94 LE almost stalls when stopping, stutters when accelerating

[ridgerunner55]

I'm new to this forum but I posted this at Toyota Nation and the Yahoo Previa board as well.

I have a 1994 LE, non S/C, 2DW, with about 216,000 miles. I have been working on it for the past 2 months with no improvement.

The van starts fine (usually on the first crank). It idles fine. When I drive it it runs well, but when I come to a stop the RPM drops and when I accelerate
it really sputters and almost stalls for the first few seconds. When I get back to 35-40 mph it runs fine again. It does this whether it's cold or warmed up.

If I lift off the gas while cruising along I can hear the RPM drop , bottom out, then go back up to "normal" idle speed.

I tried shifting to neutral as I came to a stop and it did not do it (stutter) when I stopped, but I think it's because the RPM increased as I put it in neutral
to offset whatever else is going on. I'm not really sure, though. Is there a possible drive train issue?

Here's what I have done:

- replaced rotor, dist. cap, all plugs and plug wires
- all plugs are getting spark and all injectors seem to be working (pulled wires and injector plugs off one by one while idling)
- replaced coil
- replaced TPS sensor
- checked TPS wires to ECM, both resistance and to see that they would carry a current (used van's battery and a tail light bulb)
- replaced fuel pump and fuel filter
- replaced air filter
- checked snorkel for any leaks (none found)
- pulled off throttle body and cleaned (it was pretty clean, as I had done this about 2 years ago)
- pulled off and checked EGR valve (about 1.5 years old) and checked all lines going to it
- pulled off and cleaned IAC valve
- replaced engine coolant temp. sensor
- replaced upstream O2 sensor
- replaced both SAD bushings (the front was terrible, with 4 of the rubber parts completely torn loose)


Any parts I replace now would be just guessing, and they are starting to become more expensive. Here's what is left on my list to try:
- fuel pressure regulator
- volume air flow valve
- cold start injector valve
- injectors
- intake manifold gasket
- check compression (maybe bad head gasket?)
- TPS wiring harness
- knock sensor

Anyone have any advice or suggestions?

[ridgerunner55]

Since my last post I took the oil cap off while it idled and the RPM immediately dropped, so PCV valve and hose are probably okay.

I took it out driving and I tried shifting to neutral as I came to a stop and it did not do it (stutter) when I stopped, but I think it's because the RPM increased as I put it
in neutral to offset whatever else is going on. I'm not really sure, though. Is there a possible drive train issue?

When I pull the fuel pressure regulator vacuum hose off the RPM picks up a little (while idling). Someone suggested pinching off the return line to test if the regulator was operating at too low pressure but gas immediately sprayed out of the hose connection to the regulator, so I stopped that.

I did notice a small gas drip from the regulator and I pulled it off and checked the o-ring. It was a little rough so I went ahead and ordered a new regulator. It's not a smoking gun and I don't expect it to fix the problem, but I needed to fix the leak.

I also checked the whole air intake system again for leaks but found nothing.

[ridgerunner55]

Update:

I replaced the fuel pressure regulator; no effect.

I eliminated the cold start injector as a cause:
- I unplugged it and drove around; no effect
- I took it out, made a plug for the hole in the manifold, sealed off the fuel line, and drove around to make sure it wasn't leaking into the manifold; no effect.

Someone on the Yahoo Previa forums sent me a used VAF meter to try out. If that has no effect I still need to check the valve lash.

Other items still on my potential list:
- replace plug wires (maybe the set I bought is bad?)
- replace EGR valve. It's only 1.5 year sold but who knows.
- replace the IAC valve. Cleaned it and it seemed to function okay by maybe it's bad.
- replace TPS wiring harness
- coil ignitor

[timsrv]

I've been following this thread with anticipation. I wish I had something definite to help you solve your problem, but these type of problems can be tricky. If nothing else I can possibly help rule out some things. I wouldn't expect anything on your "to do" list to cause this problem except maybe the igniter. When I read your initial post I was thinking this could be the problem but then again, who knows. Another possibility (although rare) could be the ECU itself.

Another thing I'd check for (if you haven't already) would be look for oil inside the distributor cap area. Due to the sideways distributor, if the lower shaft seal fails it can allow oil to leak into the distributor and this will cause driveability problems. Were there any trouble codes stored in the ECU?

[ridgerunner55]

Someone loaned me an igniter and I'll swap it today to see.

No oil in the distributor (I pulled it off). I changed the o-ring about 2 years ago.

No codes showing either.

[ridgerunner55]

Update:

I swapped the igniter and ir had no effect.

I had several suggestions to replace the aftermarket plug wires and dist. cap with OEM, so I ordered them and replaced them plus the rotor. It had no effect: the van still stutters and chugs sometimes when I stop and then start accelerating again.

It seems like there are two problems: the stuttering on acceleration and the occasional full-blown meltdown when it will barely run and belches smoke and fuel vapor out the exhaust. The two may be related to maybe a bad injector. I would like to replicate the second issue and then pull the plugs to see if one or more are wet, but I have not been able to get it to happen in the last few weeks.

[ridgerunner55]

Another update:

I don't know if this is positive or not, but after driving the van for a few weeks I got a CEL and two codes:

43 - Signal to ECM from starter (not supposed to be something to worry about), and the infamous
71 - EGR system

The EGR valve is about 2 years old and has about 8k miles on it. I have pulled the throttle body twice and cleaned it and the port from the EGR, two years ago when I put in the EGR valve and in the past few months (it was very clean that time). The EGR vacuum modulator is also new. The EGR tube to the back of the engine was pulled and it is clean as well. I cannot find any vacuum leaks. When I do the suction test on the EGR valve while idling it does stall.

Any suggestions?

[jkaustria]

hi. any updates with your previa? i am actually following your topic. i have the same problem. and i even printed everything that you did and showed it to my mechanic. but unfortunately, it still has the problem. it stutters when i am about to stop. on high speed, i feel that it doesn't give the power that i need not unless i feather the gas pedal.

things we did:
change spark plugs
cleaned throttle body
check and cleaned EGR
replaced IAC valve

still nothing changed. i just noticed that after having the stuttering and engine almost dying, i turned off the engine and start again, stuttering is gone. then it will appear again after a few miles.

[ridgerunner55]

All the things I have done have improved it a little. It no longer stalls when I stop. I was driving it daily until the battery started to give me problems. I am replacing the alt. brushes to deal with that.

My symptom now is that on an ordinary drive to work, about 11-12 miles, it will stutter on acceleration about 25% of the time. As it picks up speed it goes away. It seems to idle fine and cruise fine.

One time it started to run really rough and put out gasoline fumes from the exhaust. The only way I got it home was to baby the accelerator at stops to keep the revs up. I should have pulled the plugs when I got home because I suspect a fuel injector was stuck. The fuel injectors are one of the few things I have not swapped, mainly due to the cost (about $60 rebuilt and about $140 new, each).

If I fix the charging issue I will go back to driving it daily. I plan to get 2 rebuilt injectors and swap them out 2 at a time to see if that improves anything.

If that does not work and the CEL code 71 returns, I may tear apart the whole EGR system and throttle body, and maybe pull the intake manifold to clean everything out.

[timsrv]

I'm not sure where you're located, but we have a shop (Dr. Injector) in Gladstone, OR (a suburb of Portland) that will clean & test injectors for $20 each. He tests them 1st, documents results, cleans, then tests again. Assuming they pass he will return them shiny clean with new o-rings installed (o-rings alone can cost this much). Here's a link to a thread where we have discussed this: http://www.toyotavantech.com/forum/showthread.php?522-Other-parts-to-replace-while-replacing-Head-Gasket (scroll down to post #15). If you're not in this area you can put the injectors in a box and ship them to him. He will work his magic then ship them back. His turn-around time is usually pretty fast. Tim

PS: Keep in mind the thread I linked to above is a discussion about 84-89 vans. General information given there still applies to Previas, just disregard part numbers etc.

[edcutah]

I found this thread interesting as I have a 94 non-supercharged LE Alltrac. See my thread at http://www.toyotavantech.com/forum/showthread.php?1316-My-tired-94-LE-AWD-Prev-non-SC-with-HG-and-likely-other-overheating-complications

I have to be suspicious that you are experiencing the initial failure of your head gasket. Here is why I think that and I admit there is an inconsistency with your story and and potential symptoms. Let's presume you have a beach in your water jacket, not a bad one, but a breach non-the-less. You start up, the car is cold, the cooling system is not under pressure, you drive a bit and get up to normal operating temperature. The cooling system is now under pressure. When you get off the gas, you obviously have much less compression, so little in fact that coolant enters a cylinder, enough to mess with combustion, and present you with your misfire symptoms.

The inconstancy is as follows: I would expect a bit more trouble when you start as I would think you run slightly rough until you had full combustion in the effected cylinder. I might expect you to have more trouble starting if you started your car and only ran it for a couple of minutes and stopped it, let it set for five to ten minutes and try to restart. Sluggish starting would support the head gasket theory.

If you haven't done so, I would access the status of your thermostat and monitor your coolant level very carefully. Even if you're not blowing water vapor, upon starting the car, put your hand to the exhaust to access the amount of water vapor in the exhaust and see if it changes when the car warms up. In my experience, it doesn't take much of a breach to cause your symptoms if the breach is in the right spot, so you might not notice a change in fluid level in a short period.

For my prev, water vapor decreases in the exhaust as the car warms.

I've had similar symptoms as of your. Maybe not the full-on near stall out. But sometimes a new breach will reveal itself in the manner you describe where the idle is a bit shaky. For me it doesn't last long as the stuff I use to fix the head gasket fixes it on the fly.

All I'm saying is based on what you described and from my experience with mine, your Prev is about the right miles.

As for my prev. Note the last post I made to my thread about replacing the radiator. I have 500 miles on it since and have yet to overheat.

[jkaustria]

All the things I have done have improved it a little. It no longer stalls when I stop. I was driving it daily until the battery started to give me problems. I am replacing the alt. brushes to deal with that.

My symptom now is that on an ordinary drive to work, about 11-12 miles, it will stutter on acceleration about 25% of the time. As it picks up speed it goes away. It seems to idle fine and cruise fine.

One time it started to run really rough and put out gasoline fumes from the exhaust. The only way I got it home was to baby the accelerator at stops to keep the revs up. I should have pulled the plugs when I got home because I suspect a fuel injector was stuck. The fuel injectors are one of the few things I have not swapped, mainly due to the cost (about $60 rebuilt and about $140 new, each).

If I fix the charging issue I will go back to driving it daily. I plan to get 2 rebuilt injectors and swap them out 2 at a time to see if that improves anything.

If that does not work and the CEL code 71 returns, I may tear apart the whole EGR system and throttle body, and maybe pull the intake manifold to clean everything out.

thanks for the reply. will wait for your update.