Triple Whammy (Really hot exhaust, poor acceleration, lack of smooth throttle) - MR2 Owners Club Message Board
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post #1 of 19 (permalink) Old May 4th, 2019, 12:44 Thread Starter
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Triple Whammy (Really hot exhaust, poor acceleration, lack of smooth throttle)

Hey guys, been working on my fixer upper for three months now but I've got 3 issues I can't seem to diagnose and fix.
1) My exhaust has been getting so hot that the stainless steel turned blue immediately, it's also sputtering intermittently so maybe afterfiring slightly? (not sure if that's normal but I thought it'd take longer to blue/gold out)
2) When I give it a little bit of gas, the RPMs will bounce between like 1.5k and 3k, so I can't idle at 2k rpm if I wanted to, (I adjusted the TPS to be in spec but maybe it could just be a bad TPS regardless?)
3) When accelerating in higher gears, the car won't rev up so for example, I'll be able to rev fine in like 1-2 or 3rd gear but when I hit 4th or 5th and add throttle it'll taper out at like 45-50 mph

I recently replaced the fuel pump, exhaust system and checked ignition timing but I don't know where to start at this point
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post #2 of 19 (permalink) Old May 4th, 2019, 17:02
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Sounds like the fuel injectors or the pressure regulator. Not being able to gun it in higher speeds is usually a fueling issue.
A rebuilt set on ebay is $100. If that dosen't fix anything check the fuel pressure regulator.
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post #3 of 19 (permalink) Old May 5th, 2019, 17:21
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Where is the exhaust heating? Before the cat or after?
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post #4 of 19 (permalink) Old May 5th, 2019, 17:23 Thread Starter
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Originally Posted by rmeller View Post
Where is the exhaust heating? Before the cat or after?
After, the muffler's super hot after driving around for a while, also after adjusting with my TPS some more now it wants to bucks forward and back while accelerating so maybe the TPS is just bad?
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post #5 of 19 (permalink) Old May 8th, 2019, 18:19
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It sounds like it's running too lean. Do you have a check engine light? Have you checked for vacuum leaks? I'm a Mark I racer myself so I'm not familiar with this car. Does it have vane airflow sensor? If the car sat for a long time the above suggestion of injectors might be worth checking out. After a while the injector pintles can gum up clogg or freeze. Does it misfire? If there is a vane airflow sensor make sure the intake tube between it and the throttle body isn't cracked. The carck can open up as the engine moves around and it becomes a massive vacuum leak.
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post #6 of 19 (permalink) Old May 9th, 2019, 07:05
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I agree that the problem is a lean condition. Re-adjust the TPS [move it back to the original location] I would verify the fuel pump pressure. Dead head the fuel line into a pressure gauge. Connect the gauge before the injectors. You need to see 38-40 PSI, at a min. It not uncommon to see low pressure from a 30 yr old fuel pump cause these issues. davew
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post #7 of 19 (permalink) Old May 9th, 2019, 13:52 Thread Starter
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Originally Posted by davew View Post
I agree that the problem is a lean condition. Re-adjust the TPS [move it back to the original location] I would verify the fuel pump pressure. Dead head the fuel line into a pressure gauge. Connect the gauge before the injectors. You need to see 38-40 PSI, at a min. It not uncommon to see low pressure from a 30 yr old fuel pump cause these issues. davew
I'll check it again but I replaced the fuel pump last month with a TRE 255LPH aftermarket pump
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post #8 of 19 (permalink) Old May 9th, 2019, 14:40
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I would start with checking the cam timing and then ignition timing. You don't say your history with the car, how long have you had it, has it ever run well, maybe the timing belt jumped a tooth or 2.
Does the car have a cat?
Is it SC or NA?
The hot muffler makes me wonder if raw fuel is making it to the muffler and then burning.
Good luck.
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post #9 of 19 (permalink) Old May 9th, 2019, 22:21 Thread Starter
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Originally Posted by 88Super2 View Post
I would start with checking the cam timing and then ignition timing. You don't say your history with the car, how long have you had it, has it ever run well, maybe the timing belt jumped a tooth or 2.
Does the car have a cat?
Is it SC or NA?
The hot muffler makes me wonder if raw fuel is making it to the muffler and then burning.
Good luck.
I bought it not running in a shed outside Austin, I've had it for two months and everything's fair game at this point. The water pump and radiator were no good, so I swapped them out along with the thermostat. I did a compression check and got about 130 on all cylinders and 140 wet, also checked the ignition timing and its at 10 degrees like its supposed to be. It's NA, I swapped out the cat and muffler since the old cat had crumbled and fallen apart inside. It was running alright on the highway before with quirks but now doesn't respond at high speeds. The fuel is giving me 40 psi on the line and 30 psi for return so I'm guessing either the injectors are clogged, the O2 sensor is bad or theres a vacuum leak/something air related isn't working well so its resulting in a lean burn. Also the spark plugs are coated in black soot so maybe it is the injectors/the spark plug wires need to be replaced?
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post #10 of 19 (permalink) Old May 10th, 2019, 00:13
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So the car is mystery meat? New to you. Close to stock? Stock ECU? Good ideas mentioned above.

If you unplug the O2 sensor, the car will stay in open loop on default maps and run safely rich.

Is the clutch slipping? Rolling in on top gear when you've got the torque to pull will be the first place a worn clutch starts to slip. Is the battery holding a charge? Because a dying alternator will cause the ignition to miss at high rpm first.

When the tach bounces around, does the engine sound/feel like it is hunting/revving up and down, or is it just the tachometer bouncing around? If it is just the tach, check the sender and also plan to probably change some leaking capacitors in the back of your soon-to-be-dead tach.

Three ways the exhaust gets hot and the car runs like crap:

1) obstructed cat or exhaust. Nope, you changed it.

2) fuel burning in the exhaust. So, as suggested check the cam timing. Retarded cam timing would cause the engine to fall flat at higher rpm and dump unburnt fuel late to the party into the exhaust. Or a gummed up injector not closing clean could dump extra raw gas all the time, burning up in the exhaust. Or weak spark could allow unburnt charge to burn up in the exhaust (coil, cap, rotor, plugs and wires??). Is the ignition advancing as the revs increase? Strobe timing light will tell. You'll see the timing marks move away as you rev up and return as the revs fall.

3) Running lean. Any air leaks between the AFM and the combustion chamber will cause it to suck un-metered air and run lean. But this is usually worse at idle and cleans up at higher RPM as the unmetered air is a smaller proportion of the entire charge. This sounds like the opposite of your symptoms. Use an unlit propane or MAPP torch and work it around all of the intake joints with the engine running. If the RPMs climb, then you found an air leak.

Fuel Filter clogged? Testing static fuel pressure or even fuel pressure at idle doesn't tell you if the fuel pumping system is keeping up with demand at high rpm under full load.

Is there wetness in the vacuum signal side of the Fuel Pressure Regulator? There shouldn't be. If so, BAD FPR. A maniac might pinch the return line almost closed with a spring clamp to see if there is any change in engine behavior at high rpm. Not forever, mind you, as you are giving your pump a workout.

How's the Positive Crankcase Ventilation valve. If it gets stuck open, you would have excess blow-by oil mist blowing into the intake manifold diluting your mixture and fouling the ____ out of your plugs.

Where does the ignition get its trigger signal? From the cams or the crank? I would assume nothing and start by pulling all the plugs and dropping the dipstick down the #1 cylinder hole to confirm that indicated TDC matches with true TDC. You're harmonic dampener rubber could have let loose and the outer ring of the crank pulley starts slipping and could actually be retarded. With a breaker bar on the crankshaft bolt, you move the crank back and forth at indicated TDC and feel the dipstick top out in the #1 cylinder at the same time. Thumb and forefinger pinch the dipstick just outside the spark plug hole with the dipstick riding the top of the piston.

Assume nothing is right and that you might have multiple faults. Give it a serious tuneup: plugs, wires, cap, rotor, maybe a coil, PCV, Fuel Filter, Air filter. Dissect and clean up the Idle Air Control Valve. Remove and clean the fuel injectors. Replace and be careful with the injector O-rings. Or at least dump some good injector cleaner in the tank. Listen with a mechanic's stethoscope or a long screwdriver with the handle on your ear that the injectors all sound the same.

How's the wiring? Does if look like it has never been molested? Any electrical gremlins?

Can you jumper the diagnostic port and record any fault codes? Count the flashing lights.

Dark thoughts... blown head gasket. coolant in the oil? oil in the coolant? you got it with a bad water pump and radiator so assume it has overheated. Does the engine oil on the dipstick look like a malted or chocolate milkshake? Oil droplets in the coolant floating by under the cap?

And since I mentioned everything else how's the AFM?
Give it a thorough tune-up and cross your fingers.

Good luck,

Brian C.
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Last edited by BrianC; May 10th, 2019 at 00:28.
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post #11 of 19 (permalink) Old May 10th, 2019, 07:16
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The problem could be timing. l had the engine damper outer ring shift more then 20 degrees. Pull plug #1, and put a screw driver or rod down in the plug hole. Crank the engine by hand and bring the cylinder up to TDC. Then verify your engine damper notch is at the zero mark on the timing indicator. Late timing could cause these issues. DaveW
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post #12 of 19 (permalink) Old May 10th, 2019, 14:52
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Could just be weak ignition. Checking the plugs and replacing the wires, cap, and rotor should be one of the first things you do. These components are cheap, and there is no sure way to evaluate them except by replacement with new.
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post #13 of 19 (permalink) Old May 11th, 2019, 12:17 Thread Starter
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Originally Posted by davew View Post
The problem could be timing. l had the engine damper outer ring shift more then 20 degrees. Pull plug #1, and put a screw driver or rod down in the plug hole. Crank the engine by hand and bring the cylinder up to TDC. Then verify your engine damper notch is at the zero mark on the timing indicator. Late timing could cause these issues. DaveW
Holy crap! I think you've got it, I have everything off the car and turning the crankshaft so that the closest piston to me (passenger side) to TDC shows that the ring has also shifted 20 degrees apparently. How can i readjust it if its the case?

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post #14 of 19 (permalink) Old May 11th, 2019, 13:06
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It is going to keep moving so you need to replace the damper pulley. If you have a degree wheel, you could mark TDC, then the marks BTDC and set your timing to that. But that's silly because the outer ring will just keep slipping.

If your ignition timing is set to the current marks, then your ignition timing is retarded. Cam timing would be unaffected by this shift.

Last edited by BrianC; May 11th, 2019 at 13:09.
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post #15 of 19 (permalink) Old May 11th, 2019, 14:16 Thread Starter
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It is going to keep moving so you need to replace the damper pulley. If you have a degree wheel, you could mark TDC, then the marks BTDC and set your timing to that. But that's silly because the outer ring will just keep slipping.

If your ignition timing is set to the current marks, then your ignition timing is retarded. Cam timing would be unaffected by this shift.
#1 What's a good OEM or aftermarket replacement for it?
#2 I'm reading that I can just put it into 5th gear and grab a breaker bar to pry it free along with a hammer apparently?
#3 Could this have damaged components on my car already like the oil pump, alternator etc? My compressor makes weird noises at idle and the clutch likes to slowly move around while the A/C is off (could just be a bad compressor clutch is what I chaulked it up to, but maybe the two piece pulley snapped and is rotating freely?)
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post #16 of 19 (permalink) Old May 12th, 2019, 07:25
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What I did before I bought a new pulley was to file a new notch in the outer damper ring, to correctly set the timing. I then painted a mark on both the inner and outer rings of the damper, to be able verify that the ring had not continued to shift. You might want to look at an aluminum after market pulley. Some actually cost less then a stock Toyota pulley. Be warned, you will probably need an impact wrench to get the pulley off the crank, if you go that route. davew
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post #17 of 19 (permalink) Old May 12th, 2019, 14:53
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I don't see how a slipping crank pulley outer ring could cause damage to other accessories. But If your AC compressor is seized, that could cause the damper to break loose and become retarded. I would deal with the A/C compressor before replacing the crank pulley. Can you run a belt that omits the A/C compressor altogether?

I don't own nor have I ever seen the engine on a MK1. No matter. Your crank pulley should have a mark for TDC. Also, the plastic timing cover on the engine will have marks for TDC, (0 degrees) and several degree increments Before Top Dead Center (BTDC). As rpms rise, the spark has to happen earlier so the mixture will burn and make power at the right moment.

Remove all of the spark plugs, find TDC using the dipstick in the #1 cylinder, mark it on the pulley with a file like Dave suggested, Short terminals T & E1 in the diagnostic connector. Set the timing with a timing light in diagnostic mode to 10 degrees BTDC, lock it down, remove jumper and you should see about 16 degrees BTDC.


You find TDC with a dipstick, dowel or screwdriver by feel. Use a breaker bar or box wrench on the crank bolt to rock the engine forward and back until it is as high as it can go. Hold it in your thumb and forefinger, rest your hand on the cam cover and you will be suprised by how close you can get it by feel.

Bottom line, if the damper pulley starts to slip, it doesn't change any of your timing, but it just cannot be trusted to set the timing against it in the future. Is the distributor turned to the extreme limit of its adjustment? If so, that's a clue that someone tried to set timing against the retarded pulley. If not then even though the pulley is off, the timing could still be OK.
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post #18 of 19 (permalink) Old May 15th, 2019, 15:26 Thread Starter
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Update on this, TPS was replaced so no more hopping up and down when i press the throttle, the pulley actually does still have its marks on but other factors didnt let me get accurate readings so timing is set now. Just need to test drive it and see if its good to go now.
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post #19 of 19 (permalink) Old May 16th, 2019, 20:36 Thread Starter
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I was mailed a different configuration pulley even though the seller said it would work for the MR2 AW11, can I just run a 4pk on both and call it a day? The alternator would be turning a little faster and the compressor would be turning a little slower
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