89 5.0 Code 40 Loss Of Power

[Dirtslow5.0]

Hello guys I'm having some issues with my 89 lx hatchback stang

Sometimes the car bogs at low rpm sometimes it backfires through the exhaust not just once but over and over until I rev it up, also feels way down on power from a roll, also I just noticed oil pressure doesn't go up with rpms and is sitting kinda low.

It's been a project but I recently bought a obd1 scanner to help diagnose the problem. Had to fix a couple things but now I get

koeo code 11

koer code 44/94 smog pump has been deleted by previous owner

Cylinder balance test I'm constantly getting code 40

So what I've done
Spark plugs
Plug wires
Compression check all cylinders all are within 10%
Changed the injector
Checked the injector pulse with a noid light
New fuel pressure regulator
Checked timing and put to 10° btdc
Checked the ecm was connected correctly
The coil is a newer msd one. I can see spark on #4 plug wire

I also pulled the valve cover and checked the springs for cracks and if the valves were moving while cranking.

Guys I'm at my wits end. I don't want to go carburetor.

Anybody got any advice on what's going on?

Happy Father's day to all the dads

 

[Mustang5L5]

If you pull the spark plug on cylinder 4, how does it look.

Also, just to be 100%, cylinder 4 is the rearmost cylinder on passenger side.

 

[Dirtslow5.0]

Thanks for the reply!

The spark plug for #4 looks pretty good, but today I noticed a little oil around the insulator. I pulled the upper intake, valve cover, and fuel rail today, not sure where the oil is coming from. But the car doesn't smoke! So I'm not sure what my problem is. But the lower oil pressure is another problem I'm having right now


And thanks for the tip, I have been diagnosing the passenger rear cylinder the whole time. I've been trying to fix this for about 3 weeks now double and triple checking things. Trying this trying that. I also went thru cleaned my salt pepper connectors and opened the male side up and used dielectric grease.

 

[General karthief]

Any mods? Check all grounds, they are very important. Put a manual gauge on temporarily to double check pressure. If you have the stock coil swap it for the msd unit. Make sure your alternator is charging, needs 13.5 at idle.

 

[Mustang5L5]

Could be leaking valve seals.

The code 40 indicates cyl 4 is dead. Things to test are for air, fuel, spark and compression. Sounds like you did this.

You can try swapping the injectors between cylinder, or swapping spark plugs to confirm the parts aren't faulty.

The plug getting oil fouled is a possibility if the valve seals are leaking. But for the plug to not fire at all...that's gotta be a significant leak.

 

[Dirtslow5.0]

Hey guys quick update

At idle on thè battery terminals 14.30 volts even though the gauge on the cluster says 12.5

As far as mods just lt headers h pipe and intake and smog delete, 3g 130 amp alt

I don't have the stock coil

And I will havè to check oil pressure with a manual gauge later.

My only idea next is to do a leak down test

 

[General karthief]

You said that plug had some oil on the insulator? Not the tip of the electrode? What does that plug look compared to others?
I'm with mustang5l5 with switching injectors and/or plugs and see if the problem follows the part. A noid light will tell you if the injector is getting pulsed, also check your grounds as I mentioned before, did you upgrade your ground strap on the drivers side head to firewall?
Another thought, how many miles on the engine? If it is alot, check slop in the distributor.

 

[Dirtslow5.0]

I've switched plugs and plug wires multiple times

I forgot to menton the first time I got the 40 code and I checked everything then pulled the fuel rail the injector for cyl. 4 had the pintle cap broken off. I still have it at home I can take a picture later, ive Been wondering if that could've done some damage internally when it fell off

I put in its place a 19lb 4 hole injector with 13 ohms resistance on the coil, It clicks when voltage is applied.

but I didn't swap the injectors around y

 

[Dirtslow5.0]

I have swapped plugs and plug wires same results

The other plugs look brand new and good, the electrode of cyl 4 plug looks good too! Ive tested the spark with a spark checker its got strong spark. I'm running autolite 25s

I used a noid light good injector pulse on cyl 4

I forgot to mention when I took the stock injector out for cyl 4 the pintle was broken off and missing, I wondered if that could've damaged something internally

I replaced that injector with a 19lb 4 hole with 13 ohms on the coil and it clicks with voltage, but I will try swaping the injectorsnext chance im slow.

I don't know the exact milage the odo reads 72k I would guess 172k

I didn't know there was a stock ground on the back of the driver head to the firewall, I'll check that right now

I have upgraded the ground wire from the block to the frame by the battery

 

[Dirtslow5.0]

I don't see any ground on the drivers side head to the firewall, I'll try and find a picture of where it's supposed to go

 

[General karthief]

There should be a small hole that a self tapping screw went, just below the clutch cable grommet. Just bolt a ground strap to the back of the head and that hole in the firewall.