captainOCD

My blue 86.5 seems to be idling fine, but above idle it doesn't seem right. It doesn't sound like it's missing (all plugs looked fine), but it seems to stumble. I put in new ngk plugs and replaced the ignition ignitors/amplfiers and that didn't change anything.



I put a fuel pressure gauge on the rail and with the motor running and am seeing about 28psi at idle. When goosing the throttle it looks to jump up towards 36psi.



With the motor off the fuel pressure sits at 36psi. Squeezing the return line from the regulator makes the pressure go up, so seems like the pump is working normally.


I'm a bit confused with what the fuel pressure is supposed to be. Searching around here seemed to suggest 55psi, but I see the regulators saying 2.5bar/36psi.

Any suggestions for what could be going on here?

davek9

Those are normal Fuel pressures for an 85 to 86.5, an S4 has the higher numbers (about 10psi higher).

Get a cheep timing light and make sure ALL the plugs are getting spark, (I understand all plugs look fine) confirm they are all firing.

What is the history on the car, was it OK before and when did this start, your issue could be as simple as a bad sensor/wire or the MAF is out of Cal and requires rebuilding.
Good job on measuring things, next is vacuum , should be about -17 at idle

Dave K

jej3

Could you have injector issues? I just did an intake refresh on my S4, including new injectors and injector ends.

David Roberts (from 928 Specialists) let me borrow the below tool which helped QUICKLY pinpoint the non-firing injector.




Good Luck!

davek9

Nice tool, but on an S3 they are harder to see let alone get to, although that tools right there just may do it
On the S3 it is usually the back two (4&8) that get the wires mashed by the Airbox

DR

Hi Dave,

Works on an S3 also, as a matter of fact I haven't found a car (or truck) yet that it won't reach the injectors for testing. Handy little gadget.

All the best,

Dave

captainOCD

Unfortunately I don't have much history with this car. The air and fuel filters both had 2004 as the date on them in marker, but don't know when it was parked for sure. The guy I bought it from bought it in a package deal to get an old Jag that he wanted. This guy bought it, but then decided he didn't want to spend the time fixing it up and wanted to get one that didn't need work instead. He said the previous owner bought it as a runner.

So I really don't know what has happened to the car in the past 10-15 years. It wouldn't surprise me if it's got some sensors that aren't working, stuck injectors, or bad rubber parts.

I did test the vacuum at idle the other day and it looks about right from what you're saying.



The car did seem to be running rougher when I first fired it up to drive it into the garage. It seems like it's running better to me now (all it's had done is fuel pump, fresh gas, and plugs so far), but still rough off of idle.
This was the first time I fired it up. Feel free to ignore me and my buddy bantering. We both needed a beer that day.


I have a MAF on the tan 86.5 that I could try on it, but I don't know the condition of that one since I haven't gotten that car running yet. I have another set of computers, but same thing, don't know the condition of them either.

I did get a timing light too, but it didn't work so I need to get another. Does that injector probe go into the wire, or is it just induction?

davek9

OK all good to know, first off glad to hear it is running a bit better as it should once you actually get it up to temp and run (not idle) the engine.
These engines run very rich from a cold start and don't lean out until that temp gauge gets out of the white area on the dial.
This results in a poor running engine that has been started and stopped frequently w/o it being up to temp and driven, like typically happens a a service/body shop as they move cars around.

As no history, you should note where the T belt is tracking on the gears via the vent hole on the top gear covers, it should track w/o wiggling (much) and should be about a 1/4" from the front face of both gears.
However w/o any service records a T-belt job is in your near future w/o question, else this can go south really quick if you bend valves (think engine pull and valve job)

Dave K

Edit: and thanks DR for the tip

captainOCD

I haven't run the engine up to temp yet. Just long enough to move it into the garage and a couple times to see if it would run smoother because I'm worried about the timing belt.

I have most of the timing belt job parts on the way for this car already. I was hoping to get to that this weekend, but outside issues are probably going to be consuming my next couple weekends now. Amongst other things I have to ferry my brother either to MI or VA to find a replacement for his E46 bmw that was totalled by a drug dealer last week.

545svk

Can you share some details on the tool? Name, serial number and use will be good.
Thanks

Wisconsin Joe

A quick search found this:

https://www.nationaltoolwarehouse.co...yABEgLze_D_BwE

I've never seen, let alone used, one of these before. Looks interesting.

captainOCD

Life has fonally calmed down some for me so I'm starting on the timing belt today and it kind of looks to me like the passengers side came is half a tooth off. Maybe this is making it run rough?







What do you guys think?

Landseer

captainOCD

Here's the mark on the rear of the passengers side cam. So it looks like that cam should have been lined up with the tooth of the belt on the right of the mark on the front of the cam. Instead it was lined up almost with the tooth on the cam gear itself. Not sure if that little bit make much of a difference? I'll have to see where it all lines up with the new belt.

John Speake

It rather sounds like the MAf or its connections are faulty, and the car is in "limp home mode".

captainOCD

I'll start taking a look at that stuff when I'm done with the timing belt job then.