Jumping timing mark/ TPS?

[wavegobbler]

Hi, new member working the bugs out of my 87 4wd automatic van. Just failed CA smog with high NO (nox?). I found some vacuum leaks and the broken BVSV. I have diagnostic code 11 blinking. I think I need to replace the Throttle Position sensor.

When I check the timing, the mark travels all over. I think a little travel might indicate a timing chain issue but this travel seems major.
Can a failing TPS make the mark travel?

Any other possibilities?

Thanks for any help!

[timsrv]

Did you jump the "check engine connector" before checking timing? That needs to be done before timing can be checked/adjusted. Otherwise the electronic advance will mess with the timing. Tim

[wavegobbler]

To check the timing I warmed up the engine, checked the idle speed (about 700, automatic) and jumped the diagnostic plug near the air filter.
The strobe showed the mark traveling and jumping around.

The van runs pretty good. It has decent power and gets 18mpg. I drove it for about 400 miles before starting to work on it.

I've kept my 2wd, manual, about 250,000m, running for almost a decade with the Chilton manual. I'm really enjoying trying to take my 'shade tree' mechanic skills to another level using the factory manual and this Great site!

[timsrv]

It sounds like you're doing everything correctly. The TPS is part of the electronic advance system. Depending on how it's failed, it may or may not affect the electronic advance. When the diagnostic connector is jumped, the electronic advance is disabled anyhow, so a failed TPS would have no effect whatsoever while in the diagnostic mode.

If you've read any of my past posts on the subject, you likely already know my attitude regarding the throttle position sensor. IMO the TPS should be replaced every 100k miles as normal maintenance, so if the van has this many miles on it or more and/or you don't know history, I'd just go ahead and replace. Here's a thread that gives information on that job: http://www.toyotavantech.com/forum/s...-Throttle-Body (scroll to the bottom of the initial post for info on the TPS).

As to the timing mark jumping around, that shouldn't happen while in the diagnostic mode. Even if the chain is worn and loose that shouldn't happen (the cam follows the crank, so at constant rpm, chain tension would remain constant). When you say it "moves all over", approx what range are we talking? 2 deg.......5 deg.........10 deg........off the scale??? For erratically changing ignition timing, I think I'd be looking towards the distributor or perhaps the ECU. If you haven't already got them, I'd start looking for a used ECU and distributor (among other things) to have around for testing and/or for emergencies.

Although I don't think the timing set is responsible for your problem, for any van with over 200k miles, I would seriously consider replacing it (just because). If you're planning to replace the timing set, read this 1st: http://www.toyotavantech.com/forum/s...2491#post12491. Tim

[wavegobbler]

Tim, thank you for your reply. My efforts to trouble shoot my vans timing (it is part of my CA smog fail: Ignition timing....Mechanical Problem.)

As I imagine you guessed, the jumping timing mark was my mistake. I have a new timing gun with lots of buttons, unlike my old one, which had one. One of the buttons is a flashlight option which is kind of in the middle, like the old button. Press the flashlight option and watch the mark dance!


I really wish I could say this solved all my problems but, sadly, I'm floundering.

I checked the timing again with the light functioning (I believe) properly. My mark failed to appear.
When my mark failed to appear, I:
Checked to make sure I was attached to #1 plug wire. I Believe this is the wire that exits the cap, lower side, passenger (it also has a '1' mark) and goes to the #1 cylinder which I believe to be the forward most one.

I borrowed another timing light and got the same result.

Then the wheels really came off. I removed the distributor. I pulled the #1 spark plug, covered hole with finger, rotated engine clockwise (when looking from front to back), and waited for the air pressure of the compression stroke. At TDC of the compression stroke I look down and the mark on the crankshaft pulley is nowhere in sight, in fact, its 180deg, straight down.

I know I'm doing something wrong. With the compressed air pressure feel, and a flashlight, I can pin down the TDC of the compression stroke on the cylinder closest to the front of the van within a deg or two. I could go on describing my folly but its painful. I'm barely clinging to the bottom rung of the ladder to van mechanics competency. It sucks down here!

Someone please set me back on the path!

[Burntboot]

If #1 cylinder is at "firing TDC" and the timing mark (notch in pulley) is 180* off that pretty pretty much indicates a problem with the crank pulley.
Either the pulley has failed or the Woodruff key that holds the pulley in position has sheared.

Time to pull the pulley and investigate, assuming your confident that you really are on the compression stroke.
If in doubt, pull the valve cover and observe the rockers, making sure the valves are closed, then see where your timing mark is.

[timsrv]

. I had a pulley that was 8 deg off. I probably should have replaced, but instead I made a new timing mark on it. It's weird when they move.......how does that happen? In my case the rubber insulator looked good and showed no signs of deterioration. Of course now I have to wonder if it's still moving. If/when I do something that will require me to reset timing on that engine, I'll definitely be checking timing BEFORE I mess with it (just to verify it's still in the same place as before). Tim

[wavegobbler]

Thank you Tim and Burntboot for responding to my post.

I have removed the crankshaft pulley and the valve cover. Between watching the valves, peering down the spark plug hole, inserting an object into the cylinder through the spark plug hole, and turning the crank shaft I believe the crank pulley is 180 deg off. The indent on the pulley in marked pretty close to BDC.

I believe the location of the mark on the outer ring of the pulley has rotated or always had this orientation. When the keyway is straight up, the mark is about straight down (or about 10deg. right). From looking at the manual, going over the timing chain removal, it looks like the crankshaft keyway is pointed straight up when the engine is at TDC. Below is a photo of my pulley.




One finger points to the keyway and the other to the indent meant to indicate TDC. Can someone confirm that normally the indent is supposed to be above the keyway, a little off center? The '0' mark on the timing chain cover seems to be a little to the left of the keyway. That would put the indent a few degrees left of the keyway when viewing while installed.

I have read on a post of Tim's that there is a rubber connection between the outer and inner part of the pulley. Mine appears to have some damage on the inner side (see photo). The outer side looks ok. I'm wondering if the outer part has spun? But I'm having a hard time believing it spun exactly 180deg.

So, can anyone tell me where the keyway is supposed to be oriented in relation to the indent meant to indicated TDC?

I'm still puzzled and parts are strewn everywhere.

[timsrv]

Wow, that's messed up. It looks like it moved to the place that was the furthest away from where it belonged. Here's where it's supposed to be. The tip of my pencil is pointing at the timing mark. Tim

[wavegobbler]

Thanks for the photo Tim. The perfect 180deg off mark really threw me for a loop. I think I can move ahead now.

My plan was to drive the van for awhile before putting new parts in it; but since its already opened up, I'm tempted to move forward with a big part splurge.

The engine has 175,000m. It appears to have had an overheating event. The valve cover around the oil fill cap is kind of reddish. All the electrical connections relating to water temperature under the radiator cap were cooked. They were hard as rock and had expanded into a round shape. The cold start connector was also cooked.



On what I hope is a positive note, the compression test seemed ok. The manual wants to see around 178psi. But they also don't want the difference to be more than 14psi between each cylinder. I'm hoping this is not that critical when the compression isn't low. I tested the cylinders from front to back, not the firing order. I removed all spark plugs and opened the throttle. The engine is supposed to be warm but I tested it cold. It was about 70deg outside.

#1-200psi
#2-200
#3-215+
#4-215

Are these cold engine compression test results any good?
Any opinion on putting a bunch of good parts on this engine? I plan on keeping the van.
Should this be another thread?

Thanks again for helping me get pasted the 'Jumping timing mark'!

[timsrv]

Yes, that's good compression (almost a little too good). I had always been told compression should be within 10% between cylinders, and this is well within. Tim

[Burntboot]

I'd want to get another pulley, it's obviously spun somehow, for whatever reason.
Replace what you need to while you're in that deep and be done with it, but don't go looking for problems that don't exist (yet).

Compression numbers are high but given the problems so far (TPS, Vacuum leaks, Timing...) its understandable being a little carboned up.
Just driving it with everything dialled in will help clear things out, a little Seafoam regime wouldn't hurt either.
Maybe toss in a new T-stat just for peace of mind.

BB