Hey guys, this is my first post on this fourm so iI apoligize if i am posting in the wrong thread etc. if so please let me know, thanks.

As far as my knowledge on working on vehicles i am learning to the best of my ability via fourms and youtube videos. Besides doing oil changes and brakes and tune ups (plugs, filters, dropping a few gas tanks) i am not the most experienced or knowlegeable. I have done a succesful engine swap on a 99 corolla before so im not completeley clueless but took me a good 2 weeks (pausing and playing a youtube video every part was removed/attached) so i am not too experienced but am trying my best to learn more.


2000 XJ with a swapped 98 head and block 128K miles and body has 175K.

Started throwing a P0300 (+p0302, 03, 04, 05) code every 100 miles or so, money light would blink, then shut off after about 5 miles and wouldnt come back for another 100 miles. Naturally replaced spark plugs, and also replaced coilpack. Same problem.

As of recently it started misfiring at 3k RPMs every time. Wont let me go past 3000. Tach also fluctuates or bounces around 150 RPM up and down. but no code being thrown at the moment.

Replaced TPS, IAC valve, fuel filter, air filter, cleaned throttle body, replaced speed sensor. I also tested my fuel pressure and it read 49 PSI.


Any ideas on what else it could be would be very greatly appreciated. I am learning alot about my jeep trying to figure this out, but at the same time its never fun shooting the parts cannon at it.

Thanks again,
Branden

 

not familiar with the p0300 code off the top of my head but swapping to a 98 head are you running the coils bolted onto the head or a distributor? I had a similar issue with mine it's a 2000, swapping from the factory head bolts to an arp set, the grounding strap on the driver rear of the head did not have the correct continuity for my coils I had to add a grounding cable from the head to the block to get the issue to go away, not sure if that one will help you but just a thought

 

Here is a video that works through the same problem:


Here is another:


The first had real misfire symptoms and was related to a bad coil pack, but the misfires were pretty isolated to a single cylinder. The second was logging misfires across all of the cylinders, with flashing check engine light, but ended up being a crankshaft position sensor. In this case the sensor was thinking there was misfires due to probably slight variations in the signal, but it didn't appear that there were any actual misfires going on.

If you have actual misfire symptoms (chugging, stalling, fish-bites, etc) I would probably go more towards an actual ignition problem like video 1.

 

 

 

If the CPS signal is missing, or bad enough that the computer can't make sense of it, or can not be synchronized with the cam sensor signal, then the vehicle won't start.

In the case in the video, even when scoped, the signal and timing of the CPS signal looked good. However, with waveforms, sometimes the overall pattern can be right, but that doesn't mean that every few hundred cycles that it is not experiencing some type of disturbance. He was never able to catch any problem in the signal, and he was apprehensive to blame it on the CPS, but he tested everything else, and then swapped out a no-name cps with a OEM one, and it solved the problem. So I thought it might be something you should see, just in case it gets to that.