Chewonit64

So here it is. I've searched a bunch and no one seems to have quite the same issue I'm having at the moment. I picked up a 91 P/U awhile back and just recently the engine has been doing some weird things. The engine has about 350,000km on it. It was rebuilt as some point in it's life. It's the 3VZ-E I'm pretty sure. And it's mated to an auto tranny.

For starters, the engine won't idle anymore unless I have my foot on the gas idling around 1500rpm-1700rpm (Guessing the rpm from engine noise as I don't have a tac). That's problem number 1.

Problem number two is it often dies instantly once shifted in drive. I've tried shifting in 2 or Low, but with the same results.

Problem number three is, if it doesn't immediately die when shifted into drive, the engine stutters and is completely gutless. It will then stall more often then not. But once in awhile I'll be able to get going but it's super slow and the engine is still stuttering.

Now the "weird" part. If you can call it that.....
Once I'm moving, say about 30km-40km an hour, the engine runs mint. No problems at all. No power loss. Nothing. But once you slow down, it will stall again.

I'm at a complete loss. (Well, I have one idea. But I'll leave that out as to not influence other peoples diagnosis) It might not be important, but I'll mention it anyway, I've noticed that the ECU makes a lot of fairly loud clicking noises when I drive. Is that normal? I haven't noticed a pattern in the clicking like it only clicks when I brake or something like that. It almost seems completely random.

Any help would be appreciated. Thanks in advance.

Kiroshu

The computer is in the passanger side kick panel. You say the computer is "clicking." Thats not really supose to even happen... If you have a hint of your problem lying there take the kick panel off and give the computer a "slap" while the trucks running. If the performance of the truck or the engine speed changes in any way your computers bad. Check EGR valve it could very well be stuck open and or opening at idle. Unplug vac line to it and see if it helps. Timing? Distributor/Dist. cap? Check timing belt/timing marks.

Chewonit64

Sorry I forgot the mention the first thing I checked was timing. It's pretty good. I'll try the EGR thing tomorrow. I took off the kick panel because I could hear the clicking, and it's definitely coming from the ECU. I've got an ECU from an 89 2WD that had a 3VZ in it. Would there be any problems in tossing it in there just see if it is the ECU effing up?

thook

The clicking would be relays intermittently reactivating. Like Kiroshu said, the ECU wouldn't click. Sounds like to me you're having poor voltage/connections to the ECU or, like Kiroshu said, the ECU may be bad. Is the CEL coming on at all? As in throwing a code? Do you know how to check that?

As far as I know the part numbers have to match on ECU's for them to be compatible.

Chewonit64

No CEL. Not throwing any codes. She just stalls. I went outside and tested the EGR valve. No change. I referenced my vacuum lines to the ones in this diagram, and they seems to all be in the right place.

There does seem to be a bit of a leak around the hose that goes into the throttle body though. So I'll fix that tomorrow as well. If the MAS is getting wrong readings because of that, I'd throw an engine light, no?

Also, how often should the relays reactivate? Because it clicks pretty often. I'd say 10 times a minute or so.

Huge thanks for the quick replies and info guys!

Jeenyus04

a buddy at work just had a timing belt slap on him but before that happened it ran poorly until up to about 3500-4000rpm. When doing him timing belt he found the woodruf key and the crank timing gear both were worn down quite a bit so it had play to turn either way. might want to check that out. Its not back together yet so he doesnt know if that has anything to do with his stumbling problem but theres a decent chance it does.

thook

Theoretically if you had leak at the intake, you'd throw an O2 code, but not always. What hose are you talking about, though? Makes a difference, but any vacuum leak is a vacuum leak. Just depends on the severity.

Depends on the relay, but the ones that I can recall near the ECU.......namely the fuel pump relay (circuit opening relay technically speaking) should only click when it's receiving voltage upon ignition. And, now that I mention that, there's a circuit in the airflow meter (what you're calling the MAS......which is not a correct term, but I know what you're talking about, regardless..) that controls fuel pump relay activation and sustain. If that circuit on the AFM is giving you problems, then you could have the issues you're experiencing.....fuel cutting on and off.

So, what I'd do is confirm you're getting consistent voltage to the ECU and relay from the battery. Use a voltage meter to monitor. Of course, you could just visually check all the connections and fuses/EFI relay to see if there's anything obvious, first. Anyway, if that all looks good, then test the AFM. The FSM covers all of this. See the sticky on the front page with links to FSM's. The link in the second post of the second page is the one I use most often......as do many others.

Kiroshu

^Like he said.

Have you looked at the timing belt marks like i told you? Have tried the computer slap test? Like thook said the only relay over on that side is the "fuel pump relay"(circuit opening relay). It should not be clicking during engine operation if its "clicking" then its very possible theres and issue with the relay and is turning the fuel pump on and off during engine operation. In these trucks theres alot of things that "turn on" the fuel pump. Like thook also went to mention theres acctaully a micro switch in the Air flow meter. When the "flapper door" in the air flow meter opens the fuel pump cuts on thats why in a toyota the fuel pump only comes on durning "cranking time." Check that relay though. THeres an OHM test for it that the FSM will show you and you can also try energizing it. Check grounds. Body grounds/engine ground/battery termianls <-- Clean them.

NewOldRunner

I had this happen to me after working on my truck one day, my recomendation is that you,

1) Look to see that the MAF wires are still connected ( that was my problem after i was working on the airbox)

2) Ensure there is no water in the MAF

3) Start truck and be happy

locked&rollin

sounds to me like the egr valve is stuck open. this condition is more noticable with an automatic. it is creating a major vacuum leak (will not idle, dies when foot is lifted off pedal). how did you check the egr valve? will not necessarily set off check engine light.

Chewonit64

The clicking is coming from the ECU itself. Not from something near it.

Timing marks are spot on. And I tried kicking the ECU while driving to work today. No change other than it's hard to drive and kick at something on the passenger floor. Hahaha.

Definitely connected.

I removed the vacuum line running to it. No change in how it ran. Then I ran a separate vacuum line from another spot on the intake to the EGR valve. This made the engine die almost instantly. So I'm pretty sure it's working.

Team420

Nope...I am currently running the ecu from my 93 auto, in my 91 p/u 5spd, with no cel codes. I highly doubt a 5spd ecu would work in an auto, but it does work the other way....


My bet is on the egr, or the intake hose going to the throttle body, the conditions you mentioned, point me directly to vacuum leak, vacuum leaks are much more noticeable at idle, and would contribute to major power loss on takeoff.

locked&rollin

what you need to do is make sure the egr valve is closing at all times. if the egr hangs up just a little you have a vacuum leak. when in good running condition. no dying, disconnect and plug egr vacuum line. drive until you are comfortable that it is or isn't the problem. good luck( it needs to open and CLOSE properly). you should be able to drive this way for a few days if it has an egr temp sensor without setting a code. if it does disconnect battery for about an hour, to shut light off.

thook

Well, if it's definitely the ECU, then there's a problem. Potentially it's not getting constant voltage or it's just going out. Yeah, the EGR could cause the same symptoms that you're seeing, but the EGR wouldn't explain the clicking.

I hate to persist and ask this question as I don't want to offend, but are you positive it's the ECU clicking?

thook

Shows what I know about that...lol. I do know a 5spd ECU will not operate an electronically controlled transmission, though. You can't even hook up the wiring harness to it. The terminals just aren't there.

Chewonit64

Will do. I know it opens, but whether it fully closes is another issue. I don't have time tonight to look at it, but maybe tomorrow. Is there a way I can easily verify it closes without taking it off the engine and inspecting it? No problem. It's one of thing that you think can't/should never happen. But it is from the ECU. I didn't hear it click even once today, but I only drove to work and back. (About 30km round trip) I fixed the line going into the throttle body. Used duct tape for the moment as no one in town had one. Had to order one from the dealer. And it doesn't stall when shifted into drive now. The idle problem still exists, and the engine shakes a lot. To a point where it shakes the whole truck until about the same RPM range as before. There is no loss of power though.

thook

I suppose, then, checking the EGR is in order. If there's no problem there, then we'll all start looking at other possibilities, eh?

Kiroshu

Unless its stuck open. Unplugging the egr vac line should show you whether thats the issue or not. Now if it is possibley stuck open... have you tried tapping on the egr valve with a hammer while the trucks running. Ok i just remember a post you said you plugged another line to the EGR and it shut almost killed the engine? this means the egr is not stuck. Have you tried to use a lil'vacuum pump on the egr to see if it will kill the engine? Its almost the same as you did with the other vac hose but a more 100% confirm. If it cuts off while you pump the vac pump into the egr the egr is working. Well if your sure the AFM is good timing and tune-up parts are good... (have you checked plugs and their gap?) hmm.. The computer slap test is not a 100% confirm test as a computer may be bad without this test showing but if it were to change then it would be accuate. There still may be a vac leak somewhere your not tracing... Whats the timing "set at?" How far is the idle screw turned in? Sparkplug wires good? Intake manifold leaking? Try spraying carb cleaner around the intake plenum and manifold if the engine idles up while doing this then theres a leak and needs intake/plenum/manifold gaskets. You can do this with any vac leak but be careful of exhaust...(Flames) Is this problem noticeable at hot,cold, or all temps?

Chewonit64

Haven't check the plug gaps. But this seems like an unlikely cause do to the fact that the engine runs mint above a certain RPM. A fouled plug wouldn't work better at a higher RPM. I'm going off the basis that because each plug has good spark, the wires are in good enough condition. ;I'm not entirely sure how many turns out the idle screw is. It's just below flush with the hole it's screwed into. What is a good starting point, in say turns counter clockwise, from it being completely bottomed out? And the problem occurs through all temperature ranges.

betelnut

I vote for thook's suggestion. This explains both the clicking and the cutting out.