Janos01

You may also want to replace your Cat if you are going for smog/emission inspection. Otherwise, glad that reman MAV is working good.

zytra

Thanks! Pretty happy about seeing some progress.
I thought about replacing the cat but I have yet to check how much that'll cost me.

Janos01

Its about $170 for a bolt on. You can get one at an auto parts store.

zytra

Looks like it's a little more than that here in CA, so I'll try smogging it first.


Regarding my idling (and power) problems I've been thinking and I believe the 3 major things I have left on my list can all be the cause.

The ECT if gunked up could give wrong readings as the engine gets warmer (its cold readings check out compare to the brand new sensor I have).

My leaking brake booster is making my vacuum line readings a tad low (12 in vs 18 in) and could cause idle problems.

And a poorly adjusted TPS could definitely create this type of problems.


The weird thing I can't really explain is that cold the engine seems to be running a little low still, but not as bad as before. However once warmer the engine runs higher than it should around 1100 RPM. And that's with the idle adjustment screw all the way in...

So whatever the problem is makes the engine idle a little bit too high.

I have yet to run some power tests to see if it's better or not.


Also, I forgot to mention but I did take the CSI off to make sure it is sprinkling when cold and it is. I have not tried it when warm but I'll give this a try next week-end.

superex87

you have a vacuum leak. many of the emission devices are vac controlled. One of the vac switches (vsv) may open/ turn on once the truck is warm causing a higher idle. Its all so possible the vacuum hoses are mixed up causing a similar problem. All so pay close attention to which side of the vsv the hoses are attached to because it makes a difference.

zytra

Hey here's an update.

On Saturday I replaced the ECT and I don't think that did anything.

And yesterday I tried taking off the TB and couldn't get any of the 2 coolant hoses off and had nothing to replace them in case I'd damage or cut them. I did take the intake off and cleaned up the butterfly valve. Also checked the TPS with a meter and and it checked out, so I just didn't replace it.

I also replaced the brake booster with one I picked up at a junkyard. Replaced both gaskets and no more air noise in the cabin (I had identified that noise coming from the brake booster as the noise would go away when I'd push the brake). Anyhow that one is fixed.



I am pretty happy with the results of this and last weekend's repairs. Took the truck on test drive and it's got much more power than that it had. My steep street is a nice benchmark as I could never climb it without going into first gear and today I was able to climb in second.

The engine's response also feels much better.

I still have somewhat of a low idle when cold (!600-700 RPM), and high idle when warm (~ 1100 RPM).

Right now timing is back to where it was when I got the truck which is past 15-degree (20?) not sure as it's past the scale..



Another thing is although I clearly fixed a vacuum leak by replacing the booster, I didn't see any improvement on the gauge. With idling at 1100 RPM, I measured a vacuum value of 14"... which is still not great.

So I wanted to ask you where should I take my vacuum measurement from? I've a got a simple gauge with 1/8" tubing and a Tee connector... I thought I could use any vacuum line but maybe that's not right.



some pics, and vid. Any idea which sensor is circled in red in the first pic?

edit: I think it's a TVV that has been repaired... I'll spray this one with carb cleaner to see if there is any leak. and replace it if so





and in the video I was trying to capture the sound that's coming from air filter/MAF area. not sure if that's normal.
View My Video

zytra

Hey guys,

Gonna try to pick your brains a little.

Not any progress this week-end I haven't done anything other than a quick oil change but did a lot of thinking on this low rpm idle issue.


Today, started the truck and the engine idled around 400 RPM for a while, no stalling. Giving it some gas to bring it up but it would eventually go down to 400 or so. It basically kept doing that until the engine got to higher temperature.

Then, once warm, the idle was a little too high, most likely because (I think) I had to have the idle screw quite a bit open not to stall when cold.



My ECT is brand new and checks out fine. I am wondering if I could have a bad ECT harness? Looks like I need to measure the THW pin on the ECU...



Problem 2: I am pretty sure I have a little bit of vacuum leak still. Not sure where from yet, but my vacuum reading confirms that and today I found that pushing the brake still brings the rpm up a little bit. but not as much as before. and one thing for sure is that I cannot hear any air noise like I did before I replaced the booster... but it's possible that I still have a leak there. :/ Anyhow I don't think problem 1 and 2 are related as I did fix most of the air leak and the low rpm symptoms are no better nor worse than prior to changing the booster....



Any idea?

thanks

zytra

Hey guys,

Replaced most of the vacuum lines (all of the ones I could easily access), replaced the EGR which I don't think was bad actually but didn't realize I could test it without taking it off the engine.

And also replaced the oil pressure sender.. and other than for the oil pressure which now works I'm still having this idle issue (low with cold engine, high with warm engine).

And while a couple weeks ago it felt like I had gained some power after a longer run today I can't say it's actually improved.


I still have the TVV to inspect/replace - based on the picture a couple posts above it doesn't look right...
When taking the EGR off last night I noticed the barb fitting (going to EGR valve) on the EGR modulator was chopped off and they had it clamped. Begs the question if the modulator is working properly or not. Not sure how to test it though.
Another thing I need to do is to measure the resistance of the THW pin on the ECU - maybe the harness coming from the ECT is bad or something.

anywhere I look symptoms can indicate several things but the best match is a bad engine coolant temperature...

zytra

so, ECT testing on ECU side checks out fine... so I think ECT related stuff is definitely ruled out. :/

finished replacing most of the vacuum lines, and also some parts on the intake.

I need to finish testing the EGR system. But since EGR opens at high RPM I am not entirely sure that'll get me anywhere... (I manually pulled vacuum on the EGR and that brings the idle even further down almost to a stall)

Damn I'm running out of ideas now. If it was only about that lack of power I would figure it's an old truck but this idle issue just doesn't sound right...

I'm going to take the TB off again and clean up the AIC - gotta pick up some by-pass hoses first (if anyone knows the ID of those hoses that would be GREAT!). And with the TB off I will be able to readjust the TPS stop screw. Either of those could explain the low idle... but won't do anything to the lack of power I think.

zytra

Today I took the TB off, cleaned up thoroughly as well as the IAC valve.
Found that a weird hole plugged with some kind of short sheet metal screw, on the side of the IAC valve. I replaced that screw with a M4 screw plus washer.

No idea what that hole is for, I'm guessing a fix from a PO?

I also rechecked my tps and found that the IDL-E2 resistance would read infinity no matter the position of the throttle. My TPS also had both mounting ears broken so I replaced it and readjusted it properly.

Seems like it's idling much better than better.

It still fills pretty underpowered and I'm starting to believe this may be as good as it's gonna get...

The cat converter on the truck seems to be stock so I think I'm gonna replace it before I take it for smog check.

Once I pass I'll take out the differentials and send them out for regearing... I got the parts already.

zytra

Hi,
quick update... Passed SMOG a couple months ago without any problem, I didn't even try to move back timing to stock.

I had bought a new cat just in cat so I installed it afterwards and couldn't feel any difference. But at least that's done.

Yesterday I filled up the tank and added Red Line SI-1 to try and clean the injectors. I had to drive 300 miles so I figured it was a good time to do that. I got thrown a check engine light quite a few times on that first tank, sometimes for just a couple seconds, and up to a few minutes. I figured it was related to the SI-1 and gunk it possibly cleaned up. I don't know. Not CEL on the following tank. I can't say i see any difference though.


As for the original low idle issue, I can't say it's fully fixed. The stuff I did in november was really the biggest help (that big hole in the air cleaner was really messing with the metered air).

Cold, the engine still idles a tad low (500-600 RPM), and I do get some back firing when cold too. Both idle/back firing go away as soon as the engine's warm.

I'd still like to get that completely resolved though so if anyone has any suggestion I am all ears =]

Cheers

zytra

Hi,

Ever since I use the Red Line stuff to clean up the injectors I was getting some intermittent CEL which I figured were related to junk coming off the injectors and burning, maybe affecting O2 reading or something.

Anyway, that was a 2-3 weeks ago and had a CEL gradually coming back and decided to read the code yesterday.

Got a Code 22 which points at the ECT (which I replaced a few months ago). I took a quick look to check out the wiring and it looked OK. However, just next to it, I found one sensor with a broken wire (single wire sensor).

I am still trying to figure out which one it is.

Here's a pic in case someone's got an idea..

thanks




sensor with broken wire.

JToyota4x4

Zytra, I know you weren't getting a ton of response on this, but I wish you had posted any possible final results! You were doing such a good job updating. I am having VERY similar issues and wish to know the reasons. I've been through almost everything in the troubleshooting sections of the manual. Twice.

People, please post your findings!

Edit: I see you posted in your TVV thread. Thanks for that. The TVV doesn't seem to be my problem, though, and frankly I have good vacuum. 21 in, no variance.