idling


eb89

15+ Year Member

Joined
Jan 22, 2009
Messages
28
Points
3,101
Vehicle Year
1990
Transmission
Manual
Lately my trucks been idling at about 600 or so. just above 500, but usually when i drive it will idle at around 800 to 900 which i believe is normal. Any thoughts on why its idling so low now?
 
The 2.9L specs say it is supposed to idle at 800RPM. Is it auto? If so, in gear it will idle lower because the TC is putting a load on the engine.
Nick
 
no its a 5 speed. and when i have it in neutral now it idles at just above 500 and shakes a little sometimes. i can't figure out why.
 
Check for carbon on the backside of the throttle plate. That can cause low/ shaky idle.
Also, pull the tube that goes to the intake from the throttle body for the IAC and see if it runs better.

Check for vacuum leaks, check fuel pressure, and get codes are all you can do. It could be something like the O2 sensor, throttle position sensor, IAC, FPR, or many other things.
Nick
 
yeah i've cleaned out my IAC recently and made sure it was seated tightly. I was wondering about the FPR but I'm not exactly sure how to test that and also I can't fint the schrader valve to check my fuel pressure. is it under the hood or under the cab like near the fuel lines and fuel filter or what? also I've found out that whoever had the truck before me really screwed with the vacuum hoses and did some crazy shit with it so I'm tryin to sort through that right now. I unplugged one of the valves that he had plugged and the idle speed shot back up so I'm thinking the engine isn't getting enough air. I'm also going to change the air filter. Does anyone know of any good diagrams of the proper vacuum set up?

Also does anyone know what the part the screws onto the intake manifold is called? it has several vacuum hoses connected to it, one goes to the FPR. I'll try and get a pic and post it if i can.
 
Last edited:
To test the FPR usually you can pull the vacuum line off and see if there is fuel dripping out. The valves is on the fuel rail, just in front FPR. Also, pull off the vacuum line while the engine is running when you check the pressure. It should be around 30-40PSI.
If you left the vacuum line off, does the idle go down? If so, then you are fighting the computer and it is could be something like a something sensor related.
Nick
 
if i leave the vacuum line to the fpr does it go down? I'll check tomorrow and see. Any ideas. I'm really stumped on this one. Some times itll idle fine around 800 but it always ends up dropping down to just above 500. it also bogs down real bad on hills. any suggestions please
 
Need help! rpm's seem to go lower each day. Any and all suggestions welcome.
 
Could be a plugged cat. Let the engine idle until warm, and look at the cat. If it is clogged, it usually glows red or orange hot.

Does it idle that low when it is cold? Or just after it has warmed up?
Nick
 
It idles at its normal warm up idle, but then once it gets warm it drops way down. I'll definately take a cruise around town tomorrow and then check out the cat to see what its lookin like.
 
Thanks, yeah I plan on checking for codes when I get a chance to go by the auto parts store. I was thinking vacuum myself because as I posted in another thread, I think my vacuum set up is screwed up but I can''t find any good diagrams and the Haynes isnt really a help. I'll see what codes come up if any though.
 
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