OT: '90 Toyota Camry stumbling/bucking

[sargentrs]

Ok, I know it's an import but it's my DD while my truck's being rebuilt. 210K miles on a 2.0 four banger. Was running great until about 2months ago then started stumbling under load, i.e. uphill with declining rpms. If it was my bump I'd say it was a timing/vacuum advance issue. But with this fuel injected, computer controlled, sensor overloaded stuff, I don't have a clue. Been getting steadily worse until it almost left me stranded last week. Will run great at 2000+ rpm but let it drop below that and it starts bucking and stumbling. Downshift and punch it and it runs good. I'm thinking fuel pressure, air flow meter, or, heaven forbid, leaking intake valves. My plan is to install a fuel pressure gauge at the injector manifold and verify good fuel pressure to rule that out. Pull the plugs and check compression to rule out the valve problem. And I've got a diagnostics test to check out the MAF. Any other suggestions/comments/advice? I really need this car and can't really afford to buy another POS right now. All advice is greatly appreciated.

[basketcase0302]

And I've got a diagnostics test to check out the MAF.

Do you mean an OBD II tester? That toy should have OBD II controlling the car don't it? You can take it to discoont or autozune or most any other parts store and they'll hook up diagnostics for free, (in hopes of selling you the part).

[DuckRyder]

Is the check engine light on?

Don't overlook the basics, plugs, wires, coil packs (or cap/rotor/coil) (I am not up on Toyotas)

[sargentrs]

Thanks Jeff. Na, it doesn't have an OBD II port. I have to check voltage and resistance at the ECU where the harness plugs in for those kinds of checks. Besides, it doesn't run good enough to even make it to the parts store.

Thanks Robert. Yeah, I was going to check out the plugs, etc, while I was running a compression check on it.

The check engine light is not on. I MISS MY TRUCK!

[evan_flatt69]

I might try buying a can of Mass Airflow Sensor cleaner. If that doesn't fix it it definitely wont hurt.

[flyboy2610]

Sounds like a fuel pressure issue to me.

[sargentrs]

That's a good idea, Evan. Thanks!

Flyboy, that's my first point of troubleshooting. Bought a fuel pressure gauge yesterday, now just gotta figure out where and how to hook it up. The manual shows where on the fuel rail but it's a banjo bolt style so I gotta figure out how I'm going to to do that. I was poking around yesterday and noticed that the EFI main relay in the engine compartment fuse box is really hot. That circuit operates both the fuel pump and the air flow meter so I'm going to replace that first, then check fuel pressure. Thanks!

[NM5K]

I bet the engine is super carboned up. We had a 92 Camry that had this problem.
What will happen is the carbon heats up when the engine warms up, expands, and then
keeps the intake valves from fully closing. The carbon snowcones behind the valves.
Then when it cools off, the carbon shrinks back down, and the engine will run again.
If it always starts and runs normally when cold, but gets gradually worse when hot, I'd
be considering this. Also... When this happens and you lose compression in some of the
cylinders, when you try to start the engine, the starter motor will sound weird. Often a
tad faster, and will be uneven if only some of the valves are not closing. If they all open,
the starter will turn faster than normal, kind of like if you removed all the plugs.
This is just guessing, but I suspect when you get a fuel pressure gauge hooked up, all
will be normal. It was in our case. I actually used a long hose, and had the gauge in the car
with me so I could watch it while I drove.
This will happen the fastest when the engine is under a heavy load, and going up hills is
one of those.
The cure is to decarbonize the engine. But adding a bottle of techron to the gas will
start eating it up. Just takes quite a while. When I had to do it, I added techron to the gas,
but I also fed it into the intake via a vacuum line to speed things up.
BTW, I think it's fairly normal for that relay to feel hot.
This may not be the problem, but I would keep it in mind as those engines are prone to
have it happen.
As far as the pressure gauge and banjo connector, I had to make an adapter using a bolt
with a hole drilled in it. Or I think that's what I did anyway.. I should still have it somewhere.

[sargentrs]

Thanks for that explanation. Replaced that relay and i's worse now. Idles fine but the second I put it in gear, it dies. What are you calling "techron"?

[NM5K]

Is that with the engine totally cold, or warmed up?
If it's carbon, it will usually start and run OK until it heats up.
Techron is made by Chevron. You can get it at any auto parts,
wal-marts, etc..
It's usually called Techron Concentrate Plus I think. Black
plastic bottle with skinny necks to fit in gas filler restrictors.
It comes in two sizes.
As far as a carbon buster you can buy, it's about as good as
anything.
It took me a week to get all the carbon out of the one we had.
And that was feeding it through the intake every once in a while
in addition to the gas.
Also.. One thing about Techron.. It actually does the most good
when the car is hot, shut off, and heat soaking.
It does very little while driving around. So it's faster to do many
run cycles than to just go out and burn a tank of gas in a few cycles.
I'd spray cleaner, start it up, let it get hot and finally start to die out,
and then I'd let it sit and cool off an hour or so.. Over and over..
After a week, it was pretty much totally clean, and the car ran
normal again.
If you are cutting out when it's totally cold, that *could* be a fuel
pressure issue..
But it wouldn't take ours too long to get hot enough to flake out,
when it was really bad. It would eventually totally flake out, and
you would be kaput until it cooled off again. Which could take a
while..
if you are in a hurry, you could take it to a shop that has a motorvac
machine, or they can use flush kits, etc.. Assuming that's what it is
anyway.. But being cheap, I just did it myself the slow way.

[sargentrs]

Thanks for all the info. I'll give that a try. Yeah, it idles fine when it's cold and first started. Now though, it dies immediately when I put it in gear. Haven't tried letting it warm up to see what happens but I'll get some carbon buster and try your suggestion. Thanks again!

[NM5K]

Hummm. It usually kicks in after it warms up a few minutes, but I suppose it could vary.
Often running super lean can cause it to die out when putting a load on it. So you still might
want to rig up that pressure gauge.
But extreme carbon can also cause lean running as it soaks up fuel vapor, and often one
that bad will have semi clogged injectors too..
As I recall, ours would also often die out when putting it in gear once the problem
started kicking in.
I'm trying to remember the size of the bolt you need for a banjo adapter. Something in
my brain pan thinks 19mm, but don't get me to lying.. I think I cut the head off of it,
and then drilled a hole through it. I'll see if I can find it, and take a pix..
I then clamped a hose to it, and off to the gauge. I used a long hose so it could reach around
into the car. On ours, the fuel pressure was fine all the time..
This carbon dilemma is why I only burn top tier gas in my Toyota.. Supposably they have
enough cleaner to keep it from building up.
Chevron and Texaco both use Techron. Shell uses their proprietary "Oxy" formula, and
Exxon also uses their own type cleaner.

[CrypticRacer13]

to each his own ive used seafoam in all of my cars/trucks with great results. You can look into that as well to help clean the carbon gunk out of it. also it should not have an OBD II, thats before that time for a 90' your car should still have a cap an rotor ( at least i know my 91 honda did) so check the cap rotor as well as the plugs, fuel filter. all of these things can be looked at for nothing but your time to look at them. with that many miles on it its most likley carboned up like crazy

[BRUTUS_T_HOG]

A 90 won't have OBD2. Only flash codes.

Unplug the MAP sensor and see how it runs. Not sure that a 90 would even have a MAF sensor

[sargentrs]

No MAF, just an "air/flow meter". You're right about no OBD II and cap and rotor. There's a small diagnostics port next to the fuse box in the engine compartment but I don't think it accomplishes much. I've got an electrical diagnostics chart from AllDataDIY that shows how to check the air/flow meter, fuel circuits, etc and the ECU with a VOM. Just a PITA and I've been avoiding it. Tried for the past couple of days to just buy another car but nobody wants to loan me any money for a $1500 car and my budget just got blown on a new water heater for the house. Oh well, guess I'll have to work on the Toyo now. Thanks for all the input guys!