Engine running very rough
 

Got my 2001 Focus w/SPI back on the road the other day after replacing the head. The engine ran flawlessly for a couple of days until today..I was driving along and the engine died. I coasted to a stop and it restarted fine but began to run very rough and stumbling after a mile or so. Was close to home and when I pulled into the drive I turned it off and could smell a strong sulphur smell(dont think the cat is stopped up because it looked fine when I bolted it up to manifold). Anyways, I checked for loose hoses/connectors and unplugged most connectors one at a time and restarted only to have it run Very rough each time. Also pulled plugs and they are all black and sooty indicating a rich condition.(plugs are new and looked fine 2 days before) Any ideas what this might be and where to start troubleshooting? Any help would be much appreciated.

Fuel pressure regulator would be first on my list. Has the CEL activated?

Have you detected any vacuum leaks? The ecm is trying to richen up the system in what is prehaps a lean condition on a cylinder(s). Who installed the head....used, new, rebuilt..etc ?

I don't see or hear any obvious vacuum leaks and I checked it over pretty well. The head is a rebuilt and looked like they did a really good job. I installed the head and did use new bolts. Like I said it ran great for a couple days..the engine ran better than it ever had and so quiet you can barely tell its running. Whatever happened seemed to be all of the sudden. Thanks very much for your reply.

[QUOTE=FocusRus;4621912]Fuel pressure regulator would be first on my list. Has the CEL activated?[/QUOTE
Check engine light never came on. Is there a certain procedure for checking the fuel pressure regulator on these vehicles. I have worked on cars all my life but mostly older carburated vehicles. My knowledge of fuel injected and computer controlled vehicles is limited but I learn new things as needed and will use this issue to expand my knowledge. Thanks very much for the reply.

Dan, what is the condition of the up stream 02 sensor? This could very well be the issue if the ecm is seeing a 0v signal from the sensor, so in return the ecm thinks the engine is running lean. Do you have access to a scanner? I'd bet that your ecm is in open loop status. Lets start here and see if the 02 sensor is the problem.

Thanks for the reply. I don't own a scanner but I will buy one in the next couple of days or possibly rent one for now. What scanner would you recommend buying? I have been wanting to get one for a while anyways. Of course I'd like to get by expensively but I don't mind spending a little more for something that's going to be as useful as the scanners probably are. Thanks again for the reply.

I can recommend this
http://www.scantool.net/media/catalo...l_software.jpg
It's $50 and works with a laptop (or desktop if you're really desperate) and the OBDWiz software that comes with it is simple and fairly useful, the site has other software packages available and I bought the Ford enhanced one for $80 but it's probably not worth it, there are a lot of datastreams it should be able to look at that don't work for some reason.

Anyway, OBDWiz would allow you to look at real time o2 sensor operation as well as fuel trim information. Well worth $50 IMO, and although you'd need a laptop to use it, having the laptop screen makes it much more useful than the type of low-end scan tool sold at parts stores.

http://www.scantool.net/obdlink-sx.html

For me, thats a hard question because there are so many scanners on the market. Depending on what your plan of use would be, if its for professional or personal use, if you need bi-directional capabilities, etc. I personally use high-end tools in the field (diesel) but only have need for a basic scan tool for personal use. These things can get pricey so it depends on what you intend to use it for. Basic: Anything the autopart stores carry...Actron CP9580 Auto Scanner with CodeConnect OBD II, CAN and ABS. OTC 3111 w\ ABS.... and so on. I personally use a Code Scout 2500 and a Auto Xray AX7000 TechScan for my Tahoe, Contour, 3500 and Focus.

reminds me of my toughbook software for heavy duty standard OBDII.....and you're right....nothing beats a 'big' screen for visual.