Problem Quitting While Driving

[kcpete]

My 92 transport 3.1L had started quitting on me while driving. After sitting for about 15mins I could get it started and then continue on driving. Now its doing it more and I can't take the chance of going anywhere in it.

Help me out please! got a CEL so I flashed codes 34, and 45. Any suggestion on where to start troubleshooting with what these codes are saying that I should do? Thanks

[Tech II]

Does this have a distributor?

34 is the Map sensor

45 is the O2 sensor(running rich).....

When the car won't start, do you have spark?

What is the fuel pressure when it won't start?

[kcpete]

Yes it has a distributor. It along with the rotor and module were replaced awhile back. There is spark during the crank. As for the fuel pressure I really don't know. Never had a way to test when its quit on me.

[LMP]

WIth TBI, you can pour some fuel into it after removing the air filter....if it starts this would prove the problem with fuel supply...
Fuel pressure with TBI is merely 10-12 psi....but then the fuel pump must run. Can you hear it run ?
http://www.avigex.ca/xport/fuelpumptest31.jpg
http://www.avigex.ca/xport/31fuelcontrol.jpg

keep this for codes
http://www.avigex.ca/xport/codes31.jpg

[Tech II]

Is there any fuel coming out of the injectors in the throttle body when it won't start?

[kcpete]

As of now it runs but I don't take the chance driving it. I sometime this week will get someone to follow me and hopefully it will quit. I will then check the fuel supply. Question- How would lack of fuel cause a running rich. Anyway I will get back with some observations. Thanks guys

[LMP]

Originally Posted by kcpete

Question- How would lack of fuel cause a running rich.

I would just see it the opposite. A false rich reading might cause leaning of fuel injection to the point where it cannot ignite.....but this is probably an extreme condition......where the O2 sensor would be way off calibration...

Anyway...."closed loop operation"...that is when the computer really takes O2 reading in consideration....applies only once engine has warmed up......to 145°F I think...which would explain why it (the problem) happens only after a few minutes.....otherwise it runs on "default" parameters. One way to test this hypothesis would be to fool the temperature sensor....like by simply disconnecting it. Once disconnected, it reads infinite "ohms" resistance.....corresponding to very low temperature. This would inhibit "closed loop" operation.....then test what happens then...... of course it would pop a "low temp" code.....but ignore that and run for a test.....and report.....

[kcpete]

I have not been able to spend any time trying to solve problem. I am in and out of town as of late. Getting ready to leave again this morning. Hopefully I can try to test in a few days if cold weather holds off. Will keep you posted. Thanks

[kcpete]

I let the vehicle run for about 20 mins and then turned it off and disconnected the temp sensor. When I tried to start it (sensor disconnected still), it just cranked however I could smell gas.

After leaving it sat for awhile and than connecting sensor back, it if finally started. I let it run for a good while then disconnected the sensor while running. The only change was that the fan kicked on immediately and continued to run, the vehicle never died.

Finally shut the engine off and tried my first beginning test above, and it started. No cranking. Any ideas what all this means?

[LMP]

Originally Posted by kcpete

..then disconnected the sensor while running. The only change was that the fan kicked on immediately.. :

..ok..it probably detected a failed temp sensor and to be "fail safe" it kicked the fans ON. ANd....this must have come with a DTC15 code for low temp reading/failed temp sensor...

[kcpete]

To update I replaced the pressure regulator just to give that a shot. I then drove it around about an hour and probably for 75miles. I thought I'd solved my issue but then got a block from home and the CEL appeared, same codes.
Its very cold outside so I can't do to much now. What are some other easy replacements or does anyone think I am definitely looking at replacing a fuel pump?

[Tech II]

Check for vac leaks, especially at MAP sensor......could have a contaminated/lazy O2 sensor....

[kcpete]

Well got home and played around with trying to find a vac leak. I didn't feel nor hear anything. I will spend some more time later it just gets dark early and to doggone cold out. Oh any tricks to locate a leak? thanks techII

[WelmoedJ]

Originally Posted by kcpete

Well got home and played around with trying to find a vac leak. I didn't feel nor hear anything. I will spend some more time later it just gets dark early and to doggone cold out. Oh any tricks to locate a leak? thanks techII

Smoke (either like from a smoke machine or alike).
No cigars or cigarettes though

Spraying with brake cleaner sometimes can do the job.
Cleaner gets sucked in and may cause change in engine run.

[Jeffrv]

I suspect you may have a physical problem with the MAP sensor or associated wiring, rather than the sensor itself. Trace the vacuum line from MAP sensor to intake for leaks; also check that it is free of condensation that may be freezing and blocking it in cold temps.
Next check the wiring harness for intermittents , as your problem seems to pop up at random times. With engine running and warmed up, carefully squeeze, and gently tug, push ,wiggle the wiring harness following the MAP sensor through all connection you can. Be careful around rotating parts: if you find the break in the wire, the engine will change and CEL light should come on.
Jeff