Zero vacuum at fuel pressure regulator???

I have a 99 4runner with the 2.7 5sp 4x4, 140k. Ive started having a stumbling issue in 4th and 5th gear like when pulling a hill, like it cuts out and if I let off it stops and ease back its fine, put when try to accelerate to get going it stumbles. No check engine lights on either. My fuel mileage has dropped from high 19's to 14.5. I have new NKG plugs cleaned MAF and the throttle body. Also checked the fuel pressure regulator when I noticed no vacuum on the line from the intake tube. I thought that had constant vacuum? So in my research i've found out where the fuel filter is and read that they are suppose to be lifetime? Never heard of that. Also found some stuff on the VSV and egr valve stuff. I'm not familiar with either. So is one of those two items why I don't have vacuum at the fuel pressure reg. or are they not realated? I don't see a shratter valve to test fuel pressure or how to test the VSV and or clean the EGR valve. Am I looking at the right stuff that mite be causing the stumbling and drop in fuel mileage? Any help on this would be awesome, thanks y'all.

 

last I remember I heard of cracked exhaust manifolds causing similar issues....might wanna check that out

 

Thanks, can someone provide pics of how to test the fuel pressure on these 2.7s? And are these fuel filters really suppose to be lifetime? I just need to get a Haynes manual I guess. This no vacuum at the box under the air intake tube is weird to me, how is the fuel pressure regulator suppose to work without vacuum to it?

 

Any chance someone could check their vacuum at the fuel pressure regulator and at that box that hangs under the air intake tube and then reply, please! . I'm really confused about this i dont know if it only creates a vacuum at high rpms or what? My truck has vacuum at the FPR at idol, so I'm stumped. Thank for any help here.

 

The 2.7 has an unusual style of operating the fuel pressure regulator. The vacuum line is not connected to a port on the throttle body. Instead it is connected to a port in the intake air chamber. The system uses the venturi effect to create a vacuum at the vac line to the FPR. This means you typically won't be able to "feel" a vacuum on the line like you typically expect. You can however measure it with a vacuum gauge.

 

Interesting. Thanks BamaToy1997. So am I on the right track for the stumbling issue and poor fuel mileage? And do you suspect they are related?

 

It is very possible. The best way to know for sure is check ALL reading on the scangauge and compare to expected results.

 

Yea I've been checking the parameters with my scan gauge but not sure what some of the readings are suppose to be reading. Like I can read fuel trims and o2 volts and stuff and my research has let me to believe its good. My cat got stolen so it's new with new o2 sensors, so that should be good. I don't know if it's the fuel filter or EGR or VSV solenoid. Was gna check the fuel pressure but not sure how with no port to hook to.

 

UPDATE: Well this issue has finally caused my check engine light to flash. We was on our way to a wedding and it started bucking, or stumbling at highway speeds when trying to accelerate or maintain speed going up a hill. Cel started flashing and then stopped. Left the wedding and reception and had about a 20 min drive home and no check engine light, and it never stumbled once and has been fine since. Tried to pull a code and no codes stored. My research led me to believe its a misfire. I checked my plug wires with voltmeter and the ohms was like 11.5 on the long #4 wire down to about 6.75 on the shortest #1 wire. Had good spark on the wires to the coil packs but not real sure my test for those was correct. Anyway anybody have any thoughts?

 

u changed the plugs...did u buy new wires?

 

I did not. Shame on me, I know. I was going of how they looked and they look brand new. I did inspect them and was and are in really good shape. I've never noticed any improvement in the past when changing plugs and wires. I just read somewhere that if the plug wires say what cylinder they go to then they are originals!!!! Yikes, 140k miles. But I just checked for spark leakage with a spray bottle and couldn't see any sparks and of course I also just did the ohms check. Can't find any info in my Haynes manual that says what the ohms should be on the plug wires and a google search is all over the map on what they should be. I will buy new plug wires but not real sure it will fix my "fish biting"

 

do you know which cylinders are misfiring? try swapping the coils around and see if you can point them out.

 

No I don't. The CEL just flashed for like a minute or less then stopped. I was hoping it would've left a code but it didn't. I didn't have my code reader hooked up at the time and I guess since it just flashed it didn't store a code. My Haynes manual isn't real clear on how to test the ohms on the coils for the primary and secondary. It shows how to test that the coils are getting power but not the resistance. Do you know how to test the coils with a voltmeter?

 

My Ultragauge can detect 'pending' codes (before it throws a CEL). Does the Scangauge do that?

 

Well I'm not sure if the Scanguage does or not. I guess I just have a scan tool. I bought an Elm WIFI adapter and an app on my phone. It does scan codes and parameters. I was gonna get the Ultraguage but a guy told me about this adapter thing so went with the $20 adapter and $10 app. I did go to the parts store to see if the flashing check engine light left a code and they scanned and confirmed, no code.

 

Another UPDATE: Well finally got a check engine light on the other day. P0300 and P0301. So I pulled the spark plugs again and #1 looked pretty dark while the other 3 looked great. So I went ahead and replaced the wires and all new plugs but now I have a rough idle on the first start in the am. If you tap the gas a couple times it clears up and rides out great. So any thoughts? Is this another new problem or still dealing with the misfire? I'm still not sure how the check the coil packs. Remebering I did clean the MAF and throttle body so not sure what to look at next. I really thought changing that burnt looking #1 plug was the problem but now I'm curious if that was the affect of something else being bad, like the wires, but now not sure what to think. Thanks for any input.

 

Well I give up. To the shop it goes. Goes in friday so if anybody is following this I will update with the findings. Be back in a couple days.

 

Well.... The report is in, and it's not good. Blown head gasket! $1100. I'll try to remember to report back with the mpg gained back, if indeed it goes back to the high 18s and 19s that is. Thanks to everyone for chiming in.

 

Bummer

This likely goes without saying, but be certain that they use brand new head bolts, and that they check the head for worn/burnt valves, etc.

 

Man that sucks... Sorry to hear.