mac2881994

I recently completed an engine swap in my daughter's 92 XJ. Initial start up worked as advertised and was running fine during the first 4 miles of the test drive. Just before I got to the gas station to test the new fuel tank sending unit the engine started missing badly. During troubleshooting I have found that the distributor connector is getting 5 volts on one outside plug and almost 9 volts on the other outside plug with the key ON and the engine OFF. I was under the impression that only one outside pin would have a 5 volt signal and that the other would show voltage only when the camshaft turned and tripped the signal from the sensor. Am I correct in this assumption? These voltage readings were taken with the distributor unplugged and on the wiring harness side of the connector and using the center pin as the ground.

Dave51

Using the 1993 manual:




Exactly which pins have what?

Dave51

Again from 1993:




So I think your values are OK, but I'd be looking for the 5 volt pulses. IDK why you're seeing 9 volts. That could also just be your voltmeter. Maybe ECU, but WAY too early to worry about that, the difference is probably insignificant. How's all the fuel stuff?

mac2881994

I will go to the garage after breakfast and reshoot the wires to see exactly which wire has what readings. I may have to get an analog multimeter all that I have now is a cheap Harbor Freight digital one.

Dave51

I think the HFT is fine. According to the schematic K7 is 8V so at this point I don't think that's the problem. Do the pulse test but again this sounds more like fuel.

Dave51

Or dare I say it? Crank position sensor. Thermal error.

mac2881994

Signal output wire works as advertised above. Fluctuates from 0-5 volts when distributor turns while cranking engine. Engine will start but runs tough at idle and misses badly when any throttle is applied, even in park. The following has been replaced during the engine swap: fuel pressure regulator, fuel sending unit and pump, fuel filter, all injectors, crank pos sensor, MAP sensor, spark plugs, O2 sensor and catalytic converter. Cap, rotor and wires were replaced within the last year prior to old engine having the rod start knocking. Fuel pressure was checked at the rail and is holding 39 PSI. It seems to me that either the injectors are not firing correctly or the timing advance is not working correctly.

mac2881994

I originally put a set of cheap Chinese 4 hole injectors in but changed them out for a set of remanned Bosch metal body 4 hole injectors.

Dave51

Autozone near you? Borrow their noid set to check the injectors. Clean the throttle body. Are you SURE the wires are set to correct firing order as well as placement in the cap? Pull spark plugs off one at a time to try to find the guilty party. Is the coil good?

By any chance to you put in an OBDII test connector during the swap?

Hey, had to ask, ya never know.

Speaking of which, what year engine did you put in?

Dave51

Any vacuum or intake leaks?

If worse comes to shove, I got an oscilloscope to check that (although if you're going in that direction, you would be looking at the sync between the CPS and the CkPS).

That said, that you went fine for a few minutes and then kersnap kinda says its something that you handled.

And it's something simple!!!

mac2881994

I will swing by Autozone in the morning to borrow their noid kit. Throttle body and IAC valve were cleaned. I have found no vacuum leaks. The engine was out of a 98 YJ. I had to drill and tap the back of the head for the coolant temp sensor while it was on the engine stand. I am sure it us something stupid simple that I have overlooked and will cause me to kick myself once it is figured out.

Dave51

Are all the sensors from the 92 or the 98?

ADD: And the flexplate?

mac2881994

All sensors and flexplate are for a 92.

third coast

I am just guessing here at a couple of long shot but easy to check items that are worth a quick look:

* Is the ground strap from the back drivers side of the head to firewall installed (I believe that should be at head bolt 14 with a double nut) and is there almost zero resistance from the head bolt to the battery negative side?
* Did you use anti-seize on spark plugs? If you did check for fowling on the electrode and clean all anti-seize off the threads. Most anti-seize acts as an insulator

Dave51

Did you try to isolate the problem cylinder?

What's the history of the replacement engine? If it's been lying around for 10 years maybe a valve is stuck. Check compression.

If an injector fails the noid test probably means a driver in the ECU. But again, why would that happen now? Seems like the issue has to be something in the replacement engine or in the hookup.

In For A Penny, In For A Pound Department:

Get an entry level oscilloscope. Then you can more completely analyze injector performance, individual ignition performance behavior and cam/crank sync (seen here):