Bricky EFI question

[85lebaront2]

Thank you Sir. The gentleman is bringing his pickup over this evening and we'll have a go at it.

My son did find a Ford-specific OBD1 reader at the repair shop where he works, left by the PO, who retired. We'll see if that plugs in.

Good luck with it and let me know if you need any more information on it.

[RenoHuskerDu]

Good luck with it and let me know if you need any more information on it.

We found the conx, pulled codes, got a 41 which is lean O2. Sent our buddy off to NAPA to buy a starter, PS pump, O2 sensor, and 20' of vacuum hose to renew all of that under the hood.

 

[RenoHuskerDu]

We found the conx, pulled codes, got a 41 which is lean O2. Sent our buddy off to NAPA to buy a starter, PS pump, O2 sensor, and 20' of vacuum hose to renew all of that under the hood.

Based on code 41 we decided to replace the O2 sensor. The one we took out was in miserable shape. We also replaced the starter, PS pump, and 6' of vacuum hose. She smokes less and runs a little better.

But still not right. Idle isn't clean, she acts like she'll stall on throttle opening, and only smooth out above 2000 rpm. Our friend is going to buy a cap and rotor, they look old, time for new ones anyway. And I'll look for carbon tracing under the old cap.

Can anyone confirm ID these components? For each, we would like to test it with a DMM to see if it's in spec.

Idle Air Control AIC:

Coolant temp sensor:

Throttle Position Sensor

[85lebaront2]

Based on code 41 we decided to replace the O2 sensor. The one we took out was in miserable shape. We also replaced the starter, PS pump, and 6' of vacuum hose. She smokes less and runs a little better.

But still not right. Idle isn't clean, she acts like she'll stall on throttle opening, and only smooth out above 2000 rpm. Our friend is going to buy a cap and rotor, they look old, time for new ones anyway. And I'll look for carbon tracing under the old cap.

Can anyone confirm ID these components? For each, we would like to test it with a DMM to see if it's in spec.

Idle Air Control AIC:

Coolant temp sensor:

Throttle Position Sensor

You have the correct ID for each, top one is indeed the IAC. Question, what do the plugs look like and what brand are they? I have seen some strange things on Fords with platinum plugs where they weren't originally specified and even with non-Motorcraft ones (friend had an F150 that had AC plugs in it, He changed to Motorcraft and nearly doubled his gas mileage.

Also check that the EGR valve isn't leaking or stuck, that will cause a very rough idle.

[RenoHuskerDu]

You have the correct ID for each, top one is indeed the IAC. Question, what do the plugs look like and what brand are they? I have seen some strange things on Fords with platinum plugs where they weren't originally specified and even with non-Motorcraft ones (friend had an F150 that had AC plugs in it, He changed to Motorcraft and nearly doubled his gas mileage.

Also check that the EGR valve isn't leaking or stuck, that will cause a very rough idle.

Bringing this thread back to life because the rich, rough running came back.

We had achieved considerable improvement and the 300 six was running pretty well, but still a little rich.

List of work done:

New cap and rotor, plugs, air filter.

Throttle body removed and cleaned.

IAC cleaned (cured stall when put in Park).

EGR valve tested for correct operation.

New O2 sensor.

Thinking we had things under control, we decided to fix the exhaust leak that had been there forever. The second converter was split open, empty. We welded it up tight and installed a new side dump exhaust with a MBRP stainless muffler. She sounded nice and quiet, but right away rough running and black smoke started too.

What the heck??? Could there have been melted converter bits in there, blocking the exhaust? We cut it off and examined closely ... nothing in there. And it still ran like dookey with the exhaust open again. We double checked the cap and rotor, both look normal. We pulled and cleaned the O2 sensor, it was all sooted up. We pulled a couple plugs and they are sooty but look like they'll fire fine (see pic below). We checked that both butterflies in the throttle body are opening on throttle. We checked for objects or nests in the intake tract.

Something is making the EEC run way too rich. First thing in the morning, it runs fine for about 30 seconds, then black smoke and rough running.

Possible clue: Noted on pulling throttle body that the intake manifold is lined with black gunk. Could that be caused by EGR valve malfunction? (but it tested OK). Could it be caused by a faulty PCV valve? It looks dirty as sin but they are simple devices. I think we'll pull and clean it anyway. Right now we've unplugged the EGR as a test. And we're welding back up the exhaust.

What if the TPS were faulty? Would that possibly cause all this drama? Is unplugging it an option for debugging?

This is a friend's truck. He lets his daughters drive it. I'm afraid the rich mixture will cause premature cylinder wall wear. We are not good at this EEC stuff, we drive diesels. Hopefully one of y'all has the magic tip.

[grumpin]

Bringing this thread back to life because the rich, rough running came back.

We had achieved considerable improvement and the 300 six was running pretty well, but still a little rich.

List of work done:

New cap and rotor, plugs, air filter.

Throttle body removed and cleaned.

IAC cleaned (cured stall when put in Park).

EGR valve tested for correct operation.

New O2 sensor.

Thinking we had things under control, we decided to fix the exhaust leak that had been there forever. The second converter was split open, empty. We welded it up tight and installed a new side dump exhaust with a MBRP stainless muffler. She sounded nice and quiet, but right away rough running and black smoke started too.

What the heck??? Could there have been melted converter bits in there, blocking the exhaust? We cut it off and examined closely ... nothing in there. And it still ran like dookey with the exhaust open again. We double checked the cap and rotor, both look normal. We pulled and cleaned the O2 sensor, it was all sooted up. We pulled a couple plugs and they are sooty but look like they'll fire fine (see pic below). We checked that both butterflies in the throttle body are opening on throttle. We checked for objects or nests in the intake tract.

Something is making the EEC run way too rich. First thing in the morning, it runs fine for about 30 seconds, then black smoke and rough running.

Possible clue: Noted on pulling throttle body that the intake manifold is lined with black gunk. Could that be caused by EGR valve malfunction? (but it tested OK). Could it be caused by a faulty PCV valve? It looks dirty as sin but they are simple devices. I think we'll pull and clean it anyway. Right now we've unplugged the EGR as a test. And we're welding back up the exhaust.

What if the TPS were faulty? Would that possibly cause all this drama? Is unplugging it an option for debugging?

This is a friend's truck. He lets his daughters drive it. I'm afraid the rich mixture will cause premature cylinder wall wear. We are not good at this EEC stuff, we drive diesels. Hopefully one of y'all has the magic tip.

I don’t know this system well. But, what popped into my head was engine temp sensor, because it runs well for awhile.

[red1980F150]

I don’t know this system well. But, what popped into my head was engine temp sensor, because it runs well for awhile.

A few years ago on my '93 I changed the spark plugs... and the exact moment I started the engine after changing the plugs the diaphragm on my fuel pressure regular ruptured, leading down a rabbit hole similar to this one, I read the engine code with the morse-code engine light and everything. I ended up changing plug wires, 02 sensor, probably 1 or 2 other things, until I figured it out. The timing of the failure couldn't have been worse because it made me think I did something wrong.

If the fuel pressure regulator has failed it'll make it run extremely rich and idle very poorly. It'll smooth out at high RPM, probably because the engine needs more fuel then anyway, but it's still running rich. My MPG went from 16-17 to 9. I guess the only way it would be intermittent is if the regulator is okay and you have a collapsing vacuum line or something (as someone mentioned above)?

Anyway, might be worth checking. On my truck it was a cylindrical can about 1-inch in diameter up near the firewall.

[RenoHuskerDu]

A few years ago on my '93 I changed the spark plugs... and the exact moment I started the engine after changing the plugs the diaphragm on my fuel pressure regular ruptured, leading down a rabbit hole similar to this one, I read the engine code with the morse-code engine light and everything. I ended up changing plug wires, 02 sensor, probably 1 or 2 other things, until I figured it out. The timing of the failure couldn't have been worse because it made me think I did something wrong.

If the fuel pressure regulator has failed it'll make it run extremely rich and idle very poorly. It'll smooth out at high RPM, probably because the engine needs more fuel then anyway, but it's still running rich. My MPG went from 16-17 to 9. I guess the only way it would be intermittent is if the regulator is okay and you have a collapsing vacuum line or something (as someone mentioned above)?

Anyway, might be worth checking. On my truck it was a cylindrical can about 1-inch in diameter up near the firewall.

That's a great tip. We searched and found it on the injection rail.

However, the tank and in-tank fuel pump were replaced about a year ago, because the truck had been sitting in a farmer's field for 7 years.

I wonder if that mechanic (guy I don't know, GM fanboy judging by his yard) put in the wrong pump? The truck has always run rich since, as far as we know. But previously it did not run at all.

If someone has a diagram indicating what components should be in the 1990 fuel system, 300cid six, and approximate location, that would be very helpful.

Here is what RockAuto says the fuel pressure regulator looks like. It's $42 at NAPA so I ordered one.

[red1980F150]

That's a great tip. We searched and found it on the injection rail.

However, the tank and in-tank fuel pump were replaced about a year ago, because the truck had been sitting in a farmer's field for 7 years.

I wonder if that mechanic (guy I don't know, GM fanboy judging by his yard) put in the wrong pump? The truck has always run rich since, as far as we know. But previously it did not run at all.

If someone has a diagram indicating what components should be in the 1990 fuel system, 300cid six, and approximate location, that would be very helpful.

Here is what RockAuto says the fuel pressure regulator looks like. It's $42 at NAPA so I ordered one.

Yep, that's exactly the part I had to replace.

Mine was a 302 with MAF, however.

[85lebaront2]

That's a great tip. We searched and found it on the injection rail.

However, the tank and in-tank fuel pump were replaced about a year ago, because the truck had been sitting in a farmer's field for 7 years.

I wonder if that mechanic (guy I don't know, GM fanboy judging by his yard) put in the wrong pump? The truck has always run rich since, as far as we know. But previously it did not run at all.

If someone has a diagram indicating what components should be in the 1990 fuel system, 300cid six, and approximate location, that would be very helpful.

Here is what RockAuto says the fuel pressure regulator looks like. It's $42 at NAPA so I ordered one.

I was hoping AllData had some good diagrams or pictures of the EFI fuel rail etc. Does that truck have the small cooling blower in the right front of the engine compartment? If it does then that is the earlier system, and runs around 35 psi fuel pressure. Ford changed to a higher pressure system on the 4.9L to eliminate vapor lock under hot soak conditions, these engines run around 60 psi fuel pressure. If the wrong pressure regulator was used, ie, one for 60 psi on a system designed for 35 psi, it will run rich enough the O2 sensor can't compensate for it. If the emission label is still on the underside of the hood, it may show the fuel pressure spec.