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Hey everyone. Recently purchased a 1990 Comanche 4.0L. Truck runs great but recently has been stalling after I drive. It starts no problem and idles fine at first, but after it runs it stalls occasionally when I let off the gas or it will idle very rough, from close to 0 - 2,000 RPM's. No issues overheating. Just cleaned all the lines from the valve cover and vacuum lines from IAC and replaced the valve cover gasket. Emissions Maintenance light has been on since I bought the truck from my neighbor, close to two months ago and I don't know of anyone with the OBD1 diagnostic. At the time he said it had a bad O2 sensor, but wasn't giving me any problems. It has a very slight exhaust leak in the cat converter. It also seems to happen a lot less often if I keep the RPM's under 2,000, which is making me wonder if it can be the throttle positioning sensor. Any helpful information is greatly appreciated.

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The Emissions Maintenance light is on a timer. Comes on at 80,000 miles regardless of the condition of the emissions system. It's intended as a reminder to get the system checked out, but it won't hurt to check your O2 sensor, though. I'm sure someone who knows can chime in with the procedure for that.

 

Also, your '90 is a Renix, not an OBD1.

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I can help with the light......and start you on the path for the stalling

 

http://comancheclub.com/topic/19732-random-informative-picture-thread/    

 

Look at Pic#9

 

That box is located to the right of your steering column....unplug it....no more light

 

 

Look at Cruisers Renix tip thread..http://comancheclub.com/topic/36382-cruisers-renix-tips/..start with the ground refresh  :thumbsup:

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The Emissions Maintenance light is on a timer. Comes on at 80,000 miles regardless of the condition of the emissions system. It's intended as a reminder to get the system check out, but it won't hurt to check your O2 sensor, though. I'm sure someone who knows can chime in with the procedure for that.

 

Also, your '90 is a Renix, not an OBD1.

 

:agree:  Sounds like your truck is not transitioning from open to closed loop due to a bad O2 sensor. It's time to replace it. 

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these guys know there stuff about the sensors....but you did say it seems to happen when you apply the brakes. just an off throttle coincidence, but you may want to check the vacuum line that runs from the intake manifold to the power brake booster and also the fitting/gromet at the booster.

 

Can't help it, I'm from the old school, thats what I'd check 1st because of your description.

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these guys know there stuff about the sensors....but you did say it seems to happen when you apply the brakes. just an off throttle coincidence, but you may want to check the vacuum line that runs from the intake manifold to the power brake booster and also the fitting/gromet at the booster.

 

Can't help it, I'm from the old school, thats what I'd check 1st because of your description.

 

Where did he say that?  :hmm:

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First off it's not OBD-1 but Renix.

How are the plugs, wires, cap and rotor?

Ever clean the throtte body and IAC?

Are the intake manifold bolts loose?

 

Have you ever done the ground refreshing that's in my signature?

:dunno:  :dunno:  :dunno:  post 3....... :thumbsup:

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