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Author
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Topic: 87 GT stumbles
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 09-27-2000 04:46 PM
   
My 87 GT misses and almost dies when I am driving it and turn the AC off. Anyone know what may be causing this?
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Stewart
Pit Boss Posts: 3620
From: Monterey, CA Mustangsandmore Member #437
Registered: Apr 2000
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posted 09-28-2000 01:18 AM
Hmmmm, I haven't got a clue, but let me ask a few friends. I'll also see if I can find anything like that in any of my books.In the mean time, Capri? Charlie? Dave? Ian? Any of you guys have a clue? Stewart
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jimb
Gearhead Posts: 106
From: s. holland, il usa
Registered: Nov 99
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posted 09-28-2000 08:33 AM
I do know that the computer adjusts the idle speed of the engine when you turn on the AC. Does this hapen when you are just crusing along or stopped and at an idle? I have some info at home that may give you some things to look at. I just need some more info first before looking up the problem.
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 09-28-2000 08:44 AM
Hmmmmm. Lets first look at the basics. When was the last tune up? What is the car Idling at? Is the Throttle position voltage been checked, and is it at 1 volt? Have you put a Code scanner on it as of yet? My personal opinion is there is a Throttle position sensor problem, but we all know that anything is possible!!!!!Tony.
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 09-28-2000 11:13 AM
If I turn the Ac off while crusing or at idle, the car will miss and almost die. It runs fine other than that. the last tune up was about a year ago. I have replaced the TP sensor a couple times. I think i set it to .98V when I replaced it last year. I have not checked the codes yet. I was not sure it would give me a code since it happens only when turn the AC off. It idles at about 800 r.p.m's. I think there is a idle adjust screw on the throttle plate. I think that is to adjust for AC idle.
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FISHTAIL
Journeyman Posts: 83
From: Waldorf MD USA
Registered: Sep 2000
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posted 09-28-2000 11:23 AM
Ok, that doesn't sound like much like a tps problem, that's more of a surge... I have a few questions for you. Does the car only do this at idle, or does it do it at speed while your driving down the road? Does it act fine when you turn the a/c on, and while the a/c is running? Have you pulled your belt, and checked your ac clutch to make sure it's not sticking? If the clutch is sticking, it might be restricting belt movement and causing the car to stumble.....------------------
-FISHTAIL
92GT "The Ghetto Sled"
CMPS major @ University of MD college park
Best run so far: 14.74 @ 100.3mph....damn wheel spin.
VP and co-founder of CMTC www.geocities.com/dastangboys
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Stewart
Pit Boss Posts: 3620
From: Monterey, CA Mustangsandmore Member #437
Registered: Apr 2000
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posted 09-28-2000 11:48 AM
Hey Mike!! Ya finally made it! Glad to see you register as a member. Y'all, Mike is the one I turn to when I have tech questions about my 'Stang...I've been trying to get him to register here for awhile now. He's pretty good at helping to figger out probs with the 5.0's. Mike, when you get a chance, ya gotta come hang out at Sam's Place. We have lots of fun over there. In fact, I think I'll go announce you...so don't leave me hanging, make sure you post over there too! Stewart PS - Do you remember Gearhead, from the GT board? Ian and his '79 Indy Pace car...lives up in Canada? He's a member here too. ------------------
"If you go fishing, bring a fishnet  you might catch a hummingbird" 1990 Platinum GT (my poor baby's sheet metal has been violated!)
- Some mods, but not enough!
1996 Blue Crown Vic
- Suspension and exhaust mods, but nothing else...YET! Blue Oval Believer, thru and true. [This message has been edited by Stewart (edited 09-28-2000).]
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 09-28-2000 01:44 PM
Ok guys, I have to ask this question. If the ac clutch was sticking, what do you think would happen to the belt???? Is the a belt squeal being heard? I suggest unplug the electrical connection at the compressor just to verify that is does not happen. I am sure it wont, but it wont hurt to take 2 minutes and try it. When the Compressor Cycles, it does draw the power down and Idle drops a bit. But why would it pull it so far down that it would die?? This is what we are in search of. I am leaning toward a bad IAC motor on the side of the throttle body. Pop it off, and clean it up a bit inside. If it helps some, then keep an eye on it. It could be so full of jive, the IAC is not getting the proper air intake signal.Tony.
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FISHTAIL
Journeyman Posts: 83
From: Waldorf MD USA
Registered: Sep 2000
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posted 09-28-2000 02:25 PM
LOL, hey stew....what's up? Thanks for the intro...hahahaha. I've been meaning to come over here for a while, but school has kept me busy..plus keeping after my own page and club  . yeah, I rember gearhead, and the 79 pace car . They are old school. Remeber purple haze and 1hot5l? They are all over at teh corral....lol. Capri, I was also thinking along the lines of the idle air control, but I wasn't sure if the car was doing it at idle, or under power. Also it may not nessiarly be the clutch, but I was thinking something along the lines of teh compressor. If for some reson it's causing excess resistance but not nessiarly locking up, it would be a problem at idle. Under power though, the belt would just slip over it and eventually break. There are other ways to check....try turning the wheel from lock to lock etc at ilde. See if you can put the motor under a little more load to see if it trys to die out...------------------
-FISHTAIL
92GT "The Ghetto Sled"
CMPS major @ University of MD college park
Best run so far: 14.74 @ 100.3mph....damn wheel spin.
VP and co-founder of CMTC www.geocities.com/dastangboys
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 09-28-2000 04:56 PM
It does not matter if it is at idle or you are cruising down the highway. before getting the ac charged, it did not happen. I would think it is an electrical or sensor problem, because it happens when disengaging the clutch. That means lessening the load on the motor is when it happes. If I remember correctly, it only happens when turning the ac off. I willcheck.
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 09-29-2000 08:33 AM
I checked and it does not matter if the car is at idle or at higher rpms(3000). It does not happen when I turn the AC on, just when the AC is turned off.
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FISHTAIL
Journeyman Posts: 83
From: Waldorf MD USA
Registered: Sep 2000
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posted 09-29-2000 01:25 PM
Ok, that is kinda odd, but here is a way to rule at least one thing out. Pop open your hood, start the car and turn the a/c on. Get out, walk around to the front, and keep an eye on the compressor while you have someone else shut the ac off....see if the pulley is dragging upon disenagement...however, given that it will try to cut off even at higher rpms like 3k, I doubt this is the case. chances are it's electrical. Next, unplug the compressor and repeat...this will help figure out if it's somehow related to the compressor directly, or a problem in the wiring somewhere.....lets take this one step at a time and figure it out ------------------
-FISHTAIL
92GT "The Ghetto Sled"
CMPS major @ University of MD college park
Best run so far: 14.74 @ 100.3mph....damn wheel spin.
VP and co-founder of CMTC www.geocities.com/dastangboys
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Stewart
Pit Boss Posts: 3620
From: Monterey, CA Mustangsandmore Member #437
Registered: Apr 2000
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posted 10-14-2000 08:00 PM
Heya Rob, have you tracked down that problem yet?Stewart
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cpmaverick
Pit Boss Posts: 590
From: Auburn, AL.
Registered: Jan 2000
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posted 10-17-2000 12:01 AM
Sorry, but I just found this post!I've got lots of experience tuning on EFI Fords at work, and you should never try to adjust the throttle screw. What happens most often is the throttle body gets dirty and the IAC as well, this makes it hard for the computer to compensate for any change in idle... But usually this means stalling when MORE load is put on the engine. Hmmm.. It could be that the AC clutch is sticking, causing the compressor to stay engaged. This obviously wouldn't hurt the belt since it would simply be turning the compressor the same as it does with the AC on, the only difference would be that the computer thinks its off and doesn't compensate. Unplugging the compressor would not change the problem if the clutch is stuck locked. However, at high RPMS this should not a big problem. Is it possible the that the computer opens the EGR valve with the AC on and closes it (at least most of the time) when it is off? Possibly pointing to an EGR valve sticking open?
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 10-18-2000 09:42 AM
Now that is something I hadnt thought of. I believe they make a chemical to help release a sticking EGR valve too.Tony.
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 10-23-2000 08:35 AM
I have not checked for a defect code. Would the EGR valve give a code? I have been busy and have not checked the codes or try to correct the problem. It is getting cooler and I have not been using the AC.
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 10-23-2000 10:17 AM
Im sure it would Rob. Any time there is a problem occurring, the computer stores codes. There are 2 ways to check them. Key on, engine off, and Key on Engine Running. If you can get a code out of it, then we can determine the troubles for sure.Tony.
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cpmaverick
Pit Boss Posts: 590
From: Auburn, AL.
Registered: Jan 2000
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posted 10-24-2000 02:41 PM
It will probably set a code, but if the CEL is not on then I'd just pull the EGR valve off and see if it is carboned up bad, in some cases you can see a physical 'chunk' of carbon shoved between the needle & seat, then you know you have a problem. Carb cleaner works ok for this sort of cleaning, I used to use a GM cleaner called X-something but I don't think its around anymore.
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 10-25-2000 10:33 AM
GM cleaner?!?! Hey now, Keep your GM Car all MOTORCRAFT!!!!!!! heheheTony.
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FISHTAIL
Journeyman Posts: 83
From: Waldorf MD USA
Registered: Sep 2000
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posted 10-25-2000 12:28 PM
Whoa...never thought of that....makes sense, but it sounds as if the stumble is only caused by a temporary engagement problem. So, if he disconnected it after it was done stumbling, it might still give a clue to the problem . cleaning the EGR, throttle body, and IAC valve is always a good idea anyway....but at this rate he'll have a motor that sparkles but still stumbles j/k. And speaking of check engine lights, the older cars(before 89, or before 88 in cali) don't have them. So he wouldn't know if the computer was giving codes or not until he hooked it up.....------------------
-FISHTAIL
92GT "The Ghetto Sled"
CMPS major @ University of MD college park
Best run so far: 14.74 @ 100.3mph....damn wheel spin.
VP and co-founder of CMTC www.stangbirds.com
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 10-26-2000 08:45 AM
They dont??? Intresting. Is my 88 Cougar and 86 Capri a freak deal then? Check engine lights have been around for longer than 88. A check engine light doesnt need to come on for the computer to store codes.Tony.
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cpmaverick
Pit Boss Posts: 590
From: Auburn, AL.
Registered: Jan 2000
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posted 10-26-2000 01:39 PM
Fishtail, you're wrong about the check engine lights, they're in ALL Ford EFI cars and some electronic carb'd cars as well. EEC made its debut in the 1977 Lincoln Versailles and the CEL appeared soon after in EEC-III, I once owned a 1984 cop car that had a VV carb and a CEL. EFI cars are EEC-IV. Believe me, I've hooked up a scanner to hundreds. -CP
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Rob Parsons
Gearhead Posts: 108
From: Lebanon,TN
Registered: Jan 2000
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posted 10-27-2000 12:27 PM
If the EGR valve was clogged or dirty wouldn't that cause drivability problems all the time?
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Capri
Pit Boss Posts: 918
From: Lyons, ILL, USA
Registered: May 99
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posted 10-28-2000 01:51 PM
Rob, It might cause drivability sometimes. Then again, it might not be hanging open all the time.
What happens when you dissconnect the switch on the evaporator line? Near the firewall, there is another cycling switch. Im curious.Tony.
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cpmaverick
Pit Boss Posts: 590
From: Auburn, AL.
Registered: Jan 2000
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posted 10-31-2000 01:19 PM
Rob, if the EGR was stuck OPEN that would cause drivability problems only when it is supposed to be closed, not when it should be open anyway.I'm still not convinced thats it though. -CP
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