Mechanics

BAFFLED BY ISO-HEET

1992 Ford Explorer • 6 cylinder 4WD Automatic • 202 miles

Because of some recent rapid temperature changes, I decided to put a bottle of ISO-HEET in my fuel tank. Shortly after I did, my engine started running inconsistently rough, the engine light comes on and goes off and the engine keeps dieing. What's going on?
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PhilipC
March 20, 2011.




You really need to take your rig to Autozone, Advance Auto, others to have The Codes Read (IT'S FREE!) Engine light means the computer is throwing a code. Many times the parts store will assist you in what to do next. If your rig is having trouble trying to idle, maybe removing the IAC and cleaning it might help (instead of replacing it, right off the bat, this might verify it is a problem, before you spend $$$) Let me know how it's-a-goin'--The Medic
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CJ MEDEVAC
Mar 20, 2011.
It was running fine before I added the ISO-HEET. No rough running, No engine light and no dieing.

Tiny
PhilipC
Mar 20, 2011.
Lots of Real Estate in good shape prior to Tsunami. Had good mental outlook on life prior to Evil Female I was once married to tearing pulmonary muscle in half. Looks to be worse than Pearl Harbor now, An I have this permanent Bitter Thing going on now. What are the results of Free Coding, I warned you about?---The Medic

CJ MEDEVAC
Mar 20, 2011.
Have the diagnostic fault code(s) read first, otherwise anything else is a guess. For running rough, only a few cylinders aren't firing due to spark, fuel, or compression problems. The additive you used is basically alcohol which absorbs moisture in the fuel. Most gas today already contains 10 percent alcohol so adding more is not necessary. It's not likely a compression problem occurred suddenly. I'm not qualified to think like a chemist, but if the alcohol you added and the alcohol already in the fuel are not compatible, I could imagine that the combination is harder to fire in the cylinders and requires a higher spark plug voltage. Your ignition system might not be able to reach that voltage which would result in random misfires. Perhaps the combination makes the fuel resistant to spraying from the injectors. If either of those are the problem, I suspect the rough running will clear up once the additive is run out of the tank. The best way to do that is to run it close to empty before adding fuel. If you just run it half empty, then fill the tank, you will be constantly diluting the additive but not eliminating it. Another thought is the additive burns hotter and damaged some of the spark plug electrodes. That won't clear up until the spark plugs are replaced. We used to worry about the cleaning effect alcohol had on the fuel system and where the dislodged debris would collect. There are screens in each injector that could become plugged but the filter really should collect that stuff first. I find it hard to believe that is the problem because one bottle of additive is about as much alcohol as you'll find in half a gallon of gas.

Caradiodoc
Mar 20, 2011.
As it turns out, there was a 1 in 1000 coincidence in this case. The problem turned out to be the MAF sensor was fried. I replaced it and the problem is gone. For some reason, it just happened after I put in the ISO-HEET. I thought it was too much of a coincidence, but as I said, I replaced the MAF sensor and the problem cleared up immediately. Thanks for the input guys.

Tiny
PhilipC
Mar 21, 2011.
I always think about the possibility of a coincidence but when I used to mention that, I was always proven wrong. Oh well. Very happy to hear it's solved.

Caradiodoc
Mar 21, 2011.
Thanks for the input Doc & Medevac.

Tiny
PhilipC
Mar 21, 2011.

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