94 Caddy starts missing after driving 20 miles

[midlf]

Change the fuel filter and check the removed one for rust. If the new filter does not cure the problem and rust was found in the old filter, then the pickup sock/screen may be loading up with rust and starving the engine for fuel.

 

[coffeeman]

I had a 1990 GM product, different engine. It would warm up and die after about 15 miles. No codes. Factory service manaual listed ignition pack, computer etc. I used an oscilloscope to track it down, It was the crank sensor. On the scope you could see a healthy signal of about 1.5V p-p deteriorate to below a volt then die. When I removed the sensor I could see a hairline crack.

This makes sense to me. As I think over my problems they all seemed to start when a front seal on the engine was changed. It was leaking motor oil. Sometime with an old piece of equipment you have to be gentle when connecting and disconnecting parts. I'd guess the crank sensor might be near that part of repair. Might even be a loose connection of some kind near there. Also, someone suggested it might be some kind of module either under the water pump or maybe under coil pack. I got a junk dealer who has the same engine in an old Buick who is going to give me the module to swap it out. One thing I'm gonna do is take a scanner with me when I run the car. If the engine lite comes on I'll plug the scanner in and maybe get a code.

Hope you had a nice turkey day.....Coffeeman

 

[coffeeman]

Change the fuel filter and check the removed one for rust. If the new filter does not cure the problem and rust was found in the old filter, then the pickup sock/screen may be loading up with rust and starving the engine for fuel.

Never thought of checking what might be in filter. That sock problem could fit. When engine is cold the car has set for a while. Also any dirt has a chance to settle down and fall to the bottom. After running for a while the dirt stirs up and jams the sock. Had this problem once on a van. Ran good for a while. Then run like crap. On the car were talking about now I thought about that. The tank was down near empty. So I filled the tank. I was looking to see if the thing might start running better. Didn't seem to change anything. In the van I mentioned, if the tank was full it ran fine. Around 1/2 tank it started its foul running after shaking the dirt in tank around.

Hope Thanksgiving treated you good.....Cheers Coffeeman

 

[czechsonofagun]

I had the same thing happening to me on my CJ7 - it was the coil.

 

[automech]

LT1's have dist cap/rotor on front of the eng. You must have seen it if you did the plug wires and water pump. When the pumps leak, they leak right into the dist cap. They also get a dose of oil if your front seal is leaking. This was a crappy design, if you ask me. They are expensive too. You can try to do a manual power balance when your miss starts occuring. That is old school, pulling plug wires off with insulated pliers one at a time to see which cylinder is causing the miss. No scope hookup for these caps that I know of. You should have a fat blue spark at the plug wire end when running.You should be able to hear the spark snap. Make sure you use insulated pliers or you'll get a nice jolt, or a few nice jolts. I do the caps when I do the wires on these so I know everything is good.

 

[coffeeman]

LT1's have dist cap/rotor on front of the eng. You must have seen it if you did the plug wires and water pump. When the pumps leak, they leak right into the dist cap. They also get a dose of oil if your front seal is leaking. This was a crappy design, if you ask me. They are expensive too. You can try to do a manual power balance when your miss starts occuring. That is old school, pulling plug wires off with insulated pliers one at a time to see which cylinder is causing the miss. No scope hookup for these caps that I know of. You should have a fat blue spark at the plug wire end when running.You should be able to hear the spark snap. Make sure you use insulated pliers or you'll get a nice jolt, or a few nice jolts. I do the caps when I do the wires on these so I know everything is good.

Thanks for the input. I didn't do the wires and plugs myself. The front seal was replaced for leaking oil. I had the water pump replaced since it was off, lots of miles on it and not real expensive. There was oil all over the place; especially leaked when at interstate driving speeds. I know the cap and rotor wasn't replaced. I don't know why, though. That seems like a good next step.

Drove 40 -50 miles today. Just short 10 -15 mile spurts. Ran good. It's in the 30s temperature today. Good winter car. Maybe I can sell it to a little old lady who will only drive to church on Sunday and short trips to the market.

Cheers

 

[coffeeman]

LT1's have dist cap/rotor on front of the eng. You must have seen it if you did the plug wires and water pump. When the pumps leak, they leak right into the dist cap. They also get a dose of oil if your front seal is leaking. This was a crappy design, if you ask me. They are expensive too. You can try to do a manual power balance when your miss starts occuring. That is old school, pulling plug wires off with insulated pliers one at a time to see which cylinder is causing the miss. No scope hookup for these caps that I know of. You should have a fat blue spark at the plug wire end when running.You should be able to hear the spark snap. Make sure you use insulated pliers or you'll get a nice jolt, or a few nice jolts. I do the caps when I do the wires on these so I know everything is good.

Hi all

Just a follow up on my car problem. I had been running the car for short trips. As time has gone by I have been traveling more miles in a day. I did put some injector cleaner in the tank. I guess that's just a little profit center for the parts stores as I wonder if it's just a waste of $$. For the last month I have had zero problems. I am thinking the distributor may have had some moisture in it and would screw the spark up when engine waqrmed up. I am also guessing that the moisture has gone. Your right automech, it is a crappy design. I guess since it's a Vet engine they may have designed engine to take up as little space as possible. However, how much space could a distributor take up? Whatever the reason, it's a crummy place to put it.

Tomorrow it's going to be 50 degrees here. Instead of taking my Jeep to work at 5 AM, I'm going to take the Caddy. When we had those wet snow mornings, I wasn't taking a chance on the Caddy running good.

TOMORROW IS THE BIG 5AM TEST DAY!

Cheers....Coffeeman

 

[dbdartman]

TOMORROW IS THE BIG 5AM TEST DAY!

Cheers....Coffeeman

Well...? Or are you still trying to get home?

 

[coffeeman]

Well...? Or are you still trying to get home?

Got home OK! I would have answered sooner but I haven't been on TBN for a while. Just to refresh; I had a problem with Caddy missing after about 20 miles driving. Then the miss went away. So I was going to take a 5 AM morning run to work in the no longer missing car. The Caddy has been running good since January and I don't know what caused to 20 mile miss or why it went away. Put about 4000 miles on it since started running good. Use Jeep more in winter.

I'm sure I'll be reporting about how the car went belly up before end of week. Every time I brag up anything it goes to the dogs. However, this car has 206,000 miles and deserves a pat on the hood.

Cheers....Coffeeman