The Classic FJ60 "Stumbling/Hesitating Acceleration/Running Problem (1 Viewer)

[ravenplague]

Knocking pinging detonation all the same.
Fine tune your inline valve* so you have no stumble but also no pinging. It can be done.
Well explained here:

*If you use the one suggested you may want to try sucking on one end to get a feel for how much you restrict and use some flow restrictors inline.
Alternately and better get fine adjustable needle valve e.g. http://www.mscdirect.com/product/de..._54767707024_c_S&mkwid=s|dc&pcrid=54767707024

Thanks for the video..totally helps.

I think that I will need to figure this out as my rig actually does ping with the EGR golf tee trick. I will also try adjusting the timing to see. I love how much more responsive the bottom end is but not at the cost of pinging though
thanks

 

[Slow Left]

Improper metering of exhaust gas through the EGR (Exhaust Gas Recirculation) is a common culprit for mid-RPM (~1,500 RPM) stumble/hesitation symptoms in the 2F because recirculation of exhaust gas changes the Air-to-Fuel Ratio (AFR), therefore spark time requirements.
Exhaust is allowed to flow back into the cylinder chambers through the EGR system when the EGR Valve is open.
When the EGR Valve is shut, no exhaust gas is allowed to recirculate back into the cylinder chambers.

From 'Troubleshooting' page 2-3 of the FJ60 Emissions FSM

 

[Slow Left]

The opening/closing of the EGR Valve is controlled by the EGR Valve Modulator and the EGR Valve Modulator is controlled by vac.

There are 2 main parameters that control vac delivery to the EGR Valve Modulator:
BVSV
Throttle Plate position (relative to the Advancer port and the EGR port at the base of the carb)

At engine operating temperature (above 44C or 111F), the BVSV is open.
When the BVSV is open, when the throttle plate position moves above the Advancer port (under acceleration), vac is generated at P. Under this condition, the EGR Modulator 'dances' back and forth between one of two scenarios (opening and closing the EGR Valve in response to pressure balances).
And when the throttle plate position is moved further (like when you stomp on the gas to get through this dilemma), to a point above the EGR R port on the carb, vac is now delivered to port R on the EGR Modulator (by way of the VSV), opening completely the EGR Valve and putting a stop to the 'dance'.

 

[Slow Left]

With:
1) BVSV OPEN (engine at operating temp) and
2) throttle plate positioned ABOVE the carb Advancer Port, but BELOW the carb EGR R Port (Engine RPMs below ~1,500 RPM)

then...the EGR Valve will Open/Close based on the balance of pressures across the EGR Valve Modulator

Scenario 1:
Atmospheric Pressure is greater than EGR pressure, so vac delivered to port P at the EGR Vac Modulator is stopped at port P. As a result, the EGR Valve remains CLOSED.

Scenario 2:
EGR Pressure is greater than Atmospheric pressure, so vac delivered to port P at the EGR Vac Modulator is allowed to pass through port P, out port Q of the EGR Vac Modulator and is delivered to the EGR Valve and opens the EGR Valve.

 

[Slow Left]

With:
1) BVSV OPEN (engine at operating temp) and
2) throttle plate positioned ABOVE the carb Advancer Port, and ABOVE the carb EGR R Port (Engine RPMs above ~1,500 RPM)
3) VSV OPEN

then...vac will now be delivered to port R on the EGR Vac Modulator, keeping the pathway between ports P and Q on the EGR Vac Modulator OPEN which in turn keeps the EGR Valve OPEN

Scenario 3:
At engine RPMs above ~1,500 RPMs, two things happen.
1) the throttle plate moves to a position above the carb EGR R port, generating a vac in that vac circuit
2) the Computer reads a signal from the coil...grounding the VSV circuit and OPENING the VSV

The combination of these two events results in vac being delivered to port R on the EGR Vac Modulator. When vac reaches port R on the EGR Vac Modulator, it permanently (as long as the vac on port R is being delivered) keeps the pathway between port P and port Q on the EGR Vac Modulator OPEN...which in turn keeps the EGR Valve OPEN.

 

[Slow Left]

The throttle plate position is mechanically controlled by the accelerator pedal and linkages to the carb...which control the primary throttle shaft (upon which the throttle plate sits), so it's position should be able to be held constant independent of what all the other components in the EGR and spark control systems are doing.

The spark control (ignition timing advance curve) at ~1,500 RPMs is controlled mechanically (weights and springs), since the vac advance only comes into play right off idle and cruising. Vac advance will come into play here, so vac leaks in the dizzy pot/vac lines on the vac advance circuit will disrupt the spark timing.
EDIT: The Advancer Port on the carb (from which the dizzy advance pot draws it's vac) is ported vac...not manifold vac (manifold vac drops off quickly under load). Ported vac is generated when fast moving liquid (fuel/air mixture in this case) moves past the surface of the port (hole in the wall of the throat of the carb) and creates a pressure difference. This happens as soon as the throttle plate is positioned above the Advancer port.


Could a weak spring opening too early cause a 'rough' ignition timing advance curve where too much advance arrives too early in the RPM band...causing incomplete/missing combustion...leading to poor vac...causing the EGR Valve to 'dance' open and closed...which in turn leads to further missed ignition...

The EGR Valve opening/closing below ~1,500 RPMs is controlled by pressure differences across the EGR Vac Modulator.
Above ~1,500 RPMs, the EGR Valve is kept OPEN because the computer receives a tach signal to ground the VSV, which opens the vac circuit for vac generated at the carb EGR Port to be delivered to port R on the EGR Vac Modulator. Constant vac at port R on the EGR Vac Modulator maintains the vac circuit from port P to port Q on the EGR Vac Modulator OPEN and as a result vac is delivered to the EGR Valve keeping it OPEN.

A malfunctioning EGR Vac Modulator (like a dirty/clogged filter element) would certainly lead to erratic/mistimed EGR Valve opening/closing.
Could an exhaust leak at the exhaust manifold-to-J-pipe or J-pipe-to-EGR cooler not allow for sufficient pressure to be built up at the base of the EGR Vac Modulator...so then the EGR Valve opens late? But that would probably lead to pinging, not hesitation/stumbling...I think...

 

[Bear Lake Cruiser]

WOW!

 

[ravenplague]

I just tried to explain to my girlfriend what I was reading and she is convinced that we have lost our minds!!

 

[Slow Left]

I just tried to explain to my girlfriend what I was reading and she is convinced that we have lost our minds!!

Ha, Ha! I wonder what the schematic for that one looks like..."Let's see...now where did I put my mind...it must be around here somewhere...oh, wait...there it is...! ...no, that's not it...it must be over there..."

 

[Slow Left]

WOW!

The Emissions FSM does a pretty comprehensive job providing steps troubleshooting the components of the EGR system...the issue becomes (once the cause and effect between components of the system become clear...after repeated attempts to understand them...) imagining what could go wrong that would cause the ~1,500 RPM hesitation/stumble...and then what is the best way to test to rule that suspicion out...

For example, for ~1,500 RPM hesitation/stumble symptoms, I'm fairly certain we could rule out VSV and computer problems, because from what I understand in reading the Emissions FSM, the tach signal tells the computer to ground the VSV at ~2,500 RPM (grounding the VSV allows vac to reach port R on the EGR Vac Modulator...which in turn permanently opens the EGR Valve) and the throttle valve is positioned above the carb EGR port R at ~2,500 RPM (and the throttle valve position is independent of the EGR system...meaning it is directly, mechanically controlled by the position of the accelerator pedal).
EDIT: I think I've got this wrong here...after rereading the Emissions FSM, I believe that the VSV is supposed to open above ~1,500 RPM. I'm still not sure if the throttle plate is above the carb EGR port (a requirement for vac to be generated on the vac circuit at port R on the EGR Vac Modulator), but it might be easy to test.

If the VSV does open and the throttle plate position is above the carb EGR port, then a faulty VSV or computer could affect ~1,500 performance would be if the computer is grounding early (at lower RPMs), opening the VSV early...because that would send vac to port R on the EGR Vac Modulator...opening the EGR Valve early...

 

[Bear Lake Cruiser]

I was teasing @slowleft! Your posts have saved me a ton of time. At 60 years old that time becomes increasingly important. I owe ya bud!

 

[Slow Left]

I was teasing @slowleft! Your posts have saved me a ton of time. At 60 years old that time becomes increasingly important. I owe ya bud!

Yeah, I know...I was just trying to pull you down into the rabbit hole...misery loves company! Nah, this small performance symptom has had me chasing my tail since last fall...I've made some progress, but I don't have fancy tools to isolate the exact problem...so my approach has been to test each individual system as best I can and then try to balance all the systems to work in harmony. The problem with this approach is that there are often hidden, underlying assumptions...which brings us to MUD...the powerful tool for testing and addressing those assumptions through the power of peer review...iterative attempts to try to explain (through measurements and discussion) how the system is working and how it should be working...diagnosis...problem solving...

...and when those attempts to accurately understanding the system fail...you get MUD farts ...all completely healthy part of the process, mind you...but unwelcome, never-the-less...

 

[ravenplague]

Yeah, I know...I was just trying to pull you down into the rabbit hole...misery loves company! Nah, this small performance symptom has had me chasing my tail since last fall...I've made some progress, but I don't have fancy tools to isolate the exact problem...so my approach has been to test each individual system as best I can and then try to balance all the systems to work in harmony. The problem with this approach is that there are often hidden, underlying assumptions...which brings us to MUD...the powerful tool for testing and addressing those assumptions through the power of peer review...iterative attempts to try to explain (through measurements and discussion) how the system is working and how it should be working...diagnosis...problem solving...

...and when those attempts to accurately understanding the system fail...you get MUD farts ...all completely healthy part of the process, mind you...but unwelcome, never-the-less...

I'm thinking we should get a Kickstart going to fund you to buy the needed equipment!

A lot of this information is over my head but I am learning so much by reading and testing things out as suggested on this forum. Its driving me crazy that my rig stumbles and hesitates. I feel like I am so close yet so far sometimes!!

 

[Slow Left]

I'm thinking we should get a Kickstart going to fund you to buy the needed equipment!

Well, I'll tell you I have been kicking around the idea of doing an all electric build using available technologies...but applying them to off-road LC type applications...instant torque off the throttle.
The outcome there would be to identify technology gaps...specific to LC type applications but also more generally to identify power-electronic development needs for supporting technologies.

Jim C. would be the guy to talk to about these systems/technologies...he's got the Sun Machine to properly recurve the dizzy, for example...and pretty has the whole desmog recurve, engine rebuilds...etc. for these 2Fs dialed in.
Thing is, you need to have the dizzy off the truck and sent to him for the dizzy recurve. And he's a one man shop...so he's really busy...
And since you need to pass smog, you really only need to make sure the systems are working as Toyota meant them to. So, for example, if you knew which springs have the stock spring rate, you could just buy those and swap them out yourself.
If you get into the trial and error approach, testing different aftermarket springs, then the only real option you have to take measurements is with a timing light and timing tape on the flywheel...it is not that accurate.
I think I posted up a thread a while back to see if anyone in the MUD community knows which aftermarket springs to get to keep the stock ignition timing advance curve...maybe I'll give that thread a bump and see if anyone has any new information.

A lot of this information is over my head but I am learning so much by reading and testing things out as suggested on this forum. Its driving me crazy that my rig stumbles and hesitates. I feel like I am so close yet so far sometimes!!

Yeah, that's the nice thing about these older LCs, they are very patient with you as you ride the learning curve...and the experience that the learning process offers is awesome...and I really love the 'smileage' we get driving these things when we figure out how to maintain them properly...it's definitely worth it in my book, too!

 

[ravenplague]

I just purchased a pair of the irrigation things from amazon
http://www.amazon.com/dp/B003MZ1EUU...1438959516&sr=1&keywords=drip+irrigation+rain

pretty cheap so I thought I would give it a try. Ill post results when they come in. I have a feeling that I will need to tweak it a little to fit onto the vacuum lines

 

[Slow Left]

@ravenplague , I installed a VCV (blue/black) at port P of the EGR Vac modulator and saw an improvement, but can't know for sure if that essentially 'disabled' the EGR or not (and possible pinging the engine to death). There was also considerably more exhaust smell after cruising.

I've since switched the VCV to port R (this is the one that is responsible for holding the EGR Valve wide open) and am ambivalent about the results...but I haven't gone back and reset the base timing yet...so I'm not convinced that my observations are of any value yet.

I'm about ready to start trying a new dizzy spring (replacing the weaker of the two and keeping the stronger one in) to see if smoothing out the spark advance curve helps.

My timing light isn't fancy, it just does the strobe thing, and doesn't allow me to measure RPM and set advance (I have to put some tape along the outer edge of the flywheel and then mark out *BTDC, using the distance between the TDC line and the 7* BTDC bb as a scale), but if you have one that does, you can get a fairly accurate advance curve.
If the base timing is set to 7* BTDC at idle (650 RPM), if you turn the advancer knob on the timing light to 7*, you should see the TDC line align with the alignment mark in the viewing window (instead of the bb) because you have instructed the strobe light to light 7* in advance...

So, if you have a buddy twist the throttle torque rod to hold the RPM steady at your next data point (say 1000 RPM), then you just move that advancer knob on the timing light until you align the TDC line with the alignment mark then note the number on the dial and that is the total advance for that RPM.
This way you build a timing advance curve.

If you do this with and without the vac advance plugged, then you can subtract out the vac advance from the total and get mechanical.

And if you repeat with a new spring installed, then you can compare curves between new and old mechanical advance to see if replacing the old spring smooths out the curve at all.

Now that I think about it after writing this, I think a couple weeks ago someone updated another thread on this topic, so if I get any new info, I'll update that thread...

 

[ravenplague]

awesome! @Slow Left
Keep me posted on the spring progress and ill let you know how the irrigation thing goes. Should be in tomorrow.
Ill also try a VCV. I have a few laying around but I think they are green / white and something else that I got at the local junkyard.

 

[Bear Lake Cruiser]

Closely watching this thread. Same random ping

 

[ravenplague]

alright...wanted to share my results with the irrigation valve with pics.

I took statistics in grad school and know the importance of scientific research so I wanted to share the constant variables and some facts before i dig in so others can have the same results

Facts:
- California smogged stock FJ60 running Arco 87 octane.
- Valves recently done and timing is stock at *7
- I did Slow Left's distributor spring spacer mod but didn't notice a difference
- I did the green wire carb solenoid ground mod also did not notice a difference
- I did the lean drop test prior

When i did the golf tee mod I loved it but totally pinged under load especially on this hill. This hill is approached in 2nd gear and revving up around 2500 rpm+ . With the egr cut off , it pinged 3/4 up. Pretty loud and noticeable. Same hill with the Egr hooked up, 2nd gear, no pinging what so ever. This hill would be my testing ground. Its steeper than it looks, its one of those hills people run up and down to exercise with

So I purchased the irrigation valve from amazon that another mudder suggested
http://www.amazon.com/gp/product/B003MZ1EUU?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00
just noticed there was another valve with 1/4 ends that might work better as i had to mod the valve to work with our vacuum lines. I had to cut off the cap and cut the tip. A 2 minute job.

the valve basically works in 90 degree angles. When the arrow is facing 90 degrees from the lines, its fully closed. Open when in line with the vacuum lines in either direction. I had to find #3 vacuum lines to fit over the tip and regular #4 on the other side ( 3.5 mm and 3.0mm). The cut side is a little wider. You can use old vacuum hose that is stretched out a bit or just work it for a while; it will fit.
I marked the valve with white paint and guessed where the half way mark is by sucking on the line. I marked the half way point with the white dot. I put it in the cruiser and drove it.

the white line is closed when aligned with the white mark on the vacuum line.

Once the rig warmed up, I set it at 45 degrees or at the white dot. No difference what so ever....stumbling at 1400 rpm etc. I slowly cranked it clockwise ( when i was bench testing it, I noticed that the valve doesnt really work linearly. So the most of the adjustment would have to be small, fine, and at the last 25%. Just before the white line).

My goal was to crank it in a little at a time (like 1/16th of a turn...barely anything) while doing city driving and get to a point where it felt alot like the Golf tee mod. Once there , I would attack the hill. I found a good adjustment and ran up the hill.

well... it WORKED!!!
I had both windows rolled down to make sure to hear for pinging. No pinging what so ever! Ran great. I had it adjusted where it ran like 95% like the golf tee mod.
Here is the final setting marked with the orange dot. Remember that the white line is fully closed.

As you can see, it's barely open. I sucked on the valve at this position and it was really restricted but guess it was enough. I think that every fj60 will have a different end position as the our EGR and dizzy springs are worn to different tensions at this age.

@Slow Left . If you PM your address I would like to send you a copy of my valve to test and verify these findings. ( You get two valves when ordering from amazon)

I am curious to see if Slow left has the same results and be able to chime in about the potential harm. I am guessing that this valve opens the EGR slower, which allows it to run better, but must close slower as well. Would it run leaner off throttle?

I hope this helps others and is a cheap way to possibly fix the stumble. It worked for me! Hell yeah!

 

[ravenplague]

and my rig at the top of the hill!