2.3L ('83-'97) 93 ranger exhaust gets red hot

[black_demon69]

2.3l exhaust gets red hot . have checked and replaced timing belt timing is dead on . head had leaky valves so head was pulled to do a valve job. there are no vacuum leaks. o2 sensor has been replaced spark plugs replaced all 8 fuel pressure is good.. any suggestions to the cause of this ? obviously running rich.

 

[fastpakr]

Anything showing up via CEL?

 

[RonD]

What did the old spark plug tips tell you?

Any cylinder running rich?
Or all cylinders?

I would open up the computer and have a look at the circuit board, the 3 blue capacitors specifically

 

[black_demon69]

No cel or codes
Old plugs looked a little bit white like it is lean but it smells really rich

 

[tinman_72]

Make sure your exhaust is not obstructed.

 

[black_demon69]

Ron Caps in ecm are good
tinman cat is hollow and exhaust flows real good

 

[black_demon69]

MAF and EGR were also replaced. we noticed that it runs fine when cold but loads up when hot. could it be the iridium spark plugs?

 

[RonD]

When an engine is cold the computer runs in Open Loop, it runs pre-set air/fuel mix tables in memory
Computer doesn't use O2 sensors because they are too cold

When coolant temp gets above 140deg and O2s are heated above 650deg then the computer switches over to Closed Loop
And uses O2 sensors as feedback to calculate air/fuel mix on the fly

Computer doesn't use many sensors in Open Loop, basically its RPM and throttle position

Computer also runs a Choke when engine is cold, Richer fuel mix and high idle

 

[gw33gp]

Experience with my 4 cylinder race engine tells me the exhaust runs hotter when running lean than when it is running rich. Rich usually show a drop in exhaust temperature. There is a curve that at some point running too lean will start dropping in temperature too. Ignition timing advanced too much will also increase exhaust temperature.

Rich will make the catalytic converters run hot. If it is running rich and it is the catalytic converters that are hot, you could check that the O2 sensors are working properly. Possibly bad injectors could cause it to run rich too.

 

[Peter's 93 Ranger]

I replaced the EGR,MAF, All 4 Fuel Injectors, Checked the ECM. the O2 sensor is Brand new. Exhaust is still getting red hot. Runs great for about a minute but then losses its power shortly after. cannot even climb a small incline in first gear.
Any ideas on what to look for next. Timing is on. no vaccumm leaks either. totally stumped.

 

[black_demon69]

plugs stating to show rich condition after all the parts that have been replaced. and yes this is peters truck we are talking about. could the iridium plugs cause issues like this?

 

[Dirtman]

I've heard iridium plugs will melt!

 

[Peter's 93 Ranger]

We believe we figured it out, it was the EGR valve cylinoid. I also replace the thermostat control module.

 

[black_demon69]

Coolant temp sensor and EVR (exhaust valve regulator) or EGR soliniid. Exhaust was not plugged

 

[Peter's 93 Ranger]

Coolant temp sensor and EVR (exhaust valve regulator) or EGR soliniid. Exhaust was not plugged

I was off on the names a little. Lol