QuestionThanks for the help! I had already changed the air boot going from the air intake to the air filter unit because it had a crack in it, but it did not help. The car as stated before always starts with ease but it does cough and backfire, just not near as bad when you put the car in gear or accelerate.
I tried clearing the fault code from your intructions, but I must not be doing it right.
Any farther help is appreciated. It's the wife's car and she is on me to fix it!
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Followup To
Question -
I have a 94' 318is automatic that coughs, stumbles, backfires and loses rpms when I try and accelerate. I have changed the air filter, gas filter, spark plugs, oil and filter, gave it a dose of water out gas treatment, and fuel injector gas treatment. I have also checked for vacum leaks by spraying starter fluid all around the vacum lines, all seem to be good.
I was getting a number two knock sensor code reading, but at that time was only having trouble idling at stops signs and red lights. Now I am getting knock sensor test pulse code reading.
The car starts with no trouble at all and idles pretty good until you put the car in gear. Then it starts the coughing and backfiring. The car runs extremely rough and all but doesn't accelerate. Seems once you get the car moving 20 mph or so it does get better but anytime you try to accelerate the least bit it acts up by backfiring and even loses rpms. If I accelerate very very slowly I can run the car pretty good from 20mph all the up to 60 plus mph.
This same problem occured about 6 months ago for a couple of days then disappeared.
Answer -
Hi there,
Could be one of many faults. Since you are getting a backfire and your idling is okayish, we can assume you have spark and compression. That leaves fuel and air. The poor acceleration sounds like lack of fuel pressure but could also be incorrect information getting to your ecu via a dodgy A)Mass airflow meter reading; B) Exhaust gas recirculation valve/sensor; C) Lambda/ Oxygen sensor; D) Intake manifold air control solenoid.
Try the easiest first. Disconnect the Lambda sensor and see if the car runs any better. Replace the MAF/ EGR/ IMS with a loan unit to check those.
Is your car the 16V 140BHP model or do you have the 8V engine? I know you said you sprayed around the motor but check under the air inlet hoses on both sides of the MAF as this is a favourite place for cracks and due to the corrugations, is hard to detect.
Have the fault codes been erased from the ECM? If not, when the fault codes reads 0000/1000/2000 (end of output) depress the accelerator pedal fully for at least ten seconds to erase the code.
Hope this helps.
Regards
Rob
AnswerHi, You need to let me know if your car is EUR or US spec and the model code for the engine.
Have you checked the fuel pressure?
Have you checked for the correct resistance on the following?
Camshaft position sensor....800-2000 Ohm
Crank position sensor.......400-800 Ohm
Knock sensors both..........1 M Ohm MIN
You sound like you know what your'e doing but I don't know if you have the equipment to check these items out yourself. As my profile states, electrical is not one of my strong suits, so all I can advise in this instance is the path I would follow in trying to diagnose the fault.
If you are getting a fault code from the Knock sensor, have you tried to replace it with a loaner to see if there is any change?
I still think it sounds like it is suffering from fuel starvation but it's hard to say without seeing the car.
Also if the car is a US spec, you guys have a very different fuel supply system than the cars we have here due to all the emmisions laws.
Sorry if I can't be of more help or more specific.
Let me know how you get along.
Regards
rob
