Slight hesitation

[Brandon]

My 89 Civilan car has got a slight hesitation when I just mash the gas a little bit. It also surges on idle when I crank it. It stops if I let it run for a minute or two. It'll still do it when its warmed up and I cut it off and crank back it'll idle up and down for a minute.

Sometimes the slight hesitation is not as bad as some times. Seems like it Varies from time to time. Plugs, wires, cap, rotary button is all good. Any thoughts on this to what I can check? Yes it is the 5.0L that is stock. Thaks guys

[Brandon]

anybody?

I'm not a 100% sure that it isn't the plugs but pulled one of them out and seemed to be fine. They've been changed at some point along with the wires.

I did unplug that one sensor that goes behind the throttle boddy that has two bolts holding it on. I cant think of the name for it. LOL. But when I unpluged the motor died. So It's working right. correct? It also has a new sensor that sits directly top of the throttle boddy. I think TPS? has two wires running from it and goes into a plug.

The hesitation is getting a bit annoying. It does it when I give it a little bit of gas then stops when I give it more gas. Sometimes it's worse than other times. If I gave it more gas past the hesitation point it would spin in gravel. Kinda annoying. Also It seems to be a bit worse on a cold start and taking off. I let it run for a minute and take off and it seems to be worse than if I would have let it run for 5 minutes then take off. idk

[1990LTD]

the 'thing with two bolts' behind the throttle body is the idle air control valve. it meters how much air gets past the throttle plate at all times.

a problem with the IAC valve would cause all kinds of problems coming on and off of the throttle. you can definitely try cleaning it, though. pull it off, protect the wiring, and blow the shit out of it (via one of the ports) with a can of carb cleaner or intake cleaner until the fluid running out of the other port it is clear. DO NOT reinstall or try and use it until it is completely dry.

[gadget73]

Could be a vacuum leak. Make sure all the lines are in good shape

[Brandon]

I checked the vaccums of what all I could get too and they seem to be okay. I haven't tried cleaning out the IAC yet but will give that a try.

[1990LTD]

if you clean it, clean the throttle body too.

[Georges86]

Coolant temp sensor. I had the EXACT same problem, and that fixed it. Along with the Vac. line under the plenum.


George

[87gtVIC]

Can someone explain why the coolant temp sensor causes this type of problem?

[Georges86]

I thought, and this is secondhand knowledge, that the computer uses the temp to determine idle kick-down or speed or something? I'm not a 100% on it though


George

[91waggin]

The computer uses the coolant temp sensor (ECT), along with MAP, and several others to determine the appropriate mixture. The ECT tells the computer whether the engine is warmed up or not, and how rich to run it in order to get the engine warmed up as quickly as possible. If you're having cold start problems, I would definitely look at the ECT first.

You can put DVOM on the ECT and check the resistance readings against a thermometer in the radiator to see if in fact the ECT is reporting the correct information.

Rockauto has the ECT listed under the "cooling system" subheading; they have a Motorcraft part listed for about $35. I'd go with that one, simply because Motorcraft generally has the best stuff.

[Brandon]

Okay guys. I checked the iac sensor and it's real clean. Throttle body is clean too.

So is the Coolant temp sensor under the uper intake? Another words I have to remove it. And I know this might be dumb one, but where is the map sensor? I know it has something to do with fuel but not sure of what it looks like. I've never had to look into replacing one.

Also the car is using oil (quart every two weeks) It's not burning it and see no oil spots but it's using it. It also seems to be using water (coolant) some where as well. I see no signs of the radiator being bad as I have removed the fan shroud. While in that process I converted it over to the 90 Town Car shroud and air breather. Again if I have to remove the upper intake that is no big deal for me. I've done it before and plan on replacing anything that needs it while I got it off. Valve cover gasket for a fact. It's not smoking under the hood or anything but it sure probably wouldnt hurt. I've got a preety darn good grasp on working on these cars. I'm just not so familar with the sensors. More of a carburator guy. LOL.

Anyways, thanks for all of your input guys. Much apreciated

[Brandon]

:bump:

Just curious about using the oil and coolant and what an where is the MAP sensor. Thanks

[Georges86]

You'll see it when you pull the upper, I did mine when I did the valve cover gaskets/pvc. O'Riley's had a good Borg Warner one for super cheap.

[91waggin]

Um....I don't know what you mean about seeing it when you pull the upper. The ECT is right by the water neck to the upper radiator hose, set into another water hose. The MAP sensor is under the wipers slightly to the passenger side of the centerline. It has a few wires and a vacuum hose going to it. Shouldn't have to pull the upper for either one.

[Georges86]

Oh, guess I never bothered to look for it until I did, I had a lot of other shit to do when I was there. Thanks for the correction, my mistake. But if you do pull it that vac line with the red stripe on it went soft on mine. Be a good time to replace it.

George