98 gt running sluggish/stalls

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Whitefox89

New Member

Jul 27, 2019

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North Carolina

Jul 27, 2019

#1

• Jul 27, 2019

• #1

Hello all, I am new to the forum and have joined to hopefully resolve some issues with my newly purchased 98 mustang gt. I'm inclined enough to work on it but not enough to pinpoint the issue LOL. I drove the car an hour home upon purchase and during the drive I found a few problems. The sore thumb though is how weak the car is running and that it was stalling when I came to a stop. When I give it gas it it's like the car is running on 20% power throughout all rpms. It spits and sputters as the rpms rise. I changed the plugs today and cleaned the Maf, fuel rails, and throttle body with absolutely no change. I did notice that after resetting the idle the car stopped stalling as bad. Oil was found in a few of the spark plug holes. Any help would be appreciated for I'm on the fence LOL. Thanks in advance!

 

wmburns

SN Certified Technician

Aug 14, 2009

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Jul 28, 2019

#2

• Jul 28, 2019

• #2

Welcome. What is the condition of the battery and charging system? Do yourself a favor and don't over look the role that a bad alternator diode could play in your symptoms.

Howto perform charging system voltage drop test

Howto perform charging system voltage drop test

To anyone else reading any of my posts I usually include the line: Today's cars simply will not run right without a strong battery and charging system! Cut corners here at your own risk I'm a big believer in starting with the basics. As such I...

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So what did the spark plugs look like? Some google searches can give pictures of what the different "conditions" look like.

I'm assuming that you did clean out all of the oil and moisture.

What is the condition of the spark plug wires?

Does the car stall every time it comes to a stop?

HOW did you reset the idle? Note, for the 1996+ model years the idle is not adjustable by the user. The stop screw on the throttle body is not for adjusting the idle. Please see the following:

Troubleshoot IAC idle problems 1996-2004

Troubleshoot IAC idle problems 1996-2004

Back to the basics. Check for blown fuses. Especially fuse F2.2 and F2.8 in the Central Junction Box (CJB 1999-2004 MY). Confirm key on power using a known good ground. 1999-2004 MY fuse panel schedule...

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Do you have an ODB2 scanner? We need to know what the mode6 misfire data looks like. ALWAYS resolve any outstanding misfire issue before working on other problems. Here's some information on an affordable Windows based unit.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...

www.stangnet.com

 

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Whitefox89

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Jul 27, 2019

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Jul 28, 2019

#3

• Jul 28, 2019

• #3

The old plugs were definitely worn out some in better condition than others. I did clean out the debris from the plug holes with some q tips. As far as charging system goes the altenator is brand new and the battery is as well. Plug wires looked fairly new and all of them had good spark from the coil pack. Upon second look with a friend we found that cylinders 2,3, and 4 are misfiring by testing the injectors while the car idles. I reset the idle using careful procedure stated by another member of this forum specifically for my 98. I did adjust the throttle screw it didnt seem to do much. Yes the car stalls everytime I come to a stop from rolling.

 

wmburns

SN Certified Technician

Aug 14, 2009

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Jul 28, 2019

#4

• Jul 28, 2019

• #4

Just wondering. Have you read the information given in the how to trouble shoot IAC issues? Any TPS "adjustment" procedure that seeks to set a voltage range for the closed throttle TPS does NOT apply to any 1996+ model year Mustang. Why? Because the 1996+ model years "learns" the TPS position every time the key is turned on. Sooooooooooooo the closed throttle absolute voltage of the TPS means NOTHING. What does matter is for the TPS to return the SAME voltage every time the throttle is closed.

If this were my car one of my first questions would be, "is the IAC working at all"? Followed closely by, "is the MAF sending a reasonable value". IE, is the motor quitting:

• because the IAC isn't actually adjusting the idle?
• because the MAF isn't sending a "reasonable" value? For example because of a vacuum leak? If the MAF value is too low then the motor could be quitting because there just isn't enough fuel. The solution is find and fix the vacuum leak.
• Low charging system voltage. The battery voltage at idle has been checked right?
• or for some other reason? Note one of those reasons could be poor cylinder power balance. If you have (3) cylinders misfiring this is certainly a power balance issue.

IF you MAKE the motor idle by raising the throttle body stop screw to the point where the motor does idle what will happen is it will work until the weather changes. Then it will fail because the PCM isn't really controlling the idle using the IAC valve like Ford designed it.

For a suspected injector problem I have had great luck with an injector cleaning flow test service such as InjectorRX.com. Once cleaned and tested they are as good as new but cheaper.

Suggest also using a "noid" style tester to verify that the injectors are getting an injector pulse from the PCM.

 

Last edited: Jul 28, 2019

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Whitefox89

New Member

Jul 27, 2019

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North Carolina

Jul 28, 2019

#5

• Jul 28, 2019

• #5

Thank you very much for the information and links sir. I am going through everything now I'm taking the car over to a friends house to check it out and look for vaccum leaks and try and resolve the problem. Very good information you shared with me. I will get back this evening with what we find.

 

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Whitefox89

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Jul 27, 2019

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Jul 28, 2019

#6

• Jul 28, 2019

• #6

Okay sonim here with the car now looking things over. We checked the iac and it looks new. We checked all the plug wires on both ends and they are sparking fine. There was 2 small vaccum leaks that we patched and checked the injectors to see if there were any leak/failure. Everything seem to be fine but the car is still running about the same. It does seem to start just a bit easier now but no real difference in how it runs.

 

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Whitefox89

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Jul 27, 2019

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Jul 28, 2019

#7

• Jul 28, 2019

• #7

Ok so we've been on it for a few hours now. Everything was checked we have good power supply and spark coming from the coil pack all the way to the spark plug. Was thinking injector issue also but they are spraying just fine and getting sufficient fuel through the rails. The fuel filter looked good with no leaks. We found a small vaccum leaks that were both patched. Going to get a compression tester now to see if we have sufficient compression on 2,3, and 4.

 

wmburns

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Jul 28, 2019

#8

• Jul 28, 2019

• #8

What is the ODB2 Mode6 misfire data? Which cylinders are misfiring?

Just because an part is new doesn't mean that it works. Has the wiring been confirmed? Has key on +12 volts power at the IAC been confirmed? What is the IAC duty cycle? Does the voltage across the IAC change as the throttle is changed while running?

It seems to me that given the lack of improvement vs the problems found some thought should be given to checking the motor's basic health. Consider performing a compression test and/or cylinder leak down test.

 

Last edited: Jul 28, 2019

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Whitefox89

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Jul 27, 2019

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Jul 28, 2019

#9

• Jul 28, 2019

• #9

We are back on it checked compression in cylinder 2, 3 and 4. As suspected cylinder 3 is low compression around 100psi. So I've found my culprit. Now where to go from here?

 

wmburns

SN Certified Technician

Aug 14, 2009

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Jul 28, 2019

#10

• Jul 28, 2019

• #10

It would be helpful to know WHERE the leak is from (rings, exhaust valve, intake valve, head gasket).

The next step depends upon what your plans/goals are.

If your goal is to get the car back on the road for the least amount of $$, then it's hard to beat a whole salvage yard replacement. Search car-part.com for some sample prices. Want more options? Consider using the motor from a Ford Panther (Town Car, Grand Marquis, Crown Vic).

 

Last edited: Jul 30, 2019

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Whitefox89

New Member

Jul 27, 2019

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North Carolina

Jul 28, 2019

#11

• Jul 28, 2019

• #11

Well we didnt bust into it but we both think that its a bad head gasket. The motor seems to be running fine no smoking or tapping, ticks. I would like to get back on the road running reliably for as little $$. But the tbought of pulling the whole motor makes my back hurt.

 

wmburns

SN Certified Technician

Aug 14, 2009

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Houston Texas

Jul 29, 2019

#12

• Jul 29, 2019

• #12

Whitefox89 said:

Well we didnt bust into it but we both think that its a bad head gasket. The motor seems to be running fine no smoking or tapping, ticks. I would like to get back on the road running reliably for as little $$. But the tbought of pulling the whole motor makes my back hurt

Click to expand...

Knowing what I know now likely I would pull the whole motor rather than perform an "in car" head gasket repair.

The Mustang motor isn't so hard to pull. The reward is the increased access should additional "problems" be found. Problems that may not be found with the motor in the car.

Have you look at the cost of whole salvage yard motors? $600 is typical. Expect to pay extra for an engine from a Mustang. Possible to get a better "value" from a Panther. Again car-part.com for some sample searches.

 

Last edited: Jul 30, 2019

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Whitefox89

New Member

Jul 27, 2019

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North Carolina

Jul 30, 2019

#13

• Jul 30, 2019

• #13

Yes sir I did find several for around the $500 mark with unknown mileage. I am considering that just font want to spend that much and do all that work if it's just a headgssket but I am in the dark. I may just buy a new long block for the car.