Good evening all,

Here is the short version of a long story:
6 months ago I was given a 2000 S-type (4.0) with bend valves because of a timing chain slip/break. Since then I have slowly torn down, fixed, and built the engine.

After some help from this forum to figure out the coolant plumbing I was able to get the car started. However it runs fairly rough at idle, almost like it is missing on one or two cylinders.

The first thing I checked was compression. I wanted to make sure the valve job was successful. Compression read (front to back, in psi): passenger bank:210-220-220-220, drivers bank: 220-230-220-220. I am happy that they are fairly consistent, and that none are 0 psi, like before. However, are my reading too high? I have never worked on a petrol car that got over 195 psi on compression test.


Assuming that the compression is good, I am wondering what my next step is to diagnose the rough running. I am left with fuel, spark, and timing(engine and spark) being the outstanding issues.

spark: The plugs look pretty worn I plan on changing them for good measure, but they don't seem THAT bad. Does the old "yank out a plug and see if it get worse" method still apply, so i can narrow down if one cylinder is not getting spark?

fuel: Anyway to make sure I am getting good fuel to each cylinder?

timing(spark): not sure how to check this. I'm used to the timing gun and clip on the #1 cylinder wire technique. I doubt that method applies anymore.

Do I have to reset the ECU somehow to have start from a baseline?



Sorry for the flood of questions, any help is appreciated

Best Regards
Michael Sershen

 

The PCM (ecu) is reset every time you disconnect the battery. It then has to relearn the car and will run somewhat rough until it does. I'd say you NEED an OBD tool so you can read the many values including any DTCs (codes), fuel trims and whether the car is even going CL (closed loop) happily on both banks. Spend serious time learning what else you can do. You can get an elm327 for about $30 and some OK software for $80 but if you really want to read a lot of the car's data take a look at AutoEnginuity. (You'll likely get or can download some free software with the elm327 and it will probably be just about enough for initial testing.)

Also, doesn't the workshop manual ($10 ebay) specify compression values? (I've not looked). Or the Specs here https://www.jaguarforums.com/forum/a...4&d=1269505095

 

Thanks for the quick reply.

I do have a OBD tool, I know it works for OBD I, not sure if it will work on the jag.

I will look into the ELM327 you mentioned.

I have a membership to ALLDATA for the jag, the only compression info i can find is: "Lowest cylinder within 75 percent of highest" which it clearly satisfies. No real compression range, or max listed. I will get a paper workshop manual, the online ALLdata version is difficult to navigate.

By the way, the link you provided does not work for me, I get a "thegreatms, you do not have permission to access this page." error.

Thanks again,
Mike

 

Not OBD I - you must use OBD II (OBD2). Do NOT connect the other as maybe it will cause damage.

Alldata - get the $10 ebay workshop manual as well.

That error is in the FAQs. More posts needed, most likely.