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TBI PROBLEMS

 
steiner14
I love my Chevy Chevette!
Posts: 1
Joined: 03/13
Posted: 03/30/13 09:40 PM

i have a 95 chev tbi 350, recently i was getting a resistance of power, so i gave her a good maintenance check. change the fuel filter distributor cap and rotor, plugs (wires looked good)fuelpump was good so i hooked up my buddies snapon scanner and no codes read. im getting fuel to the throttle body, and when inspecting my fuel presure regulator i noticed it was leaking badly so i bought the new one and a tbi gasket rebuild kit, cleaned up the tbi with throttle cleaner after disasembling , put the new regulator and ALL gaskets and o rings carefully following directions, i put the tbi back on my chev and now its running even worse, idles at 1100rpm when you give it gas it gives a bad missfire, lots of smoke, and just plain and simply runs like *** , i dont know where i went wrong , maybe i damage TPS or another sensor by cleaning the tbi with throttle cleaner? gaskets arent leaking and injetors are spraying fuel, if anyone has any advice i would greatly appriciate it.  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 03/30/13 10:56 PM

a few things.... you will want to print this chart

TBISCANDATE87


so you can compare it to what you have on your truck...  you might want to post some of the live data stream voltage and numbers you get from your friends scan tool readout.

you will also want to examine the sides of the coil..

COIL Highvoltageleakage

while you are up on top of the motor.. take the distributer cap off.. and pull the rotor.. look for cracks in the various magnet layers... the cracks in either the reluctor or pick up coil can cause ghost wave forms that freak out the electronic timing system...

Smallcapheicracks

this is a cardone reman distributer with a far improved pickup coil and reluctor design a much cleaner signal for the module to handle.

V8smallcapheicardonereman

you will want to examine the fuel pump ground connection on top of the frame rail by the left rear tire...

Chevypickupfuelpumpgroundframe


please also check the ground wire connections on the intake manifold..  and on the back of the heads..  they must be properly attached..

also..

bring the engine RPMs up slowly  while somebody monitors the scan tool...

or have a vacuum gauge hooked up to the intake manifold vacuum port..

the manifold vacuum or MAP sensor should show an increase in vacuum.. NOT a decrease..

you could have a blocked exhaust system.

while you have the scan tool hooked up... key on.. engine off... please.. verify the TPS voltage goes from around 0.60 or 0.070 to about 4.25 volts at wide open.

work the throttle a few times.. the voltage needs to drop back to the exact same minimum voltage each time... no variations or it won't drop into idle programming.. there are wear issues in the throttle shaft bore... allowing the throttle shaft to close to slightly different angles each time...


coolant.. warmed up... 185 to 215F
TPS voltage .. under 0.99 volts at idle...
idle air counts... 20 to 50 at idle.. warmed up fully..

block learn. 128 if its running perfect..
this could be long term fuel trim
integator... 128 if its running perfect.
this could be short term fuel trim ..

or reversed..

you should see the oxygen sensor voltage going from 0.1 to 0.9 volts..
and you should see some crosscounts on the scan tool..

so many things it could be..

post the data stream numbers...  

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Tim_1972
I love my Chevy Chevette!
Posts: 2
Joined: 04/13
Posted: 04/10/13 05:44 PM

Im having problems .i have a 89 gmc with a 35..0 and i drive for 15 min shut it off and try start and it just turn over . I have replaced coil, pick up coil, cap, button and other things.i don't have a bottomless pocket can you tell me what will fix this.i live in Ocoee, FL plz give me some cheap way to fix  

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Tim_1972
I love my Chevy Chevette!
Posts: 2
Joined: 04/13
Posted: 04/10/13 05:46 PM

My email is tim72mcdonald@gmail.com or 407-272-2041 thanks  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 04/10/13 08:32 PM

a few things...

when you turn ON the key... do you hear the fuel pump run for 2 seconds???

you may have to have a friend help by listening at the bottom of the fuel tank.. for the hum or spinning noise from the fuel pump???

fuel pumps are controlled by an oil pressure switch under the distributer... and the fuel pump relay...   either or both could be bad...

your fuel pump in the tank could also be bad...

on the 3 wire oil pressure switch there is an ORANGE wire on one of the 3 connector cavities. the middle wire is just for the gauge and a tan or grey wire on the other side.. of the middle wire..

the orange wire can voltage all the time...

the tan or grey wire goes to the fuel pump fuse.. then from there to the fuel pump in the tank...


in parallel...

at the fuel pump relay.. the Orange  wire is also here...  supplying voltage all the time...
the Tan or grey wire is here too... this wire joins the one from the same color wire from the oil pressure switch and continues thru the fuel pump fuse to the fuel pump...

the fuel pump gets grounded thru the frame rail of the pickup..  there is a black wire that connects to a ring terminal either on the cross beam or top of the frame rail..  corrosion on this connection will effect how many electrons the fuel pump gets... and many times.. corrosion of the ground connector is where the issue is..


the fuel pump could be bad also... when it fails to spin as the key is turned on.. or while cranking.. take something like a big rubber mallet and pound on the side of bottom of the fuel pump while somebody else is cranking the engine..  this will most of the time get the brushes inside the fuel pump to connect with the commutator and get it to spin the pump motor..

yes.. like the fonz in happy days.. it really does work.. . i have spent hours under some mini vans with a rubber mallet pounding to pump the full tank down far enough to drop the tank without spilling it all over the shop floor when i disconnected the filler hoses..

since its almost midnight there i am not going to call you..  

if you want to talk.. click on my user name.. send me a PM  post your number there.. and times to call east coast time..

you will also want to click the edit post button below left on your post above.. to remove the direct email address and phone number from public view and WEBBOT view...  or plan on changing both..


if you have a working fuel pump..  

do you have spark????  you seem to have replaced everything..

did you use dielectric grease under the module to allow the massive amount of heat it creates by switching the coil current ...  the dielectric grease is a thermal grease... it will transfer the heat from the back of the module to the distributer housing where it can be dissipated to the air flow going by.. this prevents the module electronics from overheating and pulling away from the circuit board...  i have seen the module so hot there was actually clearance under them as they bowed..

you can use a timing light over the coil wire or one of the spark plug wires to see if you are loosing spark by taping or using rubber bands to hold the timing light trigger on and placing the light on the windshield under a wiper arm.. so you can see the flashing...

you are not setting the timing with it.. just seeing if the system is sparking properly..

since its an 1989 its throttle body fuel injected..   can you aim the timing light at the CONE of spray from the fuel injectors while somebody cranks the engine..  it should be a NICE crisp cone shape.. if its off center. or ugly.. you might have a fuel filter  thats restricted and blocking flow or fuel pump thats not putting out enough pressure. either is possible..  

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