1995 Eddie Bauer Full Size Bronco with 5.8L engine.

I get a ~250 rpm increase (engine surge) with the defrost or mix on. The surge is accompanied by the air conditioning compressor clutch engaging then it releases and the surge stops.

Normal idle is about 750 and it surges to about 1,000 rpm and it does it constantly when defrost or mix is on.

Does it only for about 2 seconds each time, but constantly. Does not do it on vent.

Not only is it annoying, but if you didn't have your foot firmly on the brake at a stop light, you could rear end the car in front of you when it surges.

Any thoughts how to fix this?

 

My 94' 5.8w E150 did the same thing. I believe the cycling of the compressor is part of the factory a/c function. It is mentioned in the sticky in the a/c forum on this site.

"Problem: The A/C compressor runs in different climate control positions.
A:Generally, it’s supposed to be enabled in all settings except OFF, FLOOR, and VENT. Refer to your owner’s manual."

What actually triggers the activation of the cycling I'm interested in myself as my 86 Bronco does the same thing with the EECIV puter removed. How often it cycles or for how long is my question.

Since the compressor will not run w/o enuf charge..I wonder if the level of charge may effect how often or how long it does or doesn't cycle.? Making sure the system is charged adequately is my first question. Hopefully someone here can illuminate how that system works and in your case help you to adjust the throttle response involved.

In my case I have removed the throttle solenoid actuator and merely raised the idle to compensate. I have a carbed 300-6 so in my case I get the momentary "drop" or drag when it kicks in. Annoying for sure...but probably necessary for adequate moisture control year around I guess... In your case, I would suppose that maybe a high idle solenoid is used somewhere to nudge the TB setting?..Don't know..I sold my 94 EECIV powered van so can't check that out. Maybe it is just a solenoid that can be adjusted....

Hopefully you'll get your questions answered..I'll be listening as well

 

Dear JohnSmith3524: So, it's Winter now which means I am too old or too brain dead to remember last Summer. But now that you put your friggin' finger on it!!! My air conditioning did not work last Summer.

Once I get the A/C recharged I will post the results...

It may be obvious to everyone else but me, but your advice is brilliant. Thanks Dude!

 

backatcha brother...

 

I would check the idle air control valve before spending any money. It seems to be the main culprit in idle surge/engine surge. Mine did the same thing.

 

Just f some more information I learned when messing with A/C is that it is good to run it at least 5 minutes or more each month.

So if it is your AC that is causing the surging and you get it fixed, make sure to use it every so often! The reason behind this (from what I understand) is that the running of the AC compressor helps move oil throughout your system. This in turn helps keep all the seals in the compressor (and lines) safe and oiled. If it isn't run for a long time, the seals can start to dry out and get damaged. This can cause leaks in your system and also contaminants from o-rings/seals breaking down!

A couple years back, I ran my defrost in my 96 bronco during the winter and the AC compressor kicked on and seized up then went to shred my serpentine belt! Anyways, good luck finding the issue and hopefully it's not too expensive to fix!

 

Thanks guys. And yes Bubba, I let the vehicle sit for almost a year on a trickle charger, starting it every so often, but I don't recall ever turning on the AC...

 

In the meantime just unplug the pigtail on the compressor. Should stop the surge without messing anything up.

Make sure to wrap the pigtail and the socket with electrical tape to keep out grime.

 

I have had two threads going recently:

1. Engine Surge with Defrost or Mix

2. 1995 5.8L Bronco stumbles/misses/bucks when accelerating, under load or climbing

Last week before driving to work I did what Zombieslayer and Conanski advised and disconnected AC compressor (by disconnecting the two pin electrical connector at the AC compressor).

1. This totally fixed the engine surge.

2. But for some reason, possibly related, possibly unrelated the engine also did not stumble/miss/or buck on the way in and from work or during the rest of the week (all flatland driving). I accelerated harder than I normally would to get it to stumble, but it didn't.

This weekend I drove from Sacramento, CA up Hwy 50 through the mountains to South Lake Tahoe. If you aren't familiar with this route, it is a steady climb. The engine stumbled twice requiring me to manually downshift out of overdrive to 3d, and it didn't stumble in the lower gear (which was my previous experience). At other times it shifted out of OD to 3d or from 3d to 2d without stumbling first - operating at is should.

I then drove from Hwy 50 to Hwy 88 and uphill through the Carson Pass. This is a very steep uphill grade. The engine stumbled once and only once.

This is a phenomenal improvement in engine performance. Previously, the engine would stumble so often that I would have to drive a significant part of that Hwy 50 uphill route in 2d to prevent it from stumbling.

Zombieslayer said this to me in a PM: [/QUOTE] By unplugging the pigtail on the compressor you are killing the electrical signals (and the A/C while the pigtail is unplugged) so the compressor is just sitting idle. The clutch still spins which allows the belt to move. [/QUOTE]

So, the problem is solved, at least temporarily until I want to have air conditioning, but the mystery persists. Why did disconnecting the AC compressor help? And what would be a permanent fix?

In the interim, I would suggest that everyone who is experiencing an engine surge or a stumble/miss/bucking with a 90's era 5.8L disconnect the two pin plug at the AC compressor and see if there is any improvement. It is a simple test, and does not cost a cent.

Finally, on my way home this weekend, the belt tensioner broke (the entire pulley came off) and I had to be towed home. (It started squeaking last week and I thought I had a few days to get around to replacing it, but I was wrong.) I mention this only to be complete. I don't know whether or not the likely bad bearing in the pulley is related to this problem or not.

 

Keep in mind I am by no means a mechanic, but I don't think a bad pulley would cause the surging or stumbling. I myself had the surging issue which went away after unplugging the pigtail on the compressor. Reason I unplugged it was because the compressor itself froze and rather than risking further damage with an accidental turning on of the a/c ... I just unplugged it The stoppage of the surging was just a pleasant side effect

Hmmm if the stumbling isn't happening on level ground (does it happen downhill?) perhaps you have something in your fuel tank moving around, or maybe something in the carb?

Also did you check your "idle air control valve" as brought up by seattle64?

 

Hmm too me sounds like bad news unfortunately.

When the A/C system is functioning (Compressor engaged and turning), it will take some power and add drag to the serpentine belt system. However, the amount of power it takes shouldn't be very noticeable when operating normally, and would not cause stumbling.

To me, it sounds as if your A/C system is on it's way out. This is because if your A/C compressor is causing stumbling/poor performance when it's functioning (i.e. connections plugged in and A/C turned on which both defrost and mix utilize the compressor), then the compressor is having too much trouble trying to turn. This adds much more drag on the belt than normal and will cause performance issues.

Recently, I did some work on my mom's 2001 explorer. She was having idling issues and performance loss. When I dug further into it, I quickly noticed that her A/C compressor was causing the issues. In fact, it got so bad it started to smoke the belt when it was turned on. There was no noise, nor apparent loss of cooling from the A/C system, but it was for sure causing her performance issues.

There could be several reasons why your A/C compressor is harder to turn, but they all lead to the same fix.. which will be $$$.

Reason 1

You have a leak in your A/C system and your compressor is cycling on and off too frequently due to low refrigerant levels. If the compressor cycles on and off a lot, it can give the effect of stumbling while driving (the compressor kicking on will put drag on the serpentine belt, which take some power away from the engine, then when it kicks off, you get the power back.)

If your system is low on refrigerant, you have a leak in the system and it needs to be repaired. Unfortunately, this means the system has to be opened, and minimum your leaking part must be replaced along with your A/C accumulator and orifice tube (an accumulator should be replaced every time the system is open and the tube is a cheap filter that is good to replace.)

Systems that are low on refrigerant often times don't get lubricated properly and this causes the seals in the compressor to become brittle and break down. Once these seals start to break down, they contaminate the entire system which leads to the next cause:

Reason 2

Your compressor is starting to seize due to contaminants in the system. These contaminants can come from what I stated earlier about the seals breaking down. I've read also that contaminants can arise from compressor oil/refrigerant breaking down over time from the A/C system not being operated frequently enough. I don't know if that second case is true with things breaking down causing contaminants, I do know however that if the system isn't operated enough, it can cause the seals to become dry which will break those down.

If your compressor is starting to seize, the only recommended fix (besides getting rid of your A/C entirely) is to replace almost your entire A/C system.

This involves a new:

Compressor
Condensor (can't be reliably flushed so is not worth trying to save)
Accumulator
Orifice tube

You will want to flush your A/C lines if you do not replace them, and you should be safe to flush your evaporator (the orifice tube generally prevents most contaminants from getting in there, so a flush will suffice here).

Apart from those parts, you will need to proper amount of Compressor oil, and refrigerant (r-134a, if you have r-12 it's too expensive to try and get that and easier just to switch to r-134a at this point).

Also, once everything is installed and sealed on your vehicle, in order to make sure you don't have leaks and get rid of left over moisture in your system, you'll need an A/C manifold gauge set which lets you pull a vacuum on the system. It's good to have a vacuum pulled for at least an hour. The longer, the better. Some people say to do it overnight, but an hour should be sufficient. If the vacuum doesn't hold, then there is a leak in the system and it must be found and repaired before adding refrigerant.


As you can see, this is going to be an expensive en-devour.




I have fixed the A/C myself on my Bronco and mom's Explorer. I'm getting ready to tackle this on my 91 Camaro now also. If you feel bold enough to tackle fixing A/C yourself, you can PM me and I can give more specifics on what needs to be done.

You may be lucky enough to just fill your A/C system with one of those bottles at the auto parts stores. If that prevents your A/C compressor from cycling on and off a bunch (which might be your cause of stumbling with the A/C on), then you can limp by with that for potentially the next year or so. However, be mindful that if you do have to do this, a real A/C repair is going to have to be in your budget eventually.

Otherwise, if you leave your compressor unplugged like it is now, the pulley on the front shouldn't go bad and you won't have to deal with fixing the A/C, however, you won't be able to use yours, and when you do go back to trying (if you leave it off for a long time), the compressor may seize up.

 

Bubba Jones: Thank you for the time you put into your post! I will report back when I get into the AC system! At the moment I am installing the new tensioner pulley, idler pulley and serpentine belt.

The tensioner pulley (bottom middle) is missing so obviously screwed up, but the idler pulley (top right) spins with a clunk clunk clunk. So both are being replaced. I bought them locally because I need them now, but best prices I found were at

fordparts.com

Being proactice and ordering them before you need them will save you about $150 less than what I paid.

All the other accessory pulleys seems to spin fine.

According to the Ford 1995 Bronco Service Manual, the torque specification on the torx bolt on the automatic tensioner pulley is 35-46 Lb-Ft. I will assume that it is the same spec for the torx bolt on the idler pulley, since I can't find it in the manual. One more thing, a member in the 7.3 PSD forum warned that we should always re-set our torque wrenches to zero to relieve pressure on the torque measuring spring after using it. I used this opportunity to get into all of my torque wrenches to do that.

I haven't replaced a serpentine belt in a while, after fiddling with it for a while this worked for me: Putting the belt on every pulley except the idler pulley, then using the 15mm box end wrench to pull against the belt tensioner spring to relieve tension, and only then slipping the belt under the idler pulley. And then getting under the vehicle while relieving some tension on the tensioner to move the poly-V (apparently meaning "multiple" "V") belt off the rim and into the proper grooves on the crankshaft pulley.


New pulleys work great! After I am done doing the door window regulators, I will look into the AC issue.

 

No problem! If you do find things wrong with your A/C feel free to PM me for more specifics. You may be able to find good threads here too or I think there may be an A/C thread on this website somewhere too but I don't remember.

For the torque wrenches, you definitely want to put them back to zero after using them. With my first torque wrench (a cheap harbor freight one), I left it at like 100ft-lbs after one of it's uses. About a week or so later I went to use it again and the 100ft-lbs setting was more like 20ft-lbs. That's not a good thing when installing your wheel bearings and hubs.

It gave me an excuse to buy some nice kobalt torque wrenches though, and now I have a rachetable breaker bar!