1994 Es300 Sudden Engine Hesitation

[ukyo]

Hi all. First post here. Not really a Lexus owner (closest in our driveway is a 1997 Toyota Supra TT), but I am good friends with one. Any way, on to the story...

1994 ES400, automatic tranny, 168K miles. My friend was about to make a right turn on red (barely slowing) when he noticed a vehicle approaching the intersection that would have knocked the crap out of us. He slammed the brakes on and the car cut off. It took a second to realise what happened, but soon he shifted to neutral and tried to crank it. The car would crank then die immediately. We ended up rolling back down from the intersection and sitting in a parking lot while I was trying to figure out what was wrong.

We popped the hood and the first thing that crossed my mind was the MAS. I unplugged it and replugged it hoping for just a bad connection. No dice. The car ran the same (meaning not at all). I then unplugged the MAS and had him try it. The car died even faster. Initial findings to me were the MAS was good. I then started looking for vaccuum leaks. I didn't see any. Engine was really hot from just shutting off, so I couldn't prod around as much as I would have liked (not to mention being in work clothes at the time, and not wanting to get too filthy). The car sat for a while before he tried to crank it and suddenly idled OK out of the blue. We hop in and as soon as he puts it in gear it dies again. :cries: We wait a few minutes, he cranks it, holds the throttle open a little, and shifts to neutral as fast as possible. The car tries to die but doesn't. From there he basically does a low RPM neutral drop and we get moving. The car runs llike crap, but gets him to the Lexus dealer where he drops it off.

He gets a call a hour or so later stating that his MAS is bad and that it's going to cost $1,000 + parts and labor. We talk it over, and decide to get the car back and change the MAS. $240 for the part, $0 for the labor. Steal of the century...

We get the MAS, get the car, swap them out, and while doing so I notice a gaping crack in his intake pipe close to the throttle body. With nothing better to use, I wrapped the crack with clear packing tape as a test. The car ran good for a few minutes, then began to run like !Removed! again. Expected behavior for a car that is being held together with packing tape, I'm sure.

I take the car home with me and hack the pipe in half, take one of the stock intercooler pipes from our Supra and cut it down. I slide it in to the intake pipe and clamp both sides of it. Seems air tight to me, so I put it back on the car and test drive it. Runs fine the night I test it, on a drive of about 15 minutes with various RPM load.

I drive it back to work the next day and it hesistates a little in the 2K RPM range once, but clears up and runs OK the rest of the way. Upon getting to work I put it in reverse and cut the wheel to get in to a space and it almost dies on me, but recovers before the engine shuts off.

Over our lunch break he took the car out and it ran fine initially, but once shut off and recranked it died as he backed out of a space. It then hesistated badly at roughly 2K RPM as he ran some errands.

I've done a lot of research here, and thanks to you guys I have a lot of things to check. Some I suspected to begin with, others I would not have thought of (EGR valve cleaning / replacement, dist. cap / rotor, etc.). We think maybe my air tight fix is not so air tight. Replacing the intake hose is going to be one of the first things we try. I'm also going to change the plugs and wires (wires??? Do these cars have wires or coil on plug like the Supra???). From there I was going to move to the fuel filter. From there... well, from my searching I've built a nice list.

* Vaccuum leak -DONE?- found one, could be more

* Clean / replace MAS -DONE- replaced with new unit, maybe uneeded

* Remove EFI fuse for "quite a while" then put back in

* Check CAM timing

* Plugs & wires

* EGR cleaning (filter / contact area)

* Full Sea Foam treatment

* Dist. cap & rotor

* Fuel filter / silt filter in fuel tank

* Bad gas???

* PCV Valve / grommet

Any advice on what I should try first / last? Anything I may have missed? If you made it this far, thanks for reading this loooonnnnnggg post. Any help is appreciated since this guy has an hour commute one way, and this car really needs to be there for him.

[Toysrme]

1mz-fe enigne is coil on wire ignition. There is no distributor to check/replace. (Nor is there timing to fool with)

I normally scoff at plug wire changes. If they're not grounding out, and the electrodes haven't been damaged when changing spark plugs. They're simply not an item that typically becomes a problem. Cheap replacement wires suck when used on Toyotas, and OEM wires are almost as expensive as the big wires found in "performance kits".

In order I would check:

1) More vacuum leaks (replace, or make a new air tight hose)

2) Clean IAC valve

I think the problem lies in there. I've hacked a million different intakes on my engine. Anytime I would let one get loose and leak between the AFM and TB (in his case MAF and TB) they will OK run as rpm rise, but nearly die out at a slow speed, if they run at all.

3) Clean EGR valve

Seafoam won't fix this (Tho I advocate it's use along with spraying a 16oz bottle of water directly into one of the holes before the throttle body,. I am one of Seafoam's strongest supporters, It is awsome at cleaning the heads, valves and such, but just a spray bottle full of water get's more carbon out of the combustion chamber than even seafoam can.)

The fuel pump and filter are OK. The engine is getting enough rpm to rise.

It wouldn't be bad gas. The ECU can pull a ton of timing on 1mz-fe's when need be.

PCV - a problem at high rpm. Blow-by & crank case pressure rises with rpm. It wouldn't run at all at 2000rpm if it couldn't idle because of a PCV problem. Grommet is fine.

[SKperformance]

fyi

the 94 is straight coilon plug

the 95/96 and later changed to the rear banks using plug wires with a seperate coil

[ukyo]

Thanks for the replies! I was afraid it was going to be coil on plug (i.e. NOT cheap, if that is the problem... and I doubt it is...).

I'm going to convince him to either buy a new MAS to throttle body intake hose or build one out of metal piping with silicone couplers. I guess if we look around, there's probably an aftermarket intake setup that matches that description already produced.

Playing it back in my head I think I know exactly what happened now. His "dog bone brace" is busted (to me it looks like an engine roll damper, located on the left of the engine bay when facing from the front of the car). The core of the mount is just bouncing around like crazy even at idle. The Lexus dealer also noted his front engine mount is busted. In my mind, when he slammed on the brakes, the engine rocked forward violently. Since the intake hose is old, heat cycled, brittle, and firmly attached between the throttle body and the air box, it tried to flex as designed but cracked instead. From there all the symptoms we experienced were from that one rather huge crack.

I'm still going to talk him in to a Sea Foam treatment, and I'll try the water method as well. When you say "holes before the throttle body", do you mean where the resonator or oil blow by tubes attach to the intake pipe, or something else. Bear in mind I've only looked at the engine bay twice now, so I'm not too familiar with it from memory just yet.

Again, thanks for the replies. I'll let you guys know what ends up being the fix.

[SKperformance]

BTW i forgot to add you made a great first post ,very detailed ,i love it.

I would clean the maf with a cotton swab and throttle body cleaner.

I had the same problem once after a highway downshift ,all of a sudden it stubbled and ran like hell.

As soon as i cleaned it 2 weeks later it ran like new again.

[Toysrme]

Ya the oil blow by for the front head. Un plug it and just shove a squirt bottle (Like windex) into it so it doesn't leak and can run.

You'll hear the rpm's lowering the faster you squirt.

SK had a great idea about cleaning the MAF.

You can get some metal exhaust pipe at Autozone for like $5 & cut it to fit. Then turn around and go to lowes and get their rubber pipe couplers. (It's a rubber section, with two hose clamps installed on it) They cost a couple dollars a pop. They stand up to low pressure turbo's so it shouldn't have a problem leaking if you seal it well for him.

You can repair the dogbone mounts for about $15. I did mine with some of the 3M poly window sealer. (You can't go and use polyurathane like liquid nails. That can't take the vibration. I know, it didn't!) You bust the rubber out and put the new stuff in. The warning I have about it is you can't put the mount back in for at least a couple of days. They won't be fully cured in the middle until like two-three days.

It's a good friday project, to replace on sunday evening/monday morning.

Otherwise my mounts were all in great shape. I drove around (easily) without my dogbone for a few months without any problems. So if his mounts are in good condition, he shouldn't be damaging anything if he goes easy on it for a few days.

Ditto on the good first post. It's nice when people research first, then ask question.

[ukyo]

BTW i forgot to add you made a great first post ,very detailed ,i love it.

Thanks. I've got a lot of experience with Supra, 3000GT, and DSM forums. I had a feeling the same general practices would work here. :)

I would clean the maf with a cotton swab and throttle body cleaner.

I had the same problem once after a highway downshift ,all of a sudden it stubbled and ran like hell.

As soon as i cleaned it 2 weeks later it ran like new again.

←

When you say "2 weeks later it ran like new again", do you mean it ran poorly for two weeks and then got better? I ask because we have a new (remanned) MAS err, MAF (in the 3/S world it's a MAS in the Supra / Toyota world it's a MAF... I get confused... lol) on there along with a new intake pipe that he purchased from the dealer today. It's still running poorly. We put the new hose and old MAF on there first. It ran OK for about 5 minutes, then the hesitation returned. We pulled over and put the new MAF in there, and within 2 minutes of cranking the car it started hesitating again. Note, we did pull both EFI fuses for about 5 - 7 minutes after installing the new hose and old MAF.

Could it be that we have it fixed, and it's just going to take a while for it to return to normal from the trauma? Is that possible???

Ya the oil blow by for the front head. Un plug it and just shove a squirt bottle (Like windex) into it so it doesn't leak and can run.

You'll hear the rpm's lowering the faster you squirt.

SK had a great idea about cleaning the MAF.

Cool. We'll run the water through there once I can get him to bring the car down to my place. I don't want to be doing all this in the parking lot at work, ESPECIALLY when we Sea Foam it.

You guys think there's a good chance the old MAF is OK? He's got 30 days to return the remanned unit he bought. The car ran the same with both MAFs today, so you think maybe cleaning the old one will save him $240ish on this issue? I'm willing to give it a shot...

You can get some metal exhaust pipe at Autozone for like $5 & cut it to fit. Then turn around and go to lowes and get their rubber pipe couplers. (It's a rubber section, with two hose clamps installed on it) They cost a couple dollars a pop. They stand up to low pressure turbo's so it shouldn't have a problem leaking if you seal it well for him.

That is the route I would have like to have taken, but he already got a new OEM hose from the Lexus dealer ($63 if anyone is curious... they had *10* in stock). Even the parts guy was in shock. He put me in hold and went and checked the stock because he couldn't believe they would have that many intake hoses in stock.

You can repair the dogbone mounts for about $15. I did mine with some of the 3M poly window sealer. (You can't go and use polyurathane like liquid nails. That can't take the vibration. I know, it didn't!) You bust the rubber out and put the new stuff in. The warning I have about it is you can't put the mount back in for at least a couple of days. They won't be fully cured in the middle until like two-three days.

It's a good friday project, to replace on sunday evening/monday morning.

Otherwise my mounts were all in great shape. I drove around (easily) without my dogbone for a few months without any problems. So if his mounts are in good condition, he shouldn't be damaging anything if he goes easy on it for a few days.

Ditto on the good first post. It's nice when people research first, then ask question.

←

I'll tell him about fixing the dog bone and see what he thinks. I'd like to do it, as it will give me some experience working on mounts so hopefully in the future I can hollow out my stock VR-4 mounts and make more firm inserts for them. Win for him, win for me. :)

Thanks for the compliments on the first post. It pays to research!!!

Oh, and if the 2 week period goes by and the car is still acting up, what next? We'll be doing the water and Sea Foam regardless, so if that too fails, then clean the IAC? How would that affect anything apart from the idle (car seems to idle OK now that the gaping hole is gone)? I read on one of the threads that the EGR can cause symptoms like this, and cleaning it solved them. Possible???

[Toysrme]

If it's still crazy when he get's the new pipe on, I would clean the IAC first.

Awww man have some balls, seafoam it at work!

I swear at some point in the future I will put some in my washer tank so the water injector I have will squirt atomized seafoam into the engine. Smoke screen! It'd make for a funny video hahahaha!

[SKperformance]

smoke screen ,you are too much ,but it is worth an idea i would like.

P.S. i am planngin on mounting a pinhole camera with mirror motors and a washer nozzel connected to a certain fluid for precision sniper shooting, but enough of my madness.

My car ran perfectly immediatly after i cleaned the MAF , it was 2 weeks i took to figure it out after changing plugs and fuel filters for no reason.

Put it this way if the problem is with the IACV all you have to do to keep it from shutting down is press the gas and it will rev until it warms and no longer needs the extra air for cold/hot starts.So if pressing the gas pedal makes no difference i wouldn;t bother with it although it is always agood part of maintance.

[ukyo]

Just an update...

The car is running much, much better. He was supposed to have Sea Foamed it over the weekend, but not being mechanically inclined, he chickened out. So basically all that has been done to it is a new MAF and a new stock intake hose. He said it'll still hesistate briefly at times, but it's getting less and less frequent. He also noted that it only happens at cruising speed.

So that brings me to this question:

In my experience with EGR, the largest impact it has on the system is when you are partial throttle cruising. Is it possible his EGR is somehow clogged or otherwise messed up, and is causing the hesitation he's getting now?

[SKperformance]

clean the throttle body it may be the egr and/or acoustic carboned up

[Toysrme]

The long term fuel trims take a while to be set in OBD-II.

If it's getting better every time he drives it enough to warm the enigne up, the LTFT's are being adjusted.

Pull the EFI fuse, count to one and put it back in. That'll clear the fuel trims and make it re-learn them.

It takes the ECU less time to start fresh and trim, than it does for it to re-program old trims that are on the opposite side of how it's being trimmed. (vacuum leaks lean it out some what - the cracked intake hose accomplished that!)

SK one of out other drummers in high school did that with his pimp wagon. Turned one of his four washer nozzels backwards and bored it out.

FYI an 80lph fuel pump in the washer tank will squirt a thick stream of water about 20-25' out of 1/4" ID! ;) Just a thought hah!

[SKperformance]

water ?

not viscous enough for my idea