OleBones

My nephew's '94 5.7L(350C.I) TBI has about 170,000 miles on it and has been a really good truck since he bought it new. When he is taking off, the engine seems to miss/surge/sputter until he gets to about 55 MPH. If he tries to burn rubber(which this truck will do), it runs just fine. I am thinking it is a Throttle Position Sensor going flaky but don't know where to find the TPS on this Throttle Body Injection. Once good cruising speed is reached, the truck runs as smooth as it should. Does anybody have any ideas? All help would be greatly appreciated.

OleBones

Think I might have figured out what is wrong with this truck but don't really know how to go about correcting it. This came stock with single exhaust and he had dual exhaust put on it. The problem is the oxygen sensor is only monitoring one bank since when the duals were put on, another oxygen sensor was not installed into that bank. Now would it be possible to correct this by drilling, tapping, and installing another oxgen sensor connected into the same circuit as the original 02 sensor or would it require some changes to computer and such?

j cAT

misses under load are usually plugs or bad wires...could also be a bad valve..check compression...tps is usually a problem when trying to hold speed as engine tends to drop out..

OleBones

Plugs, plug wires, and the O2 sensor has been changed and the wiring to the O2sensor checked. Compression is good. Maybe the 'missing' part of my description shouldn't have been there to start with. The truck runs smooth after reaching about 55MPH. If he romps down on it from a dead stop, the truck doesn't surge, just when taking off like a 'normal' OLD man is when the problem is there. Wouldn't this truck only having one O2 sensor cause problems with air/fuel ratios? After all the computer is only seeing 4 cyclinders but adjusting for all 8.

j cAT

the TPS is a resistor that varies resistance when throttle is moved this can be removed and tested with ohm meter...if the ohms jump to high resistance when rotated this usually means its bad..


It is possible that the dual exhaust has effected the EGR operation because of the lower back pressure...I had not seen this myself...I did have a vehicle like this one where the single exhaust was replaced with dual and only one O2 sensor and there was no problems...the cat was also removed and it had more power...

j cAT

the TPS is mounted on the side of the TBI and threre are two screws, one slotted this can be adjusted slightly...try this..

Cgroh89

The If the 02 is only monitoring one back you could have a fuel issue. I was I have long tubes on my car and one o2 was bad which caused surging down the road and bad stop and go driving. Mine did that same with the All or nothing.

This is because at Wide open throttle the computer does not use the 02 since it does not want efficenty . Just power.

My suggestion would be to put a x pipe in it

j cAT

I had an O2 go bad on a vehicle my son had an olds cutlass and this caused the engine to run leaner and idle a little ruff..he had the fully dual exhaust after O2 replacement that car could go fast for a small v8