Bad Idle

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Bad Idle

Postby johnio69 » Mon May 01, 2017 5:29 pm

I have a 94 Amigo with 2.6 I just bought. I had to put a new head gasket in. It runs great when cold but as soon as it warms up to operating temp the idle goes crazy. Up and down.
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Re: Bad Idle

Postby Oregon RS » Wed May 03, 2017 1:50 pm

Did the truck have similar idle issues before head gasket replacement ?
Did you replace the head gasket yourself ?
Assuming that proper procedures were followed for the head gasket, there are lots of hoses, wires, and other important stuff that need to get back together correctly.

It may run great cold because the cold idle is higher than the warm idle setting.

In my experience, the most common cause of hunting idle can be traced to the 3-1/2 miles of vacuum hose that serves the 2.6 I-Tec.
Check everything twice and replace anything suspect...pay close attention to the ends of the 3/8" vacuum hoses on the passenger's side of the engine bay, and check the all those little hard plastic hoses for cracks.

Double-check the routing of your vacuum system...should be a diagram on a sticker on the under side of the hood.

From there, you might consider squirting some PB Blaster down the hose leading from the IAC up to the intake and let it sit overnight in case it's gummed up.

A bad coolant temp sensor...the poorly placed one on the under side of the head can cause similar issues once the engine is warmed up, but so can a number of other things.

If none of these things help, we'll have to dig deeper.

Good luck.
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Re: Bad Idle

Postby johnio69 » Wed May 03, 2017 2:14 pm

I replaced the head gasket myself and did it correctly but its hard to tell how it ran before. I bought it with a bad head gasket. I replaced a few of the vacuum hoses already but will check again for bad. Everything is hooked up correctly. Ill take your advice on the iac and replace the temp sensor seeing how its relatively inexpensive. Thanks for the input.
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Re: Bad Idle

Postby Oregon RS » Wed May 03, 2017 3:24 pm

No sweat man, just passing along my experiences with these trucks as others have done before me.
Glad to hear that you're doing the work yourself so you know what's going on in there.

I may have had too much coffee today, so this might be a long post...

Did you check the valves or have the head re-worked while you had it apart ?
If not, I strongly suggest adjusting the valves either way...especially if the truck is new to you !
The 2.6 can get lopey idle like this if the valves are out of spec, and it's especially easy to burn exhaust valves if you don't adjust them as recommended.

Just to be clear though, there are two coolant temp sensors on the 2.6.
The one that runs to the gauge is on the front passenger side of the engine near the oil pressure sensor.
The one going to the ECM that could effect engine performance is located under the intake and is a PIA to get to, even through the passenger side wheel well. Look here for a picture :
http://forum.planetisuzoo.com/viewtopic.php?f=1&t=101434&p=5226714&hilit=coolant+temp+sensor#p5226714

The plug and wire on the lower one sticks out awkwardly and can get tweaked if you set the head down without a 2x4 or something under it to take the weight. Either way, maybe you'll get lucky and find that the plug's just not firmly seated on the sensor.
Stranger things have happened.

Also did you separate the head from the intake when you did the head gasket ?
Use a stethoscope or length of fuel hose to listen around the intake, the air filter box, and the big plastic tube thing that runs between there and the intake for a vacuum leak. Wiggle stuff around and shoot a bit of starting fluid or brake cleaner around those areas with the engine running to see if you get a surge.

If none of these things helps, hit us with more details about the wild idle you're experiencing such as the RPM range it surges between and any other little details you can provide.
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