HELP: Engine lag, IMRC?

[DrKlawz]

Really in need of some help here…

I have a 2000 Ford Ranger 4.0 V6 OHV w/ 165K miles. Recently I’ve been getting the worst performance I have EVER gotten out of my truck.

SYMPTOMS:
- Engine “lags”
- Loss of power in acceleration
- At highway spd, above 55, transmission will shift to neutral
- Backfiring, loud engine noise
- No “check engine” or error codes

** My theory: exhaust leak before cats, at the headers or collectors.

1st TRIP TO GARAGE:
- Cat efficiency test at less than 22% (this is weird, as I replaced the cats 2 yrs ago, but it was BLACK and caked)
- Erratic readings from MAF sensor
- Transmission pan pulled and inspected – no chunks, discoloration, etc.
- Replaced catalytic convertors, air filter, MAF
- Tightened all header/collector bolts

** Result: minor performance increase, still lacking power.

ROAD TEST 1: On highway road test, topping 75 mph at 92% load, the engine FINALLY throws a series of error codes: P0174, P0040, P2004. Check engine goes on, revs high, slight “whining” noise. Codes cleared, restart, “Check Engine” does not light up, continues to run weak.

ROAD TEST 2: On highway road test, topping 65 mph at 55% load, “Check engine” light turns on briefly, engine stalls. Stop car. Start up… no error codes, no check engine. Performance still weak and irratic.

Googling and my Ford Service manual helped get an idea:
P0174 – mix too lean
P0040 - switching O2 between banks
P2004 – Intake manifold runner control (IMRC) stuck open

There’s plenty online about similar issues with the 2.9 liter engine in previous models, but I’m having a hard time w/ 2 specific questions:

1. Where are the IMRC units on the 4.0L OHV V6.. I keep looking for an actuator assemply but no luck… Anybody know where the IMRC’s are on this engine/intake?

2. The ODBII codes talk about Bank 1 and Bank 2… which bank is which? Drivers/Passenger’s side?

I’m still not even sure we’re on the right track here. ANY suggestions or experience could help.

 

[DrKlawz]

In case it helps somebody...

After about $1200 in new sensors, road tests diagnostics, and other B.S. - the shop couldn't fix the problem or diagnose. Best guess, needed a new transition. F-me...

So I decide to wait and see. After a couple weeks, on the way home from work the coolant temp spikes. Lower intake manifold gasket failed in the back toward the firewall. Blew antifreeze down the back of the engine. After disassembling, it turned out the lower manifold gasket was breaching in a few places, but it was hairline.

THUS, I wasn't crazy, there was a weird noise at the back of the engine. Engine hadn't been able to hold proper/consistant manifold pressure, so it began messing with the mix and throwing error codes on the cylindar toward the leak.

After engine reassembled w/ new seal, she runs like new. NO NEW TRANNY, MAF, ETC. REQUIRED.

HOPE THIS SAVES SOMEBODY THE TIME AND MONEY.

 

[MadeInAmerica]

Glad you got it taken care of, and also glad to see you follow through on your posting. Hope it's still running like new...