420A Unsteady Idle

[BLACK'98DSM]

I will start by saying that I have already replaced the TPS. It threw a code for the TPS last year and I resolved it, and it hasn't came back. I have new plugs and plug wires, new coil pack as well. So my question is why do the rpm's fluctuate when I am at idle? The tac usually moves from 700 rpm to 1000 rpm. It just goes up and down at random with no pattern. I suspected misfire, but all the components that could cause that are new. And it runs very well at high rpm, so it's really only an idle thing. I have run fuel treatment through it so I think the system is clean.

 

[dustyboner]

Sounds likd a small vacuum leak

Could be a problem with the evap purge solenoid. Pull the hose off the top of the throttle body and cap the port or just cover it with your finger to check

 

[ThunderChild]

EVAP solenoid is a good check. How about the IAC valve, and is your egr still hooked up/functional?

 

[BLACK'98DSM]

is your egr still hooked up

I fixed a vacuum leak on the egr just before I posted this, and it didn't fix the problem. I will try the throttle body trick tonight.

 

[BLACK'98DSM]

I checked all of my vacuum hoses and they are good. No leaks and not clogged.

 

[BLACK'98DSM]

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[BLACK'98DSM]

The last part of the video shows it. It usually does it much more than the video shows, but I think you get the point.

 

[BLACK'98DSM]

Dammit you could hear the vacuum hose sucking in air when I rev it. I resolved it now though, and fixed the cruise control at the same time.