?

[Don Plumley]

The fuel pump in my Wife's Volvo failed 1x to 2x per year until it failed in front of the mechanic last month...

[kstylianos]

James,

The Coil could be faulty. A faulty coil can short out internally when it gets warm, exhibiting the same symptoms. Try switching it out with a good known unit, just to eliminate the coil as a culprit.

[mjshira]

thanks guys. A coil I can change, is it hard to change the air meter?

[RickM]

I guess there could be other clues that might help.

Does the car cut out and then surge back to life or "buck"?
How long does it cut out for?
Does it die completely? Will it restart when it cools off?

[mjshira]

it cuts out and then comes back and then repeats. it seems to go away if I let the car sit and cool for about an hour. it does buck when it does it and in the extreme cases I have to engage the clutch to prevent the car from rocking too violently. In the worst cases it will sometimes not idle at all. However since I tuned up the car it seems to be less dramatic.

[mjshira]

opps sorry, it will restart when it cools. on the way back from indy I had to stop over in columbus b/c it was so bad. then the next day it hardly did it at all... I am trying get the girlfriend to travel with me again this year but this little glitch scared the pants off her!

[RickM]

God...I can tell you one helluva funny story about me, 3 friends, a bad fuel pump and the Lincoln Tunnel.......

[mjshira]

send me a PM, I'd love to hear it. I drive that way all the time so I know how hairy it can it during traffic!

[1fastredsc]

It sounds like your fuel mixture, possibly fuel pressure regulator is bad. I'd try and adjust the air fuel meter on your car and have the fuel pressure checked under a load (your shop will probably have to take care of this one). One time when i had my 951, i bought a fuel regulator for it and was mistakenly given one from an s2. The car actually had a little more power and less lag until it got past 8psi boost. Then it instantly went from "holy god this rocket is going to kill me" to "holy ***** what did i break" with the biggest buck i've ever felt in my life. Apparently there's a certain rich point in the mixture that will blow out the flame of the spark plug. Also there are sometimes hairline cracks in vac lines that are so small it won't affect anything when cold, but as heat is introduced the crack will expand to a hole and screw things up.

[Eric Coffey]

Throttle position switch?

[mjshira]

thanks to all.

we were able to determine that it is not the throttle position switch. B/c the air temp is such a factor and based on the posts thus far I think it might be the air meter.

[jmohn]

Originally posted by mjshira
thanks to all.

we were able to determine that it is not the throttle position switch. B/c the air temp is such a factor and based on the posts thus far I think it might be the air meter.

There's an air temp. sensor also, although I can't see how a failed air temp. sensor would cause the violent reaction you're describing.

Jerry M
'78 SC

[mjshira]

thanks. I can't either but I'll change it just the same. This is the most odd problem I have ever had with a car! If I lived in a colder climate I'd never know something was wrong.

[Harold_89_911]

Fortunately I don't have any similar experience with my 3.2 but on my 89 Saab 900, which uses a similar ECU system as the motronic, I also had a random loss of power. I never linked it to the outside temperature. It went away when I changed the O2 probe. Before replacing it, I put a voltmeter on the O2 probe and it looked like it was working fine. However, with age, the rate of change seems to change and affect the performance. So my vote would be also for the O2 probe.