Rough idle, low oil pressure, bucking from a stop, bogging down and dying...

Phil04

Registered User
Ok, after reading through three pages of search results, I am left with lots of possible reasons for my problems, but I havent found anyone that experiences all of my problems, nor have I found any definitive answers on what the actual cause is.
Ok, my car:
92 5spd with 116k mi on it
no smoke, not overheating, no coolant boiling in overflow...
Put Royal Purple Synthetic in about 2k mi ago, but don't remember what grade... whatever it said in the manual... I will check...
3.27 Ford racing gears with perfect backlash and pinion depth and royal purple gear oil/additive
New MAP, TPS, MAFS, hmmm...
Have not had the opportunity to check plugs/wires
Ok, problems: Starting the car is no problem, but keeping it running at idle is. At idle the RPM's will fluctuate from 900, down to a bogging 400, back up to 600, down, up... until it eventually goes low and dies if I don't rev it. Oil pressure gauge tends to drop with it... going to no pressure and then back up and down and up ... The car always idles rough, the whole car shakes slightly. Once the car warms up, whenever I start from a dead stop I get a really really bad bucking (about 5 good jerks per second) until the clutch is completely released, then all is good. My oil pressure gauge also drops to nothing while cruising at highway speeds (70ish). This causes my check gauge light to come on. I am about to replace the IAC since that is a heavily mentioned possibility. I will run down in a few and see what is happening with the vacuum at idle also. Oh, and my mileage is also very bad. I don't think it is head gaskets, but who knows. I am always worried that driving the car is leading to a very very big problem... but I don't have any choice, its is my only transportation. The oil pressure gauge, though I know they are proned to fail, does scare me since it seems to change with my engine rpm and idle conditions.
Any input would be greatly appreciated. I know this topic has been covered many times, but I figure why not try once again. Worst that happens is I get ignored right? lol. Thanks guys. Phil
Oh, and I am super tired right now so sorry if I left out important information.
 
i hate to break your heart but there are no definite answers to this one cuz it could be one of a million things the car has so many gremlins if we were all smart wed junk these things and do something different. but like any bad relationship when its bad its impossible but when its good ha ha i think you know where that one goes
 
yeah, I have definitely figured out that this car is not the easiest to trouble shoot. I am just hoping that one of these days someone who had the same exact symptoms actually figured out the prob on their car and will come across my post and let me in on the secret. Until then, my quest continues...lol
 
i had similar problems well as far as the oil pressure drop concerns...but like what the other guy said, it could be so many things...well mine was just some low weight cheap azz walmart brand oil...guess that couldn't be ur problem as royal purple isn't near the botton of no good oils!
GOODLUCK!
 
Have you tried checking for codes? Might be a bad vacuum leak or bad plug/wire. As for the oil pressure trouble, I would get a mechanical gauge and check it manually. A Koer wouldint be a bad idea.
 
Got the $30 code puller, have yet to see any codes... I will probably get around to a gauge here shortly... any suggestions on an easy way to get a mechanical oil pressure gauge onto this car? Location, gauge model, etc?
 
IF you want to keep that car without blowing it up, THEN STOP DRIVING IT!!!!!!!

Loosing your oil pressure like that is NOT a good sign and it is there for a reason. It could be a simple thing like the sensor itself dying, OR you could have a serious problem causing that pressure drop.

If your standing in front of your car and look down to the drivers side of the front of the motor between the alternator, power steering pump and water pump, there's a gap. In there you should see a wire going to a sensor..... thats the oil pressure sending unit. That sensor is just a on/off switch and does not show actual oil pressure, but you could use that to set up a mechanical gauge.

Now you've mention that you've added a few things like MAFs etc..... is this all stock stuff for your car, or upgrades? If its upgrades, part of your rough performance etc could be that you need a tune. You just can't throw performance parts at the car and expect it to run good without a tune. If you can't afford to put a chip in, then I'd suggest going back to stock MAF etc and see if the car can run good that way.

Of course it can be a bad vacuum leak as well. Start off by resealing the IC tubes first cause their the most popular for leaking.

And finally, if you used the weight of oil specified in the manual, its too light..... 5W30 was good for the car when it was new, but you've got a few miles so run a heavier weight. Some say go all the way to 15W40 diesel oil, but I prefer using 10W40 dyno oil for the summer (I don't run synthetic cause I change my oil every 3 months, and not by miles) and my oil pressure is good even when its hot out.

Anyways, good luck

Frit
 
Thanks for the reply. I am pretty sure I am not losing oil pressure, as this would have already been detrimental, and the engine temp should be super high due to the friction I would imagine? I have noticed a corrolation between the oil pressure gauge and rpm's, higher the rpm, higher the pressure... so this is making me think electrical issue somewhere. As to vacuum... at idol I am between 18 and 20 ... I am going to try to test my alternator and also for voltage drop in various places. All the parts I mentioned were stock btw. Oh, I have yet to change the IAC, so I need to check that as well. I went to it and unplugged it and my engine just shut off and the car wouldn't start with if unplugged...is that normal? Usually when you unplug a sensor the system just goes into limp mode, but doesn't completely die. Hmmm... this is gonna be fun...
 
OK, went out and bought a oil pressure gauge and a voltage gauge. I really hope I don't ACTUALLY have low to no oil pressure... it doesn't seem like that would be causing all of my problems... As far as hooking up the oil pressure gauge, I read above where to tap into, now do I have to drain the oil before I do this or will it not flow out much since the car and subsequently pump will be off?
 
Phil04 said:
OK, went out and bought a oil pressure gauge and a voltage gauge. I really hope I don't ACTUALLY have low to no oil pressure... it doesn't seem like that would be causing all of my problems... As far as hooking up the oil pressure gauge, I read above where to tap into, now do I have to drain the oil before I do this or will it not flow out much since the car and subsequently pump will be off?

If your using the stock sensor location for the oil pressure then no, you don't need to drain the oil. I did the upgrade to mine so the stock oil pressure gauge actually runs like a pressure gauge and I didn't drain the oil out when I did it.

Good luck :)

Frit
 
Ok, well come to find out the tube that runs from the crank case to the air inlet tube was disconnected... so after reconnecting that idle substantially improved, still not perfect, but much better. What I need to know at this point is what does idle feel like under "properly working" conditions. Does the car slightly jossel at all? RPM's range from around 900-600? I will maintain 900, which is very smooth, but then goes to 600, and gets the car moving around. My power stearing is making a lot of noise at low speeds, I checked and noticed it was low, so I filled it with fluid, but still making noise. Also, the stupid oil pressure gauge continues to be unable to sit still. Goes from mid norm, to low norm, to below norm, to pegged left, and everywhere in between. I am pretty sure it is just a bad sender, since I haven't noticed any driveability problems. I will stick a mechanical gauge on in a few days just to be sure.
 
Real dirty oil (black and chunky) can be a sign of bad oil pressure. I would do the gauge thing sooner than later. Your power steering trouble is normal. Thiers a trick on the forums that lets you test your IAC, dont do it, its a waste of time, if the iac is the original, just replace it. I would also check for codes, takes 2 minutes. get a short wire, ground out the self test lead, turn key to on, but dont start. count the flashes of the cel, then write it down somewhere.



http://www.corral.net/tech/maintenance/eecivtest.html
 
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