MAXIMUS1968

I was wanting to knowabout the tps. My tps seems to be working properly but i havent checked it with an ohm meter, that being said. If it is outta spec will it cause the timing to be off? I can jumper my connections and it drops the idle like it should, im not sure if it would make my timing be off tho, any ideas?

trythis

If the TPS is worn out, or off tiny bit, the ECU will think the throttle is at 1000 rpm when it is really at warm idle. (As a, for instance) So it will throw more fuel than it should. Every thing involving your emissions will then be off.

THeroy alert, not speaking from actual knowledge:
As far as timing, I can only come up with a theory that since the timing is not purely mechanical in our eingines, that it is controlled at least somewhat by the computer. I am not talking each cylinder with its own coil, but if the computer is being told that a certain throttle position requires certain fuel and spark frequecy, then having the TPS off would throw off the timing.

Either way, if the TPS is malfunctioning, all sorts of other problems will be mysteriously wrong. Are you looking for something that could be wrong, or are you trying to fix a known problem?

MAXIMUS1968

i JUST CANT SET THE TIMING AT 5btdc WITHOUT IT PINGING, IM USING 91 OCTANE FUEL......ooops sorry for caps! I have to set it at TDC to get it to run correctly, i have replaced the timing chain a while back and i have checked everything rather thoroughly, im just at my wits end, maybe i should just leave it be

farmerj

If your TPS is not set correctly, and won't see a closed throttle, you won't be able to check your timing. The ECU must see a closed throttle once you install the jumper to check the timing.

So if your timing is falling back, you may have more issues.

Pinging is pre-detonation. Causes include carbon build up, advanced timing or a lean fuel mixture among others. You might want to check your knock sensor.

I am having a similar problem. So far I have found my TPS was set to not close on the idle setting. Re-adjusted and it is now allowing me to set timing. Verified that timing was actually at 5 dBDC.

Had two bad plug wires. Caused carbon tracking between #2 and #4 in the distributer cap.

Ran Sea-foam into the vacuum fitting for the power steering pump last year. Helped for about six monthes. I think my timing was causing it to load the intake and engine up with carbon.

Will let you know if I find anything more different. Next thing for me to check is the knock sensor and cold start systems.

silversup

If the TPS is worn out, will the idle stay at whatever the ECU thinks it is? For instance if the ECU thinks its at 1000 RPM, will the car be at 1,000 RPM at warm idle?

MAXIMUS1968

I am getting a 1.10 reading on my ohm meter with the throttle position closed is this ok?

farmerj

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Check this out. Has nice pictures and easy to follow instructions.

And yes, it will idle around 1000 rpm if the tps is out of adjust or bad.

rdharper

I suspect you might be reading 1.1Kohm, which is 1100 ohms. You should read 10-19 ohms when the throttle is correctly showing idle position.

As to your original problem, I'm not an expert on replacing the timing chain, but I'm wondering if something isn't a tooth off as a result off that work.

MAXIMUS1968

Anythings possible, i just made sure it was all lined up with the dots, its fairly tight on the drivers side, I just dont know what else to do, it runs great like it is, but i can tell the power is just a bit weaker than it should be. I got the TPS adjusted it didnt really change the timing any. Any ideas?

mr toytech

dont get to worried about ohms if it is even close, i would check for proper voltages to be accurret. and if the tps is bad or not adjusted right it will throw off yuor timing. i just replaced mine for this same reason. pinging is gone and timing is correct now. was 5 degrees advanced.

MAXIMUS1968

Mine is 5 degrees retarded 0TDC and i adjusted the tps, it was outta whack just a bit but not much, it didnt change anything

MAXIMUS1968

If i pulled the distributor out and moved it one tooth would it advance it to where it should need to be? The dots on my crank and cam shaft are in line and i have no slack on the driver side at all..I think i will just let it go, i dont know what else to do, i do wanna thank everyone for all of the insight and help!

rdharper

As I said, I'm not an expert on the timing chain/distributor bit. But I seem to remember reading several posts on being off a tooth, symptoms related to that etc.

If you had to pull the distibutor to change the chain, then I'd pursue the possibility that that is what happened, a bit further. You might do a search on <off a tooth> or some such to see if you can pull those up.

Maybe some of the experts around here can chime in on this.

MAXIMUS1968

I read this at 4crawler, i didnt follow the last sentence here, could this cause me to be off a bit?

*Chain tension placement is crucial in making the guide install easy.
Since the engine rotates in a clockwise pattern the driver side should have the most tension and the passenger side the slack.
If you look at the way the guides install you will see the driver's side has virtually no slack and the passenger side has a lot.
To achieve this you need to find the proper alignment of the chain on the gears then very carefully preload the cam gear/valves by placing a punch in the hole on the top the cam and twisting the cam ever so slightly clock wise to get the cam gear on.
Afterit's on very gently twist it back to the original position which will tighten up the chain on the drivers side.

rdharper

I would guess that if the procedure to tighten in the direction of rotation was not done, you could get enough slack to be off the equivalent of a tooth on the distributor. Seems like it might cause the timing mark to jump around as well... although I'd like to hear the opinion of those that have actually done this job.

MAXIMUS1968

bump^^^^^^

farmerj

Because of the tensioner and the rotation of the engine, as soon as you go to turn the crank, the drivers side will be tightened. Nothing you could do to stop it. What it would do though is retard the cam (ignition) timing to the crankshaft. It would lope or run so poorly you would be lucky to get it running or driveable.

MAXIMUS1968

Maybe we are on to something,I have to set it on TDC to keep it from pinging so damn bad, this is the only thing i could run across that i havent done in the timing swap, i did the timing chain swap about 5,000 miles ago i will check this out this evening, thanks for the input

GrimReaper

I have read through this a couple times. Let me see if I have al the facts.

You are jumping the test connector

You can get it to 0*TDC but not the prescribed 5*BTDC

You have tested that you get the IDE circuit with throttle closed and that you verified TPS is working.


Here is a couple questions I have.

Have you checked for any codes? Just because the light is not on doesn't mean it doesn't have a code. Read them if you haven't

Have you checked for vacuum leaks? Any unmetered air that gets into the system after the afm will throw off the ECM..it would be a lean out problem and present itself as ping and idle issues.

Have you tested the AFM (on 4crawlers page)?

Have you tested the EGR?

Have you adjusted the idle to 700-850 (22re)?

Have you done any checking of the knock sensor?

O2 sensor?

Are the plugs all about the same color and what color is that? Color off on one or two could indicate a leaned out injector, vacuum leak on the O-ring at the head or a harness problem.


The FI used on Toyota's is actually a Bosch design. They use it under license.

BigMike (Marlins son) has a couple really great posts on the Marlin Forums on how this system works. Well worth going and reading.

The basics are this... The AFM controls most of it. The TPS just lets the ECM know how far you are pushing the peddled. The amount the door is open in the AFM controls the fuel supply. The truck will run and drive with the TPS unplugged. It just makes it sluggish and creates idle problems.

Under hard throttle or deceleration the EGR closes. EGR opens around 1800 rpm with steady cruise

Truck runs in open loop till it achieves a steady cruise

Ping can be many things.
timming
fuel
compression

What I haven't found in your posts is exactly when you are hearing the ping. Is this under hard acceleration or is these steady driving you come up on a slight hill and it starts to ping?


If you are hearing this at steady cruise slight throttle I would really start checking the EGR and O2.

What happens is when you achieve a steady cruise is the ECM leans out the fuel mixture when the engine goes into a closed loop mode (reads the o2 sensor). This is done for economy and emissions reasons. Once the mixture leans the combustion temp starts to raise and you can start to get detonation (ignition without spark or spark knock or ping...what ever you want to call it). The EGR introduces exhaust into the intake to dilute the mixture (removing some of the oxygen to get back to a stoic fuel mixture of 14:1 as read by the O2) and lower the combustion temps and prevent detonation.

Now the thing that troubles me is this...the motor has a knock sensor that should dump timing if thats the problem. I really don't think you have a problem with valve timing. If it was off a tooth it would really run like crap. I also don't think you have the distributor off a tooth either. I don't think there is enough adjustment to overcome being off a tooth and get back to 5*BTDC So I would start checking other problems and possible causes.

There is precedence for harness problems with the Knock sensor circuit on most 80's and early 90's Toyota's with this style FI. I would find a wiring diagram and meter out this connections between the sensor and ECM. The Boosted Supra crowd I use to hang with ran into that problem often.

Hope that gives you some ideas on what to check. I don't come to this forum often but I will try to keep an eye on your thread to see what the outcome is. Hit me on Pirate (same nick) if you have any questions and I am not responding here.

farmerj

I have been thinking about this since I wrote it last night.


The drivers side is slack. You will rotate the crank and take out that slack first time you rotate the engine. Either by hand or the starter.

the crank shaft now advances as you ratate before the camshaft is pulled along by the chain.

The amount of advane would be dependent on how much slack was in the chain.

If you left equal to a half a link it could cause up tp about 4.32 mm of slack. Chain spec is 147 mm over 17 links, 1/2 links total 34 147/34 = 4.32 mm.

How many degrees advance on the cam could be found by dividing the circumfrance of the cam gear by 4.32mm. I would think you would have to figure this more as a ratio of 4.32:x = 5:360

half link is 4.32mm long

x=circumfrence of the cam gear

Degrees cam advance = 5

Degrees in a circle = 360

Circumfrence of the cam = X

Degree ratio is 5/360 = .0138

To solve for x, divide 4.32/.0138

X= 313.04

Circumfrence can be found with Circ = PI x Diameter

PI= 3.14159

Measuring my spare gear = Tooth tip to tip = 112.67, Bottom to bottom = 102.62 Difference is 5.25. Add that to the minor Diameter you get a diameter of 107.87

Circ = PI*107.87 = 338.88 MM

Using Excel to figure it, your more likely about 4.75 degrees advanced with the cam. But who could tell....





I would think that is the mathimatical evidence to say, pull your timing cover and reset your chain........:pat: :pat: :pat: :pat:

My mind does funny things to me when I have hd only 2 hours of sleep.....