Geoffrey

Technically, you are correct. 14.7:1 air to fuel ratio represents the chemecially perfect ratio where all fuel and air is burned. However, fuel is used to cool the engine, so, while the engine is running rich at say 14.:1, it is running too "lean" for the conditions ie full load, high volumetric efficency.

mjshira

thanks Geoffrey for adding to the thread.

I've now got the old FPR out. It doesn't look like the new one I got. It seems to have an adjustment nut above the vac line connection point. It also is not a sealed unit. It has allen head bolts (small ones) that one can use to open the unit.

I've got the new FPR in the car. It is connected on two of the three sides with the last connection giving me a lot of grief. The rear line connects at a slight downward degree towards the top of the engine and getting the end of the fuel line to mate perfectly to the regulator is just so fun. I've thought I had it a couple of times only to feel it slip off.

So after this little lunch break I will take another shot at it. Then we've got to go out of town until tomorrow so I may end up finishing then. I'll post some pictures of the old FPR later. With respect to CR, I don't think this was increased during the rebuilt as stock pistons were retained and while head work was done (port, valve angle, etc) and she is running a mild cam over stock, I don't think the car is lean due to CR. Just me view. But the engine was rebuilt at the request of the former owner by EBS and the documentation simply speaks to the parts that were used and the hours of labor, nothing about CR.

A final note, I did find some fuel residue/sludge in the throttle body, is this normal?

PCar SBA

Hey James, lots of good information and some miss-information floating around here. And it seems you got your work cut out for you. Let me chime in here.

1. Timing: Use the hammer and see what timing you get under load. The distributor has NOTHING to do with timing on a 3.6 The advance mechanism in the distributor merely makes sure the rotor is following the advance. The DME alone determines advance based on load and RPM. I don't think that is your issue if you have a stock chip.

2. Intake leak: A small vacuum leak could be the cause. However, it would kill your idle first. In the upper RPM ranges there is so much air flowing through the engine that a small leak would not really do much harm if any. And if you use starter fluid to hunt that leak it will change the idle. It will get sucked in through the little muffler connected to the idle control valve. I won't bother. It will be a false positive at best.

I would put my money on the fuel pressure. The fuel pressure regulator changes fuel pressure with intake vacuum. At high vacuum (closed throttle) the fuel pressure is lower. As you go to WOT the intake vacuum is reduced and the fuel pressure gets raised to help increasing the fuel delivery rate. The dynamic range of the injectors alone is not enough to do nice idle and deliver enough fuel under WOT and load. Since the fuel flow is more or less proportional to the rail fuel pressure it is a nice way to extend the dynamic range of the fuel delivery system.

Measure the fuel pressure at the rail at idle both with the vacuum hose connected and disconnected to make sure it is in spec. If it checks out next on my list would be the injectors. Maybe one is partially clogged and can't flow enough and that throws your average mixture off under WOT. Maybe have them checked and cleaned.

Keep us posted.

Cheers,
Ingo

mjshira

Ingo

Thanks for your post. I think I am on the right track. I believe the issue is the FPR given the condition and nature of the old one. Challenge for tomorrow when I am back in town will be the threading of the final fuel line (the main one) into the regulator. Once that is done it is all down hill as I just need to reinstall everything I took out to access it.

Updates to follow

mjshira

a couple pictures. here you'll see that adjustment aspect I was speaking about.

mjshira

second picture

fast951

You had a adjustable fuel pressure regulator.

mjshira

agreed. not sure why it started to go bad. We'll see what the results are tomorrow.

mjshira

UPDATE

I got everything back together but from the movement of the intake I've now got a vacuum leak. I've checked and re-checked all the bands at the throttle body connection points and intake ports.

Does anyone have a good picture of the vacuum system? I've got a T connection right behind the throttle cable with one open connection point. I've looked at some pictures of throttle body's and I don't see a vaccum pick up point in the rear of the throttle body...

Close to being done but not there yet!

mjshira

OK...

So I found the small vacuum port on the throttle body and connected the vacuum line to it. Car still has a miss, when you drive it she feels like 2/3 power there and 'wants to go' and stumbles. So I parked her and will tackle this again after work tomorrow. I think what I am going to do is remove the complete intake system again, marry the two halves with the throttle body, make sure (even though I think all these connections are good now) that these connections are good and then install the intakes again.

it was not running this bad with the lean condition. frustration is a part of learning, I've gone slow and taken my time in attempt to avoid mistakes but clearly I've made one which I've got to determine the source of.

fast951

Before going any further, I would pressure test the intake system. It's probably the easiest test you can perform and will flush out all vacuum leaks.
A adjustable FPR was there for a reason. You never did check the fuel pressure before removing it. Maybe someone put it in place to band-aid a problem? At this time, your only option is to eliminate any vacuum leak, then see how the car runs.
I have seen more than a few adjustable FPRs fail, which is why we stay away from them.

mjshira

John

So I should have left the adjustable unit on the car?

I think the issue is an intake leak or vacuum leak. I would pressure test it in a heart beat if it were that simple.

fast951

No, using the adjustable FPR is not a good idea. I have seen many of them fail! The factory FPR is very good.

mjshira

I appreciate that I am not a mechanic. That said, I'm not an idiot either. I simply have to 'learn as a I do' which requires patience on my part and understanding by those like yourself. I'll figure this out with the help of the forum and by going through the steps taken prior to the problem. The car is missing. So what is causing the miss? That is what I've got to determine. Then once that is done I can find out if the FPR replacement has addressed my lean condition.

mjshira

I went out and checked everything again. All the vacuum lines are connected. Since my car is a 1990 these are a little different then some of the posts I've reviewed on the forum for newer cars. My resonsance flap is vacuum operated and connected.

I honestly don't know what is causing this. I've felt with my hand and the connections on either side of the throttle body are sound. I've felt with my hand while the engine is running to see if I can detect air flow. I got some water with soap and sprayed some on the connects at the intake stacks to ports, nothing bubbled.

So about the only thing left to do is pull it all apart and repeat the install process. The way the engine is acting reminds me of an exhaust leak (I know I don't have one) in that when you attempt to give throttle to the engine under load it stumbles and stutters.

The one thing I didn't do was attempt to clean the throttle body so I will do that next time based on some of the posts I've read here.

All I know is the FPR is installed properly and not leaking. The engine wants to run... but stumbles