What is the behavior I should be looking for if I disconnect the vac line? Should it stop surging under heavy load?


I'm pretty sure I can rule out the clutch. It is certainly an engine issue.


Thanks for the feedback!

 

Yeah would go away completely with the EGR disabled if it's the cause.

Random EGR image.. It's the top vac line, which comes from the modulator.


Here is the tech sheet for the EGR system. Modulator is covered on page 3.

 

Great image. Thanks. My friend has the EGR block off plates so I may try installing that and seeing if it helps.

I've figured out that my Fuel Pulsation Dampener is leaking. Any thoughts on whether that could cause these symptoms?
It looks like it can be removed by using a bolt from a 89+ 22RE to secure the fuel line instead.

This is bumming me out. There's a HUGE get together at Hidden Falls this weekend. It's looking like I'm either going to miss it or have to leave my truck parked and ride along with others.

 

If it is leaking that means a rip/hole in the diaphram,so it's not functional. You'd have the same problem if you by-passed its function I would imagine. However my model doesn't have one and works fine w/o it. I never really thought it was big enough to make much difference anyway.

Here is some more reading material.

Pulling the vacuum line off the pressure regulator might be benificial. Fuel pressure is dependent on engine load,which it senses from the manifold pressure.

If that solves it you'll want to inspect the vacuum switch and pressure regulator. And of course replace o by-pass the dampener, fuel leaks are bad

 

Ok, thanks. I'll try messing with the pressure regulator. Hopefully my friend's driveway is steep enough that I can reproduce the problem there.

I went ahead and ordered the union bolt for the end of the fuel rail from a 89+ 22RE to replace the pressure dampener. Along with new copper gaskets. I got three gaskets just in case because I read that the new bolt needs a little extra space to make a good seal at this thread: http://www.celica-gts.com/forums/ind...?topic=16826.0


Parts for anyone else looking to get rid of the fuel pressure dampener, though I can't verify that they work yet.
http://www.toyotapartszone.com/oem/90401-14010.html
http://www.toyotapartszone.com/oem/t...430-14007.html

 

Alright, I disconnected the vac line for the pressure regulator and the problem seems to go away. Thanks! Feels great to have a lead. Diving in deeper.

 

Well, I replied too soon. I just got it to surge again with the fuel pressure regulator disconnected. Back to the drawing board.

 

Inspect the drive line stuff, have you done something in that system recently. Sorry old man syndrome maybe.. I read something last night about binding I think it was and made me think of your symptoms.

I might not rule out pressure problems without putting a guage on it. Or atleast till after you get the dampener issue worked out.


Gl and stick with it you'll find it, it's always the last thing you check haha

 

WOW! Nice build man, keep it coming.

 

It did first start after I put a lunchbox locker in the front diff, but I can get it to do it in 2wd now, even in 2wd High. (Happened to me at a 4-way stop on the way home just now.)

Tonight I messed with the Fuel Pressure Regulator (ended up bypassing the VSV - http://www.4crawler.com/4x4/CheapTri...ne_Pix/10.html), EGR, and TPS. Disconnecting those didn't change the issue.

I've got a new [hopefully] clearer video I'll get posted in a few minutes.

 

My friend's driveway was steep enough to let me reproduce the surging. If I drop the clutch at low RPM while trying to climb, the engine surges like this. The truck drives fine otherwise. At the end of the video I slip the clutch more to show that the engine can have smooth power. That's impossible when climbing steep inclines or trying to crawl, though.

I can even put it in 4-lo at the bottom of the driveway and the truck will drive itself up the driveway smoothly while idling without any throttle input from me.

In case anyone's thinking it: this isn't an issue of me just driving a manual poorly. I've been driving manual for 12 years. This problem just developed on the truck, and my driving style hasn't changed at all.

As you can see, this issue makes it impossible to slowly work up a steep obstacle while wheeling.

 

Thanks!

 

Ocell - your truck is really looking great. I'll throw a few ideas out there for your surging...
- Make sure the AFM flapper moves freely, could be sticking causing a temporary higher idle...free and easy to check and clean.
- Another thought is that the truck is temporarily losing fuel due to the AFM signal to the COR relay, you could put the Fp to B+ jumper wire in the diag connector to bypass the COR as a check. Here is a neat video someone did on putting a bigger capacitor in the COR to smooth out the signal fluctuations
Anyway, both of these are free to try and fairly easy, so at least we can rule them out.

 

Hey Cory,

Thanks, those are great suggestions and a very helpful video.

I've been thinking about it more, and I do think that the engine isn't actually surging, but it is CUTTING fuel. So your suggestions make sense.

 

Now u have me digging around my head again over my "bogging temporarily on hot restarts".... DANGIT! Hehe.

Think ur fuel cut system is malfunctioning? Cant see being on a grade causing that.... hmmmmm.

AFM and its relationships are good checks to do.

Also, in case u havent tried it, get on that grade and unplug ur TPS. Ive had sputtering/bogging under initial load, taking off, where I could not get it going until around 2500rpm, where it would just DART off. TPS was the culprit.... and my numbers/readings at the TPS were fine.

 

Hey Mark,

Thanks for chiming in here. I've already ruled out the TPS, problem exists with it unplugged.

It has been getting worse, and now I can cause the problem on flat land in 2-hi. It does it if I'm crawling along slow, around 800 rpm or so, then I stab the throttle to 1/3 or 1/2 and hold it there. The truck will lurch forward (as it should when you stab the gas) but then the fuel cuts and it dies, then the fuel kicks back in, and out, and in. So the truck bucks HARD (enough to chirp tires) until it gets moving quick enough to rev over 2,500 rpm or so. Then it drives like normal.

I'm anxious to check this COR relay.

 

My COR did give me issues big time b4 rellacing it.... But was mostly causing not restart when hot. Thing was so hit it literally burned my finger... would have melted any time.

 

Should there be any indication when the Fp and +B ports are being jumped? I jumped them, but there's a bunch of grease in my connector so I'm not 100% sure it's making contact.

Jumping those ports, if they're making contact, didn't fix the problem.

I also swapped AFM's with my friends 4Runner and the problem remains.

 

Yeah you might be able to hear the pump running. But in your case unless you changed out that pulse dampener it'll be leaking

I don't think the locker in the front would have much if any effect on your 2wd performance. Just incase you were still wondering about that.

Check gear lube, maybe the seal between the Tcase and tranny has let loose or something else. Anything "interesting" in the rear driveline?

 

Thanks for continuing to chip in on the trouble shooting. I'm happy to say, I've fixed it!

When I put my AFM back in after swapping with my buddy I cranked the engine and heard some squeaking. I was pretty sure it was a belt, but I wanted to make sure hadn't missed tightening a bolt on the AFT so I was tugging on the intake. When I tugged it one way, the engine would bog down. When I tugged the other, my idle would increase!

Whenever the engine was under heavy load, it was twisting the motor in the engine bay and "tugging" the intake assembly.

I took it loose from the throttle body to see if something was inside blocking it. Once I got everything off my buddy John found the problem. A huge tear on the underside of the elbow that goes to the throttle body. It was pretty well hidden from view while everything was still installed. The fact that it opened up when the engine was torqued and twisted in the bay was really throwing me off because it was acting like a sensor issue. So when it opened it would let unmetered air in to the system, messing everything up.



He had done the intake/battery swap on his 4Runner, and luckily he saved his stock intake parts, so he had the same elbow piece. I put everything back in with his untorn elbow and the truck runs perfect now.

A free fix is the best fix, right? I'm so pumped!

Thanks again for all the help everyone.