mystery 3.2 problem - please help if you have 3.2 knowledge
 

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:(

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.

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

db

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!

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?

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

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

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.

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

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?

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.

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!

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

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!

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.

Throttle position switch?

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

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.

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.

The air flow meter does two things. It detects air flow for relative load detection and air temp for relative air density. Both of these (especially the first) affect your fuel delivery greatly. If you get too much fuel in hot weather, then usually you'll get a just right mixture during cold whether. The o2 idea isn't bad either, the computer is supposed to adjust to 14.7:1 under circumstances other than WOT. Although it adjusts based off of the base input of the air flow meter, and that altered adjustment by the o2 is'nt very big, so if your flow meter is way off your screwed anyway. The only way to find out your air flow meter's setting is by disconnecting your o2 (prevents correction) and use a sniffer in the exhaust. To adjust it, there's a by pass tunnel on the side of the air flow body (a lot like a throttle bodies idle screw) that's controlled by a plug with a small allen socket head. Screwing it in goes richer, screwing out goes leaner.

Reviving an old thread.

I have a very similar issue.

For the first time this weekend, after driving my car for about an hour+, when I was cruising in 5th on the highway at about 3500rpm, my car woould momentarily lose power, and a second or two later it would come back. It felt like the injectors shut off or the fuel pump shut off. It did it 2 or 3 times over the weekend but only after running the car for about an hour. The one time, instead of taking my foot off the gas i just kept my foot down and the car hesitated and jerked slightly but then continued to run fine.

I have a brand new fuel pump, DME, and speed and reference sensors in there so I was hoping to rule out those.

My thought is it may be a failing Darlington transistor in the DME that controls either the fuel pump or the injectors, which is acting up when the box warms up enough. Does this make sense? Any other thoughts on what could be causing this?

It may be a separate issue, but the other problem which recently started about the same time was, if I start the car for the first time in more than a day it sometimes just turns over. I need to do this a few times until it fires up. When the car is warm, or has been used in the last day it will start right up. Not sure if the two issues could somehow be related?