Ive been experiencing missing issues on my 89 325is for some time now. Throughout the revs up untill about 5k, it misses very slightly. Its definately noticable and my passengers have said it as well, but its a very light kind of jerk, where it feels like the car is hesitating. The randomly, and when i say randomly i mean RANDOMLY, the car completely jerks back, and drops in revs very quickly then regains itself in less than a second. Im kind of stumped and dont really know where to start. Could this be as simpler as a cap/rotor/plug wires? Plugs are brand new. Could it maybe be an injector? Im pretty frustrater by now cause ive tried replcing the AFM, the idle control valve, and i checked the cap and rotor and they SEEM to be fine and not in bad shap at all.
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I get this sudden jerk too sometimes. When it happens the check engine comes on for less then a second. Usually happens once in a day and doesns't happen again, but today I took a fast corner and right after it must have done it six times within a 30 second period.
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Have you ever replaced the fuel filter, and/or fuel pump?Comment
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Ive replaced the fuel filter but not the fiel pump...Comment
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Originally posted by mazur View Post
That is EXACTLY what happens to my car! I'm glad im not the only one with this problem... maybe someone else has had this and was able to fix it? Any help would be so much appreciated!Comment
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I've been through this exact scenario. the engine would "miss" momentarly, randomly, on the freeway. it jerked me around and drove me nuts. the check engine light would also flash for less than a second. it was a nightmare until I figured out what it was, then it was pretty easy to fix.
the three things you need to check:
1. throttle posistion switch. the procedure for testing it is in the bentley.. it's pretty simple. You can also unplug it and see if there is any change, your idle won't be right but the "miss" should go away. I ended up driving around with mine unplugged for a couple months until the weather got nice enough for me to really fix the problem. my switch was actually fine but there's part 2:
2. injector harnes. it's right under the throttle body, a round plug, can't miss it. it can get water inside and corrode the connector and wires, shorting out and causing havoc on your motor. the plug for the TPS also goes into here. if it's corroded, you need to clean and dry it out. spray some WD-40 down the wires if they're wet (WD-40 will push out any water that might be trapped in there). clean off the connectors and put some dialectric grease on them (same stuff you use on spark plug wires).
3. throttle body coolant passage. there is a cork gasket that tends to leak over time. could also be leaking from the two hoses that go in/out. this is the most common source of the water found in the injector harness. it's a cheap fix, and not too hard. you have to remove the throttle body to get to the screws. get the gasket and both new screws (the screws are almost certain to snap off when you remove them). seal with a light layer of sillicone and let it dry before you add coolant. mine had been leaking for some time, but it was just a pinhole leak so I wasn't going to worry about it until spring. boy did I ever regret that decision!Comment
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nando- I REALLY appreciate that in depth write up, im going to go check the injector harness right now.
With the TPS, how would you know if it is bad? You said with yours that it took care of this miss for the time being by unplugging it, why did this "fix" it?Comment
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it "fixed" it because the harness it was connected to was full of water. I don't know for sure, but I think everytime it shorted it would send a wacky signal to the ECU, causing it to do really wierd things. there was nothing wrong with my TPS, but that might not neccesarily be the case with yours.Originally posted by JoeyJoeJ0 View Post
as I said, testing procedures for the TPS are in the bentley.. I don't remember off the top of my head, but all you really need is a basic multimeter. you are testing the switch to see if it turns on/off correctly, if it's getting power, etc. there may be a writeup on the 'net somewhere too.
btw, with it disconnected, your car will be a bit slower. since the ECU won't know if the throttle is open or closed, it runs a default program. but I found that to be far less anoying than jerking me around at 75mph!Comment
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Alright I see what you mean now. I dont have a Bentley myself but Ill be ordering one asap.
I cant thank you enough for that response man, Ill let you know if it all works out well.Comment
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