trouble

[technocj]

Over the winter, I replaced the exhaust manifold and head gasket on my 86, it only has 86k, but the manifold gasket was leaking. I also replaced other parts, including the throttle position sensor. The engine will not start without the throttle being opened now, and is running very rich.
I have removed and adjusted the TPS 3 times and am in the process of tracing down all vacuum hose connections to insure they are correct. I did a compression test, OK. I think I have the TPS adjusted correctly, per the factory manual. My next step will be to remove the upper intake again, and change out the fuel pressure reg. I would appreciate any comments or suggestions. Thanks!!

[foreverly]

It will definitely run rich when the fpr goes. In my experience once the fpr goes its only a matter of a couple of miles until the plugs are completely fouled & are inoperable.

Are you getting any codes?

[timsrv]

No need to split the manifold just to replace the FPR .........especially on a 2wd. I would however advise testing before replacing. At least then you'll know ahead of time whether or not it's needed. Here's a thread where testing & replacement is outlined: http://www.toyotavantech.com/forum/s...sure-regulator. Also, here's a thread regarding the throttle body & TPS. There's a video at the end that shows how to adjust the TPS: http://www.toyotavantech.com/forum/s...-Throttle-Body

[technocj]

Okay thanks, I had checked out the threads as described. I finally got my hands on a gauge and found a solid 40 psi on it. the gauge is from work, and was just calibrated. I'm going to order a pressure regulator. it's killing me to have this van laid up in the summer, i have an 85 for a daily driver, to haul my windsurfing stuff around. Thanks again, good luck to you.

[technocj]

It will definitely run rich when the fpr goes. In my experience once the fpr goes its only a matter of a couple of miles until the plugs are completely fouled & are inoperable.

Are you getting any codes?

It's not running long enough to store any codes.

[timsrv]

Okay thanks, I had checked out the threads as described. I finally got my hands on a gauge and found a solid 40 psi on it. the gauge is from work, and was just calibrated. I'm going to order a pressure regulator. it's killing me to have this van laid up in the summer, i have an 85 for a daily driver, to haul my windsurfing stuff around. Thanks again, good luck to you.

40 psi isn't bad. Does it hold pressure after pump is shut-off? If so I wouldn't waste time replacing the FPR. Tim

[technocj]

Thanks, Tim, I went ahead and replaced it anyway, and I'm still in the same boat. The only clue I have is the fact it will not start or run if the throttle is not held part open. I don't have 100% confidence in the set up I did on the throttle position sensor.My ohm meter does not have clips on the leads, so I used a continuity test light and followed the directions in the factory manual, which seem to mirror the procedure here in the forum. I was thinking of swapping the throttle body from my 85 to confirm the issue, but that's my driver, don't want to wake a sleeping dog!!

[timsrv]

Some problems are just too difficult to troubleshoot/diagnose without hands-on. Some are tough even with hands-on. That being said, this type issue is most often caused by vacuum leak(s). Possibilities are damaged gasket(s), A wire or something else pinched in-between a gasket surface, or hose(s) hooked up incorrectly or not hooked up at all. Based on the severity of the problem I would think it has to be a large leak (so it's probably safe to rule out the small vacuum hoses). Check your throttle body intake hose carefully for tears or rips around the ribbed area. Also check the metal tee that hooks up to the bottom of it. Make sure the air valve hoses that hook to that tee are attached on both ends. Also check the pcv hose/valve & the brake booster vacuum nipple (there on the intake manifold). Tim

PS: TPS issues will create problems but not to the degree you are having. Have you checked the ECU for trouble codes?

[technocj]

Thanks, Tim, I'm thinking the same, I checked the vacuum system today[again] and have not found the culprit. I'm not so sure of the running rich part, those plugs I pulled may have been carbon fouled from before. I also checked the tps on the vehicle, the adjustment seems ok. How critical is the feeler gauge size? I have to use 2 together to get as close as possible to the correct dimension. The plug I pulled today smelled of gas.It fires and tries to run, but won't really start until you crank with the throttle cracked open. I replaced the air intake hose with a new one. I can't help thinking I have something pinched somewhere, I've had that thought since day one.

[cusco-awd]

I hate to ask, but is everything plugged in correctly? I have seen many plugs on other vehicles that look the same and will even fit. I knew a guy who plugged the coil power trans into the ac socket on a Talon. Have you rechecked the timing since the head came off?

[timsrv]

It starts and runs right? Assuming it runs good enough to idle, while idling pull a plug wire. When you do that it should stumble.....maybe even stall. If it does then that cylinder is good. Hook the wire back up & pull another. Do this on all 4 wires. If you pull a wire & find it doesn't affect the way it runs, then that cylinder is dead. If you have a dead cylinder then pull that plug and see if it's wet with fuel. While it's out check it for spark (crank the engine with the base of the plug grounded). If no spark then pull the distributor cap and check for problems. Also check the wire very closely. If it sparks, then you have an injector problem. It could be plugged up but most of the time the injector connectors get messed up. Best case scenario would be #1 or #2 injector connector. If #3 or #4 then the intake will need to be split again. Tim

[technocj]

It does not run enough to diagnose, although the brief seconds I can keep it running by adjusting the throttle, it seems to fire on all cylinders. It is acting as if it has no vacuum, but not running enough to confirm that. I don't see why the ignition timing should be an issue, the distributor was not removed or disturbed. I will pursue the vacuum angle for now. I did a compression test, just to verify that there was not some issue with the installation of the rocker assembly, I may remove the valve cover to further check that. Thanks again for the input, guys.

[cusco-awd]

It does not run enough to diagnose, although the brief seconds I can keep it running by adjusting the throttle, it seems to fire on all cylinders. It is acting as if it has no vacuum, but not running enough to confirm that. I don't see why the ignition timing should be an issue, the distributor was not removed or disturbed. I will pursue the vacuum angle for now. I did a compression test, just to verify that there was not some issue with the installation of the rocker assembly, I may remove the valve cover to further check that. Thanks again for the input, guys.

I was thinking of the mechanical timing. You mentioned you had the head off.

[technocj]

This is not an overhead cam, it is a pushrod motor. Unless I am missing something, the cam timing is not disturbed unless you remove the timing chain.

[timsrv]

Yeah, these are old school engines. No timing components to deal with when removing the head. If it won't run long enough to diagnose, that's pretty serious. It would have to be MAJOR vacuum leak......probably bigger than a pcv or brake booster hose. Or it could be something unrelated to vacuum. Probably too much of a coincidence to have a component failure at the same time as a head gasket replacement. So, that pretty much only leaves mechanic errors to look for (sorry). All I can say is recheck everything. Wish I could be of more help. Tim

[technocj]

No problem, Tim, I always say, ''I thought I made a mistake once, but I was wrong''. I will get back at it as soon as i have time. I wish I had complete confidence in the set up of the TPS. I changed out some old vacuum hoses today, did not find any that were visually cracked. Next will be to inspect the rocker arm for correct assembly.

[technocj]

No problem, Tim, I always say, ''I thought I made a mistake once, but I was wrong''. I will get back at it as soon as i have time. I wish I had complete confidence in the set up of the TPS. I changed out some old vacuum hoses today, did not find any that were visually cracked. Next will be to inspect the rocker arm for correct assembly.

After eliminating every possible problem, other than injectors, I back tracked, removing the upper intake. I read the post regarding removing material from the head surface, and taking a like amount of material off of the valves. I had the head serviced while it was off, by a very good shop, I did not tell him the valves were not adjustable. I visited him today, he does not recall how much he might have shaved the head. I removed the head today.
My options as I see it: ask him to take .002 or .003 off the valves, he doubts he would have taken more off. Purchase a new head off E-bay. What do you think? I was also thinking of removing the fuel injectors and have them checked, and replace the harness,the connectors are not in good shape at all. Auto Zone now sells pigtail connectors for about 7 bucks each. What is the trick to removing these connectors without damaging them?
The van is really in great shape, I can't give up on it, it's a cargo with no side window.

[timsrv]

There's quite a bit of leeway here. 4y hydraulic lifters have a range of around .180" (fully extended to fully collapsed). As long as the lifter operates somewhere inside this range it really doesn't matter. When machinists are aware of these limitations & compensate for large changes, things will typically fall into this "happy zone". Simply shaving .002" - .003" of the deck surface won't amount to much, so probably not worth worrying about. If however there were large changes to multiple machine surfaces there can be issues. For instance, say he grinds .01 off the valve seat, then grinds another .01 off the valve, this will make the valve stick-up about .02 taller than before. Now if he shaves .03 off the bottom of a warped head, this creates a combined .05 change. Assuming the lifter was previously compressed to the nominal .09, making a .05 change still leaves a ~.04 margin of safety. If however one or more of the lifters were already compressed .130 (quite possible) and you make a change that will compress them another .05 or more, you will bottom it/them out and the affected valve(s) will no longer close.

In short, any changes .01 or less probably do not warrant compensation to valve stems. But unless you know how far each lifter was compressed before, it's best to not take a chance with bigger changes.

If you have a new head that's fully assembled, assuming it's been manufactured to Toyota's specs, you should be able to simply install.

On the injector connectors, assuming you got the ones with wires connected, just cut the old connectors off and solder/shrink tube the new connectors onto the harness. Tim


PS: FWIW, I had the valves ground on a Ford 460 once & the machinist didn't compensate by grinding the valve stems. Like the 4y, the Ford 460 also has hydraulic lifters & non adjustable rockers. The end result was having 3 or 4 valves that would not fully close (no compression in those cylinders). Rather than pull the heads back off I cheated by shimming the rocker studs to compensate. It ran fine but it was a hassle. Ever since then I've made it a point to tell my machinist when the heads I bring have non adjustable rockers.

[technocj]

Is there a spec for the head, I will could have the shop measure it. he said he might be able to find the info??

[timsrv]

I'm sure there's an engineering cad drawing or something that gives these dimensions in an archive somewhere. It's not a tool of the trade for a mechanic (not something we would typically need). Machinists may or may not have access to such drawings, but my guess is they don't. When something comes in for reconditioning the assumption is these dimensions are "good enough" (how could you run it long enough to require reconditioning if these dimensions were outside the range?).

A good machinist is aware & will keep track of the material he removes then compensate for it (if required) by removing some material from the valve stems. As assembly mechanics, it's typically not something we need to worry about. In the unlikely event a lifter is bottomed out the valve would stay open & you would have no compression in that cylinder. If it's too loose (very unlikely), you would have a noisy valve train, but it would still likely run okay.

While assembling a 4y I wouldn't worry about such things unless something caught my attention or didn't seem right. On engines with individual rocker assemblies it's easy to check, so I usually will, but on engines with combined rocker assemblies (like the 4y) it's a hassle. Example: a Ford 460 has individual rockers so you can position the engine with the cam lobe at the base and spin the push-rod with your fingers while tightening the rocker nut. When you start feeling resistance (push-rod doesn't want to easily spin) you know the lifter is beginning to compress. Knowing the compression range of the lifter, fulcrum distances, & how many threads per inch on the rocker stud, you can calculate how many more turns before the lifter will bottom out. Ideally the nut should bottom out in about half the turns it would take to bottom out the lifter.

On the 4y all rockers are combined on a single assembly so performing this test would be a PITA. If I were to do it I would probably install a single push rod on the lifter in question, set the cam lobe to the base, evenly tighten the rocker assy until there's resistance on the push-rod, set up a dial indicator on the push-rod end of the rocker, then seat the rocker assembly & measure range of compression using the dial indicator. Ideally you'd want to see around .09, but anything within the lifter's compressible range is acceptable.

If you find out after assembly the valve geometry is outside what a lifter can compensate for, a possible solution would be to have custom length push-rods made. There are companies that do this, but I suspect the cost would be high. If all lifters are outside the range I would consider placing metal shims between the rocker assembly & the mounting posts. Tim