Good afternoon,
I have a 1990 F250 7.5, E4OD, with about 70,000 miles on it.
My truck had a bunch of broken exhaust bolts, so I pulled the heads off, but the machine shop couldn't drill out so I purchased reman heads for my truck. (F3TE)

Ever since then my truck is giving me a code 41 (O2 sensor lean / not switching) The idle is steady, not high or hunting, and the truck pulls 21inlb of vacuum. So I don't believe it is a vacuum leak. The wiring is all good, Power is getting to the O2 sensor. I've also replaced the MAP sensor, plugs, wires, rotor button, cap, intake aur temp, O2 sensor, IAC and ECT. The Cat, smog and EGR valve has been removed, with the EGR Eliminator plug installed.

What I do not understand is the high timing, When I pulled the spout and set base timing to 10 degrees, when the spout is reinstalled the ECM advances the timing to 30 degrees. When driving I can hear the engine spark knocking and pinging.

Any pointers on where else to go? I've looked for grounds I might have missed with no luck, Swapped in a good ECM with the same issues, There is no exhaust leaks. The engine doesn't have any miss when under load but does have a strange random "miss" when at idle.

 

With the engine idling and one at a time...
What happens when the IAC is dsconnected?
What happens when the TPS is dosconneted?

If neither of those results in lower idle then it is possible the throttle blades are not completely closing. There is a stop screw on the side of tre TB that is only meant to prevent the throttle blades from sticking in the bores, at the correct setting the engine should just barely stay runing. This screw was set in locktite from the factory so if it's been messed with it should be pretty obvious, and if so dial it back out to that barely running setting (with the IAC disconnected). With that done the computer should now be able to control idle speed via the IAC with feedback from the TPS.

 

You have also added a bunch of new variables into the troubleshooting by throwing unknown new parts into the mix. Would you explain what you did to remove the cat, smog and EGR valve?

 

I'll have to test when disconnecting the TPS. If I disconnect the IAC, the truck dies.

 

Most of the sensors I replaced before the head swap. The truck sat for 12 years before I got it, I drove it about a year replacing small parts before jumping on fixing the broken exhaust manifold bolts. More or less I just wanted it to be known those items have been replaced.

I removed the cat because it was coming apart are ratting inside, removed the smog and EGR to clean up the engine bay and remove items that weren't being used anymore. I also removed the vacuum canister and hosing for the EGR valve, but left the TAB and TAD plugged in the harness and in their original positions.

 

I asked..

and you said

which doesn’t really answer my question. Is the o2 sensor in the stock location? What are you calling “smog?” What did you remove? I’m not familiar with the 460 and how the EGR is routed. You said you removed the EGR hose so how did you plug the exhaust leak?

 

sorry I guess I thought you asked why. O2 sensor is in its stock location. It’s down stream about halfway of the transmission (roughly under the passengers seat). And by smog I mean the smog pump and cat plumbing. Simply unbolt it from the bracket and remove the pump and air plumbing that originally went in the cat. On my 460 the factory cat was located further down the exhaust system, under the extended cab portion flooring.

EGR simply runs out of the driver’s manifold and into the intake behind the throttle assembly. I installed a pipe plug into the manifold and a block off plate onto the intake.

 

Ok that is good info, interesting to see what happens when the TPS is disconnected. If it has no effect it is possible the computer is ignoring it.. which isn't right, then you have to figure out why. It could be that the new sensor is faulty, quality on these things is terrible these days.

Another question, what codes are present? You should have some for the missing EGR stuff which can be ignored, but it would be telling if there are other sensor codes.
Has any of the engine wiring been replaced? If you found there are a bunch of codes that won't go away that could indicate miswiring somewhere in the harness.
Another thing to look at is the ignition module, there are 2 versions that have slightly different internal circuitry that were originally differentiated by color, older trucks before 92 or 93 used the grey module while later models used the black version. This truck would have had a grey module initially but the aftermarket has completely messed up the color codes and now seem to offer both versions in a black case. The computer controls ignition timing through the ignition module so a miscommunication here could be responsible for your timing problem.

 

Last night I unplugged the TPS. and the truck also dies when it is unplugged.

As for Codes, there are 2 codes present. 41 (O2 sensor lean, lack of O2 sensor switch) and 31 (Insufficient EGR flow detected).

I see no missing wiring, and As far as I know the ignition module has not been replaced, it is grey and remote mounted. I do find it interesting that if I disconnect the SPOUT the spark knock goes away, and truck truck actually runs better. So something is causing the ECM to throw the timing high.

I'm honestly starting to wonder if the PIP sensor is causing these issues, since the ECM relies on the PIP for Injector timing and ignition timing.

 

You need to get what is called a piston stop tool. You thread it into #1 spark plug hole, and rotate the engine BY HAND SLOWLY. You then mark the balancer where the timing pointet is showing. Then rotate the engine in the opposite direction. Again mark the balancer where the pointer shows. Then measure the distance between the two, half way is your REAL zero degrees. There is a possibility that over the years the balancer has slipped on the rubber ring. And 10 degrees is really 14 or 15 causing your spark knock. My 5.0 used to be off by 4 degrees. I haven't checked it in a few years, but ill bet it has moved again.
Start there. Because if you have a mechanical problem, it will make it harder to chase a computer issue.

 

There have been other posts about the aftermarket EGR eliminators not working as advertised.

The 2 codes you are getting are because the EGR gas flow is not present.
In a proper operating EGR system, exhaust gas is recirculated into the intake manifold the, the computer advances the timing to try to burn the fuel mixture that has been mixed with the inert exhaust gas.
Without the inert gas being introduced into the intake manifold, you have more oxygen in the fuel mixture making in more volatile and that is why you are getting the pinging.

You are either going to have to hookup the EGR valve again or back off on the timing and ignore the 2 codes you are getting which is easy since they don’t produce a check engine light.

I have the same codes on my 7.5 with a block off EGR valve and the rest of the same mods you did to your system.

One thing I did find when cleaning up my engine compartment was the cobra head to intake manifold gasket was leaking. You might try checking to see if yours is also.

 

I have looked and looked, eve spraying carb cleaning around the intake, and cobra head with no changes in idle. I honestly do not believe I have a vacuum leak.

I may test your theory about the EGR Eliminator not functioning properly but plugging in the old EGR valve and letting it sit on top of the engine and a short test drive. I the past I haven't had any issues with the an EGR Eliminator, but i see where that could be possible. I imagine the quality of those aftermarket parts are not as good as they used to be. If I plug the spout so the computer doesn't advance the timing, I get no pinging or spark knock. If necessary I can reinstall the EGR valve, but I will have to get a new manifold adaptor for it as the original was rusted and broken. (Another exhaust leak I had before doing the head swap)

Right now once I drive a short distance I am getting a check engine light, which i believe is caused my the Code 41 (Lean)

I'm also going to pickup some electronic cleaner and may spray down the PIP sensor, while the engine was apart I had to take the plastics off the distributor, may be some trash might be on the sensor.

 

If all else fails I will do that, I've never experience that issue before.

 

The code is for a lean mixture and the O2 not switching. Sounds like a shorted O2 sensor. Sure, the sensor was replaced, but did you test that circuit, with the sensor plugged in?

Voltage goes out of the sensor, not in. Actually, there is a bias voltage but that is too complex. I would measure the signal with the O2 sensor installed. It should swing around the .5v value [.1-.9v]. If it does not, then unplugging the O2 sensor and testing that signal should give you some voltage signal. It won't cycle so you may have to change the fuel mixture by accelerating the engine. On decel, the value will be close to 0v. Accel will be closer to 1.0v.

The ECU is telling you why it's upset. Spend your time addressing that and leave the rest out of your head. With all the wires in the truck, all you need to be concerned with is the O2 sensor. The answer should be a bad O2 sensor, wiring, or EEC-IV ECU. Simple easy.

 

So today I was able to perform KOER and KOEO tests.

KOER Codes:
33 insufficient EGR flow
65 Traction control system no change

KOEO Codes:
33 insufficient EGR flow
63 Throttle pos circuit lower than min voltage.

I cleared the codes and performed the tests again. KOER came to the same results, KOEO passed no codes.

I’ll probably replace the throttle position sensor since it seems to be giving some intermittent issues. Sometimes, randomly, I will have a hard shift so that could be the problem. Wiring all looks good.


As for the code 33, I’ll have to do more research on. I still have my EGR valve and pipe but the special fitting at the manifold was broken, it’s about $120. So I’d like to keep the EGR valve off if possible.