Rpm idle speed differences?

[Darrman]

My '91 with 216k miles runs and idles great...now. If its cold it will start around 1200 rpm and within 45 seconds will idle down to warm start, which is around 800 rpm, then when in gear it idles down to 600. This is my auto 2wd truck.
My '92 with 91k, starts no matter what around 1300 rpm and eventually will idle down to 1000 rpm, and then maybe down to 8-900 rpm and will twitch like crazy. This is my 5speed 4x4 truck, and I just got it and I am saving for a new tranny, so I havent really dug in yet as far as tuning it up.
I am curious, what are the idle speeds ya'll are getting? Is there a difference between transmissions? Thx.

 

[alexefron]

ive got an M5OD, and mine starts at 2k, and quickly falls to about 1200. After it wasms up a bit it will drop to 1k, and when its fully warm it idles at around 650/700

 

[Darrman]

Wow, thats pretty high starting rpms, but I am sure its a lot colder there than it is here, so your computer must compensate more.

 

[Rhett]

650-750 rpm is what the 4.0 OHV is supposed to idle at when warm.

 

[alexefron]

that 2k is only for about a second before it drops down to the 1200, and yes thats only in low temps (20ish degrees)

before i cleaned the maf, and iac mine would idle at 850-900 when warm

 

[Darrman]

I have already scanned codes, and came up with a lean 02 sensor, which sucks, because I just coughed up the 55 bucks for a new one in the '91 a couple months ago.
Other than that, I cleaned the TB and IAC, but thats it, the MAF has security torx screws, while the '91 has standard phillips screws, weird, but I dont have the right tool to get em out yet.

 

[alexefron]

the right tool = hacksaw

 

[Rhett]

I have already scanned codes, and came up with a lean 02 sensor, which sucks, because I just coughed up the 55 bucks for a new one in the '91 a couple months ago.
Other than that, I cleaned the TB and IAC, but thats it, the MAF has security torx screws, while the '91 has standard phillips screws, weird, but I dont have the right tool to get em out yet.

Before I hacked it out I'd get a T-20 Security Star torx bit, they are easy to find (Sears has them and so did AutoZone).

I have never heard of a 91 with phillips screws holding the MAF housing in before. Do you think the screws were doctored in the past?

 

[96limitedX]

my moms '94 winter time fires up and idles at about 1,500 then drops to about 900rpm once warm..

 

[Darrman]

Autozone has them? I will have to go see if I can find one later today. I went to lowes and home depot earlier this week and was out of luck, Walmart had a set of Stanley Torx drivers, looking at them it looked like they had the tips drilled out, but I dont know if its for security version or not.
And I guess the '91 were switched out, there was a lot of work done to the truck over the years.
I know my idle speeds are way off in the '92, looks like I am going to have a lot of tuning to do.

 

[spindlecone]

they are

 

[alexefron]

at advanced auto today i saw a set of securitys. first security set ive ever seen in a real store, other than ebay or somewhere else online.

 

[Darrman]

well I tried autozone, no luck, oriellys had a set, but they wanted $25, which I can see paying to work on 2 screws, so I went and got one loose with needle nose vise grips, then went to Home Depot and bought some new flathead screws, had to drill out the other, but the new screws work perfect, so I am happy.
Oh, and cleaning the maf didnt do anything.

 

[alexefron]

gotta reset the computer...