Saltysnoopy wrote:
I’m not hostile to new ideas, but give me a break. Don’t you think I’ve checked the obvious as well as the no so obvious.
This discussion board is filled with many experienced mechanics. One common trait is that much of the vast experience comes from years of learning from mistakes. It’s taught us to be humble about our ability to overlook the obvious or to make incorrect assumptions. We’ve all been there.
WRONG! One static reading doesn’t rule out the CTS. What if the resistance reading changes as it heats up? Plus did you bother to check the harness from the sensor to ECM?? The ECM would see a open circuit as a temp reading of -40 degrees. But of course you checked that already.
This vehicle has fuel injection, it REQUIRES a CTS. All of my information shows a CTS, it is shown in the wiring diagrams. The CTS has 2 wires, one tan and one brown with a white tracer. Try considering the fact that your information is incorrect. Consider the possiblity that the information you have is for a vehicle without fuel injection.
Again you show how close minded you are to suggestions. You won’t accept the fact that your diagnostics could be incorrect. If you aren’t willing to accept the fact that you missed something then you should consider moving on because no one here can help you.
Your Jeep had a recall to replace the catalytic converter in 1990. It may not have been done. If it was done, a decal was supposed to be stuck near the Vehicle Emissions Control Information Label on the bulkhead (firewall). To check on the Recall, call a Jeep (Chrysler) Zone Service Office, or a dealer, about Recall Notification No. 2767 of January 1990. Have your VIN handy.
One Haynes Repair Manual says to check the M/C (Mixture Control) solenoid, in the throttle body. The M/C solenoid could be stuck.
For details of the assembly, parts, etc of the throttle body, get the Haynes manual #482 Fuel Injection Manual. Copy righted1986.
How does the engine computer decide how much fuel to send into the engine? It uses built-in tables and information from sensors, particularly the MAP, IAT, and TPS, at idle (open loop operation). Backprobe the sensors for VOLTAGE, particularly, at idle. The voltage values should be within specs, without voltage spikes.
The engine computer boosts fuel flow into the engine from signals from the power steering switch, A/C switch, electrical load sensing module, maybe others. You can see these circuits at the Auto Zone Web site. Click on: Chassis Electrical. Then, click on Wiring Diagrams. Click on Fig. 20. It may be a good idea to disconnect these switch circuits (p/s, A/C, load sensing) and check the results with an engine run.
Invest $6 dollars in a set of brand new, cheap, spark plugs. Fouled spark plugs can’t be adequately cleaned, often.
If all the sensors are good (MAP, IAT, O2, Coolant, etc), and the injector is good, and the fuel pressure regulator is good, then have you considered picking up another computer from a salvage yard and tried it?
If all the sensors are working properly, then the next thing is either a faulty connection with the computer, or the computer itself.
BC.
last time…take time to think about it, and not blow up at me for asking!
before it died:
what did you (or someone) do to it? change plugs? wires? distributor? rotor? were you under the hood working on something unrelated, that has impacted the rest of the situation?
after it died:
have you checked ALL 4 spark plugs for fouling? are they all fouled equally?
have you checked the distributor to make sure it didn’t get off the index? it IS possible for a cracked distributor to twist enough to get out of alignment, still run (sort of) and not be readily noticable.
If this dinosaur has an O2 sensor it could be dumping to much fuel. I think you should take a blackpowder Kentucky rifle of the same vintage and shoot it in the head.
EXCELLENT thinking about the possibility of a clogged cat. converter. Those older-style cat. converters were only good for 50-100,000 miles. Is it the original converter? If it is, just change it out. I am experienced in this area. Symptoms of a clogged cat. converter: Starts, but doesn’t run long. Sooty spark plugs. Smell of raw gas. Check your cat. converter out. All engines need to ‘breath’. If it’s clogged, wrap it in thick plastic then duct tape the plastic. Take to local parts store. They might just toss it in their dumpster. Better their dumpster than yours. Buy replacement. Have the parts store dispose of the old one. Don’t forget necessary hangers and clamps. Some have bolted flanges, too. They’re a b**** (female dog) to get loose so use lots of penetrating oil. If that doesn’t work, get your cutting torch out and carefully cut the nuts off. You should then be able to heat the bolts enough to pound them out of the flange(s). Of course, buy new nuts and bolts. Hangers, especially the ones that hang on springs, should be replaced. “While you’re there”, check all of the rest of the hangers for the whole exhaust system, especially the hard rubber hangers. A few extra bucks spent on these items now will save you $$$ in the long run. Be careful handling that cat. converter. Wear goggles/glasses, a dusk mask (minimum) and plug your ears with small cotton balls with a daub of petroleum jelly on each cotton ball. Keep that crap off of you and out of your ears and lungs. Don’t pound the old cat. converter on the ground. Handle it like it’s made of thin glass.
Black soot will clog cat converters, but they won’t cause the engine to run rich. The “clog” is actually the soot coating the precious metals inside the converter that are the catalyst that causes the notrogen and oxygen atoms to seperate. It isn;t really a “clog”, but a “fouling” of the converter.
That same soot will also quickly destroy oxygen sensors. They too need a clean, unclogged surface to do their things accurately. And, ironically, a fouled oxygen sensor can cause improper fuel metering.
– This 1986 Jeep Cherokee 2.5L, 4 cylinder, VIN H TBI engine DOES have a cts (coolant temperature sensor), according to www.autodata.com at page: Vehicle Level > Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Locations < . It’s a drawing, so, parts aren’t easy to identify unless you are, also, looking at the actual engine.
– Alldata.com, also, has the wiring diagrams showing the cts. The ECU (Electronic Control Unit, aka the “engine computer”) terminal 32 is power (5 volts) for the cts and air temperature sensor (ats), both. Check (backprone) the terminal 15 of the ECU. You need to check here to ensure that you are checking the complete circuit. The voltage will be the voltage drop across the cts. Check the resistance of the whole cts circuit by disconnecting the electrical plug from the ECU, and disconnect the ats. Take an ohms reading, of the circuit, across wires 15 and 32 (touch red voltmeter probe to one wire end, and black probe to the other wire end). The ohms should convert to the coolant temperature.
– This forum works best with RSVP.
I think the O.P. bailed.
If he had been open minded, retested some components and related wiring circuits, he might have found the problem but he insisted everything was OK. As you mentioned you have to have a complete circuit for the CTS system to work. I mentioned that if the circuit was open the ECM would see this as -40 degrees thus it would have a very rich air/fuel mixture.
I found the same information on my ALLDATA. A fuel injection system has to have a CTS, the OP believed the informaion he had which said there wasn’t one. You can’t always believe what you read, even ALLDATA has mistakes.
check vaccuum
One thing that would help to test that I didn’t read here is the duty cycles
of the commands to the injectors. If any of the injector pulse signals is
abnormally long it would cause the injector to run rich and the engine to
flood, causing the symptoms you describe.
If you can’t obtain an oscilloscope or a multi-meter with pulse duty cycle
capability (made by Fluke, for example), you may be able to use a dwell
angle meter, a relic of the breaker point ignition era. Years ago, Radio
Shack made an engine analyzer with this feature.
To convert indicated dwell angle to duty cycle percentage, divide by sixty
degrees and then multiply by one hundred.
If the duty cycle is 100%, there is a problem with the [computer] module
that controls the fuel injectors.
This information comes from an old General Motors repair manual. It’s
relevant because Jeeps of the late 1980s had General Motors steering
columns, and presumably, other General Motors parts, since AMC, their maker,
was in its death throes and had to outsource for many of its products’
systems.