Hello and thanks for any help you can give me! I have a 97 xk8 that will start and run great when the outside temp is above about 60 degrees. Below 60 when you turn the ignition to the on position a bunch if relays start clicky rapidly, the fuel pump cycles on and off rapidly and the throttle body will cycle. This all happens continually not just once. When you try to start the car it will crank over ok (no sign of cylinder wash) but will not start. If you keep cranking it over eventually it will start but instantly dies. After a while of this it will start and act like its running on 3 cylinders and die easily, trying to give it gas makes it sputter but it won't go over 2k rpm. After doing all of this and you are finally able to get the car up to maybe 70-80 degrees it's like a a switch flips and the car runs like nothing ever happened. If you let it cool back down all the way it will do the same thing. Aby help on this would be awesome!!

 

Welcome to the forum!

All you describe points to an electrical problem and more specifically to low voltage. The electronics will not function with voltage around the 10v level which is easily reached while cranking with a weak battery and/or corroded/loose connections. All that is subject to change with temperature.

I would start with a battery test at a local auto parts store. Then on to verifying that all power connections from the battery forward to the engine compartment are clean and tight. And that includes ground connections.

Please let us know what you find.

 

Bought a brand new battery with the same results. I will go over all the power connections are there any hidden ones?

 

There are two giant master fuses behind the spare in the trunk. Make sure the connections to these are clean and tight.

Also locate the primary power cable bolted to each fuse box and make sure it's connections are clean and tight. As you go to each fusebox, push in each relay and make sure it is firmly seated.

Also check that the ground connections in the trunk are clean and tight.

For safety, have the battery negative terminal disconnected when you go around and tighten each power connection.

 

Ok I checked all the fuse box power connections all looks good. The large fuses in the trunk are ok. I'm going to spend the rest of the day doing voltage drop test and ohm checking all power wires. I will try to wiggle power wires as well while it's running maybe there's a small break somewhere. I've been a Honda master tech for 7 years and this jag is eating my lunch!!!!

 

Could it be your starter motor not energising properly, low voltage, high resistance, loose connection, something on those lines???
Hope you work it out soon.
ArtyH

 

I don't think it would be the starter since it does the whole clicking thing before you even start it. All you have to do is turn the key to the on position and it seems like the car goes haywire.

 

If you do not come up with anything obvious in the wiring, I suggest popping open the ECU and checking for leaking electrolytic capacitors.

 

So I looked over all the connections, power and ground. I found that all look in very good shape and very tight. I inspected inside the PCM all looks good here. I tried to take the PCM out and turn on the key-found no relay clicks all seemed quiet. I was working in the dark and had a halogen light sitting in the engine bay on the right side near the PCM after checking the PCM I reinstalled it and everything started clicking again however after 30 or so seconds it all stopped at once(I wasn't touching anything) and the car would start. I Believe the halogen light warmed something up enough to stop the clicking madness. So tonight I turned the key on to verify it was cold enough and yes clicking starts I then turned off the key and took the PCM out and warmed it to about 80 degrees installed it and found no change so the PCM I believe is ruled out at least for now. Maybe I should try to take out every fuse box one at a time and warm it up to check them? Maybe we can eliminate a few things as well since it didn't click with the PCM out.

 

Have you tried reseating the relays in the right front electrical enclosure? They are all the same, swap them around just to eliminate them as a source of you problem. Please make sure that you are disconnecting the battery during all the electrical plugging and unplugging.

 

Sorry I haven't posted in a bit I was rear ended in my pilot so I've been trying to handle that. So the two relays that are clicking are located in the PCM area and there are three in a row. I have tried to warm the area problem is still there. Does anyone have access to a wire diagram for this area?

 

Your wiring diagram

Link http://www.jagrepair.com/images/Auto.../jagxk1997.pdf

 

I recommend that you check your fuel pressure. Also just a hunch but turn off you’re A/C and see if the clicking stops

 

Thank you for the diagrams!! So the two relays that are cycling is the throttle motor and ignition coil relays. So it's either the PCM cycling maybe a bad ground or PCM itself. Or it could be the power side cycling power from the engine management fuse/relay box. Tomorrow I will remove the relay and check which side is cycling.

 

It could also be a thermally intermittent relay...rare but possible. Swapping relays should identify if this is the problem.

 

I tried swapping relays no difference. I monitored the voltage on pin two of the relays which is ground from the ecu. I found that's where the voltage is dropping out but it happens so fast it almost looks like a duty cycle. I removed the ecu again and inspected it. I did find (and I apologize as I have only a little experience with circuit boards)that one of the either black flat voltage regulator or a transistor of some kind has leaked some kind of corrosive fluid out. The only number on it is k943 it's flat and black and has 3 pins I measured resistance between all the pins and compared it to another on the board and it was very close to the same. No sure if I should send the ecu in or if the transistor is even causing a problem.

 

The only things that can leak are the electroytic capacitors (round cans). but the fluid can migrate. Post a picture for confirmation. This may or may not be your problem, but it certainly has the potential to be and will only get worse and eventually do irreparable damage to the ECU. It needs to be rebuit.

 

Here are some pics but it's kind if hard to see the only capacitor close is the only large one on the board.

 

If you noticed you will find a fan directly below the ECU is it working. With as many ECU having problems could it be caused by excessive heat in that area? Steve, what are your thoughts on that?

 

The capacitor leakage is usually brownish. I do not see that issue in the photo. The whitish residue appears to be possibly flux residue. It looks more like evidence that the ECU was repaired once before. I do also see a bit of light green corrosion near the leads of that transistor. That is a bit worrisome, and looks like it also could have alternatively been moisture ingress. If it got wet in there damage could have been done.

Under the hood is a tough environment for electronics and heat is definitely a factor. Solid tantalum capacitors would have been a better design choice than the cheaper electrolytic capacitors for an ECU that lives under the hood.