Rough and very low idle...help?????

I have a 1988 Chevy c-1500 Silverado. I have installed new plugs, wires, D-cap, rotor button, Throttle Position Sensor, EGR Vaccuum Solenoid, check for vaccuum leaks (found none) and many other things yet my truck still idles very rough and so low that it almost dies when u come to a stop sign. WHAT COULD THIS BE?? EGR VALVE? Alternator? ECM?? It did have a very cool thermostat in it so i changed it due to the cold weather now my gauge reads very high even though the truck isnt that hot. Could someone have installed a Chip and that be why it had such a low thermostat?? Also once its warmed up and you come to a stop the volt gauge drops down to around 8 and if your running the heater fan headlights and anything else it really does want to die.......Help please.....any suggestions?????

Reply to
RICHARD HARGETT
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What's the amp draw on the fuel pump? what's the fuel pressure? when's the last time the fuel filter was replaced? ground strap between the engine and frame intact? How old is the battery, when is the last time it was tested? Have you had the alternator checked? You've thrown enough parts at it, not to say the basics, cap rotor, plugs and wires didnt need to be replaced. TPS can be checked with a multimeter, not a 100% perfect test, but there are readings that can be measured give a good idea. Vacuum gage between the solenoid and the egr can tell you if its active. Do not use the old school pull a battery cable off to see if it keeps running test, good way to cook an ECM fast. most places check batteries for free, and the charging system for a small fee.

Whitelightning

Reply to
Whitelightning

SNIP

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Check that the gasket between the top of the TBI, and that metal band with a vac line running to the back of the TBI is intact. Your amps are probably low because the idle is erratic and low also. It should idle after warm up (computer without mods waits for 175-180 deg.) at about 700 rpm. Cold, it should run at about 1200-1000 until then. Next thing you wanna check is the Idle Air Control Valve. It screws into the back left-hand side (looking from the front of the truck) of the TBI. Make sure all the vac lines are clear. Do you have any error codes (Check Engine light on)? TBI trucks are a wonderful simple system... don't freak out yet.

Oh yea... check that your Electronic Spark Control unit it plugged in.. both at the unit itself ( it sits on the left side of the TBI, with a four pin connector in the back), AND, inside the wire harness under the black plastic cover next to the coolant overflow tank. Its a single tan wire with a plug connector similar to the one used on the OX sensor.

The above is for the 5.7 V8, but might be the same for the V6.

HDS

Reply to
HDS

Sounds like you replaced most of the simple stuff except for the Idle Air Valve. About $36 bucks and easy to replace. It controls the idle speed. IT could also be the computer. If it's not throwing codes and otherwise runs ok you can pry off the cover over the base idle screw and up the idle with that. It's not really the proper fix but.....it might fix your problem without spending a lot of bux.

Reply to
Ashton Crusher

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