92 LeSabre Misfires/hesitates only when hot

[Salvage Child]

My 92 LeSabre 3.8 will only start misfiring/hesitating after getting hot (30+ miles) and then shutting off the engine for a short period of time. The first time, I replaced fuel filter, plugs and wires and drove it 180 miles without stopping and it never acted up). I've had it occur several times since then. And last night after getting the problem started, I replaced with an entirely different set of coils and the same problem...non-rhythmical misfires (more so at higher speeds 40+) every few seconds or so.

I just found the site for the service Engine Soon Diagnosis (http://www.geocities.com/dann8785/se...nginesoon.html) and will get the engine hot again and look at the code that has been displaying (but I was unaware of what it meant!).

I 've checked into the LeSabre forum but have not seen a close match.

[HotZ28]

Is your radiator full of collant? How hot is hot that you refer to? Could be low on collant or a bad CTS (Coolant temp sensor.)

[Salvage Child]

It's not overheating by temp gauge or coolant. It's always run well without using much coolant. By 'hot' I mean driven enough to get the engine hot. On the last few trips we've made that meant going about 30+ miles in 80+ degree temps.

[HotZ28]

Check your plugs again and see how each one is burning compared to the next one. I have seen new sparkplugs installed that have a broken ceramic insulator causing spark scatter. I have also seen new (non- Delco) brand wire sets with one or two bad wires. See if you can isolate the missfire to one cylinder and change that plug and wire with another cylinder to see if the problem moves with the change. Aftermarket carbon core (rf supression) do not work well on the DIS high voltage system from the getgo. Several years ago, I put in a new set of Autolite wires (carbon core rf) that were fine to start with but started missfiring after about 2K. I replaced them with spirl wound cooper core MSD wires and have not had a missfire since. Typical carbon core wires have anywher from 10K to 25K ohms per foot of wire as opposed to the spiral wound copper at 50 to 150 ohms per foot. Huge difference!!

[gbeeley]

Originally Posted by Salvage Child

I just found the site for the service Engine Soon Diagnosis (http://www.geocities.com/dann8785/se...nginesoon.html) and will get the engine hot again and look at the code that has been displaying (but I was unaware of what it meant!).

Yes, definitely get the code. You don't have to catch it right away - the code stays around until (I think) the engine has been stopped and started a certain number of times, even if the SES light is not on (SES light on = problem is occuring NOW, but codes are stored for a while).

- GB

[HotZ28]

How many miles do you have on the car? If you have over 100K and have a code 41 or 42 (ETS or cam sensor), you could need a new timing set. It could also be the crank sensor

[90gmcmoneypit]

Check your spark plugs again. Look for buildup on the electrode. Oil leaking into the piston from either the piston ring or valve seal will cause a buildup of a brownish ash on the spark plug, making spark impossible. If the buildup is on one side of the electrode, it's a common indication of bad valve seals. If the buildup surrounds the electrode entirely, it's indicative of piston ring failure. Also check the EGR valve for any debris.

[HotZ28]

A long story concerning a similar problem to yours.
Have you retrieved any codes yet?!


http://www.automotiveforums.com/vbul...or+replacement
Crank position sensor - '95 LeSabre Dies Without Warning

[Salvage Child]

An update! I think I've got it solved. The Code was 41 "Cam Sensor". I went and did some more research and was pretty sure that the Cam Sensor was the problem. I looked up where it was located, passenger side of engine below altenator. I took the bolts off the alternator and laid it out of the way, unbolted the coolant reservoir so I could find the 3 wire set that led to the cam sensor.

I've tested with a 60 mile trip up and back. No hesitations at all.

I'm going to try a 110 mile trip tomorrow.