1990 stalls when taken out of netural

[jimg763]

I have a 1990 Buick Century with a 2.5 liter engine. It has 156K and has been a dependable car until now. A year ago I did a major tune up replacing crankshaft sensor, coil packs, wires and plugs, and Oxygen sensor. I only replaced the coil packs because a mechanic said they needed to be replaced. He was wrong, the noise was acctually a broken lifter spring. I replaced the spring. I didn't do a very good job of tightening the valve cover gasket because it leaked a bit, but thats taken care of now.

Car ran fine until recently one day it kept stalling and finally just wouldn't start up agian so I towed it home.

It looked like it wasn't getting gas so I put some gas in a spray bottle, squirted some in the TBI and it started right up and then died. Did this a few times and was able to keep it running by playing with the throttle. I replaced the fuel filter, didn't help. I replaced the injector and regulator diaphram and still didn't help. I borrowed an inline fuel gauge from a mechanic friend and according to the guage, at the TBI I have 13lbs of fuel pressure. The catalog says 9-13lbs is whats expected so my fuel pump is fine. Over the past 3 weeks of working on this car here and there, I managed to get it to idle on its own a couple of times, and it did so for some time and ran very smooth. When I put it into gear, it will make it to the end of my drive way and die.

I know the MAP sensor has 5volts to each terminal with the key turned. I don't know how to test the MAP sensor with the key turned to the on position. The manifold sensor also has 5volts. My EGR valve isn't stuck so I don't think thats the problem. I thought it was a fuel problem, then I thought it was a vaccum problem, now I just don' know.

Appearently Buicks are known for stalling problems and at this point I'm at a loss and would appreciate some advice.

Thanks for your help in advance.

[richtazz]

Welcome to AF

It sounds as if you're not getting injector pulse from the ECM. Since the car will run when fuel is sprayed in the intake, then you're getting spark and timing is good. Your fuel pressure is good, so it has to be injector related. Check the ignition coil harness for a white wire. This is the ECM spark reference for the injector pulse. If this wire is corroded or broken, it will cause the injectors to stop spraying fuel due to the ECM not getting a spark signal.

[jimg763]

richtazz and anyone else,

I did as you suggested, I attached a EFI harness tester noid lite to my injector connection, turned the igintion key, and the test lite continuously flashed while the engine was trying to crank over. This should mean I have good electrical connection to my injector.

I haven't tested the map sensor yet, but plan on doing that tomorrow. I don't know what else would cause fuel to not be introduced to the TBI.

Any suggestions would be appreciated.

Jim

[GTP Dad]

Try replacing the throttle position sensor. It sounds like the signal to the ECM is not there which would cause it to introduce additional fuel while under load thus causing it to stall. One other item would be to unplug the electrical connector to the transmission since there is a possibility that he torque convertor is locked and causing it to stall. Just a couple of things to try.

[jimg763]

Well, I did as GTP DAD suggested and replaced the throtle position sensor. Thanks for your imput. I also replaced the MAP sensor. Somehow I got the engine to start and I actually drove it around a couple of times on Sunday. I don't know why it started, but it doesn't start again unless I spray gas in the TBI. I am noticing gas spitting out of the steel housing that holds the gas pressure regulator diaphram.

The pressure regulator diaphram is new and I'm sure I placed it into position correctly. I have good spark, if the pressure regulator isn't the problem, then what ever tells the injector to spay gas into the trottle body isn't working the way it should. Besides the ECM, is there another brain on my car I can check?

This is getting serious, I almost brought my car to a shop to have it put on a scanner and that's not like me. Your help is needed and appreciated.
Thanks, Jim.

[GTP Dad]

The ECM tells the injector to spray fuel. It is possible that it has gone bad but doubtful due to the fact that the noid light flashed properly when you tried it earlier. You may want to check the grounds to the ECM however, that sometimes will cause an intermittant problem. Finally, you may want to put a new fuel pressure regulator on the car. If there is fuel coming out of the housing that may be where your problem is. An ECM for your model car may be available from a wrecking yard for a few dollars. The older the car the cheaper they become. Try the regulator first then the ECM.

[jimg763]

I finally brought my car to a mechanic and after 450 bucks, and a new ECM my car is working again. Somehow the speedometer has gone wacko though, it says I'm doing 120mph when I'm just coasting. What and how do I check the speedometer components.
Thanks Jim.

[GTP Dad]

Speedo is electronic and runs off a sensor on the transmission. You should be able to purchase the sensor and replace it yourself. Autozone has a new repair system that will assist you in finding the sensor and replacing it especially if you don't have a book on your car.