Engine Split Second Hesitation In 4.6l 98 Gt

  • Sponsors (?)


Ive been researching this issue for awhile now and you're the first person with the exact same problem, rather than just a misfire. I've gone through new plugs and coils, new IAC and new MAF, it happens all the time, but worst when the AC is on, I'm thinking either a timing issue or tune related, I'm going to test a few things and let you know what I come up with.
 
lol How many times do I have to tell you it is the tranny. I went through this exact issue with my fathers 01 gt. First we thought it was ignition related, replaced everything. Next we thought it was fuel, slapped in new injectors and new pump, no changes....His tranny died last year which was the cause of everything.....Its your tranny slipping that is why you arent see any codes.

Have you two used any fuel system cleaners yet to see if you have a clogged injector?
 
Last edited:
Mine can't be a transmission issue because it's a manual, and it wouldn't "slip" in all gears intermittently, even if it was the clutch it would only slip when it first engages the gear and not once the driveline is engaged. Also, I don't think the OPs issue is a transmission either, I've had two go bad on me and they've never done what he's described. It's a misfire, either a lean misfire from a gummed up or broken injector, or a misfire due to a spark issue.

I've run fuel system cleaner through it on the last two fill ups, and it hasn't helped the issue at all. I data logged it and talked to my tuner, and nothing in the numbers seem to point to anything.

However I did notice some sludge around my thermostat gasket, and now I'm thinking the coil next to it (cylinder 5) might have gotten wet, and could be grounding out. tomorrow I'm going to replace my thermostat and gasket and the boot on the coil and see if that fixes my issue.
 
Regap all of your plugs to .046 - .048 (assuming you're at factory gap now). Post back if this makes any difference at all.

Replace your IAC, even if replaced previously. It's not uncommon to get new bad ones.

Did/does it ever backfire?
 
Mine can't be a transmission issue because it's a manual, and it wouldn't "slip" in all gears intermittently, even if it was the clutch it would only slip when it first engages the gear and not once the driveline is engaged. Also, I don't think the OPs issue is a transmission either, I've had two go bad on me and they've never done what he's described. It's a misfire, either a lean misfire from a gummed up or broken injector, or a misfire due to a spark issue.
I've run fuel system cleaner through it on the last two fill ups, and it hasn't helped the issue at all. I data logged it and talked to my tuner, and nothing in the numbers seem to point to anything.
However I did notice some sludge around my thermostat gasket, and now I'm thinking the coil next to it (cylinder 5) might have gotten wet, and could be grounding out. tomorrow I'm going to replace my thermostat and gasket and the boot on the coil and see if that fixes my issue.
If you have fluid near #5 then you may have a cracked intake.

Misfires should be triggering CEL lights.
 
i recently got a 03 gt thats been neglected doing the same thing always has a barely noticible hesitation / miss at 40-50 on flat ground in overdrive trying to keep constant speed its noticible every few seconds a lull then a surge in power

did u ever find a solution

already replaced and inspected everything myself and a certified 40yr master mechanic and scanner

new upper intake
iac, cam, crank, fuel vapor sensors
fuel filter
cleaned mass air and throttle body