1992 Toyota Celica Engine misfiring after warmup

Tiny
JWINEGAR
  • MEMBER
  • 1992 TOYOTA CELICA
  • 4 CYL
  • AWD
  • MANUAL
  • 192,000 MILES
I have a '92 Celica All-Trac turbo, 2.0L engine AWD. I've had it for about 7 years, it has seen quite a bit of modifying over the years, but currently is back to stock formation and has been for about 3-4 years.

I take good care of the car, always changing the oil routinely myself and have never had any mechanical engine problems. A few months ago the check engine light came on after starting it up and it began misfiring once the engine was warmed up. The car had an extremely difficult time making it up a moderate hill.

I checked the spark plugs and found the number one plug had more white buildup on the electrode so I performed a compression test. All of the cylinders are much higher than minimal tolerance, much higher than stock actually. This likely due to the amount of time the car ran extremely rich with a larger turbo and other modifications. But all of the cylinders are almost exactly even as far as psi measurements.

I wanted to do a leak down test to see if there is a valve problem but I don't have access to a tester. I am really at a loss for what can be going on. I was thinking there is a possible injector problem since the car runs fairly smoothly when cold.

I should note that the CEL code is for an engine misfire and knock sensor. I have had issues with the knock sensor in the past. Could the misfire be due to the high carbon buildup on top of the pistons?

This is not my daily driver so it is not urgent, but the car has been down for quite some time now and I would like to get it back to driving condition soon.
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Monday, August 30th, 2010 AT 8:33 PM

9 Replies

Tiny
MHPAUTOS
  • EXPERT
Hi there,

Thank you for the donation,

Excessive carbon build up can cause pre ignition problems, as the carbon heats up it can reach temps hot enough to ignite fuel, small heads of carbon will glow red hot and cause pre ignition problems.

Mark (mhpautos)
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Tuesday, August 31st, 2010 AT 12:02 AM
Tiny
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Thanks. I know that carbon can cause detonation, I mentioned that. Do you have any other suggestions? Do you have much experience with toyotas from these years.
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Tuesday, August 31st, 2010 AT 12:10 AM
Tiny
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  • EXPERT
HI there,

If you are not using iridium type spark plugs I would consider doing so, also use premium fuel only as both there will help clean out the excess carbon, I was a Toyota service manager during the early to mid 90's before setting my own business up which I still run to this day.

Mark (mhpautos)
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Tuesday, August 31st, 2010 AT 12:19 AM
Tiny
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It is a turbo engine, so premium gas is the only thing it has ever seen. Also, iridium/platinum plugs are the factory recommendations, so they are also being used.
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Tuesday, August 31st, 2010 AT 12:24 AM
Tiny
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What is your oil consumption like per 1000Km's? And what weight oil are you using? And is it synth or mineral?

Mark
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Tuesday, August 31st, 2010 AT 12:30 AM
Tiny
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Consumes about a quart of oil every 3000 miles. Does not burn excessive oil (no blue smoke). I use 10W30 synthetic oil with every oil change.
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Wednesday, September 1st, 2010 AT 11:37 AM
Tiny
MHPAUTOS
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With the miles on your car I would consider using a mineral bases oil, this has been shown to decrease oil consumption in some cases.

Mark (mhpautos)
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Wednesday, September 1st, 2010 AT 9:43 PM
Tiny
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Lol thanks, but oil consumption isn't really the concern here. The reason I lose a quart every 3k is due to a rear main and oil pan gasket leak. Oil is not causing my misfire, I am fairly certain of that.
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Wednesday, September 1st, 2010 AT 9:49 PM
Tiny
MHPAUTOS
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Carbon build up is 90% due to oil consumption problems, over rich mixtures tend to dilute oil and it will burn cleaner it will look rather sooty if rich but prolonged oil consumption will lay deposits of carbon on piston crowns, I would be doing leak down test to see what is happening around the rings.

Mark (mhpautos)
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Wednesday, September 1st, 2010 AT 9:59 PM

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