can a fuel injector get "stuck" in a position where it would cause the engine to rev high at startup and then settle down to normal rpm? my 92 ranger does this on startup. i replaced the throttle position sensor, air idle control vavle, cold air temp sensor, fuel cap. the engine shows no trouble codes. took it to the dealer. nothing out of the ordinary. they even kept it overnight so they could have the code scanner in place at start-up. it revs to about 2,300 rpm when first started in the morning and then settles down to its normal 800 rpm idle. after the engine is warm, it doesn't do it. then, the next morn..boom, it does it again. it seemed to have happened shortly after using the chevron fuel injector and intake valve cleaner. the ford dealership mechanic told me to "just drive it". yeah right.
fuel injectors
- Thread starter penzdude
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Both of our Mazda 626's do that. Only happens on really cold days. Dyno Tune checked mine and said it's normal.
Not very likely an injector as the ISC (which you have already replaced) is set open by ECU on cold start for air bypass and fast idle. As the engine O2 sensor goes closed loop in a few seconds the idle speed is backed down. Why the cold speed is now higher than before is interesting. This is something the ECU is doing despite no fault codes being set. I've seen this happen before exactly as you describe but can't say why. Not much of a problem but would bother me too. Are you sure the cold idle speed has gone up without a change to colder weather?
i don't understand what the problem is, that's normal behaviour...
MolaKule
Staff member
This is normal operation for cold start-ups on my every computer-controlled car I've owned.
This is similar to the electric choke set for the older carbed vehicles.
[ June 10, 2003, 04:27 PM: Message edited by: MolaKule ]
This is similar to the electric choke set for the older carbed vehicles.
[ June 10, 2003, 04:27 PM: Message edited by: MolaKule ]
The ECU should not be increasing the cold fast idle from the previous rpm value before Penzdude used Techron in the fuel. I'm not sure how the '92 Ford ECU sets the inital cold start value but it may be derived from stored data from normal idle feedback. If so then if the normal idle is 800 then the fast idle is locked to say +600 and should not change over the life of the engine!
thanks for the replys first of all. greg and kule, this is hardly normal for this truck, which i have owned since new, hence the purchase of the mentioned parts,trying to correct the problem. this isn't the automatic choke type of high idle. the engine never has done this before. before, i'm guessing at startup, it would rev to around 1,200 rpm or so and then settle down to normal 800. now, it's close to 2,500. not normal at all. wierd the no code thing. oh well, probably some old time mechanic will be able to tell what it is. i think most all these days go strictly by the code scanning tool. thanks for the intrest though, penz.
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