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1986 Chev Cavalier Slipping - Engine
Question: My engin started missing out and the check engin light blinks at the same time. I found if I take the fuse that covers the gages, warning lights check engin light and speed O out the miss go's away ?????? got any idea's
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Technican: Have you tried checking troublecodes? Need instructions?
If the engine light blinks when you have the Key ON Engine NOT Running... you have a computer problem or a short in the wiring.
Owner: Yes I checked the code and only got a 12 . But I do think it is acting like a electrical problem. or a sencer. do you know where the computer is on a 86 cavelir v6 2.8 RS model. the car got real wet recently . I left the windows down and we had a big rain .But It ran fine after that. And I just took out the electric seat and put in a manual. if that gives you any clues as to what is going on . I feel it will turn out to be a loose wire the qustuin is where.
Technican: autozone.com/servlet/UiBroker?UseCase=P005&UserAction=initiateVehicleRegistration
Copy this link into your address bar. Fill out Year, make, model, and engine then click REPAIR INFO... remair info will contain a repair guide for you car as well as a component locator.
I also assume this didn't happen immediately after replacing power seat?
Owner: Yes It did start right after I took out the electric seat but like I said I put in a manual seat so it is not pluged in to the power cable. but I did not tape it off maby I should.
Technican: Unless it was shorting somehow I don't see how it could matter. But needs to be investigated if it happened right after replacement.
Owner: I looked it over and there is no way to short it out as the pins are on the in side of a female conector. but I tape over it any way . I checked the eror codes again and still get only a 12. But the cooling fan relay keep clicking through the hole test. And I started it after the test and the relay was still cliking I went out and tapped and it quit and the colling fan came on. It has been working all through the problem but I think I will get a new relay tomrow maby I will get lucky but it is not on the number 1 fuse that make the car run fine when it is out.
Technican: When you take out the fuse does the cooling fan come on (with a cold engine or when it normally isn't)?
Owner: Cooling fan relay is not the problem. the man convenced me at the part store as the fan work fine when the fuse is out of the number one fuse and the car runs without the skip. It has to be some thing that is on that fuse circet. I'm about to quit woring about it the only bad thing about the fuse being out is I dont have a speed O as it has a digital dash . I had allready switched to a oil, temp and volt gages. I will need to check the milage and see if it has changed. at the price of gas now days I will have to find it if it cuts the milage. Maby I can find a junked car and get every thing on that fuse. Which is a mass air flow relay, mass air flow sensor, canaster purge solenoid valve, a/c control relay, a/c comp clutch and ecm. But I only gave 100.00 for the car and some of those parts would coust more.
Technican: The reason I asked if the fan came on was to see if this was causing the ECM to go into 'limp home mode'. If the fan comes on the ECM is only trying to keep the car running and is lessed concerned about fuel economy.
If you have identified everything on the circuit simply disconnect wiring connectors to these items one by one. Do this test with the fuse installed. Try everyone of them and note which makes a change. If you can unplug something AND have a change for the better, logic points as this part being bad. GM cars had a lot of trouble with the MAF and it's relay during those years.
Does your car also have a MAP sensor? I think your year could go either way on this issue. If it does there is a computer (or prom) update that involves eliminating the MAF. This repair likely costs more than you paid for the car too.
Let me know what you find and we'll go from there.
Owner: I'm sory I did not say that the cooling fan works normaly. I had just got home when I ran the obd test yesterday and the cooling fan had just came on before I shut the car off and ran the test. when it comes to unpluging the other parts I will have to find all of them except the mass air senser. I just found out what is on that circet from a wiring diagram.
Technican: Hello,
What I was trying to find out is-
When you remove the fuse does the radiator cooling fan run (at all times when the engine is running)?
If it does the computer (or ECM) recognizes a problem and operates on its own base values. WHat this means is the computer is not paying attention to some vital information from engine sensors. Instead the engine uses substitute values. With these sustitute (or base) values it's virtually impossible to achieve desirable fuel economy.
Did you get the online repair guide to work or do you have a repair manual?
If you visit-
partsamerica.com
Register you car then click replacement parts. Select any parts you want to view. Usually most parts have a picture.
Owner: I have been trying to say the fan works . which means it comes on when the engin is worm and shuts off when cool with the fuse in or out. And figure this I put the fuse back in today and the car ran fine. Went to town stoped done what I had to do and came home with no problem. I have not went back out and checked it this afternoon.
Technican: Okay, everthing is clear on the fan now.
Now you can either cross your fingers and hope it doesn't come back. Or try to get the problem to come back. To do this start the car and allow it to idle. Be very careful around moving engine parts. Now lightly tap on the MAF (a screwdriver handle would be fine), but not hard enough to cause damage. The idea is to tap it just hard enough to simulate normal vibrations the sensors would experience going down the road. This is an effective method to get the problem to 'reveal' itself. Try this with MAF sensor and it's relay.
Owner: I dont see a maf sensor but there is a mat sensor and a map sensor would one of them be the same on this car.
Technican: Most cars from this time used a maf or map. Very few used both. Normally the 86 didn't, but it's possible depending on production date.
The test I gave would not be as effective on a map sensor as it would on a maf. The reason I mentioned MAF is cause you said you had one on the circuit and knew where it was. Perhaps you were viewing a wiring diagram that listed this as the circuit that would provide power to the MAF (if it was equipped).
I bet you are learning a lot about cars.
Owner: OK if Maf stands for mass air flow Sensor I got it. And will test it later when it cools down here in Florida. I'm working from a book from Haynes and thay are trying to cover 1982 to 1994 so some of the info is general and the illustrations of the part location is a 3.1 mpfi engine and I have a 2.8 mpfi I gess thay did not use the maf on it.
Owner: Well I shook & taped the maf and relay and the car still runs good . The only thing I can see that is diferant about today is it is a littel cooler outside. I gess I will have to wait and see what tomarow brings.
Technican: MAF- mass airflow sensor (located before the throttle body in the large air hose)
MAP- manifold absolute pressure sensor (on cars from your era will have a vacuum hose attached)(also all map sensors are linked to intake manifold vacuum)
If your car still has both of these sensors there is an update (as I said before) that eliminates the MAF from the system. WHat this means is that the computer (actually an ECM) will no longer look from input from the MAF. There was numerous problems with these.
For future reference, autozone.com has online repair manuals that are free. They are the equivalent of a haynes or chiltons manual.
If you want something a step above, alldata.com has a do-it yourself subscription that is much better but cost $24.95.
On newer cars you can get online service manuals but this is rather costly. With the exception of Hyundai who is the only manufacturer to offer their service publications free of charge.
Owner: I have spent all day trying to get the car to run bad again and cant. the only thing I did the day it started working again is read the obd code again. I'm wondering if I might have a problem right at the obd plug. I have looked it over and dont see any thing but I cant think of any thing els.
Owner: Ok I went out about 2 miles with no problems. stoped at a store when I left the car ran good about 1/2 mile then it started the same thing again. Then about 1 mile later it went right back to runing good again.when I got home I checked the eror code hopeing to get some thing but still only get a 12. I think I will have to stop when the car is runing bad and check the code. ??? can you check the code while the car is runing
Technican: The problem I mentioned with the MAF, that is fixed by a computer update (PROM) will not set a troublecode. That is why their is an update. A problem exists and the computer never detects it.
This applies if you have a MAP and MAF sensor.
Contact your friend at the parts stores and see if he can give you a price on an updated prom/ecm. He should be able to look this information up. It should also come with instructions telling you to tape off the MAF connector.
Owner: Not that it maters But I cant find a part store with a prom/ecm upgrade maby a dealer part. But the car quit runing yesterday with smoke coming from under the dash drivers side. smelles like burnt wires so I'm gessing when I find the wire I will find what has been the problem all along.
Technican: What did you find out with your car? Was this problem near the ignition switch?
The parts department would need your vin number to see if the update applied.
Owner: Yes I did find the problem . there was a wire that came from the fuse box that had arced to ground and melted into two other wires. when I cut out the bad parts and rewired them the car run grate. Nock on wood. Here's How To Get Guaranteed Solutions In Minutes
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