How to tell if a fuel pressure regulator is bad?

[Hardwareman]

Hey guys, I just replaced and repaired my engine and swapped out my transmission at the same time for a newer one. I have a problem however. Before I pulled the motor it idled kind of wacky, like up and down on the rpm's. I thought it was a tune-up issue because I had'nt changed the plugs and wires in a while but after I got the whole engine cleaned up with new gaskets and seals and then tuned it up and put it back in, it's doing the same thing.............rpm's kind of up then down. Erratic!

It's not like the IAC valve, it's more like it lopes and idles erratically. I feel no blow by at the exhaust either. The PVC valve is new, the air filter is good, and as far as I know the head gasket does'nt appear to be leaking from what I have seen. The fuel pump and fuel filter is also new. The only other things I can think of is the fuel pressure regulator or worn camshaft lobes, which I hope it is'nt. The engine does have over 200,000 miles on it but I've had it for the last 150,000 or so of those miles and have regularly maintained it.

I know these engines can go for a long time if taken care of and not abused but I'm totally stumped here guys. Now that I've taken care of all the leaks this engine had can someone point me on where to look? Thanks.

EDIT: By the way, it only does this at idle. After idle it's fine.

Allen

 

[zamos]

A surging idle is generally caused by either the IAC ( may need to be reset ) or un-metered air is entering the engine - maybe a vacuum leak or intake gasket

 

[Jspafford]

If you pull the vacuum line off the FPR, it will usually have raw fuel in it if bad.

It does not always do this, but most of the time it will.

However, the FPR will usually make it hard to start once it's been run.

 

[Hardwareman]

Ok, that's not it I think?

The idle problem continues. I think maybe I'll do a fuel pressure and/or compression test/check.




Allen

 

[TireIron]

do you have a vacuum gauge to check the vacuum the engine is pulling? if youre below 18-20 then you have a vacuum leak somewhere...

 

[Hardwareman]

OK guys, problem solved!

I don't know what fixed it other then maybe installing a new tailshaft on my transmission for the vehicle speed sensor, replacing the original lower radiator hose that was leaking a little coolant, or just not driving it long enough after the engine tranny swap thing.

It's running as good as it ever has right now! I'm glad I took my time putting it back together right! I love it again!

I have only "ONE" problem now and that's my power steering pump not working right at lower engine rpm's. I think I need to get some water out of it though.

After that though, this is like a new truck again! Thanks guys!




Allen

 

[red85]

Try flushing the power steering pump with some fresh fluid and some conditioner. When you say it's not working right at lower rpms, what exactly is happening?