Ignition problem when hot, '93 3.0l PU

[cwilliamrose]

I'll give the full history in hopes of getting some guidance or at least confirmation that I'm on the right track.

My wife reported the truck was running very poorly, had trouble getting to 25mph and didn't want to start. She had filled the tank the day before and I suspected contaminated fuel. I drove the truck to work to experience the problem and it ran perfectly going to work, and perfectly heading home. I stopped by Autozone and picked up a fuel filter which took a while because they were busy. I got back to the truck after about 25 minutes and it did not start well and ran rough at idle. I barely got home. It would ran rough, cough, try to backfire sometimes and threaten to quit.

I changed the fuel filter and examined the old one for signs of dirt and clogging. It was fine -- nothing but gasoline came out when I back flushed it and it was wide open. I took the truck to work again and it again ran fine when it was cold. It's only a ten minute trip and nothing unusual happened. It was apparent the problem was heat related and when it heat-soaked after shut down the problem got much worse. I checked the fuel pressure and the function of the pressure regulator and all seemed normal -- good pressure from the pump (75-80psi dead headed) and in the low 40's when the engine was running. Throttle changes resulted in small changes in pressure as you would expect as the manifold pressure changed. I felt I had ruled out fuel system problems at this point.

So I looked into the ignition system. It certainly could be an intermittent timing error causing the symptoms and this could be influenced by temperature. I did find the distributor cap was toast and there looked to be some tracking across the top which could indicate the electrons were bypassing the rotor. Hard to blame it for that -- the carbon contact as just about gone -- there was no direct contact between the cap and rotor. There were also cracks around the hole for the carbon contact. I installed a new cap and rotor but the symptoms were unchanged.

I tried to eliminate components by doing some testing. I came up with the idea of getting the engine up to temperature and when the symptoms occurred I could cool a component and see if there was a change. I started with the transistor ignition unit. It was running awful when I pulled it and stuck it in the freezer for 20 minutes. When I put it back in the symptoms were unchanged. Same with the coil -- I froze it for about 30 minutes but the problem remained the same. That leaves the position sensor in the distributor and the harnesses firewall forward (I'm thinking the heat issue points to something in the engine compartment). My test method breaks down here because the sensor is built into the distributor and the harnesses are not easily cooled either. I think it unlikely to be the wiring or connectors.

Is there some way to test the sensor other than replacing it with a known good unit? That means the whole distributor unless I'm wrong about the sensor being non-replaceable. Have I missed something I should be looking at? If I do need to bite the bullet and get a replacement distributor is there a good choice beyond OEM parts?

Thanks for reading this............Bill

[RT22]

Go to a parts house or computer store and get some canned air, when spraying it it gets damn cold, you can use that to cool parts while truck is running at temp. By spraying the parts while running if it is heat related the cooling should temporarily fix the problem, I have done this on pc's who had power supplies dropping at temp. They also sell a cold air spray but not as easy to find, call some parts stores save the gas driving around looking for it. But a can of compressed air will chill good when spraying it.

[cwilliamrose]

Thanks,

I read the codes from the ECU. The only one I'm getting is 21-IGNITION SIGNAL. That could mean a lot of things according to the book.

I couldn't find any freeze spray close to home. I considered using compressed air from my little pancake compressor at home but it's not nearly as cold. I have a few parts coming that should provide a solution. I hope so anyway. My wife needs to drive the truck to work and let the good car stay in the garage and out of the sun. I'll post results when I have something to report............Bill

[RT22]

Yeah post what fixes it, may help others later if they have the problem. I like when guys post what fixed a problem, gives us good info on troubleshooting.

[cwilliamrose]

I pulled the distributor and found that the bearings are toast. I suspect the bad bearings were the source of the fine red dust I saw inside the distributor. I also suspect the bad bearings caused a lot of heat which made the Crank Angle Sensor fail where it probably wouldn't have with normal engine heat. I have a new distributor on the way.

What I can't believe is that the truck ran at all. The roll pin that holds the gear on the shaft should have sheared with that much load on it. Amazing!.........Bill

[cwilliamrose]

Closer examination of the distributor revealed several things. The bearing failed due to being dry and probably seeing some moisture because of long periods when the truck was not being used. There were also indications of a lot of heat; The harness connector's body was discolored and crumbling, the gear had a coating of overheated oil on it that looked like it was sprayed with cosmoline. Because the shaft was difficult to rotate, the gear was worn, probably more than the truck's 140K miles would have normally shown.

The replacement distributor is a new part from "The Import Experts" on eBay. The part (part# NS33) is supposed to be a direct replacement for a 22100-88G00 Nissan distributor but it was setup for a different vehicle. The strain relief clamp directed the sensor wire away from it's mating connector on the truck. There was no tapped hole for the clamp where the original was installed. Todd at Import Experts gave his blessing to adding a tapped hole for the clamp without warranty issues. I noticed while setting the timing that the timing wanders a little (less than 1 degree) and this is likely the gear on the cam shaft which is probably worn prematurely due to the failed bearing. The truck runs great again -- it has its pep back after a long period of sluggish performance.

I also gaped the plugs while I was under the hood and I have new plugs on the way. The hot start problem has been eliminated according to my wife (she drives it to work every day). Too early to know if the mileage has improved but I'm hopeful for a bit of improvement.

Thanks for looking.......Bill

[RT22]

Congrats on the fix and thanks for posting the fix.

[longtooth]

What did the new distributor cost? Also was there a core charge for it?

[cwilliamrose]

It was $210 (w/free ground shipping), $234 w/2nd day air service. No core.........Bill

[longtooth]

Cool thanks for the information. I think i may take a gander at my distributor.