Hello,

I just bought a 98 Suburban 5.7L. It runs pretty good. I have noticed that after it warms up the RPMs start bouncing between 500 and 1000. It will eventually die if I don't give it some gas. If I hold the throttle its fine. Soon as it goes back to idle it acts up. I noticed the battery was low, I am sure it needs to be replaced. I had it hooked up wo the charger and it still bounced around. Any ideas? Do these engines have an IAC valve?

 

yes they do have an IAC valve i would try cleaning it first and checking for vacuum leaks

 

Double tap on the VAC leak, also check MAP sensor and air flow metering system. Let us know how you make out.

 

The owner told me it needed a tune up. I am planning on getting new plugs, wires, cap/rotor, oil change, coolant flush, possible an oil pressure switch. I noticed the radiator is full of stop leak crap. Probably need a new radiator/termostat... It roars right to life though. Did 80 miles an hour going home. He said the converters were clogged. I will check the vacuum lines like you guys said.

I guess the truck is a 1995 not a 1998. Still 5.7L. Sorry for being retarded before. In order to check the MAP sensor do I need ODB1 or ODB2 to read this thing? I thought 95 was ODB1, I guess I could just hook up to it and see. No check engine light somehow. LOL. So I may not know if the sensors are reading high or low what is a normal range for those?

Thanks in advance for your input.

 

It should be OBD1 if its TBI it should be OBD1 you can check the MAP sensor with a Vacuum pump and a multimeter,does the check engine light come when you turn the ignition on but not start the truck if not maybe the bulb is burned out,you should be able to pull the codes out with a paper clip if its OBD1 if its OBDII you need a scanner,get all that stop leak out of there i've seen that stuff jam thermostats