white89gt

Agreed on starting a thread.... make it so everyone can search for it. Not that everyone has mastered the search function.... but some use it. .

BTW, Cris, Brew might be on to something with the cats..... I have seen a bad cat(s) mimic transmission and torque converter issues in the past. Nissan's are NOTORIOUS for this. Hadn't thought about this until he mentioned it. Also. do you possibly have something bypassed in your tune that prevents catalytic codes from rendering? Helped a fellow co-worker once that had a bad cat on a supercharged 3.8 V6 Mustang, and his tune prevented the CEL from showing converter codes, and rich/lean conditions. Made it really tough to track down.... so if that is the case, either an infrared thermometer, or having a muffler shop test it are your best bets. Sometimes you can also tell at night if they are bad, because they will glow red.

UtahGuy

I'm facing a similar issue to the OP, except I'm on 260k instead of a brand new motor and I don't think mine is as bad as his. But the truck shifts funny and struggles on grades. I thought for sure it was a transmission or torque converter issue, but the trans shop thinks it's just gutless AF. I was getting ready to tear into the top and check compression numbers, but this thread has my attention.

5.4l/4R70W, no tunes. I'm not throwing any codes. I don't know precisely where the truck idles when hot but I'm going to know in a minute (it's warming up now ), is that low idle pretty diagnostic of a clogged up cat? Worthy of taking into a muffler shop for a deeper look, anyway?

edit to add - with the coolant temp at 170f, the Scangauge is reporting RPM numbers from 680 to 710. Definitely not as low as the OP's.

joe8512

Thanks, I messaged you

Jbrew

Not looking for a certain temps. What your looking for is a difference from side to side, cat to cat. The cat/Y set ups are square with engine. When flowing correctly, temps shouldn't vary all that much. Scribble down what you get, if you can, run it at 2000 rpms for a bit, then dive under and check temps. A bad cat will get much hotter with increased rpms.

Idle with these engines tells you quite a bit for the reason they are PCM controlled vs totally mechanical. The A/F's, same way. A large enough portion is software, solid software which has proved to be reliable. Unlike the older carbed engines and with the way they manipulated A/F ratios. These set ups (the gen 10's) in particular made it much easier for the DIY'er to determine where to look for mechanical problems. The sort of cool part to these is, you can always tell whether you have a vac leak or obstruction. Ford Motor has idle parameter margins 700-750 rpms. These are service margins used to determine everything is okay. Those margins have proved to be a little wide over the years. Should be 725-735 rpms IMO, since these engines idle smoothy at 729 rpms when they aren't loosing vacuum or have an unmetered leak of some kind. So above 735, there's a leak, below 725 there's an obstruction. Your far below 725 lol. The most common issues for this is Air filter blockage/intake or converter obstruction. Less common is PCM, unless another written tune has been loaded or the original has been modified.

redranger04g

Cris have you tried the stock tune yet? Understand the shift points will be terrible with the 35s, but with what Jbrew is saying the tune is another variable and it would be difficult to tell if the RPM change is due to the tune or a problem.

CrisAnderson27

I reverted the truck to stock last night before replying above, both to verify the idle, and to see if it changed how the torque converter lockup was applied (by watching the slippage RPM number in Torque). All it really did was make the truck run crappy in general. I remember when I first bought the truck and put the lift on it. The complete crap driveability is why I immediately bought the SCT in the first place lol.

The odd thing is that the idle didn't change at 620-630rpm. And neither did the commanded idle. I can check both the commanded idle and actual with the datalogger on the SCT, and the commanded idle was 624rpm. This is after a complete reversion to stock, and a full relearn cycle for fuel trims (1min park at operating temp, 1 min in drive against the brakes, 1min with AC on, 10 miles of various kinds of driving). This morning I put in the 87 performance tune from 5 Star (commanded idle changed to 640rpm, actual idle runs between 635 and 645 or so), and it almost runs like it did before on the economy tune...at least around town. Not quite...but it's definitely closer. Higher freeway performance is still dismal.

Mileage when I filled up this morning was 8.2mpg (110 miles, 13.39gal). Granted I was in the throttle quite a bit doing testing...but prior to this mess, HARD use, in the desert wheeling...including climbing, pulling out stuck Chevys, full throttle desert romping to 60mph, and tons of idle time with the AC on (it's 199384°F here in the summer time lol) while we're shooting...would net me about 10.5mpg, calculated the same way.

I'm going to leave the performance tune in it for this full tank of gas and see what it does.


I'll try to get down to grab that temp gun today. I really do hope it's the cats to be honest. First because it's an easy fix...and it NEEDS FIXED, and second...because I've been wanting to do a true full dual exhaust with headers since I bought the truck anyway. I can pick up the headers, 3" y-pipe (cut them off at the merge to make a true dual exhaust), x-pipe, aluminized tubing, and cheap single chamber mufflers for $507 shipped. Routing will be super simple, and since the heads and stainless studs are brand new...removal of the manifolds will be a breeze. Even better, I'll be in there to do the motor mounts anyhow. I can always run it over the axle if I want at a later date, or replace the cheap mufflers with something better (or add another pair...4x glasspacks sound REALLY nice on a big tube exhaust) if I don't like them.

Pacesetter Longtubes
Pacesetter Y-Pipe
Jones 3" Stamped X-Pipe
Walker Aluminized Exhaust Tubing
Stainles Steel Single Chamber Mufflers

Here's a video of the last Mustang I built...N/A 347 with 2" primary headers, 3.5" exhaust, 3.5" x-pipe, and 4x Dynomax Race Bullets...two before the x, and two after lol. The last little part...it was real tough to steer with the drag radials smoking...and bouncing off the 7600rpm rev limiter lol.

fordguy2100

Also if you want a more accurate rpm reading. You can get it thru the digital odometer.

First video verbalizes the steps
Second video shows the tach

Jbrew

As far as torque power and speed, when they run right they are pretty quick for truck, my 98, -

https://get.google.com/albumarchive/...QoZTBcfr8CIj1l

Yours should be close, but you'll have that 5four flat spot mid range. Reason why my 98 doesn't have the flat spot is because of the header/exhaust build.

CrisAnderson27

That's really cool!

Btw, his idle is 625rpm lol!!

CrisAnderson27

That's how mine used to be!! Not quite as fast...but it felt far more like what I'm used to looking at by a long shot.