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Sensor questions...


NCReatta
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Two questions about a couple sensors in the engine in my '90.

1) when idling, the oil pressure gauge on the dash will bounce all over the place. All the way up, half way, 3/4 of the way etc.

Is this the sign of a bad sensor?

2) could a cam sensor cause a rough start? It's a little rough to start, and I haven't had a chance to tear into it yet.

Any insights on these problems?

Thanks!!

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Yes and yes, though the cam sensor should throw a 41 code.

I'm getting code 41. That's what lead me on to the cam sensor. I'm just hoping it's the sensor and not the magnet.

On a side note, I believe a bad oil pressure sensor (or an unplugged one) can cause the car to burn oil. Am I correct?

THANKS!

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Unlikely its the sensor itself though, they rarely ever go bad. Most likely the magnet.

Probably so considering my luck! :D

I'm probably going to be doing this the right way. Taking the timing cover off that is. Does the water pump need to be removed to do this? or just the pulley?

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I just don't really like the thought of using JB weld on a part that could go bad. It could be a week, a month, or 20 years. You never know.

I can probably replace the timing cover later though if it does end up going bad. I need to get this car going before it gets much hotter here. This is the only car I have with AC.

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To each his own. The JB Weld or even silicone sealant will last longer that the plastic holder that holds the magnets. That's what the real problem is. The plastic of the holder gets brittle from heat and age and lets the magnets fall out of place.

Can't believe no one has developed a replacement holder that is designed to install from the outer side instead of the inner side of the sprocket. This has to be an extremely common repair on these engines. Even if pro mechanics prefer to be able to take the longer route to keep the time to repair up, shadetreers would jump on it.

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To each his own. The JB Weld or even silicone sealant will last longer that the plastic holder that holds the magnets. That's what the real problem is. The plastic of the holder gets brittle from heat and age and lets the magnets fall out of place.

Can't believe no one has developed a replacement holder that is designed to install from the outer side instead of the inner side of the sprocket. This has to be an extremely common repair on these engines. Even if pro mechanics prefer to be able to take the longer route to keep the time to repair up, shadetreers would jump on it.

This is true. I may end up going the JB weld route.

Yeah, you'd think someone would have the sensor made so the lip is on the outside and can simply be pushed in from where the sensor sits.

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Did my 88 in about 2002 and no problem, same for the white. GM pushes into the sprocket from the back then bolts the sprocket to the cam, can see the cam through the hole when cleaned out, why to install from the front you have to glue.

If over 100,000 miles, might as well do a timing chain but below the JBWeld method takes a 1/2 hour and an $11 "interrupter". Even If I did install properly, I'd add a coat of JB Weld just to keep in place.

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No. Easy screw in-out, just to the rear of the water pump (if my memory's correct).

The one in the pan is oil level sensor.

Hmmm ok. So I need the *pressure* sensor, not the level sensor? I have what I think is the level sensor new in box that was in a parts car. I guess I just need the pressure sensor then.

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Very common failure, I keep a spare on hand, read high, read low, high at idle low on road. Borg Warner S4151 for all "C" engines.

If there is a complaint of low oil pressure, first thing I do is change the sender. Once it wasn't.

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water pump doesnt have to come off. Just need to take a couple 1/2"s out of it. Rough start when cold could really be many things. Maybe a leaking injector, blown head gasket or as simple as just needing a tune-up. From what i was told cam sensor doesnt have much drivability issues. Also oil sensor has no issue on burning oil. The valve seals and piston rings are the only things that effect that.

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water pump doesnt have to come off. Just need to take a couple 1/2"s out of it. Rough start when cold could really be many things. Maybe a leaking injector, blown head gasket or as simple as just needing a tune-up. From what i was told cam sensor doesnt have much drivability issues. Also oil sensor has no issue on burning oil. The valve seals and piston rings are the only things that effect that.

Definitely has no drive ability issues. Drove home from Winston Salem as seamlessly as possible.

I'm thinking a bad oil level switch (on the oil pan) can cause it to burn oil. I know an unplugged one can. I replaced my harmonic balancer, and I had to remove that connector to get to a bolt. I forgot to plug it back, and it was burning oil like crazy.

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Tearing into the cam sensor problem right now. Oil pressure sensor is on order.

I've taken the water pump pulley off, and the sensor itself. I've found the magnet (what's left of it at least) on the sprocket.

I'm assuming I'm expected to just push what's left of the magnet back into the timing cover? Will this cause problems later?

It's pretty much flush with the sprocket right now. Now sure what to do.

Thanks,

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Alright, I'm hooked. An unplugged oil level switch/sensor can cause the engine to burn oil?

Had my '90 in for Intake Gasket replacement last week and now I have a fast cold idle and am definitely burning some oil. (Maybe I just didn't notice it before.) Could the mechanic have missed something? (Mileage is 152K.)

Northwestsun (still sunny!) :cool:

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Fast idle could be a vacuum leak caused by disturbing the intake and related hoses. And no the sensor only effects the gauge. A plugged pcv could cause you to burn oil by overpressurizing and blowing by rings or seals. Did he replace the pcv while he had the intake off? Btw they do make new rubber grommets for the pcv. I did a review about it awhile back

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Use a nail or sharp punch and attack the plastic of the holder. Looks like there's still a metal magnet left in there. Very tough stuff. Need to pulverize the plastic part until you can get it all out. I've used a right angle drill with various bits in this situation too.

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easy way to find out is go to harbor freight and pick up a $20 fuel pressure gauge. The generic adapter screws onto your fuel rail right up top. Install it and crank the car up til pressure stabalizes then turn it off. If fuel pressure drops you've got a leaking injector or pulsator. If pressure is consistant after shut off (which it will drop some but stabalize not continue dropping) then your fuel system isnt the problem. Make sure you arent losing coolant. Rough startup means something is getting in the combustion chamber when the car is off which leads to gas or coolant in the combustion chamber. Once it burns all that out it smooths out. I think you may have leaking intake gaskets. Pretty common as you know. And no you probably wont see white smoke as it'll be such a small amount it'll evaporate before it hits the end of the exhaust system. Just a heads up, that's what was wrong with mine when I bought it.

Edited by Recian (see edit history)
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Well it's not so much a rough start any more as it is a long start. It's cranks for a while before it catches. I'll check the fuel pressure.

I'm hoping I don't have an intake gasket leak. Though, I suppose that's not a huge deal to change, right? Not like a head gasket or anything.

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naw i can have the intake off in about 30 mins. MAKE SURE if you do change them you get some blue loctite and clean the bolts and re-apply loc-tite when you tighten it back down. But a long crank time sounds like fuel pressure drop. Id think it's time to do the fuelp pump and pulsator. Trust me you'll need a new pulsator or 2" of FUEL INJECTION (not standard) hose to eliminate it. It will leak with a new pump because it's rubber seals will stick to the pump and when removed after 25 years it'll no longer be rubber but plastic and hence no seal. I've got the BOSCH fuel pump I put in the reatta but I was going to put it in my subaru since it has some rust in the tank. But before going through that extreme endeavor i'd take the 4 1/2"s off and remove the fuel rail with the gauge installed and car off and see if you have a leaking injector first.

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Check your fuel pump relay. In an 80s it's on the firewall, in a 90s it's in the interior relay center.

When you turn the key this relay starts the fuel pump immediately until the oil pressure switch makes and takes over. If the relay isn't working, you have to crank until the oil pressure gets high enough to turn the pump on.

Is this the same car with the suspect oil pressure sensor?

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