Hello Everyone,
ive got a poser here. 94 4.0 2+2 135K miles. Going to work, started losing power. I shut it down. Had it taken to shop. They replaced distributor rotor; ignition coil; distributor cap; CPS; valve cover gasket; changed oil. Ran ok, but after a couple of days, it died again, they determined coil was bad, warranty replacement made. Ran ok then threw a FF14. I replaced the coolant temperature sensor. Ran better, fault was gone, but just this morning, it started missing again, and rough on acceleration but ok on idle. I didn’t replace the sender next to the CTS. Any ideas given the history so far?

 

Take a look at the harness wires at the CTS. There have been reports that the wires start to touch one another? Look for cracked insulation, or wobbly connection points?

How old is the fuel filter? Spark plugs (I assume the shop checked these)?

After that, I’d pull the ECU harnesses off and check for any corroded pins. This is a common problem. The ECU is in the passenger footwell.

 

thank you! Will check!

 

The wiring appears to be intact and well-wrapped. No melted areas, and the harness appears safe behind the guard next to the engine.

I’m not sure of the fuel filter’s age.

mom going to access the ECU to check for corrosion next.

 

I’ve accessed the ECU, per pics below. However, I’ve never seen actual plugs that look like this, so I’m nervous about trying to remove them, not really knowing what I’m doing. There are two long plugs, one yellow, and one blue. They have a “paddle” of sorts on one end each. I don’t know if I should push the paddle in, then try to wiggle the plug away from its mate, or pull the “paddle” away from plug and wiggle the plug out.

Here are the two ECU plugs I don’t know how to unplug.

 

I apologize. I thought you had a similar ECU as the 95/96 models.

Im going to wait for another 94 MY owner, however, I now turn my attention to the fueling system. It would be great to get pressure readings from the fuel rail. That could shed some light on the state of your fueling system. Pump and/or filter? (The 95/96 MY do not allow for fuel pressure readings. There’s no valve to connect a gauge to, not sure if 94 has a way)

Please confirm last time spark plugs were replaced.

 

It’s a Lucas 15 CU as you can see.

 

Id send it back to the shop. You paid to have things rectified and its not running any better. I know that it gets tiring but they shouldnt call you just because its been running good for 15 minutes.

 

Thank you, at this point before I go digging into unfamiliar ground, I believe I’ll do just that. I can repair only so much on my own, and the shop should do what they can do.

thank you much, and I will update the thread with any resolution successfully reached.
JD
Tulsa, OK

 

Losing power or missing, which describes it best? You have described the problem both ways.

 

Replacing the fuel filter is easy and replacing the spark plugs on these engines is even easier.

 

agteed. That’s an easy one I can do.👍

 

The shop may continue to search for the problem, and at $100/hour, they will, but it'd be best to cross off as many things as possible before the meter starts.

 

It certainly does both. It acts as if it is going to stall, dropping RPM's and oil pressure, and the engine shakes, and its obvious it's missing by the uneven shaking of the engine itself, the motion, sound, etc. I love your ending tagline by the way.

 

Totally agree with that. I don't want to send them on a fishing expedition.

 

Make sure you use the right spark plug. Stick to the basics.

Champion RC9YC or NGK BKR6E

Don't use any platinum, iridium, etc plugs. The cheap copper ones work best.

 

Hi JD3711

Since we are down to Clutching at Straws, at least for the moment

As Plug Wires 5 and 6 are near enough the same length, it is not beyond the realms of possibility that out of sight behind the Plug Lead Cover Plug Wires 5 and 6 may have somehow got misplaced so what looks like Plug Lead 5 is really Plug Lead 6 and visa versa

Definitely worth Checking that these two leads are going onto the right Spark Plugs

I know it sounds like a Long Shot but it has been known to happen also Plug Gap .025

 

JD3711,

Just to clarify, does it always start fine, idle fine, and then misfire when you press the throttle?

Or does it start fine, idle fine, run fine, and then start to misfire after you've been running for a while?

PAul

 

Exactly-number 2. It runs and operates great, starts great, then after it gets warmed up, it starts the stuttering a lot upon acceleration and you can also feel it missing,and you can give it a rev, and it gets better, but as it winds down, just starts that stuttering and missing shaking.

 

another thing: no codes are being thrown. I can’t understand that.