Running rich, power loss, crappy mileage

same here...
on an flat highway it's really difficult for my 98 2.4 liter taco to go above 60mph on 4th gear (i have a 5spd).
flesheatingvirus or
96coma how did you resolve the issue??

 

This might be a really dumb question, but have you checked to ensure your brakes aren't dragging? That happened on my wife's BMW, same symptoms.

 

Just realized this is an ancient thread. Never mind.

 

One thing I noticed that wasn't really mentioned is the brake booster being bad. While parked, rev the engine and keep note it's performance. Afterwards, turn the truck off, remove the booster hose at the intake, plug it with something that wont let any air pass in like a rubber cork, turn on and see if you get better performance. If it's old enough, the diaphragm inside will have a small crack and will let air pass through causing your system to THINK it's running rich.

Keep in mind, your computer may show it's running rich, but that's assuming the air coming through the MAF is the only air coming in. If there is a leak, then there's unmetered air coming in from somewhere causing the reading. Try listening for a hissing/sucking sound in the engine compartment. Mainly around all the intake and vacuum tubing or large units like the booster. Another option would be to spray butane or soapy water along all of the tubes. Butane will get sucked in and either improve or worsen the performance. Soapy water will bubble at cracks.

If you have a 96 or newer, I recommend getting an ELM327 (bluetooth) and the Torque app. its like 10 dollars in total and provides valuable information regarding the performance of your vehicle. it's not shop/dealer grade, but it's pretty damn close if you know what to look for. Study long term and short term fuel trim.

 

The brakes are not on. I am able to push truck on neutral.

I sprayed water on all hoses and no idle change.
When removing the pcv hose and brake booster hose from intake manifold i did notice an idle drop.
When i disconnect any small vacuum hose connected to the egr valve, there is no change in idle.

Also forgot to mention:
Truck was running fine. 90mph+ no prob. It ran sluggish and went from 22pmg to 17mpg after i unplugged the coolant temp sensor and left unplugged for 500 miles. Since then I've replaced efi relay, ecu, maf sensor... And no dice. plugs are new. Ngk wires are new. New coils. New head.

 

Does Torque app pull transmission temps?

 

Only if it has a stock connection to the ECU with a PID! Then you should be able to put a custom torque addon/gauge requesting that pid and translate the info to something readable/gaugeable

 

Double check, you use the water method and look for bubbling. But use soapy water in a spray bottle. Using butane is what causes an idle change. You're not doing that.

Don't be alarmed by this (because of the following paragraphs) but, if you don't have any vacuum leaks externally (in the hoses/connections), you may have internal issues in your head or intake/exhaust manifold.

Also, you purposely removed the coolant sensor? Why? That will cause long term issues with your fuel trims since your ECU NEEDS that information to know when the engine is warmed up and can run normally.

Quick learning session. On cold start (whenever the engine isnt running at ~210f/100c, which is known by the coolant sensor), the engine runs extremely rich to make sure it warms up quickly and to provide the necessary chemicals from the fuel to be deposited into the catalytic converter(s) for nominal use. Once warmed up, the fuel trim balances out to stoichiometric (neat word that's good to know) perfection, and burns all the exhaust properly.

Your truck probably has been running SUPER RICH for 500 miles, lol. no wonder what's happening is happening.

Try this. Get someone with a scantool to clear/reset your DTCs/emissions/faults/ecu, and only use 91+ octane for 1k miles, with octane booster if you can afford it or go with racing fuel. You may just have some serious buildup in your cats. Worst case scenario, you've mutilated your cat from running so rich, and need to get a new one(s).

This seems like the most logical explanation given the information you've stated. But if you can give me more, especially about why you removed the tempt sensor, please do. I'll do what I can.

 

Hi undyingvisage58:
Thanks for the info. I'll do the soapy water and butane test tomorrow in the AM.

about removing the coolant temperature connection... looong story Dude, but I'll try and make it short: I got stuck in the Tijuana, Mexico border about 15 cars back when i hit a pothole and my truck died. I pushed it closer and closet to the border. MEANTIME a mechanic shows up trying to make my truck run. not having extra wire, he yanked off my coolant temp wire. I then drove 200 miles home, drove the truck for a week, then finally spliced the harness to reconnect the wire to the coolant temp sensor. (my truck ended up dying on me bcuz the engine bay fuse box EFI relay had a short. a tap on the fuse box fixed it. hasn't shut off for 2k miles).

Anyway... the ecu is not the problem. i bought an A/T ecu from a 99 2.4L and installed yesterday. the truck still wont go above 60mph on 4th gear (both ecu's perform the same).

About the cat converter being smoothered with deposits, that would make sense to me. i'll run high octane this weekend.

more info: The truck also idles high (i don't have a tach), but i'll guess it to be about 1500/2000 rpm. even when it ran well it was idling high.
it's not the MAF sensor since i have 3 MAF's... also, i DO NOT get the deep throaty sound when i put my foot to the floor. MAF is clean.

 

Still seems like there is an intake leak of some sort from this info. You may want to rebuild the intake system, mostly the rubber intake and vacuum tubes. Work on running high octane through your system for a while. Put your original ECu back on your truck, too. It's programmed perfectly for your truck, another random ecu that seems like it works isn't trust worthy. Just have the original reset/cleared so it restarts the self testing and calibration.

That's really all I can tell you over a computer. The rest is in your hands. Good luck!

 

I pumped 91 octane and added half a can of seafoam. at first i couldn't go above 60 on 4th gear... 20 mins later i was able to hit 70 on 4th gear. 200 miles later i was able to hit 75 on 4th gear. 400 miles later i was able to hit and hold 75 on 5th gear. 500 miles later i am able to hold 75 on uphill slope.
seafoam did the trick. i'm guessing the cat was clogged up.
truck runs like a champ now.
thanks all for your feedback.

 

Awesome!!! To go a next step further, use some

$15 CRC Guaranteed to Pass Emissions Test Formula, 12 Fluid Ounce

Guaranteed To Pass! It's another form of system cleaner that you can get at just about any parts store.

 

Snake oil.

 

Try some nice brand spankin' new spark plugs.