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Dan, Technician
Category: Car
Satisfied Customers: 24577
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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My 2000 Olds Silhouette has been hesitating upon acceleration,

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My 2000 Olds Silhouette has been hesitating upon acceleration, acting like it is going to stall, back firing, spitting and choking. Then it straightens out - sometimes-for about 15 min than back again. I love my car but I am getting scared to drive it as I haveXXXXXtrip to work each day. I have put a new catalitic converter on, intake manifold , plugs, wires, pvc - i am beyond myself, I just don't know what to do. Other people have had to have the same problem. Please help if you can.
I would first replace the fuel filter incase its starting to get clogged then the next step would be doing a fuel pressure test to verify the pump is working properly. Fuel pressure should be at least 52 psi with key on engine off if low replace the pump. You could also disconnect the vacuum line going to the fuel pressure regulator to see if that helps if so replace the fuel pressure regulator. Almost all other problems would turn on the check engine light thats why I suspect the fuel pump and its common to cause these symptoms. Let me know if you have questions, thanks.
Customer: replied 7 years ago.
the service engine light goes on and off. The service trac light goes on and off. The change engine oil goes on and off. The fuel filter was cleaned thoroughly before replacing the catalitic converter and it made no difference. It has everyone stumped. My husband thinks it has something to do with the cam because before it stalls, the rpm's go crazy up and down . he worked in Mi at one of the auto plants and his job was checking the engines. would it help if he called you to talk to you or vice versa?
That is a bit strange factoring all of the lights that go off/on. We are not able to make calls or recieve calls and only can communicate through this listing. I would would monitor fuel pressure just to see if that could be a problem since the lights going off/on may or may not be related. Then before replacing the fuel pump monitor power/ground to the pump to make sure its actually the problem. If the fuel pump appears not to be the problem the next things to monitor would be the ignition switch voltage and voltage leaving the switch. If that looks good then you would want to monitor power and grounds at the main computer to see if those are acting up. If everything looks good up to this point I would replace the main computer. Let me know if you have more questions, thanks.
Customer: replied 7 years ago.
I forgot to mention that the problem only happens when the engine is up to normal tempurature. Also, the problem only happens when accelerating from a stop or from low speed, not while cruise at speed. When the coughing and backfiring occur, the tachometer pikes erratically. The tachometer symtom is why my husband thinks the problem is timing related, i.e. bad cam info to the computer results in inproper timing advance, and backfire. Do you think this is a plausable cause of the problem, and worth time persuing?

I dont think the timing is the problem otherwise it would happen at all temperatures. You could replace the 7x crankshaft position sensor just to be safe incase the sensor is beginning to fail. After replacement do the following procedure after replacement. Let me know if you have questions, thanks. Let me know if you have more questions, thanks.



Customer: replied 7 years ago.
What other problems could cause the tachometer to do what it is doing and the back firing to happen all at the same time? If the problem is what you think, why wouldn't it happen all the time and not just intermittently? I can drive it back and forth to work 2 or 3 days in a row with hardly no problem at all, then the next day, drive it for 15 minutes and it stalls on me and spits and chokes all the way back home .
The crankshaft position sensor is what controls spark, fuel, and rpm so that would cause the problem to happen otherwise a faulty wire or computer could also cause the problem. The only reason it could happen intermittently is because whatever the problem is is not completey shot yet, just in the process. Let me know if you have more questions, thanks.
Customer: replied 7 years ago.
If it were a wire, where would I look for it? And could a faulty wire cause the backfiring, irractic tachometer etc? and have you had a problem like this before or are you just using process of elimination? This car is 9 yrs old with 140,000 miles. Will more things start to go on it? Will it start costing more to repair than it is worth? My husband has been out of work since last Sept and our savings are depleted and our cards are maxed and I am still trying to get this problem fixed. If it were your car, what would you do at this point?
If the wire were the problem it would probably be the crankshaft position sensor wire otherwise a computer power or ground. I would replace the crankshaft position sensor test the power and ground at the computer and if the problem still existed I would bring the vehicle to a shop so they can monitor all of the sensor operations while vehicle is driving to see which one is misreading while problem is happening. I am telling you that I think this is the problem from past experiences and process of elimination but the fact all of the lights go off/on makes it sound more like a power/ground at the computer or ignition switch problem but the tach going up and down indicates a crankshaft position sensor problem. Let me know if you have more questions, thanks.
Customer: replied 7 years ago.
You really have been very patient and I do appreciate what you have said thus far. Is the sensor you are talking about on the side behind the balancer or just on the side of the block? Also I don't know if it was a coincidence or not, but about 3 months ago the van was acting up all the time.I noticed when I took a corner it would almost die. My husband drove it a couple of times and noticed if he held the key in the ignition, it wouldn't stall. Then he took all the keys etc I had on my key chain off, and I just used the key. The van ran good for about 2 months. Then it started acting up again. He says it was just a coioncidence that it stopped acting up but could the ignition have something to do with it?

From what you said about the key trick this backs up the problem as likely being the ignition switch if it was going bad it was getting really sensitive to the position of the key in the ignition. With that being said I would start by replacing the ignition switch. Here is a picture location of the crank sensor. Let me know if you have questions. Thanks



Customer: replied 7 years ago.
From the looks of the diagram, the car needs to be on a lift to change the crankshaft sensor? Can it be done just driving it up on ramps? Also would the ignition have anything to do with the other problem or is that just a different problem? If the ignition switch was going, what other things would be happening from that problem?
Yes you can do it on ramps but you will want to jack it up while doing the relearn procedure so the wheels are off the ground. Its hard to say exactly what else could be the problem if the ignition switch was bad but the dash lights and radio could go off and on while problem happens also. Let me know if you have questions, thanks.
Customer: replied 7 years ago.
Even tho I didn't click ACCEPT , I just looked and the 18 was taken from my account you earned it
I'm not credited until you click accept.....until you click accept JustAnswer holds on to the entire amount. If you wanted a refund you could email the website otherwise you can click accept and continue asking questions even after you accept if you have questions. Thanks and let me know if you need anything.

Edited by Dan on 11/1/2009 at 11:18 PM EST
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Customer: replied 7 years ago.
Don, Sorry it took me so long to get back to you. The problem is fixed! While we were replacing the crankshaft sensor, the wire there was shot. The covering was totally gone and the wire itself had three or 4 spots where even the regular wire coating was gone and it was wire on wire! It cost $89 for the wire and the auto parts places did not carry it so had to get it from the dealer. But the car is running great now. Only problem we have now is the lights are crazy. But now I can go back and forth to work and not have to worry I will not get there or get home! Thanks so much!We never would have found the wire if you hadn't said to replace the crankshaft sensor. My husband was on the right trail when he said it was a tachometer related timing problem and you gave him the missing link!