QuestionQUESTION: Hello Blue,
I am wanting to have a good opinion from you about what is possibly ´limiting´ my car´s acceleration performance. My car in question is a 2.0L Toyota Camry 4WD. When I accelerate in first gear to almost 4,000 rpm (pulls/pushes strong & fine until then..), my car´s power cuts out as if it were being limited. Then in second gear, I can accelerate to around 4,100 rpm before being ´limited´ again, and in third gear it reaches about the same plateau. What can I do to increase my car´s powerband? Is perhaps my 4wd tranny limiting my car´s acceleration, or perhaps the stock ignition? *I have a large K&N air filter from an ´87 Toyota Supra installed, Tornado Air Velocity Insert installed in the air intake boot before the bend(before the throttle body), and have replaced the stock fuel pump with an aftermarket Japanese one. Also, my ignition coil tests fine, and my Ignition Wires & Cap are from Bosch - which is firing NGK iridium spark plugs gaped at .035". Thanx 4 your ideas. Uncle Jesse.
ANSWER: Describing it cutting out as "if it's being limited" I assume means as if it just flat at 4 grand, no backfiring, sputtering, jerking? If this description is true, there's a MAP sensor that your engine is equipped with. It looks like a small device with a vacuum hose attached to it, and a wire plug with wires coming out and into a bundle. Usually its maybe 2-3 inches square, and mounted on the firewall or inside fender well. Checking with a local auto parts store, especially a quality chain store like advance auto, checker, o'riellys etc they're happy to help, and look it up on their compter as to where it is located. I didn't see the year mentioned, but these same chain stores usually will scan your computer for free and tell you just what you need. Service centers charge for the very same thing, sometimes big bucks.
In absence of them scanning it for you and telling you exactly what the problem is, locate the MAP sensor, check out the wiring and vac hose connections to see if they're OK, assure the vac hose isn't cracked and hooked up to somewhere on your intake. If you can't see any visible problem, disconnect it and take your truck for a drive, see if the problem changes at all, if it doesn't odds are it's bad.
Not knowing the year of your truck, it's kind of a guessing game, I'm assuming it's computer controlled and some type of fuel injection. If it's not and a conventional carb and distributor set up, email me back and we'll discuss other problems, such as weak valve springs, cam mis timed, etc. Fully describe exactly what it does when you hit 4 grand.
It may be as simple as a partially plugged exhaust, but let's start here. Keep me informed.+
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QUESTION: Hi again Blue. That is right, no backfiring, sputtering, jerking - .. it feels like it is just plain being held back/limited` at 4000 (frustrating - yes, the cam belt timing has been checked with the cam cover off, but maybe I need to have it `retarde`?*). *First off, thank you for your good first sensible and knowledgeable rec - checking the MAP sensor... but the deal is my 1988 Camry 2.0 Alltrac(4WD)(with fuel infection with correct base timing adj.) does not have a MAP but a MAF type of sensor (AIR Flow measuring Type, I guess). So, with that in mind, following your other advice, I have checked all of my vacuum line connections to my intake manifold, and all check good & tight. Perhaps I have to recheck the condition of my 1 year old `Iridium Spark Plugs?`, or is perhaps my BOSLA stock replacement muffler system (flex-pipe back ->) causing too much exhaust restriction, for the rpm`s ¿? **Yet, I can tell you that at idle the muffler puffs out quite freely against my hand (5¨ + inches away).
So, perhaps your idea of some weak valve springs could be the answer after all? Please give me a write whenever you can, much appreciated, good luck to you, yours and your endeavors, uncle Jesse.
AnswerThanks for your compliments. I am a "professor of life mistakes", learned most of my knowledge from heart ache and break downs. From your thorough description, I'd bet the farm your exhaust is restricted. Being a uniform, flat lack of increase in rpms at a predictable and consistent point indicates it is a component that every cylinder is tied into. Weak valve springs can over time be a flat "wall" limitation, but usually is more associated with valve floating, spitting sputtering, etc.
Spark plugs usually have the same effect, unless the symptoms started right after replacing the plugs. It happened to me once and I discovered I was given the wrong heat range, a misprint in THEIR book. In any performance engine I build I make it a habit of "indexing" my pugs (you can by copper washers in a pack of varying thicknesses, and you install each spark plug so the open part of the plug electrode is facing the intake valve, not shrouded by it) AND most important, do a plug reading. To read your plugs gives you an exact idea of what your engine is doing inside the cylinder, and is a bit of an art.
To do a proper reading you need an area you can run your vehicle up to max rpms for at least 3-5 seconds, then kill the ignition and coast to a stop. Now you remove each spark plug and with a magnifying glass you carefully inspect the spark plug (radio shack makes a small magnifier with a light, it's shaped like a big cigarette pack, black and has a small opening on each end to look through, and to view objects under the light.)
The body should not have any stirations or carbon lines (sign of bad wires), the porcelain
that wraps the inner electrode should be a nice cocoa brown (white means too hot, black means too cool and/or fuel problems). Pitting in the outer electrode means erratic ignition spark.
Look way deep into the plug where the electrode porcelain tapers to the plug) for signs of globules of metal, which means a piston is melting or valve is failing. A wealth of info comes from a good reading. Some high performance engines require different heat ranges for individual cylinders. My mini stock 4 banger needed 2 heat ranges cooler on the 2 inner cyls, some chevy 350s need lower heat ranges in each outermost cyls.
Take you exhaust apart, look for collapsed baffles in the mufflers, too acute of bends, or collapsing at clamp points. Lets keep working on it together and We'll figure it out. Take care, Mike
