1988 Other Chevrolet Models engine flooding

Tiny
GEOMAN_25276
  • MEMBER
  • 1988 CHEVROLET
  • V8
  • 4WD
  • AUTOMATIC
  • 190,000 MILES
1/2 ton pu 4 wheel drive flooding/running very rich. I have replaced ign. Module, rotor button, disb. Cap, fuel press. Reg, fuel inj, egr valve, temp. Contol sensor, spark plugs, fuel pump, fuel filter all to no avail. What could be wrong?
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Wednesday, April 21st, 2010 AT 11:48 AM

8 Replies

Tiny
HMAC300
  • EXPERT
You may have a blown gasket on the bottom of the TBI and the computer is trying to make up for it or your return line to the gas tank is plugged causing it to flood.
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Thursday, May 27th, 2010 AT 8:00 PM
Tiny
GEOMAN_25276
  • MEMBER
Took truck to dealer they were at a loss for what was wrong also. I checked gas return line was not plugged, gonna replace gasket on bottom of throttlebody next, anything else you can think of that it might be so I'll have a next step? Also replaced map sensor
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Sunday, June 13th, 2010 AT 11:27 AM
Tiny
HMAC300
  • EXPERT
The only thing I can think of is that your fuel pressure is to high or yur injectors is bad. Maybe teh tps switch is stuck as well. You might try cleaning it with choke cleaner. With TBI your fuel pressure should be around 11p.S.I. If I can think of anything else i'll contact you.
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Sunday, June 13th, 2010 AT 6:43 PM
Tiny
HMAC300
  • EXPERT
Ok I had to go back to the manual and see how the beast operates. The TBI is controlled by the ecm. Unfortunately yours has what is called a prom inside it. If the ecm or prom isn't working right it could cause this. But your best bet is to get a wiring diagram and see if any references are being sent back to the computer or not and causing the ecm to flood the engine. The only thing that I could think of is to get a prom or ecm from the same type of truck with the same type of engine and put that ecm /prom unit in and see if that cures it. Try to find one that you can just use instead of buying. I doubt that you will be able to find a prom for that vehicle nowadays due to age. The prom goes inside the computer. Maybe if you can find the prom you might try changing that instead of the whole ecm.
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Sunday, June 13th, 2010 AT 7:10 PM
Tiny
GEOMAN_25276
  • MEMBER
New ecm was tried at the dealer with absolutely no difference in the problem. It seems as if it has a mind of its own. I'm gonna try the cleaning of things and a new gasket under throttlebody if that doesnt work, I dont know of anything else to do except change it over to a carb. Which is labor intensive along with expensive. I have 550.00 in the truck minus all the new parts i"ve put on it. I really dont know if it"s worth a new intake, disb. And carb. Plus I know it will take a special intake because of the mounting bolts being at an angle. Any other suggestions befor I either junk it or convert it. I really would like to fix it but. It ran fine one minute then it started this.
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Sunday, June 13th, 2010 AT 9:36 PM
Tiny
HMAC300
  • EXPERT
If the dealer used the same prom that goes in the computer it would do the same thing. I"m sure you have checked for engine codes first. You would have to get a different manifold. One other thing labout TBI units. The vacuum hose going to the map sensor is often soft or leaks. Also you have said nothing about the TPS switch. If that is stuck in the wide open position then it will tell the computer that it needs fuel all the time, causing the flooding. I am assuming that in all this time there hasn't been a timing problem like with a timing chain or distributor being in time as well.
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Monday, June 14th, 2010 AT 1:21 PM
Tiny
GEOMAN_25276
  • MEMBER
Checked tps sensor as per suggested, checks out fine. No timing issues at all. Spark plugs on the verge of fouling out all of them mostly black. Havent checked fuel pressure I need a gauge. Fuel pump and fuel filter were changed about a month before this problem arose. I let truck run for awhile and it did set a code of 45 again, thats nothing new tho. Any other ideas appreciated.
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Tuesday, June 15th, 2010 AT 10:46 AM
Tiny
HMAC300
  • EXPERT
The only other thing I can think of would be air blockage. I know that has an air cleaner similar to a carb. If it is blocked or cut down it wouldn't get enough air into the engine. That would include checking the vacuum motor ifyou have one on the air cleaner and it wouldn't open. Also if you happen to have ACCEL spark plugs in your truck get something else like ac champion/NGK, one of those brands. I've never had good luck with ACCEL plugs. I really can't think of anything more. Unless there is a valve/cam problem and they aren't opening all the way.
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Tuesday, June 15th, 2010 AT 2:13 PM

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