Help! 1991 stalls when warm

[ROCKO]

Need to see if anyone has experienced this problem. Have a 91 convert with the L89. Starts right when cold and performs well for about 3-4 miles. Once warm it loses performance and stalls out. If I let it sit for a while it will start right up but then stall again after a couple of minutes. No service engine light and no codes stored. Possiblr fuel????? Help. Thanks:bash

 

[redvett]

Need to see if anyone has experienced this problem. Have a 91 convert with the L89. Starts right when cold and performs well for about 3-4 miles. Once warm it loses performance and stalls out. If I let it sit for a while it will start right up but then stall again after a couple of minutes. No service engine light and no codes stored. Possiblr fuel????? Help. Thanks:bash

My guess is the CTS sensor causing the ECM to think its cold and adding too much fuel.

 

[k2bob]

My 89 was idling kind of ok at the shop the other day but when I took it for a spin it just died about 4 miles down the road. Two hours later it started fine. We checked the ohm readings the next day after it was warm. All injectors were out of whack. Now two were even close to specs. So I am replacing them Tuesday. I have read many different solutions- see "dallask" threads and posts to see if there are any other symptoms. An ohm test on the injectors is easy to do so do your diagnosis and ask questions before you start throwing parts to the wind. It could be fuel pressure, hot coil failure, bad injector/injectors, or others I have seen. Check out the previous threads for additional clues and questions. These guys are great. Just help them narrow down the symptoms. They'll get you pointed in the right direction.

 

[Schrade]

Does it lope idle when warm?

 

[k2bob]

No it does not lope. I checked the injector ohm readings hot on Friday last week and they were all over the place. No two were even close. We are going to replace them tomorrow and see what happpens next. I'll keep you psted.

 

[ROCKO]

thanks for your help

Want to thank everyone for their comments. Found the problem today. It was the fuel pump. When we put a fuel pressure gage on it the pressure was only 28lbs and dropped to zero when the engine shut off. Should not have done that. Put new pump and it works great.

 

[Schrade]

Want to thank everyone for their comments. Found the problem today. It was the fuel pump. When we put a fuel pressure gage on it the pressure was only 28lbs and dropped to zero when the engine shut off. Should not have done that. Put new pump and it works great.

With a bad pump, pressure should STILL hold when the motor is shut off.

If it drops to zero, you have a weak spring in the FPR, which allows pressure to drop to zero, OR, you have a hole in the FPR diaphragm, and fuel will get pulled into the vacuum line in the FPR. OR, you have leaking injectors, which allows pressure to drop to zero. Jon FIC did this let-off test with known bad injectors, and it DID immediately let pressure to 0, which I would not have believed...

To check the latter (#2), pull the vacuum line from the FPR, and see if it smells STRONGLY like gas. If it does, the diaphragm is ruptured, AND, some gas is gonna' get pulled to the intake through that vacuum line, and when it gets warm, it will lose power and stall out, like so:

Once warm it loses performance and stalls out.

 

[ROCKO]

With a bad pump, pressure should STILL hold when the motor is shut off.

If it drops to zero, you have a weak spring in the FPR, which allows pressure to drop to zero, OR, you have a hole in the FPR diaphragm, and fuel will get pulled into the vacuum line in the FPR. OR, you have leaking injectors, which allows pressure to drop to zero. Jon FIC did this let-off test with known bad injectors, and it DID immediately let pressure to 0, which I would not have believed...

To check the latter (#2), pull the vacuum line from the FPR, and see if it smells STRONGLY like gas. If it does, the diaphragm is ruptured, AND, some gas is gonna' get pulled to the intake through that vacuum line, and when it gets warm, it will lose power and stall out, like so:

Forgot to mention we replaced the FPR as well. With the pressure dropping to zero we knew that was a separate problem. Thanks for bringing that to light.

 

[k2bob]

It was the injectors. This thing runs like $999,999, just short of a million but starts easily now when warmed up to normal operating temps. Thanks for all of the help.