My winter car, a '93 DX has been giving me some trouble as of late. I've already done a search on this and didn't come across anything really enlightening to my particular situation, so if anyone could help me out it would be greatly appreciated.

Here goes:

-Sometimes when I sit at a stoplight my idle fluctuates from about 750 RPM to 1750 RPM. It stays at each RPM for about 5 seconds or so. This has only happened when the engine is warm. I don't hear any fans coming on or anything like that, and the A/C is not on.

-Occasionaly my check engine light comes on. It started happening very rarely about a month ago and would only stay on for less than a second. Now it happens every other time a drive the car and stays on up to 30 seconds.

-Shortly after my check engine light goes out, the car may begin to bog severely. It does not stall, but suddenly loses most of its power. If I press on the gas more, it makes it worse. One time this happened at a light, and the car stalled as I tried to get it moving. Fortuneately it started right back up again and made it all the way home with no sign of the problem.

-These problems only happen intermittently, usually when I've been driving the car for at least 20 minutes or so. It comes and goes on its own. I get no other indications of anything else amiss; no other warning lights, nothing out of the ordinary on the guages. It also doesn't seem to be related to gas, I've done fillup with brand name gas and the problem continued to happen.

Anyway, I'm pretty much stumped so far on this.

 

I see that you tried filling it up with some good gas, but have you tried putting a bottle of Iso-Heat in the tank as well?

That in particular reminded me of when my fuel lines froze last winter. The engine suddenly lost almost all power and hitting the throttle just made it die. I had to put the car in a heated garage for a couple hours to let it thaw out and then put a bottle of Iso-Heat in the tank and it was fine after that.

No guarantees that that'll fix the problem, but you might wanna try it anyway before you venture into something more expensive.

 

When was the last time you did a tune-up? Spark plugs, wires, cap, rotor, etc.

 

I threw in a bottle of HEET the other day. The check engine light came on again that day for almost a minute, but I didn't get any stumbling or anything like that.

Yesterday I had some time to work on it, so I put the computer in diagnostic mode and it gave me a code of 9 quick flashes, which my manual says is a problem witht the coolant temperature sensor. I used a multimeter to check the sensor and got 5.00v reference voltage coming down the harness to the sensor and 450ohms across the two terminals of the sensor after warming the car up. My manual says 5.00v is right on target, but the sensor should be between 200 and 400 ohms at normal operating temperature. I'm not sure a 50ohm discrepancy is acceptable or not. Either way, my fiddling with sensor must done something, because I drove the car over a hundred miles last night without a hiccup.

As for a tuneup, I changed the oil and filter on Friday. The spark plugs are only a few months old, but I took a look at them and they seemed rather dark, so maybe the sensor was causing the computer to run things too rich. The distributor and wires are a little embarassing; I took them off my parts car because they looked newer than the ones I had. My car has 229k miles on it and I just need it to last until spring time when I can bring my Miata back out.

Anyway, I'm going to install the sensor from my parts car if I run into any more problems. Maybe the problem was just a loose connection or something. I want to thank everyone who posted with advice. I'll keep you posted if anything else comes up.

 

omfg.. i was replacing my collant temp sensor also and that causes the check engine light to go on.

It's a bitch to take off.. first take off the air intake assembly. Be careful to not brake the breather hose assembly.


CAREFULLY Pull off the boot off the sensor, making sure u dont break it. Take your deep socket and carefully take the sensor off..

Put in the new sensor, and before you plug it in, scrape the inside of the plug to make good contact.


Put the intake back on

Start her up.. should run like new .

 

You wouldn't happen to know what size deepwell socket I'm going to need, would you?