1995 Toyota Corolla DX 1.8 4AFE Poor Acceleration


Old 10-21-17, 01:26 AM
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1995 Toyota Corolla DX 1.8 4AFE Poor Acceleration

Hello there,

I have a 1995 Toyota Corolla DX 1.8 4AFE engine, automatic transmission, 220000 miles on the odometer. This car has been running fine until a couple of weeks ago. I was stopped on heavy traffic and I saw the car temp gauge started to go up. I quickly pulled over and allowed the car to cool. The gauge only rose to about 3/4 it did not hit max temp. I refilled the cooling system with water and drove home, this time, the temps remained steady. When I got home I checked the car and found out that the rad fan was not turning on. So I bought and installed a new fan, fan relay and temp sensor. Now the cooling system is working fine.

However, now the car is suffering from severe lack of power/acceleration even while on Park/Neutral when the accelerator is depressed the engine revs very slowly. If I step on the gas hard, the engine still revs very slowly. I took it for a test drive, still revs slow with a significant loss of power. I can barely make 35mph. The only way I can get the car to shift is if I let of the gas, then on the next gear it continues to rev slow until I repeat the process.

I checked the OBD1 has Code 12, but I have had that code on ever since we got this car about two years ago, without any performance issues. I replaced the plugs, cables, distributor cap and coil. Replaced the timing belt and fixed the timing as it was a little off. Replaced the alternator and the Throttle Positioning Sensor. The fuel pump and filter were replaced about a year ago, but I went and replaced the fuel filter again just to make sure it was not the issue. The used throttle cleaner to clean the throttle. The engine idles fine and there is no smoke dark/white/gray smoke coming from the tail pipe.

Note: the car was idling in low revs while cold, when I replaced the TPS the revs went up during while cold.

After all of this checks and replacements the engine is running better but still very slow while accelerating. I am almost to the end of my wits with this one. I have read many other pages and forums but no help so far on fixing this issue. I tried many of their checks and possible repairs but nothing. I have the Haynes manual for the car but no help either. Any help?
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Old 10-21-17, 02:47 AM
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Possible catalytic converter clogged.
Old 10-21-17, 03:13 AM
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Plugged cat was also my first thought.
Old 10-21-17, 03:28 AM
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would also think it may have an exhaust restriction or timing or timing belt is off
Old 10-21-17, 09:18 AM
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My bet is the crankshaft position sensor, these things can deteriorate without failing outright. Cheap to replace, probably worth ruling out.

Could well be the cat, using an infrared thermometer, shoot the temperature of your catalytic converter’s inlet and outlet areas. The outlet area should be significantly warmer than the inlet area, usually around 100 degrees Fahrenheit. If the outlet area is colder than the inlet, there’s a strong possibility your catalytic converter is about to fail, or is currently failing.

Other possibility would be the fuel pressure regulator. Are you getting black smoke out of the tailpipe when you are trying to accelerate? Plugs sooted up?

The timing belt and distributor/coil, tps other tune up items could also be culprits but seems you have addressed these. But maybe you have a bad wire again look at the plugs and see if one looks different to the other. Sounds like you are not running on all cylinders when accelerating.

Could also be a failing head gasket but not so bad that its obvious. You might have overheated the car with the rad fan failure, the temp gage is not that accurate. Is the acceleration problem the same whether the engine is cold or warmed up? Is your coolant level steady? More white smoke coming out of the car? Sometimes you can get small internal coolant leak, might improve as the car warms up and things expand. You could retorque the cylinder head, that can sometimes solve for a minor head gasket problem. A compression check might also help narrow things down.

Even though your car is older and high mileage sounds like you are maintaining the car thoroughly, so worth doing low cost inspection and diagnostic type things to look for some additional clues.
Old 10-24-17, 09:22 AM
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Thank you all for the replies, sorry it took so long for me to get back to you.

Here is what I've done so far related to this issue.
alternator (better, stable voltage)
crank positioning sensor (still showing code 12 after replacement)
throttle positioning sensor (adjusted as per Haynes manual)
distributor coil
spark plugs
fuel filter
temp sensors (the two prong sensor behind the distributor and the one prong sensor behind the engine)

timing belt (fixed the clicking in the engine)
vacuum houses (replaced some of the bad ones, the acceleration got slightly better)
egr sensor (cleaned the filter)adjusted the idle
ran Seafoam on the throttle intake, and gas treatment, fueled with high octane gas
pulled the o2 sensor (to see if cat/or exhaust was plugged)
fuel injectors (took them out one at a time, the obvious failures happened. Same with the spark plugs)
air filter (when removed no change to the situation)
trans/motor fluids (topped off as per specs)
no visible exhaust fumes, nice and clear at the tail pipe.

i have even changed radio stations (lol) to see if the problem goes away.
three things that come to mind that could possibly be causing this, egr valve, igniter, ecm, i hope is not the ecm. let me know if I'm on the right track.

once again, the problem is extreme low acceleration even while on park. If i step hard on the gas there is no power to it. when i stepped easy on the gas pedal revs even slower. if i hold the pedal down after a few seconds the engine revs higher, but initially it bogs down yet even with higher revs it accelerates poorly. the acceleration problem is there whether the car is cold or hot. I can now make it to 50/55mph but takes about a mile for me to get there.
Old 10-24-17, 09:57 AM
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Have you pulled any codes for it? AutoZone and others will do it for free.
Old 10-24-17, 10:32 AM
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Yes i have, code 12. Obd1. Jumped the terminals. This code I had for a couple of years without issues. I've just decided to address it (see below threads) still no change.
Old 10-24-17, 11:38 AM
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Sounds like you are doing all the main things, so the problem is either in plain site, ie. a clogged cat (how much pressure is actually coming out of the exhaust), or something a bit unusual. You are in deep, so this must get fixed! Some further random thoughts...

Spray electrical cleaner on all the connectors to the ECM, make sure no surface film corrosion is sending an erroneous resistance signal.

My current guess is a broken tooth on the crankshaft reluctor gear, that's what the crank position sensor is picking up. That would explain the code thrown, which is a clue that is hard to ignore.

Make sure the relays for the engine management and fuel injection are good.

Other areas to think about would be the fuel filter, pump and regulator. Maybe a fuel pressure check would help, should be about 40psi I think. Also an injector pulse detector to make sure the injectors are firing correctly when pushing the accelerator (if not ECU might be the problem).

Could be an ecm failure. There is an ECM test procedure which you use a volt meter to measures voltages at various pins in various ignition on/off configurations.
Old 10-24-17, 12:37 PM
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Thank for the reply,
i removed the o2 sensor to add additional exhaust to escape to test the cat theory. No change there. Still low acceleration.

that crank shaft reluctor idea sounds good as well as checking the ecm pins. I will also clean all of the connections I will post back once i get this checks done. Maybe in a few days

now,how bad or expensive of a job is to replace the reluctor? Sounds like a mayor engine work.

oh, another thing, i may have forgotten to mention. The car used to start on the fly,now i have to crank it 4 to seven times before it starts.

Last edited by DaKine73; 10-24-17 at 01:45 PM.
Old 10-24-17, 01:09 PM
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For those inquisitive minds, the timing belt was replaced about a year ago, same with the fuel pump.

i can hear a minor fluctuation of rpms while on idle, the car doesn't have a tach meter so i don't know the range.
a thing about this car, is that every year or so, i had to adjust the timing belt. If this is a clue?
the car is currently timed, as per the Haynes manual. It also says that the distributor timing is adjusted by the ecm. There is no play or adjustments on the distributor to adjust the timings.

a thing i heard a while back was the valve clearance (a project i have on standby). Could the clearances be so bad that all of the sudden it lost power?

Last edited by DaKine73; 10-24-17 at 01:42 PM.
Old 10-24-17, 02:07 PM
Join Date: Dec 2016
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The reluctor gear built into the lower timing belt gear that is attached to the crankshaft, so I think labour would be a similar to a timing belt change.

But before you go there, what about the MAF sensor? This is a very common wear item on an older car that can cause all kinds of drivability problems along the lines you are dealing with. Should have mentioned this earlier. Would typically throw a code though. Here is a voltage meter test process you can do to rule it out. Part 2 -How to Test the MAF Sensor (Toyota 1.8L)

Also has links to checking for a blown head gasket (compression check), which among other things would detect a burnt valve.
Old 10-24-17, 02:44 PM
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I checked the MAF sensor. It may be failing but inconclusive results. That is my next step, to replace it.

i thought of the head gasket, i don't worry about price, i can do the job myself. I just want to make sure before i tackle the job.
Old 10-30-17, 05:12 AM
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I find Haynes manuals lacking. techinfo.toyota.com is the official site and goes back to '90. It is $15 to subscribe, and you can .pdf your repair manual. (It is not available on helminc.com, I checked.) I followed this post:

Toyota TIS download tips

The instructions aren't perfect, but helpful in pointing to the right direction.
Old 11-04-17, 02:43 PM
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compression testing

Hello DYI comrades,

Finally purchased the compression test kit. I performed the test on all 4 cylinders, the good news is that they are all within specs, out of 191psi max 142psi min, all of the cylinders read 180psi. Not bad for such an old engine.

I also performed the distributor test with a light test and it is showing constant sparks. However i will have to retest this as i did it on the fly and did not check it at different rpms.

Although with the compression test I'm able to rule out mayor engine failure, the puzzle is still there.

What causes loss of power on acceleration. Today when i started the engine from cold after a few days. I could smell fuel odors from the tail pipe. Something i did not smell before, however the fumes are still clear.

I'm starting to think the ecm is at fault or something else I'm missing on the fuel delivery or electrical distribution.

Old 11-04-17, 04:39 PM
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Did you replace the maf sensor?
Old 11-05-17, 09:18 AM
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Code 12 is a knock sensor problem. The ECU can't set the timing properly without the knock sensor working.
You may also have a coolant temp problem (sensor) which keeps the engine from going into "closed loop"
Old 11-05-17, 03:40 PM
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So i have not replaced the MAF sensor yet.

Today I had a mechanic take a look at the car. I explained to him all i have told you on these posts. He told me 3 possible things. 1 timing 2 distributor 3 ecm (but highly unlikely). He throttled the car and saw what I was talking about. He was puzzled for a moment as the engine was idling good.
While he was looking at the car, we had it running on idle and at normal temps. We started to hear snapping sounds coming off the engine. All of the sudden one last snap and the engine stopped.

He took a look at the timing belt and it was broken. He said to me to replace the belt and to ensure I use a timing light when adjusting the timing. When i did the timing job i may have been off a tooth left or right. The light should help me zero in the timings.

However once i place the car on time, while idle, i should check the timing while accelerating to ensure that the ecm and distributor are keeping up with the proper times. He said that if the times start to lag behind under acceleration, i should replace the whole distributor assembly, worn out components can make the car fall out of timing and produce those symptoms.

So tomorrow, new timing belt, (might as well get the component kit), water pump, timing light and torque wrench (to ensure proper adjustments).

i will let you know how it goes.

One thing he told me is that while on idle the car sounded sweet, he gave me praise for the maintenance.
Old 11-05-17, 03:43 PM
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I did replace the crank positioning sensor, as per the Haynes manual code 12 is crack positioning sensor, distributor or ecm failure. The code 12 is still there after replacing the crank sensor.
Old 11-05-17, 06:18 PM
Join Date: Jun 2010
Location: Canada (near The Motor City)
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Toyota Generic Trouble Codes
(Codes Apply to Most Toyota Models – See Table at the Bottom of the Page for Model Specific Codes)

OBD1 Codes
1 Normal Condition.
2 Air Flow Meter signal.
3 Ignition signal.
4 Engine Coolant Temperature Sensor signal.
5 Oxygen Sensor.
6 RPM signal (Crank Angle Pulse).
7 Throttle Position Sensor signal.
8 Intake Air Temperature Sensor signal.
9 Vehicle Speed Sensor signal.
10 Starter signal.
11 Switch signal.
12 Knock Control Sensor signal.
12 RPM signal.
13 Knock Control CPU (ECM).
13 RPM signal.
14 Turbocharger Pressure.
14 Ignition signal.
21 Oxygen Sensor.
22 Engine Coolant Temperature Sensor signal.
23 Intake Air Temperature Sensor signal.
24 Intake Air Temperature Sensor signal.
25 Air-Fuel Ratio Lean.
26 Air-Fuel Ratio Rich.
27 Sub Oxygen Sensor signal.
28 No. 2 Oxygen Sensor signal.
31 Air Flow Meter signal (Vacuum Sensor signal).
32 Air Flow Meter signal.
34 Turbocharger Pressure signal.
35 Turbocharger Pressure Sensor signal.
35 HAC Sensor signal.
41 Throttle Position Sensor signal.
42 Vehicle Speed Sensor signal.
43 Starter signal.
51 Switch signal.
52 Knock Sensor signal.
53 Knock Sensor signal.
54 Inter-cooler ECM signal.
71 EGR System.
72 Fuel Cut Solenoid signal.
78 Fuel Pump Control signal.
81 TCM Communication.
83 TCM Communication.
84 TCM Communication.
85 TCM Communication.
Old 11-18-17, 05:50 AM
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Once again, sorry for the late postings.

So I replaced the timing belt. Did all the steps to tdc and belt adjustments. No dice, timing on idle is about -5 degrees past zero. Poor acceleration still present.
I placed the ecm on test mode and the timing would correct itself to zero and automatically move to 10 degrees before zero. That's a good sign right!?. But as i mentioned while on normal mode and in idle the timing is all bad.
Now one thing to do is to mark the belt and try to advance one tooth to see if that makes the timing better.

Also while fiddling with the timing belt replacement I noticed that the timing belt adjustment pulley (which i replaced along with the spring) is missing some sort of piece that holds the pulley plate in place to create tension on the spring. That tells me now why the timing kept jumping every so often, not enough tension on the pulley.

I was able to use a screwdriver to create the tension on the pulley and lock it in place. Thus is a temp fix until i can get the piece that goes in there.

So tomorrow i will get back under the car and see what happens. Hopefully it's user error when adjusting the timing. I will let you know.

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