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Tool Hut
Tool Hut, ASE Certified Technician
Category: Chevy
Satisfied Customers: 494
Experience:  Owner of a mobile diagnostics company assisting auto technicians with difficult vehicles
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My 1990 chevy 350 tbi runs great idles fine but when i give

Customer Question

my 1990 chevy 350 tbi runs great idles fine but when i give it a small amount of throttle it will supter and die. replaced plugs, cap rotor and wirers timing is set
Submitted: 1 year ago.
Category: Chevy
Expert:  Tool Hut replied 1 year ago.

Hi, My Name is***** have over 20 years experience repairing vehicles. I am a ASE Certified Master Auto Technician. I am confident we can resolve your problem together.Please remember I don't know your skill level. I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies to get to a satisfactory resoloution. I also do not work in an office awaiting your reply. I run a small business and will do my best to answer quickly. Depending on the day and time there may be a delay in getting back to you.Try your best to respond with good detail so I can do the same.

Do you have a fuel pressure gauge?

Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Tool Hut replied 1 year ago.

I cannot place a call tonight. I can tomorrow

Customer: replied 1 year ago.
I can get a pressure gauge. I have rebuilt the tbi injectors and replaced pressure spring. Timing is at 0 new plugs wires. I checked for vacuum leak by spraying starter fluid. New cap and rotor. I just bought the truck and didn't notice this on test drive. It only happens with very small pressure on gas petal when vehicle is stopped. Sputters and if I hold the petal at approxmently 1/16 it will die. I may have to leave town for a few days. So this may take few. I have quite a bit of experience working on Chevy's and can do anything to them but fix this problem
Expert:  Tool Hut replied 1 year ago.

Do you have a scanner? can you monitor TPS Voltage see if its steady while pressing? Key on engine off

Customer: replied 1 year ago.
I was going to replace it. That was my next try. I have a scanner just looks for codes
Expert:  Tool Hut replied 1 year ago.

do you have a volt meter?

Customer: replied 1 year ago.
Expert:  Tool Hut replied 1 year ago.

the TPS sensor has 3 wires. if you use a Tpin and back probe the wires you will see that 1 wire is ground (black). 1 wire is 5 volts (grey) verify this is 5 volts key on engine off and the other (Dk Blue)should be around .5 volts at idle and 5 volts when wide open. this is the wire I want you to concentrate on. Look for drops when opening throttle slow.

Customer: replied 1 year ago.
OK I tested tps and its volts wa .555 as I open the throttle voltage climbed. Tried many times to get it to cut out. Looks like you saved me from buying a tps. Could not check fuel pressure and I am going out of town till friday
Expert:  Tool Hut replied 1 year ago.

OK. I suspect you may have a bad fuel pump. probably sufficient pressure and lacking volume. If you borrow a pressure gauge try to get one with a pressure relief. While it is running press the release and the pump should be sufficient to keep running. If it stalls you have a bad pump or plugged fuel filter

Expert:  Tool Hut replied 1 year ago.
I noticed that I have not received a rating from you. If for some reason you question did not get answered please reply. I am only compensated for my time when you leave a positive rating. Your understanding is appreciated.
Customer: replied 1 year ago.
If I rate you will you still answer my questions. I just got back and will check fuel pressure tomorrow. You have been knowledgeable and will give a positive review. I just might still need help.
Expert:  Tool Hut replied 1 year ago.

Yes I will still assist. I only get compensated if you leave positive rating. Thanks

Customer: replied 1 year ago.
I got a fuel pressure tester and saw that it would be the same amount of disassembly to test the fuel vs just changing the filter. I didn't know when the filter if ever was changed. I just happen to have one for my motor home in my shop. I changed it out and now the problem is gone. Thanks for your help. I would have not checked that as soon as you suggested it. I didn't expect it to work, but you were right. I also know now how to test the TPS. Thanks. If I had the ability I would have left you a positive comment on top of the 5 stars.
Customer: replied 1 year ago.
Unfortunately I just tried to drive my truck and it well not as bad it did still start to stumble again. Is there an internal fuel filter in the TBI? Do you have any other recommendations
.
Expert:  Tool Hut replied 1 year ago.

I would check the fuel pressure. There is a sock in the gas tank that could be plugged. There is also a fuel pressure regulator in the TBI Unit

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