Killemall

Hey guys,

I have 1994 Pickup SR5 3.0L MT 179K miles with a couple of issues that I'm trying to solve.

The symptoms are:
1) Random idle. Most days on a cold start it idles at 1500-1700rpm and eventually settles to 1200rpm. Other days it warms up at 1200rpm and idles at 800 rpm (FSM specs) but then after some driving it goes back to idling at 1200 rpm. Sometimes the engine stumbles when started and struggles to idle around 600rpm with the needle constantly bouncing. Turning off and restarting the engine or driving for a few minutes usually makes the issue disappear.

2) Lack of power. If in 5th gear and going slightly uphill, the engine can't keep up the rpm even with the pedal floored. I have to quickly drop to 4th and keep it at high rpm to keep a decent speed (60mph). When cold the lack of power is more evident. Sometimes it feels like the engine suddenly wakes up and can sustain higher speed with less throttle.

3)When I shut off the engine coolant overflows back into the reservoir. However I have no heating issues. The truck warms up fine and then the temp needle barely moves The radiator was replaced time ago with the thermostat. The cap is air tight. There are no signs of leaks.

4)I have an oil leaking valve cover on the passenger side and drove with it for the last 8K miles. I found here all the DIY to get the job done and it's next on the list.

5)The air valve of the power steering pump is also toasted, and could be spitting fluid in the intake.

So I spent a lot of time searching the forums, and found a ton of valuable info to narrow down my problems but I cant pin point one specific root cause.

1)The random idle could be due to the TPS. I haven't checked it yet since the connector looks brittle and likely to break when I'll try to pull it out. That means I'll need to buy another TPS. Throttle Body is clean and working properly. No vacuum hose leaks. No air bubbles in the cooling system

2)The lack of power and the coolant regurgitation (and maybe the random idle?) could be explained by a leaking HG with subsequent pressurization of the cooling system. When the engine sometimes stumbles upon start up could also be a related symptom. If the leak is there it must be minimal since I don't see any signs of white smoke from the exhaust and the coolant level doesn't seem to drop.

Is the cylinders compression test be the best shot for detecting a leaking HG? Did Toyota fix the HG problem on the 94 3VZE? I checked the recall list for my VIN # and there is no mentioning of the HG recall.

3) Could the problems be caused just by the leaking valve cover or the power steering air valve? Is that too much wishful thinking?

Please let me know your inputs. I'll totally appreciate it.

scope103

Your problems aren't caused by the leaking valve cover gasket (though that could cause other problems, so get it fixed.) They could be caused by ATF injected into the manifold through the idle-up valve, but that's very easy to see. Just pull the two hoses, and see if pink ATF drips out. If not, you're good.

There is no HG recall; there was a special service campaign. You can check with a dealer using your VIN to see if it was done, but even if it wasn't be prepared for at least one dealer to say "you're too late."

Coolant flowing into the reservoir is (usually) normal. That's what it's there for.

Compression test is a good (not perfect) way to check for a HG leak. Easy to do, cheap.

KBAM

My .02,

I don't think you have one specific problem. I think you have a couple small things all contributing to the problems you've described. Not in any particular order, here's what I would start with.

Check for codes. My 91 was throwing codes, both pointed at my O2. Also had strange idle fluctuations. Changed that, idle got ever so slightly better. Did other things (some are below) and it got way better.
Check for Vac leaks
Fix leaky gasket
Check/ Change plugs/wires if old
Compression check
Clean plenum if super gunked up (low on the list)
Dist. Cap and timing

Also I side with scope RE the coolant. I don't see any reason to sweat that.

Lastly, make sure your engine is breathing right. Intake and exhaust. A clogged cat can starve you of power, just as a clogged air filter can.

Killemall

Thanks for the feedback!!

@scope103 Yeah the PS air valve leaks. Im going to replace it this weekend and see what difference it makes

I didn't know that it's normal for the coolant to flow back in the reservoir when you shut off the engine. I guess with the WP running the system volume somehow increases. In any cases you pointed me to the right direction. I realized that I topped out the coolant reservoir tank with the engine running and that's why it was overflowing. Now the reservoir gets full only when the engine is off. So it's all good

That makes me hope that after all I don't have a leaking HG

@KBAM

I'm not getting any codes from the ECU. The O2 sensor was replaced 1.5 yrs ago. Plugs and wires were replaced 5k miles ago. Made no difference
Cat was replaced 10K miles ago


I think I'll try this sequence for now.

1) Fix PS air valve
2) Check again for vacuum leaks
3) Check TPS hoping the connector won't shatter
4) Check Dis cap timing
5) Fix valve gasket, replace PCV, clean plenum (I need to reserve a weekend to DIY this)
6) Compression test

I love this truck. I'll get her to run right!

fdp101452

My pickup runs a lot better with slightly advanced timing. I think the fsm calls for 10 degrees, Ive read where some run 12, but my pickup runs better at 15 so that's where I keep it. I would really check close for vacuum leaks and replace that ps valve. What brand oxygen sensor did you use? I personally don't buy anything but oem, but electronics on our trucks I would forsure by oem......good luck

Killemall

Well, I replaced the PS air valve this morning and drove her 100 miles. I'm impressed by the difference it made. The idle definitely settled down. I checked and upon 9 of 10 starts it sits a 800 per FSM specs. When stopping at a traffic light sometimes the engine still wants to sit higher around 1100 rpm, but I'm honestly quite happy with the improvement No more crazy super high idling.
Overall the truck runs better. Just a tiny bit peppier. The steering feels stiffer too.

I checked again for vac. leaks, and as far as I can tell, there are none.

fdp101452 I'm gonna check the dist. cap next. Then I think I'm gonna tackle straight the valve gasket. I feel I'm on the right track

The O2 sensor was OEM. I also prefer using Toyota parts.

kuzbro

Coolant expands when hot, so the reservoir is also an expansion tank. Thats why you have hot and cold levels. You may already know this, so please dont get offended if so. Working out problems will give you valuable experience and confidence. Your truck looks nice. I miss my 90 with 3.0.


@scope103 Yeah the PS air valve leaks. Im going to replace it this weekend and see what difference it makes

I didn't know that it's normal for the coolant to flow back in the reservoir when you shut off the engine. I guess with the WP running the system volume somehow increases. In any cases you pointed me to the right direction. I realized that I topped out the coolant reservoir tank with the engine running and that's why it was overflowing. Now the reservoir gets full only when the engine is off. So it's all good

That makes me hope that after all I don't have a leaking HG

@KBAM

I'm not getting any codes from the ECU. The O2 sensor was replaced 1.5 yrs ago. Plugs and wires were replaced 5k miles ago. Made no difference
Cat was replaced 10K miles ago


I think I'll try this sequence for now.

1) Fix PS air valve
2) Check again for vacuum leaks
3) Check TPS hoping the connector won't shatter
4) Check Dis cap timing
5) Fix valve gasket, replace PCV, clean plenum (I need to reserve a weekend to DIY this)
6) Compression test

I love this truck. I'll get her to run right!

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