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Discussion Starter #1 (Edited)
The Supercoupe took a crap in denver!! Help!(UPDATED WITH VIDEO)

I just did a tune up on the 91SC, I change the plugs with motorcraft from rock auto, Some taylor wires, changed the 02, oil, brakes. I then drove it for 2 days with absolutely no problems what so ever. Then we gassed up & headed for Denver, Co.

It drove better then it's ever ran all the way down there, Stopped in sterling, Co and filled up the tank and continued into Denver. As soon as we arrived we parked at the hotel & went inside for a couple hours then came back out to go eat, Started up the car and I could hear it missing... I was thinking wtf? I started to drive it and it was stumbling, no power & would occasionally buck! It sounds like I put a cam into it lol.

I took it up to firestone & they had it on the rack, Spark tested my plugs & wires, fuel pressure tested, performed a vacuum test and everything... After 2 hours they couldn't find out what was causing this!! :confused: I am at a loss & scheduled a car appt on Thursday morning, Anybody got any ideas?
 

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I just did a tune up on the 91SC, I change the plugs with motorcraft from rock auto, Some taylor wires, changed the 02, oil, brakes. I then drove it for 2 days with absolutely no problems what so ever. Then we gassed up & headed for Denver, Co.

It drove better then it's ever ran all the way down there, Stopped in sterling, Co and filled up the tank and continued into Denver. As soon as we arrived we parked at the hotel & went inside for a couple hours then came back out to go eat, Started up the car and I could hear it missing... I was thinking wtf? I started to drive it and it was stumbling, no power & would occasionally buck! It sounds like I put a cam into it lol.

I took it up to firestone & they had it on the rack, Spark tested my plugs & wires, fuel pressure tested, performed a vacuum test and everything... After 2 hours they couldn't find out what was causing this!! :confused: I am at a loss & scheduled a car appt on Thursday morning, Anybody got any ideas?
Have you tried octane booster?

I wonder if you are misfiring b/c of the difference in gas.

Q: What's the octane of super unleaded in SD?

I believe in CO it's 91 octane.
Regular is a paltry 85. Allegedly, you don't need as much detonation protection in the thinner air of CO... but this standard was set years ago.

-g
 

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Discussion Starter #3
Have you tried octane booster?

I wonder if you are misfiring b/c of the difference in gas.

Q: What's the octane of super unleaded in SD?

I believe in CO it's 91 octane.
Regular is a paltry 85. Allegedly, you don't need as much detonation protection in the thinner air of CO... but this standard was set years ago.

-g
That's what I thought, "Bad gas" so I put some octane booster in it and ran that tank to empty. Then I drove up to Fayette and got 93octane to drive it back home to SoDak, It drove horribly all the way home with no CEL on or anything.
 

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I'd lean toward Cam sensor or a vacuum leak. How's tack signal and what about upshift light? Also check the balancer.
 

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Discussion Starter #5
I'd lean toward Cam sensor or a vacuum leak. How's tack signal and what about upshift light? Also check the balancer.
They said they did a vacuum test and found nothing, The tack goes just fine...No dropping, flicking or anything out of the ordinary. The upshift light has never illuminated since I owned the car, It does however illuminate with all the other lights when the key is turned on. lol
 

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Ignition control module, perhaps?
 

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Don't trust what someone said they checked, when they didn't find the problem. Especially on SCs, there are way more places for vacuum leaks to form than you would think.

No upshift light and tach working properly points towards the cam and crank sensors being OK. First thing I would check is rev the motor up in neutral and see if it gets better or stays the same as rpms go up. If it gets better, I would start looking for vacuum leaks. Follow every vacuum line, and check every IC and tube joint. There are several ways to check them, but the easiest to do at home are either spray with carb cleaner, or use an unlit propane torch near the joints. When you get to the leak, the engine rpms will rise. Another thing to check would be the Mass Air meter. You said this started after the car sat for a few hours, maybe a rodent or something built a nest in you air filter housing.

If it stays the same as you rev it up, then it is a dead miss, and first thing I would check at that point would be the plugs and wires. Maybe a wire fell on the exhaust manifold and burned up, or maybe a plug was slightly cracked and didn't start acting up right away, or maybe you got a defective plug or wire. If it is a dead miss, another thing you can do (not so easy on an SC engine, but can be done) is to pull plug wires off one at a time then put them back on while the engine is running. As you pull the wire off, the engine will start running even rougher, until you pull the one that is already misfiring, and the engine will stay the same. That will tell you what cylinder the misfire is on. Don't pull the wires off at the coil though unless you are using an insulated pair of plug wire pliers, otherwise you'll get zapped with 60K volts or so, and I promise you will not enjoy the experience.
 

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Don't pull the wires off at the coil though unless you are using an insulated pair of plug wire pliers, otherwise you'll get zapped with 60K volts or so, and I promise you will not enjoy the experience.
Also, don't do this while leaning up against the body with your Levi jeans on - the old ones with the rivet at the bottom of the metal zipper. EITHER one will make your life miserable ...

Don't ask me how I know. Just let me mention that I spent a week singing soprano in the choir, whereas I was normally a bari-bass ...

RwP
 

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With all the places for a leak on a SC a smoke machine is the best method.
 

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Discussion Starter #10
Don't trust what someone said they checked, when they didn't find the problem. Especially on SCs, there are way more places for vacuum leaks to form than you would think.

No upshift light and tach working properly points towards the cam and crank sensors being OK. First thing I would check is rev the motor up in neutral and see if it gets better or stays the same as rpms go up. If it gets better, I would start looking for vacuum leaks. Follow every vacuum line, and check every IC and tube joint. There are several ways to check them, but the easiest to do at home are either spray with carb cleaner, or use an unlit propane torch near the joints. When you get to the leak, the engine rpms will rise. Another thing to check would be the Mass Air meter. You said this started after the car sat for a few hours, maybe a rodent or something built a nest in you air filter housing.

If it stays the same as you rev it up, then it is a dead miss, and first thing I would check at that point would be the plugs and wires. Maybe a wire fell on the exhaust manifold and burned up, or maybe a plug was slightly cracked and didn't start acting up right away, or maybe you got a defective plug or wire. If it is a dead miss, another thing you can do (not so easy on an SC engine, but can be done) is to pull plug wires off one at a time then put them back on while the engine is running. As you pull the wire off, the engine will start running even rougher, until you pull the one that is already misfiring, and the engine will stay the same. That will tell you what cylinder the misfire is on. Don't pull the wires off at the coil though unless you are using an insulated pair of plug wire pliers, otherwise you'll get zapped with 60K volts or so, and I promise you will not enjoy the experience.
I believe the misfire stays the same all the way up but I can't remember for sure, I tend to believe that it might clear up in the higher RPMS, I'll go check it out in a few mins and let you know for sure, Now when u say pull them off one at a time, Do I pull it off... listen... then put it back on, Then move on to the next or do I just keep pulling them off one by one until i'm not running on any of them lol.

The plugs came from rockauto and I gapped them at 0.047 as per article found on (http://www.35thatr.org/Tips/PlugsandWires.htm) and I got the taylor wires from sfxperformance.com
 

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Pull it off, listen, then put it back on. If it is a dead miss (stays the same all through the rpms) then one cylinder is not firing. When you pull a plug wire off, now you will have 2 cylinders not firing until you get to the cylinder that was not firing in the first place. You can very clearly hear the change in the way the engine is running from 1 cylinder misfiring to 2 cylinders misfiring. Once you pull the wire that the engine keeps running exactly the same, you found what cylinder it is. From there, start checking the wire, the plug, see if the injector is firing, check compression, etc. to find your problem.
 

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Discussion Starter #12
Pull it off, listen, then put it back on. If it is a dead miss (stays the same all through the rpms) then one cylinder is not firing. When you pull a plug wire off, now you will have 2 cylinders not firing until you get to the cylinder that was not firing in the first place. You can very clearly hear the change in the way the engine is running from 1 cylinder misfiring to 2 cylinders misfiring. Once you pull the wire that the engine keeps running exactly the same, you found what cylinder it is. From there, start checking the wire, the plug, see if the injector is firing, check compression, etc. to find your problem.
Sounds easy enough, I'll go do that now since it's nice & cool lol. I don't have the tools to check injectors or compression but I could check the wire & plug I assume, Would a visual check of the plug be sufficient enough?
 

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Pretty much a visual inspection is all that you can do for a plug. Make sure the gap didn't get crushed down, the electrode is in good shape, and look real close at the porcelain to make sure it isn't cracked or chipped. To check the injectors, you can do it pretty easy with a big flat-head screwdriver. Put the blade of the screwdriver on the body of the injector with the car running, and put your ear up against the end of the handle. The vibrations of the injector opening and closing will transfer through the screwdriver, and you will be able to hear it through the handle. Compare the cylinder that is misfiring to the others, and you if the injector is not pulsing, you will hear the difference.
 

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Discussion Starter #14
Pretty much a visual inspection is all that you can do for a plug. Make sure the gap didn't get crushed down, the electrode is in good shape, and look real close at the porcelain to make sure it isn't cracked or chipped. To check the injectors, you can do it pretty easy with a big flat-head screwdriver. Put the blade of the screwdriver on the body of the injector with the car running, and put your ear up against the end of the handle. The vibrations of the injector opening and closing will transfer through the screwdriver, and you will be able to hear it through the handle. Compare the cylinder that is misfiring to the others, and you if the injector is not pulsing, you will hear the difference.
Just got back, Damn that got hot in a hurry, I started it up, pulled it onto some ramps and crawled under there only to burn the crap out of both my forearms trying to reach up there :mad: So that plan went out the window fast:(, I did notice some smoke coming from above the middle plug on the pass side, Looks to be coming from the valve cover or something, Could just be oil burning off but idk. The miss is all through the RPM's, I realized I put to much anti-freeze back in when I put on my serp belt lol, It's over flowing from the top of the radiator, That lil rubber hose.
 

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I meant to pull the plug wires from the top, not from underneath. If antifreeze is coming out of the radiator overflow, then either the car is overheating, or combustion gases are making their way into the coolant. You really can't overfill it, cause the excess would go into the overflow bottle, and if it over-fills that, it will overflow and spill on the ground, but it won't keep leaking out after one cycle of warming up and cooling down. Before you go too far with other stuff, let the car cool down, then with it cold, take the radiator cap off, top off the coolant, then start the car and watch it to see if you get continual bubbles coming up out of the coolant. If you do, then it sounds like you might have popped a head gasket.
 

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Discussion Starter #16
If antifreeze is coming out of the radiator overflow, then either the car is overheating, or combustion gases are making their way into the coolant. Before you go too far with other stuff, let the car cool down, then with it cold, take the radiator cap off, top off the coolant, then start the car and watch it to see if you get continual bubbles coming up out of the coolant. If you do, then it sounds like you might have popped a head gasket.
Describe "Top it off" like do I fill it up to the bottom of the neck? top of the neck? And I hope I didn't take a headgasket =(
 

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Fill it at least until it is in the neck. If you have one of the funnels with the adapter to attach to where the radiator cap would go, then use that. The level isn't that important except that you want to be able to see any bubbles that are coming up.
 

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I usually "top it off" through the vent tube on the theremostat outlet.

If its heating up VERY quickly, and bubbles out of the radiator, im leaning towards head gasket also.

Use a sniffer to detect any fuel vapors in your cooling system.

These cars are not as easy to work on, as you have experienced, burning your arms trying to get to the plug wires ..
 

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Discussion Starter #19
I usually "top it off" through the vent tube on the theremostat outlet.

If its heating up VERY quickly, and bubbles out of the radiator, im leaning towards head gasket also.

Use a sniffer to detect any fuel vapors in your cooling system.

These cars are not as easy to work on, as you have experienced, burning your arms trying to get to the plug wires ..
According to the "temp gauge" it's warming up fine and staying at about N-O on Normal. I'm at work now but I will check for bubbles when I get a chance.
 

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Easier way is to do a Cylinder Balance Test.


Cylinder Balance DTM--SFI Engines Only

The purpose of the cylinder balance test is to assist the mechanic in finding a weak or non-contributing cylinder. The test is entered by depressing and releasing the throttle within two minutes after the Engine Running Self-Test DTC's have been output.

Once the test is entered, the IAC duty cycle is fixed and the engine is allowed to stabilize. Engine rpm is measured and stored for later use. Next, the fuel is shut off to cylinder number 4, 6 or 8, depending on engine. After a brief stabilization period the engine rpm is again measured and stored. The injector is turned on again and the process is repeated for each of the injectors down to one. At this point, the maximum rpm drop that occurred is selected from the table of rpm drops for each cylinder. This maximum rpm drop is now multiplied by a calibratable percentage. The resulting number (rpm) is now used as the minimum rpm that each cylinder must have dropped to pass this test.

Example: 150 rpm x 65% = 98 rpm

If all cylinders drop at least this amount, then a code 90 is output indicating a pass. No further testing is necessary. If a cylinder did not drop at least this amount, then the cylinder number would be output. For example, 30 for cylinder number 3. This indicates that cylinder number 3 is either weak or non-contributing.

The test can now be repeated a second time if the throttle is depressed and released within two minutes of the last code output. This time the maximum rpm drop that occurs is multiplied by a lower percentage. This number is now used as the minimum rpm drop for each cylinder to pass this test.

Example: 150 rpm x 43% = 65 rpm

If all the rpm drops are greater than 65 rpm, then a code 90 is output. If cylinder number 3 had failed the first level and passed the second, then cylinder number 3 is considered to be weak. If cylinder number 3 again failed, the code 30 would be output again.

The test can be repeated a third time by depressing and releasing the throttle within two minutes of the last code output. This time the maximum rpm drop that results is multiplied by a still lower percentage. This number is now used as the minimum rpm drop for each cylinder to pass this test.

Example: 150 rpm x 20% = 30 rpm

If all the rpm drops are greater than 30 rpm then a code 90 is output. If cylinder number 3 had failed the first and second level, but passed the third, then it is considered to be a very weak cylinder. If cylinder number 3 failed the third level then a code 30 would again be output. In this case, cylinder number three would be considered a non-contributing cylinder.

The Cylinder Balance DTM may still be repeated as many times as desired by depressing and releasing the throttle within two minutes of the last code output. All further testing (i.e. 4th, 5th pass) will be done using the third level percentage.
POSSIBLE CODE OUTPUTS
(code 30 is used as an example only)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ LEVEL ³ ³ ³
ÃÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 1 ³ 2 ³ 3 ³ INDICATION ³ POSSIBLE EEC CAUSES ³
ÃÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 90 ³ X ³ X ³ Indicates a pass, all cylinders ³ ³
³ ³ ³ ³ contributing equally. ³ ³
ÃÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 30 ³ 90 ³ X ³ Indicates a weak cylinder. ³ ù Partially clogged injector ³
³ ³ ³ ³ Cylinder is firing, but not ³ ù Injector/harness resistance out of ³
³ ³ ³ ³ contributing as much as the others. ³ specification ³
ÃÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 30 ³ 30 ³ 90 ³ Same as above, but more severe. ³ ù Same as above, but more severe ³
ÃÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 30 ³ 30 ³ 30 ³ Very weak or dead cylinder. ³ ù Open or shorted circuit ³
³ ³ ³ ³ ³ ù Loss of injector drive signal ³
³ ³ ³ ³ ³ ù Fully clogged injector ³
ÀÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
X = no further testing necessary
 
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