would you buy a '99 4.0 4x4 140k?

[Matthew Currie]

The 99 Factory Service Manual calls the thing in the distributor the Camshaft Position Sensor. It does not give a testing procedure for it as far as I find with a cursory read, but the 95 manual does, and I think the sensors are the same. For the 95, you need an analog voltmeter. Using a paper clip to back-probe the connector (connector still connected), you must connect the voltmeter positive to the sensor output wire. That should be pin # 1 on the connector. Then connect the meter negative to ground. Set the meter to 15 volt scale. REmove the distributor cap. There follows in the manual a detailed procedure for tracking down a lack of signal, but the basic test simply consists of cranking the engine and watching the voltmeter. It should cycle between about 5 and zero volts. If it does not, then either the sensor is bad or the signal getting to and from it is bad, and further testing is called for. Of course, first you must verify that your back probing has worked and that you're actually getting the voltmeter at the circuit. Basically, if you get no joy from this test, you must trace for voltage reaching the supply (#3) terminal from the PCM, the ground at the distributor, and so forth. While the sensors appear to be the same between 95 and 99, the PCM terminals certainly are not, so if you need further tracing and troubleshooting, post back and I'll try to feel my way through the terrible and badly organized 99 wiring diagrams to find you some pinouts.

I suggest that if you have noticed significant damage to the harness, you clean it up and test very carefully to make sure the wires are continuous, and not shorting, and then try again before doing any further work. It could be that simple, and wouldn't it be a grand and glorious feeling if it is!

 

[heyhar]

If adjusting the dist. works, great. But if it doesn't, try the TPS. Your problems sound exactly like what I went through with my '96. Like I said earlier, try to get an assortment of JY pieces. I could have had eight for what I paid for the new one I bought, which gave me the most trouble of all.

 

[Mediaslave]

Wow, thanks!

I cleaned-up and repaired the wiring harness connections exposed wires with liquid electrical tape. Got to the harness connected to the distributer and it.was real bad. All 3 wires exposed and twisted across each other. Had to be shorting out & i'm guessing that would pretty much destroy the sensor? Went ahead and ordered an AC-Delco replacement cam sensor for $40 online. Still going to test this one though. I can send it back if I don't need it. Also going to do the indexing in the morning along with TPS test and compression test. Want to clean the IAC and throttle body while I'm at it. It's all very dirty. Long day tomorrow.

 

[Mediaslave]

Matthew,

Thank you very much you have saved me a lot of wasted time. Your information has helped me start to really understand what i'm getting into. I do not have access to a FSM at this time only a Haynes. I'm trying to learn very quickly "good at that".

I thank.all of you!!! I have no doubt that with all your help I will be able to figure this out soon. Time to get the day started.

 

[Mediaslave]

Well guys I think I finally figured her out.

This weekend I tested the TPS and it is fine. Smooth transition from .28v-4.9v.

Tested all my wires... Good.

Went through the process of indexing the rotor/distributor... it's right on where it's supposed to be.

Changed out the CPS camshaft position sensor... no change.

Re-tested the crankshaft position sensor... Bingo! tested faulty this time. It is working intermittently therefore sometimes testing O.K. and sometimes Bad. Replacing tomorrow.

Also found a crack in the exhaust manifold so possibly a faulty up-stream o2 as well. Unplugged it and she ran a lot better. I will replace that with a new header.

I'll let you know tomorrow when I put in the new crankshaft sensor.

 

[Mediaslave]

I can officially say this thread is done. Got her fixed. It turns out I had to replace all three sensors... TPS, CKP & CMP. Also replaced the wiring harness connectors to these sensors from a Junk yard. She is no longer misfiring and runs a 110% better. Thank you everyone for your help... I probably would not have been able to rescue her without your help. Now that she's running well it's time to clean her up. Hope this thread hopes others. On to the next project.

I owe a few of you a beer or two.

Cheers!

 

[x99j]

so what was the main cause? cps, bad wiring? i read were the cps (crank) had low ohms. mike

 

[gradon]

Way to buy a fix-er-upper and fix er!

 

[Matthew Currie]

so what was the main cause? cps, bad wiring? i read were the cps (crank) had low ohms. mike

Considering the multiple sensor failures, I wonder if the damaged wiring harness shorted something out and cooked several sensors at once. IN any case, it looks as if mediaslave has ended up with a nice bargain.

 

[Mediaslave]

The main cause had to be the wiring issues. This had a domino effect on the sensors. Apparently these three sensors work together to control air, fuel & timing.

What was so frustrating was the "intermittent" failure. The harnesses would test ok in the garage, but once I was out driving they would fail. I'm Ok with the fact that all the sensors are new now even though I may have gotten away with one or two of the old one's, once the wiring was fixed. At least she's running properly.

Thanks guys... Ended up with a good deal afterall!