QuestionThanks for the quick answer. Now to answer your questions. Rough idle? Well, sort of. After it warms up it has been idling from 1000 rpm to 1400 rpm constantly up down, up down. At start up it idles at 1900 rpm and slowly (1-2 min) comes down.
My NOx was 324.00 ppm for the "driving test". I believe its 40 km/h. Second gear for my truck.
Ok, now for all the extra info I neglected to tell you. The truck has been sitting for 1 year in the garage. I put it away with fuel stablilizer and 1/2 tank of gas. I gave it an oil change and added octane booster before I fired it up. I then filled up the tank with fuel and gave it a GOOD run up and down the high-way before the emissions test. The truck was not idling up and down at the test. Shortly after the failed test I did spray carb cleaner into the throttle intake chamber(off and running) and around the choke (dash pot?). About 15,000 km's ago the timing chain was done. The head was checked and machined flat. There was a emissions test shortly after and it passed. Plug's, wires, cap and O2 sensor all have been done in the last 20,000 km's. Oil is changed every 5000-6000 km's. Can't think of anything else. Hope you have enough info and can help me. Thanks!
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The text above is a follow-up to ...
-----Question-----
Hi there. Any help would be greatly appreciated. I have a 1991 Toyota 4Runner w/2.4L engine and 5 speed manual. It has 263,000 km's on it. My problem is it did not pass the idle portion of the emissions test. It failed on the HC, 261 ppm and on the CO, 6.18%. I think I've narrowed it down to either the EGR valve or the MAF. Both parts are very expensive and would rather not have to buy them if I don't have to. I have had no "check engine" light come on on the dash. Again Thank you for any advice that may help me in this situation.
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High HC readings are always caused by an engine misfire or inclomplete combustion, some of the fuel is not burned and put out the tailpipe, this could be a mechanical or electrical failure such as a combustion leak(leaking valve)leaking headgasket, the high CO readings indicate a rich air/fuel mixture which can be caused by a malfunctioning EGR valve, all of these conditions would be accompnied by some sort of engine idle or driveability problem, is there a rough idle condition? The high CO could also be caused by a leaking fuel injector, the engine is getting too much fuel which would also explain the high HC,did you also get a NOx reading and can you tell me what it was?
AnswerThe NOx reading is way too high also, this can be caused by higher than normal combustion chamber temperatures or a malfunctioning egr system, no egr gas flow but that would turn the check engine light on. The idle fluctuation is cause for concern, is the engine running hotter than normal after warmup?
