3sfe poor mileage--eliminated usual suspects

[mattjm]

I've been lurking here for a while--gotten tons of good information. I have a problem with my 3s-fe I can't seem to track down, though. I have a 1988 Camry Wagon LE. Fantastic car.

symptoms: slightly reduced power and mileage (should be around 30 highway, getting close to 25). Acceleration lags, especially in the lower RPM range. Engine starts fine after sitting overnight in cold and warm weather. I do have an issue with a warm engine--once it has reached operating temperature, it starts up fine, revs a little bit higher than idle speed, then drops to 300-400 RPMs and frequently dies out (all this happens within a second or two). If it doesn't die, or I increase the throttle for a couple of seconds, it will idle at the proper speed (~650 RPMs).

I have a little bit of high speed miss that I notice if I rev the engine just sitting in the driveway. It used to be a lot worse but a new cap, rotor, wires, and plugs helped a lot. Also, it runs worse with the EGR hose connected (currently running with it off and plugged). I have done the EGR valve test and it appears to work properly.

Other symptom that may not be related...if I'm heading back from the moutains (~3000 ft and going lower, starting with a relatively cold engine--think after a day of skiing) it takes a long time for the engine to reach operating temperature. Probably at least half an hour. No problems in normal city or highway driving. Coolant temps are about 175 after driving around town (tested with thermometer in radiator opening).

Engine is a Japanese replacement...has good compression and otherwise works well (only apparent problem is the valve stem seals leak a little bit).

Things I have done so far:

-new cap, wire, rotor, and plugs, as mentioned before.
-new air filter
-tested intake temperature and air meter resistance.
-tested ECT--not rigorously, but resistance seemed to read about right for a hot engine when I checked it.
-injectors were professionally cleaned and tested by a reputable shop when the engine was replaced.

If it's a vacuum leak, I can't find it. I've tried spraying starting fluid around the usual suspects...nothing. I suspect it's running rich...if I spray ether directly into the intake it kills the engine.

Is there a way to check if it's running in open loop mode? Seems like this could cause the problem with dying out when the engine is at temperature due to the rich mixture. Should I check the air meter and ECT again? I feel like I've been taking a shotgun approach to problem, and would like to start down a proper troubleshooting path--seems like finding out if I'm running in open or closed loop mode would be a good start.

Thanks for any replies.

Matt

[mcx]

pull the coil and check its specs...as well as check coil for hair line cracks....check/replace your thermostat,it might be stuck open...test/replace the o2.

[mattjm]

Coil resistance checks out OK--I think I had it off a few months ago and didn't notice any cracks. I have a spare somewhere--once I find it I'll pull it and check, and swap it if it has cracks.

Replaced the O2 sensor today--I've always been suspicious that might be the problem. It tested OK on the bench with a propane torch, but supposedly they can pass that test and still not be 100%, and for $20 it's not worth fooling around with. Seems like it has more power, but the miss is still there (might be better, though). Or it could all be the placebo effect.

I'll update again once I check the coil. Car has been warming up fine around town so I'm guessing thermostat is OK. I have to do emissions this month...if it doesn't pass, at least I'll have readings of what's coming out of the tailpipe.

Thanks for the advice!

Matt

[Blakeman]

Seafoam, fuel filter and check the exhaust for oddities like a ding that could cause weird compression going out. These are all things I have heard of when something like what you describe happens.

[fredk]

put a new thermostat in it

[white90dx]

Definitely put in a new thermostat. Also, check the timing - it should be at 10BTDC with the jumper connected. You can advance it a bit if you want (and the engine doesn't ping).

-Charlie

[Mike Gerber]

^ I have to agree with the new thermostat. Thermostat may be stuck partially open. 175 is a bit low and could be causing lenghtly warmups and a slightly rich mixture. This could account for you low fuel mileage. Coil is another suspect, expecially if you have some mileage on this car (you didn't give the current mileage) so let us know if changing the coil helps with the problem.

The car dying at idle after startup could be a separate issue. To help with this issue I would also clean the throttle body paying particular attention to spraying the cleaner liberally in to the square or diamond shaped port in the base of the throttle body. That port leads to the idle air control valve where that problem may exist. A dirty idle air control valve could be causing your problem with the car dying. Here's a thread on cleaning the throttle body on the 5SFE engine. Your 3SFE engine should be similar:

How to: Cleaning Throttle Body -4 Cylinder Engines- With Pictures

Mike

[mattjm]

Mike,

I will see about giving the thermostat a try.

Car has 95,xxx miles on it. Engine is a Japanese replacement--unsure of mileage but compression is good. I think I'm using the distributor off the original engine, so coil should be low mileage. Shaft leaks oil, though, and I heard that's not good for the coil.

I cleaned out the throttle body and intake manifold pretty well when I swapped engines (May '09), and I had the throttle body off again and cleaned it and the IAC a couple months ago (IAC seemed like a good candidate for the problem). Didn't seem to make much difference, though.

I'll keep you guys posted--doing emissions Thursday.

Thanks again for all the replies.

Matt

[mattjm]

OK,

Passed emissions with flying colors!

cruise:
HC: 31 ppm, limit 160
CO: .39%, limit 1.1

idle:
HC: 26 ppm, 220 limit
CO: .11, limit 1.2

(these numbers aren't as good as the original engine in the car--but it only had 90k miles on it and had been well-cared for)

I went ahead and replaced the thermostat since I clearly had a problem after reading/thinking about it some more (I cut my teeth on an aircooled VW so I still have trouble with water sometimes. ). Also, the car is definitely running better (pulls harder, less hesitation). I still have to finish this tank of gas to see how mileage is.

The high speed miss is still there. I can describe it better, though. It revs UP fine, and doesn't miss if you keep RPMs constant. When you back the throttle off a little, it misses a few times and then stabilizes at the new speed. I'm not terribly concerned but it bugs me just a little bit.

Thanks again for everyone's suggestions. You guys rock!

[mattjm]

I know this thread is over a year old, but I'm the OP and finally solved this problem. There were actually several things I did--I'm not sure exactly which one solved the problem.

-First, I removed the coil from the distributor and realized the insulation was cracked in several places (it wasn't visible while the coil was installed in the housing). I replaced the coil. Car seemed to have a little more power, but the miss was still there, and gas mileage was the same as before.

-When I removed the distributor, some of the spark plug wire ends pulled out and stayed on the plugs (!)--I had crimped them back on and used it for a couple weeks, but then I realized it was under warranty from NAPA so I replaced it. I replaced the spark plugs with NGK BCPR5EY-11 at the same time--I had a very similar NGK plug in there before, but NGK BCPR5EY-11 is exactly what the FSM calls for.

The miss seems to be gone now. Mileage has increased by 5-6 MPG.

Still not sure what exactly what the fix was...I think the cap and wires are the likely culprit as plug end crimps pulling out indicates quality problems...but I'm sure replacing the cracked coil didn't hurt either.

Hopefully this will help someone out there.

Matt

[71Corolla]

Thanks for the update. Too many people make these kind of threads, then don't bother to post back when the problems are solved.

[white90dx]

For all those out there reading this:

Use the factory ignition components. They really do work better and last longer - and are worth the extra 2x-3x in price over parts store crap.

The only thing to 'cheap-out' on is spark plugs, where the basic NGK copper plugs work best - just replace them every 15k miles.

-Charlie

[Mike Gerber]

Thanks for posting the final solutiion.

"I removed the coil from the distributor and realized the insulation was cracked in several places"

The cracks you had in the coil indicate that was definitely part of the problem. Those cracks are common as these coil age and/or rack up lots of miles on them. The cracks allow the coil to short itself to ground on any metal inside the distributor. The problem is worse in wet or damp weather.

I agree with whitedx90 about using factory ignition components. The last a very long time. I have the origianl plug wires on my 94 Camry 4 cylinder. They are 16 years old an exhibit no problems at all.

Mike

[mattjm]

"Use the factory ignition components. They really do work better and last longer - and are worth the extra 2x-3x in price over parts store crap."

Yeah, I haven't been impressed with the quality of the cap/wires I've been getting from NAPA. A couple days ago I had them warranty the one I just put on for the plug end crimp pulling off (again). At this rate they are going to regret the 5-year warranty. :-P On the other hand, I am getting sick of changing it, so I may get a factory cap if this continues to be a problem.

I definitely agree that parts quality is particularly important on ignition components. Cheap insulation and high voltages are asking for trouble.

Thanks again for everyone's help.

Matt