EGR, vacuum line(s), COP, or ??

[1997SCEBFEX]

Hello fellow EXPY crowd.

I've put less than 8K on the rebuilt motor and now it has a slight accel jump between 13-1500 rpms, and sometimes 18-2000 rpms too, more so when using cruise control.

It had a slight hesitation starting up a few days ago, but smoothed right out, thought bad gas? It feels like it’s being “choked” or not firing on all cylinders, however will still produce 6 psi boost under full accel and scream on demand.

The symptoms occur when just “lugging” around town and short-cycle trips.
I paid for new COPS/Plugs, but they used existing wires, injectors, EGR, DPFE…..

My recent maintenance:
DATE Mileage Action
28-Oct 153118 Remove, clean, reoil, reinstall K&N air filter
28-Oct 153118 Rotated Tires
4-Nov 153259 Transmission Filter Change (Ford YC3Z7A098BA) Castrol Mercon ATF; Fram PH-8A inline filter; approx 3 gal
11-Dec 153963 Oil Change (K&N HP-2010)
25-Dec 154273 Fuel Filter Change (Fram G3850)
14-Jan 154432 Differential fluid change (Ford XL 3 friction mod & XY75W 140 3-quarts)
25-Feb 155413 Replaced Rear Brake Pads (FMC BR-3)
25-Feb 155435 Replaced Driver's side bottom seat cover
12-Mar 155831 Installed Purolator PCV Valve (PV233)

The troubling thing, NO CODES, thus stumped. Appreciate any guidance in this trouble shooting effort.

Thanks in advance!!

 

[CARO'S98EB]

Sounds like a bad coil. you need to get a code[may taek a while] or find a tech with a scanner that does a power balance to isolate which one.

 

[maverick]

I am leaning towards COP's, but check the codes first. May be a bad or dirty IAC also.

 

[1997SCEBFEX]

Caro, Maverick,

Thanks. Drove her today after sitting since Thursday. Ran fine for a while, then acted up again...seems like a "miss" & still no codes. Ruling out IAC since it idles fine and have been down that road before.

I did talk to the Blue Oval folks and they articulate "level 6" scanning which is moreso than what I have in my arsenal. She's my only ride, so have to do the balancing act on time and alternate transportation.

Best from here,

 

[CARO'S98EB]

yours is old enough mode 6 data will not have misfires on it. A ford dealer will have a IDS scanner that can isolate the miss though, but it will caost you at least an hours diag time.

 

[1997SCEBFEX]

Thanks for the clarification!

 

[1997SCEBFEX]

I pulled and cleaned both the MAF and S/C inlet temp sensor on Sunday a.m. with brake cleaner as well as cut loose ends off a few vacuum lines, and it seemed, coincidentally, to fix the problem until this afternoon coming home, it started to jump in the 1300-1500 range again :-(

I also read on another forum about replacing my [standard] s/c bypass valve as its the original from 1998 and am not showing vacuum on decel, but will show positive boost on the boost gauge. New bypass valve on the way and should be installed by Friday.

So, I'm stumped and still looking. Any other ideas?

Thanks!!!!

 

[toms89]

Not sure I am following you on your description. Is it bucking between said rpms?

 

[1997SCEBFEX]

I wouldn't call it a buck, but a few seconds increase by a few hundred rpms, then back to original rpms.

 

[toms89]

That to me sounds like its locking and unlocking converter?!

 

[1997SCEBFEX]

Trans serviced regularly as per my above post.

Thinking DPFE as it was from one of the retail auto parts chains and has been nearly 4 years on that.

Have ruled out unmetered air getting in & chasing gremlins now.
Thanks for your replies!

 

[1997SCEBFEX]

Vacuum restored after installing new Vortech [standard] bypass valve.

 

[1997SCEBFEX]

Update:

I changed the EGR, DPFE, and green vacuum line to no avail Saturday.

Blue Oval says they no longer make this trans, but have an update to it and the labor is 1/2 the price of the trans; rough $3.6K for the works including a 3 year/36K warranty.

After having the motor done last year, perhaps on borrowed time on this trans since I'm pushing more overall HP? The torque converter was replaced once when new under warranty.

 

[1997SCEBFEX]

It finally set a DTC and it was P0122, throttle position sensor. Changed it yesterday, seems to work fine at speeds, but idles a bit high, 1200 rpms. Guess it will settle out. Any experiences here?