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random jerking and dying issues

3K views 20 replies 7 participants last post by  stevew01 
#1 ·
Hello I am new to the forum and am in need of some advice. I have a 1998 mustang gt and am having issues with the car. When I bought it a couple weeks ago i noticed when accelerating it had like a random miss, kind of like it would randomly cut out real quick and come right back but that dead spot caused it to jerk pretty hard when it came back, the CEL was on and the previous owner said she was told oxygen sensors so I went to O'Reilly and had it read and they said It was rich on left bank and lean on right bank so thinking oxygen sensors were plausible I changed the 2 upstream oxygen sensors. Of course by unhooking the battery to change the sensors it cleared the codes and I drove it for a couple days with no change in its behavior before the light came on again upon which time I had it read again and they said it was lean on left bank. I changed the fuel filter and ran some sea foam through it with no change in behavior then began asking opinions and decided to get a fuel pressure guage at which time I was misinformed about what the pressure should be at. Thinking my pressure was wrong I replaced the fuel pump which made no difference and then the fuel pressure regulator which also made no difference so started searching more finding out the pressure is fine. After changing the pump I cleared the codes and the light has not come back on yet and it has been a couple days now but I am still having the issue of jerking on acceleration and occasionally dying when stopping. It almost seems like it's worse in warmer weather than colder weather but it's hard to say for sure as some days it's really bad and other days it hardly does it at all. I am getting pretty frustrated with it so any help would be greatly appreciated.
 
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#3 ·
Welcome to the site! I had a slight jerk going on with my 1993 and changed a bunch of stuff but what seemed to smooth it over was new coil, 9mm plug wires, cap & rotor and plugs. I picked it all up through latemodel restorations for exactly a hundred bucks excluding the coil which I picked up separately. The oter stuff was the cheapest thing I did! By the way the wires were ford racing 9mm wires and they were only $49.00, most others were twice the price but these worked great for me. Best of luck.
 
#4 ·
The 98 would have 2 seperate coils on it with the plug wires. However, based off of the concern and the issue he has with his mod motor I highly doubt it is a coil issue.

My suggestion would be to check out the issue with the photo I am attaching. Most likely on your issue I would suspect fuel as an issue. I am not saying that it is the only thing but I have seen more fuel pump issues and intake/vacuum leaks cause these issues than anything else.
 

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#5 · (Edited)
Slow down on the "parts changing" in an attempt to fix the problem. Sounds like a ton of $$/effort has already been spent without a solution. Research more. Test more. Then replace & repair followed by a review of the results. Start with the "basics" and work up.

Always post the full DTC codes. There are 1000's and each has a story to tell.

ANY moisture in the spark plug wells? Are the spark plug wires correctly routed? Touching ANY metal parts? Used all factory stand offs and looms?

Have the alternator tested for excessive AC ripple (bad diode). Most auto parts stores will do this for free.

Have the battery tested to be certain it holds a charge. Are the battery terminals clean and tight? How about the grounds around the radiator core support? Are they clean and tight? Bottom line. Today's cars simply will not run right without a strong battery and charging system. Start all problems with a review of the charging system.

Are there ANY vacuum leaks or exhaust leaks? With the age of this car what is the condition of the vacuum lines? Especially the EVAP purge line. But leak free PCV hoses and grommets are important as well. Even a tiny leak will cause problems. Note that frequently lean/rich DTC codes are caused by vacuum leaks.

Have you cleaned the MAF sensor? Use only a product designed for the job.

Double check that the fuel pressure regulator intake vacuum reference line is connected and leak free.

What have you done to rule out excessive EGR flow? The vacuum lines to/from the DPFE sensor rot due to exhaust gasses.

Inspect the crank damper for damage, excessive run out or dry rot.

Here's some more information regarding how to trouble shoot Idle and IAC issues.
http://www.allfordmustangs.com/foru...-dieing-idle-idling-rough-14.html#post2260649
 
#7 ·
Thank you for the information. I have check for vac leaks as best I know how and checked the lines and I haven't found anything wrong but I did notice you said in the link that the iac is supposed to let air in the black vent on top to start the car and close after running and I did notice it sounds to me like it continues to suck air through that vent after its running. I thought I was hearing a vacation leak but I was having a hard time tracing it but as best I can tell it sounds like it is coming from there. Also my engine light hasn't come back on sine I changed the fuel pump 4 days ago but if it does I will post the codes
 
#10 ·
I can't figure out how to copy a certain part of someone's post so that I can comment on that statement alone. I want to say thank you to wmburns for the advice. I went to the parts house where they tested my battery and alternator and they said they were good. I was inspecting the spark plug wells but couldn't see well so I decided to pull a plug and checked the gap which was oversized so I decided to go ahead and check/regap all the plugs. After I was done the car wouldn't stay running by itself and I tried to go around the block and it wouldn't hardly accelerate so naturally I thought I gapped the plugs wrong. I removed the plugs one more time to recheck them and made a couple minor adjustments and though better the car still cut out really bad. A few of the plugs and wires looked a little old so I decided it was a good idea to do a tune up anyway not to mention it was not motocraft plugs and wires. The new motocraft plugs were pregapped at .054 which is right in the middle of what the sticker under the hood said they should be and so I installed them and replaced all the wires one at a time to insure they went in the right place but no change in performance. I tried to fight it and drive around a while in hopes that the check engine light would come on but it didn't. The car has a cold air intake system on it of which I had to remove half in order to get to all the plugs on the right side of the car but other than that I didn't mess with anything else so I am confused as to what could have happened when all I did was a tune up. Since I messed with the air intake, and since it was recommended to do so, I cleaned the MAF and another sensor just upstream from the MAF but still no change. Any more advice anyone could give would be greatly appreciated
 
#11 ·
Just something to try but unplug the maf sensor and start it up, does this change anything? does the car run any better at all?

If it runs better with it unplugged then change the sensor.
 
#12 ·
Did you make sure that you plugged that sensor that is upstream from the maf back in? One time I cleaned my cal and after forgot to plug that little sensor back in and the car wouldn't do anything, it would just bog out. Check that!!!! mine is under the intake tube and is easy to miss!
 
#14 ·
Regarding plug gap, I know that .054" is the correct factory spec and seems to be fine for most, but after fighting an intermittent hiccup/misfire for over a year (per the advice of a knowledgeable member here) I closed the gaps down a little, to about .046" - .048" and problem solved.
 
#16 ·
And one more post.... I still think the possibility of unmetered air is alive and well. O2 sensor lean/rich dtc's are almost always traced back to this, and now especially since you've replaced the sensors would further confirm it.
 
#20 ·
Ok so here it is. A mechanic friend of mine offered to take a look (he works on school busses and used to work at pep boys shop but I thought what the hell it can't hurt) so I crippled it over to his house and as I expected he was scratching his head but started spraying carb cleaner or something like that around different common vacuum leak areas (intake manifold, IAC, TB, etc.) with no luck. Then he decided to unplug the air intake temp sensor to see if it made a difference which it didn't but finally the CEL came on. He hooked up his scanner and of course that code popped up but then a TPS code came up and so he set it to test the TPS and it was off, it read 18 while not pushing the pedal and with the pedal on the floor it only went to like 94 so obviously it was bad so I bought one and put it on but didn't really fix it although it was a little better. Then he said that was testing good but the MAF was going crazy. There was no light on but it was jumping around on his scanner so he had me unplug the MAF ( I had unplugged it before and started it with no change) and low and behold it ran great! The MAF setup the cold air intake system I have was different and we figured not enough air was getting to it. He happened to have a good one that came out of a 97 grand marquise and it bolted right up to the cold air intake perfect plugged in no problem and the car runs like a champ. Thank you guys again for all the advise and finally my car is fixed.
 
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