Low Idle after engine warms up

Joined
Aug 18, 2021
Messages
12
Location
Denver
Hello, I am new to Ih8mud but I have searched for my idle issue and have not found a similar problem. When I start my 94 up, it runs great with the idle around 1000. After the engine gets warm and the “choke” isn’t needed anymore, it wants to idle around 400. I looked at every hose and checked every clamp as that seems to be the answer for other idle issues. My mechanic sprayed starting fluid at every hose connection to see if the engine rpm would increase but that didn’t work either. He then thought since I bought it two weeks ago on the west coast that our elevation of 7000 feet might be an issue so he advanced the timing some. That worked for about 10 minutes driving (the idle rpm was around 650) but then after 10 minutes it went back to 400.
Thank you in advance for any advise!
 
Joined
Nov 9, 2012
Messages
11,636
Location
Olathe, KS, USA
Hello, I am new to Ih8mud but I have searched for my idle issue and have not found a similar problem. When I start my 94 up, it runs great with the idle around 1000. After the engine gets warm and the “choke” isn’t needed anymore, it wants to idle around 400. I looked at every hose and checked every clamp as that seems to be the answer for other idle issues. My mechanic sprayed starting fluid at every hose connection to see if the engine rpm would increase but that didn’t work either. He then thought since I bought it two weeks ago on the west coast that our elevation of 7000 feet might be an issue so he advanced the timing some. That worked for about 10 minutes driving (the idle rpm was around 650) but then after 10 minutes it went back to 400.
Thank you in advance for any advise!
You need a new mechanic.

He did not properly set the timing. There is a specific procedure listed in the FSM (Factory Service Manual) Find one above in the "Resources" tab.

The engine on these is computer controlled and will adjust for elevation and air/fuel ratios, so he has no idea what he's talking about there. If it was a non-computer controlled, carbureted vehicle, I would agree, but.....No.

Odds are you have an intake leak somewhere, but the idle should land about 600 RPM.
This leak could be spark plug tube seals, valve cover gasket, oil fill cap seal, and a lot of vacuum hose seals as well as an intake hose crack. Using starting fluid should show that sort of thing, but it can also burn things down if it finds a spark in an alternator at the same time........

Any service records?
 
Joined
Aug 18, 2021
Messages
12
Location
Denver
Thank you all for you info. I‘ll go look at all those things listed above. The previous owners did keep pretty good records of service and idle problems are not listed.
 
Joined
Feb 7, 2017
Messages
92
Location
Fort Collins CO
Bought my 80 new in November 93. Last year failed CO emissions for first time after eternal CEL code 71 and set off on a Homeric Odyssey to fix. Replaced EGR, modulator, VSV, idle control valve, throttle position sensor, refurbed MAF, all new gaskets and seals in entire chain, new O2 sensors, pulled and cleansed throttle body and manifold, all new vacuum hoses, new charcoal canister, new valve cover gasket, plugs and seals, distributor cap, rotor, and all new cables. After everything still settled in at around 450 rpm idle and moved throttle cable barely a mm. Truck now idles at 600rpm, runs and shifts better than the day I drove it off the Nye Frontier Toyota lot in Anchorage in November 1993. Just passed CO emissions w flying colors and no CEL for months.

Okay tweaking the throttle cable wasn't technically a fix but a break with intended outcome. Good luck! :)
 
Joined
Aug 18, 2021
Messages
12
Location
Denver
Bought my 80 new in November 93. Last year failed CO emissions for first time after eternal CEL code 71 and set off on a Homeric Odyssey to fix. Replaced EGR, modulator, VSV, idle control valve, throttle position sensor, refurbed MAF, all new gaskets and seals in entire chain, new O2 sensors, pulled and cleansed throttle body and manifold, all new vacuum hoses, new charcoal canister, new valve cover gasket, plugs and seals, distributor cap, rotor, and all new cables. After everything still settled in at around 450 rpm idle and moved throttle cable barely a mm. Truck now idles at 600rpm, runs and shifts better than the day I drove it off the Nye Frontier Toyota lot in Anchorage in November 1993. Just passed CO emissions w flying colors and no CEL for months.

Okay tweaking the throttle cable wasn't technically a fix but a break with intended outcome. Good luck! :)
Can I ask who do you take your 80 to? I’m more by Fort Collins than Denver but would make the journey for a good mechanic.
 
Joined
Feb 7, 2017
Messages
92
Location
Fort Collins CO
Used to have a local shop that was very well versed on everything 1FZFE, but business was sold and I've been *incredibly* disappointed at the utter carelessness of everyone else I've tried locally. I DIY everything I can and for things I can't handle from my residential 2-3 banana garage I only trust Slee down in Golden.
 

Users who are viewing this thread

Top Bottom