I have a 1987 240 DL wagon with the 5speed manual. A couple months ago my car wouldn’t start without me holding the throttle open, and would bog down/die when idling.

Replaced fuel injectors, MAF sensor, and the idle air control valve, now the car starts easy, but idles too high. I cleaned the original idle air control valve after testing the voltage and determining it was still good, and put it back on my car.

Now the car starts easy and idles great, until it warms up. It starts looping (dies down then revs up) and if I try to hold the throttle open the engine shakes a little more than normal, and it almost backfires, then will bog down/die.

Could the oxygen sensor be bad, telling the car the wrong info for the air/fuel ratio, and causing my rough idle/engine bogging down/dying?

Thanks in advance for any help/insight

 

[QUOTE=Bigmjk;513117 1987 240 DL
Could the oxygen sensor be bad,[/QUOTE]

Certainly. On a car of that vintage - just disconnect the o2 sensor. It really does very little to trim the mixture, but can screw it up if it's damaged. The engine usually will run very well without an O2 sensor. The o2 sensor is there to make sure the unburnt mixture is correct as it goes into the converter. Problems might occur with many miles if the converter is still there - (converter will melt if too rich) but usually by this point a cheap replacement or the original has broken up, blown out and is hollow.

The O2 sensor will not affect starting. It only can change the mixture after it heats up - it is in "open loop" maybe 60 seconds or so after starting before the computer goes into closed loop (that is when the ecu begins accepting the signal from the o2 sensor)