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Stephen Lesh

Rough engine with fans on

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Has anyone had this with a 2.0

The engine is as smooth as a 4 cylinder can be with no loads.

but when the cooling fans come on the engine get rough. this is felt at idle and while driving.

The same thing happens when you turn on the headlights or the blower.

Alternator is holding 14 volts or better with anything on and more than 13.4 with everything on.

 

The car has no apparent loss of power, throttle response it good, no hesitation

Could this be a coil breaking down and the electrical load is making it show?

I don't like throwing parts at a car.

 

Any insight would be helpful. Thankyou

 

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Check grounds and connections, especially the ground near the radiator.  If you have a scantool, check and see if any sensors / readings are changing when there is more electrical load.

 

Radio Shack sells an electrical contact cleaner that seems to work well, definitely helped my car (different symptoms)

 

Could be ignition but check other stuff first.

 

Guys that work on lots of these cars may have other ideas.

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No voltage drop on battery posistive or or grounds. No change on fuel trims or advance or anything else, looks the same as without symtom.

 

I'm a GM master tech and this car is beating me. Yeah I use crc contact cleaner all the time, it's great stuff.

 

Just made a interesting find. I took the belt off to check for any pulleys that might be seizing up, So I started the car with the belt off, turned the fans on and,

no symtom. smooth with not even a stutter on fan start up.   mmmmmm????

 

Guys at the dealership use this as ammo againt Ford. They already give me a hard time.

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That's weird for sure.  In my case, some of the problem was the throttle position sensor reading being affected by some combination of bad ground and corroded connectors, the ECU acts weird if it thinks the throttle is partially open when it is shut - the voltage (as reported via OBD) being 0.05V higher than it should have when closed been made a big difference.  My issue was surging and especially throttle hang, not roughness, so may not directly relate...

 

One cause was a loose bolt (my fault from engine install) on front ground - that made it act really weird when fans came on.  But sounds like you've checked that.

 

So it works OK at light electrical load, and works OK w/ no alternator - so I guess it can't be just something being sensitive to low voltage I guess...???

 

Here's a long shot - I have not seen this in a road car but did on my race car - maybe the alternator is failing in a way that puts huge noise (ie spiky voltage) out under load and that's what's affecting something.  Can you put a scope on the system and look for noise?

 

Changing alternator on 2.5 is a bit of a bear (having done it) but hopefully not too bad on 2.0?

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I already replaced Alt, It was under warranty. It's easy on a 2.0. Ford manual does'nt list this under symtoms. I was kinda thinking noise or bad alt wiring.

 

I was thinking of upgrading the battery cables. That worked in my Bronco, 26 year old wiring needed more juice.

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Did this same problem exist before the new alternator was installed?

 

As you can tell, I'm wanting to blame the alternator though I suppose it could be wiring....

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Now get this. When I wiggle the fuel return line, it goes to miss firing and the fuel trims start climbing. Let go of the line and it will straighten out.

I can't tell if it's related to the roughness caused by the alternator.

This is the strangest problem I've ever seen.

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Injector plug was'nt seated and the fuel line was pushing on it.

 

Now as far as the alternator problem, I'm now thinking mechanical drag, but I don't have a way to test for that.

All my years as a tech and this has never come up.

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Like you said in earlier post, swap out alternator, or at the least loosen belt tension (remove tensioner pulley) in order to reduce mechanical drag. Of course the latter will also reduce alternator output slightly.

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Is it really rough or just not smooth? I have a 1996 5 speed and from day one the idle was "not smooth" and if I put on the ac/defroster or even the lights it would get rougher, not horrible but rougher. Also with the ac or defroster on I could detect a slight hunting of the throttle when driving as it got older. Cleaned the throttle body this year for the first time, I'm the original owner, and it really smoothed out the idle. The IAC valve is a real pain to get to on my engine so unless it gets real bad I'm leaving it. However I'll check the throttle position sensor since it's easy to get to. I'm afraid to yank on wiring harnesses and connectors due to the weak wire insulation if it's not absolutely necessary. I did notice that after cleaning the TB on the first stop after cold start in the morning it would almost stall once but then run fine, if the first stop was a mile or less.  I can live with that :wink: .

 

Whimsey29

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Any more info on this issue? My 99 2.0 idles rough when a/c is on and its in gear. If i either turn of a/c or put it in park, it smoothes out.

I just read on here that weak motor or trans mount can cause this rough shaking???

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....from day one on the 4 cyl Contour there has been an issue with rough idle when the a/c compressor clutch kicks in re compressor drag..FWIW the AC compressor DOES operate in heat mode to dry the air and not just in AC positions..To check this out switch ALL heat controls to 'OFF' position,no fans , flaps etc...Chances are the engine will be smooth...also check out AC pressures etc..

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My A/C compressor only runs in the A/C, MAX, and DEFROST settings.

It's very humid were I live. Most of the time my windshield fogs up in PANEL or FLOOR settings.

Ford vehicles with digital auto climate controls, yes they run the compressor in all settings unless the control head has a VENT compressor override button.

 

My vibration isn't only A/C compressor running. It's any load on engine plus compressor.

Compressor running while at stop light, foot on brake, transmission in drive, the whole car is shaking. I usually bump trans in neutral at stop lights and then its smooth. Also some vibration if headlights on or cooling fan running.

 

I have changed alternator and new Interstate Battery. But I didn't change the wire on the alternator that TSB says causes false Battery warning light to stay on.

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Saw this today maybe it will help you.

 

The problem might be with Idle Air Control valve circuit.

The IAC valve is what controls the engine idle speed depending on the load imposed on the engine at idle. So for example, if the steering wheel is turned the power steering pump imposes a load on the engine at idle. The IAC valve then moves to a position to step the idle up to compensate for this load so the engine doesn't run rough or stall. The same thing occurs when the AC or defrosters are turned on. The AC compressor imposes a load on the engine at idle and the IAC valve moves to a position to compensate for this load so the engine doesn't run rough or stall. Now if the steering is turned and the AC is on at idle, the IAC valve has to move to another position to compensate for those two loads imposed on the engine at idle. So the IAC valve is a stepper motor that can move to various positions for the various load conditions when the engine is idling.

If the IAC valve fails to go to the proper position where the engine has a rough idle when that load is imposed on the engine, it means the IAC valve isn't allowing enough air into the engine. This can then cause the engine to run rich and/or cause an engine misfire. This then will cause the Check Engine light to come on.

The first thing to try for an IAC valve problem is remove the IAC valve from the throttle body, and clean it along with the idle air bleed port on the throttle body of deposits with an aerosol throttle body cleaner. Then reinstall the IAC valve to see if that fixes the problem. If that doesn't work, with the engine up to operating temperature and idling, take the handle of a screwdriver and rap on the IAC valve. If doing this has an effect on the idle speed, there's a problem with the IAC valve.

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