Car struggles in upper RPMS, need help.

[KLeech]

Ok it's my Tork tech 2v car, but same concept. Plus this forum has way more traffic and I need help. Sometimes the car will pull hard all the way through the RPM range, other times the car makes it to about 4k rpms and it starts struggling to build rpms and the power is waaaaaaay down.

Car runs perfect, doesn't misfire. Throws no codes. It's not the clutch slipping, as I've put it in fifth at a low rpm and went wot briefly and the clutch never slipped so that's out. The belts not slipping, which I thought might be the culprit. Put a brand new belt on and issue is still there.

I need ideas, where to look what to think about. It's such an intermittent issue only doing it about as frequently as every other time I go WOT I'm stumped. Give me some ideas guys!

 

[bigmoose]

Datalog it and look for anything unusual.

 

[KLeech]

I don't believe my ooooold sct xcal2 does datalogging lol

 

[c6zhombre]

definitely datalog it to check for the usual things like fuel components, maf, voltage

but I'd check the spark plug gaps first and make sure they're tight enough before the log. sounds like classic spark "disruption"....errr...blowout

 

[01yellercobra]

I don't believe my ooooold sct xcal2 does datalogging lol

You use it as a pass through with a laptop. That's how I datalog.

 

[KLeech]

Forgot to mention the plugs were changed last week. Tr6's gapped the same as they were last year. I feel like thinking back it may be a coil pack starting to go bad in the upper R's. Some of the original coils looked pretty worn out. I've felt spark blowout before and that's more of a cutting out feeling all of the sudden.

Sadly my laptop is ancient too as well as my tuner.

 

[bigmoose]

Buy a cheap elm327 obd adapter and datalog with your cell phone

 

[b_dike]

Check your voltage while your wot. Could be a bad alternator...

 

[usmcsvtwannabe]

Check the coils. When they start going they will work fine and then not work. Plus you can just leave the car running and pull them one by one to check them

 

[VA-Mach1]

Running out of fuel or spark. I'd bet fuel.

 

[cj428mach]

Running out of fuel or spark. I'd bet fuel.

That was my thought.

 

[KLeech]

Ok so after a little more digging into my car..

Fuel Pump Duty Cycle at WOT is 95%. Which I knew the DC was high, it was high when it was tuned. I have a bigger pump ready to go in, and its been the same pump since the beginning of last year and the car has always performed flawlessly. So even if that is the issue, the bigger pump will resolve that.

The voltage is 13.8-14.0 at idle. Which I believe 14.4 is normal so I don't think that's anything out of the ordinary. It will drop down to 13.0-13.2 at WOT. That's the only thing I'm unsure of whether or not it's acceptable.

I drove the car last night and tried to go wot to see if I could watch the scan gauges. It cut out hard under load, exactly like a misfire. So I am definitely leaning towards it being one of the coil packs. Sadly my wideband sensor also just recently took a crap on me, so it's stuck on 14.6 and won't move. When it rains, it pours right lol

 

[Rich'sTRsvt]

Being that high in DC it could be the alternator is starting to go or the fuel filter getting plugged and you would be lean really quick. You may want to get that A/F sensor fixed before going WOT. I think in 03/04 cobras that you don't want voltage falling below 14 when going WOT.

 

[b_dike]

Voltage drop at wot is normal. Anything lower than 13 could be a problem, especially if your fpdc is 95%.

Side note... After changing my fuel filter my fpdc dropped almost 10%. Though I had no idea the last time it was changed. Could've been in there for years. Lol

 

[KLeech]

Being that high in DC it could be the alternator is starting to go or the fuel filter getting plugged and you would be lean really quick. You may want to get that A/F sensor fixed before going WOT. I think in 03/04 cobras that you don't want voltage falling below 14 when going WOT.

Voltage drop at wot is normal. Anything lower than 13 could be a problem, especially if your fpdc is 95%.

Side note... After changing my fuel filter my fpdc dropped almost 10%. Though I had no idea the last time it was changed. Could've been in there for years. Lol

Filter isn't very old, 6k miles tops. The AFR sensor was not bad when this problem began and I know that the car was NOT going lean while this problem was happening. And it doesn't run right so I'm not out going wot anyways lol I did the two quick pedal stabs last night just to test the voltage.

I knew the voltage drop at WOT was normal, I just wasn't sure on the numbers. I'm going to put the bigger pump in and put some new coil packs on it since voltage is looking normal across the board. If the problem persists then I'll look elsewhere. Gut feeling says coil packs, so I guess we will see. Really stock ones with 97k miles and 14 years of age should probably be replaced anyways.

 

[c6zhombre]

Voltage drop at wot is normal. Anything lower than 13 could be a problem, especially if your fpdc is 95%.

+1

it doesnt look like voltage or fp is the current issue. always advantageous to have some more head room, tho

as far as the spark, there are some pids you can log, maybe they'll narrow down what cylinder #(s) to be zeroing in on

 

[MayoSVT]

Stop trying to band aid the issue. Replace what you know what needs fixed--- a/f gauge issue, swap around coil packs, ohm them out. Change the fuel filter. We just came from winter, correct? Once a year, change it. Never hurts to spend $10 to protect.

 

[Iamchris]

I would suspect coils.

 

[KLeech]

Stop trying to band aid the issue. Replace what you know what needs fixed--- a/f gauge issue, swap around coil packs, ohm them out. Change the fuel filter. We just came from winter, correct? Once a year, change it. Never hurts to spend $10 to protect.

Who's trying to band aid an issue? I wouldn't take advice from you if you were the last person on this earth.