Running rich, need guidance.

[88workcar]

Just rebuilt the whole top of this motor. What is going on actually started before the rebuild. It does indeed run better now. When I first start up and get going it runs perfect, smooth, all of it's power. About 5-6 miles out holding speed 55-60, just as the temp gets leveled out, it will make a very noticeable stumble and then looses power for a while. If I clutch it and rev the motor it seems to go away for a moment then comes right back. I can park it, let it cool down and it's back to running perfect. I keep getting 1132 and 1152 codes. Truck has new injectors, wires and coilpack. After 100 miles the new plugs are sooted, bad!! I have a new set coming. I am thinking to replace all 02 sensors and try to clean the cats. I saw a video where the guy soaked the cats in gas for 24hrs and it cleaned them. If this is bull please tell me. Before I got through the money and time I figured I'd reach out for advice. Thanks for any pointers.

 

[Curious Hound]

Check ECT sensor? MAF? Could be sticky/dirty injector?

Sounds like it’s unhappy when it warms up and goes into closed loop operation.

 

[Dirtman]

Anytime a vehicle runs good at one temp and bad at another first thing I look at is the ECT sensor. If it's stuck reading cold it will run rich on startup (which is normal and needed), but then when the engine warms up it will keep reading cold and tell the computer to keep the mixture rich when it should be leaning out. It's a cheap simple sensor that has quite a large effect on engine operation.

 

[88workcar]

I will get one today then. Just a FYI to you all I did replace the PDFE sensor. I will check the rest.

 

[RonD]

Well computer has a timer circuit that will set a Temp code after 5 minutes or so of run time if ECT isn't going up to operating temp
Like P0116 Engine Coolant Temperature Circuit Range/Performance Problem

But the change in performance after warm up is a clue, the computer doesn't/can't use O2 sensors until they get above 650degF, which is why they are "heated" O2 sensor, so they warm up faster

P1132 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1
P1152 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 2

So the upstream O2s are staying at .9volts, so detecting no oxygen in the exhaust, ever
There would need to be an injector on each bank to be leaking to get BOTH codes, so longshot on that

Could be partially clogged exhaust, you test for that with $20 vacuum gauge, simple test<<<<<<
If engine has been running Rich for awhile(before repair) then its possible the Cats are clogging up
And O2 sensors were also damaged, covered in soot like the spark plugs
Upstream O2s only last 100k miles, so changing them would not be a waste of money even if it doesn't fix this specific problem

Not sure soaking in gasoline or anything would clean them out, Cats work by using a chemical reaction, if they get coated with soot inside they stop working so don't get hot enough internally and eventually stop passing exhaust through as the holes clog up

 

[88workcar]

What do I owe you boys? LOL. ECT was the issue. I still have a struggle in the upper rpms which would make me think CATS getting bad. The 5 min test coming to work was Good!! No stupid drop in power, bucking, ect… No codes. I did replace the plugs also yesterday. They were sooted as before. That too would make me think the cats have to be dirty. I will replace all 02s just for the same reason and as you said Ron.

 

[Curious Hound]

 

[88workcar]

The two at the bottom were swapped when I was looking over everything. It was all I had for spares. It there any way to "clean the cats" ? I see what I think is 5 of them.

 

[Dirtman]

I believe one (usually the last one) is a resonator not a cat.

I don't put much stock in the idea of cleaning cats but it can't really hurt either.

 

[88workcar]

Well fellas.………… 29 miles later...………. it's back lol, same problem, same codes. I do believe 02 sensors and cleaning or gutting the cats will be next. y'all thoughts please.

 

[RonD]

Yes, as said ECT issue would have set a code

While both upstream O2s failing at the same time is a long shot, if there were previous engine issues then it can happen

If they look like the spark plug tips then for sure change them

 

[88workcar]

I pulled one 02 this morning, could not get the other two out. Sooted just as expected. I was hesitant to order new 02s till I actually looked at them to see 2,3 or 4 wire units. Mine are 4 wire. I just put that one back in and will drop the whole exhaust Saturday, to remove the other two sensors. This morning it ran like before the ECT sensor change and codes are 1132, 1152 and 401. 117 miles on that tank of gas

 

[pjtoledo]

is there a flex fuel module on the frame near the filter??? if yes check it's output.
if it is telling the computer there is too much alcohol it will add more fuel causing a rich condition.

I checked my 2000 with an Ocilloscope. I'm not sure which scanners will show the alcohol percentage.
the signal is a square wave that changes frequency, so a voltage reading is meaningless.

 

[88workcar]

How do I see if my truck is flex fuel? or just cause of the year, it is? That lil item would throw a rock in this project lol.

 

[88workcar]

I have been thinking that I bought flex injectors and that has been the issue, but it did this before I tore into it.