idles too fast with the air charge sensor connected

greaseyfingers said:

my 87 ranger's 2.9, usually, idles between 1100-1500 rpm's when the air charge sensor is connected...

if I disconnect the air charge sensor's plug in plug, it will idle down, nicely...

all the sensors have been replaced, new IAC, new spark plugs, new ignition wires, new air cleaner, new fuel filter, no vacuum leaks, all electrical connections seem to be good and intact... the engine's throttle cable isn't sticking, either...

I haven't replaced the distributor's ignition module, yet... I don't think that would be causing the engine's high idle problem, do you, or could it ??

the one thing I haven't done, yet, is to replace my transmission's fm145 neutral switch, which has two wires going to it, that are broken off, at the very base, of the neutral switch... so, I can't splice them back together, again...

I don't know how these wires managed to get broken off there... but, that's how it was, when I bought my ranger from the previous owner...

I plan on replacing this neutral switch, whenever I'm able to get one... however, most older vehicles, around here, have been getting crushed, these last few years, being the price of scrap iron is as high, as it is...

if it's possible this non connected fm145 tramsmission's neutral switch is, in fact, causing my ranger's 2.9 high idle... why would disconnecting my air charge sensor, make the engine idle down, nicely, to around 900 rpm's...

if I was to leave the engine's air charge sensor disconnected, to keep my idle down... would that cause any issues and concerns, with my engine's performance and depenability...

what do you all think, is causing my engine's high idle problem, as explained...

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IMenriched said:

Well...it seems you have done a lot of work.....by disconnecting the air charge sensor & you get a better/proper idle...that tends to make me think that it is bad...

what codes are you getting?
have you checked for vacuum leaks???...& don't for get about the brake booster and the cruise control, if you have it.

sounds like your on the right track.

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IMenriched said:

Well...it seems you have done a lot of work.....by disconnecting the air charge sensor & you get a better/proper idle...that tends to make me think that it is bad...

what codes are you getting?
have you checked for vacuum leaks???...& don't for get about the brake booster and the cruise control, if you have it.

sounds like your on the right track.

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Natedog said:

X2 and don't forget the little plastic elbow that connects the vacuum hose to the brake booster...mine was split at the mold line from when it was made and looked fine until I really looked very closely at it.

Pull codes and post back.

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holyford86 said:

well, a faulty o2 sensor may cause a high idle, the EGR problem could as well. some info about your truck would be a good idea, things like year and transmission type would be helpful.

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cleat said:

Hi;

With any Ford I have worked on a high idle is almost always caused by a bad TPS. This will be real evident if when it is idling high and you shut the truck down and immediately resart it and the idle is normal. Other than that try cleaning the IAC and throttle body and also listen and check for vacuum leaks.

Cleat

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