Cold engine causing high idle?

[Hotrod1988]

Hello folks first post here. First I'd like to thank all of you for The wealth of knowledge I've found here as its help me a lot since i bought this truck a couple of years ago. But back to the point, the truck has always had some issues I've been chasing (plenum leak, missfire, clogging cats) but I think I've finally got all that nailed down. Plenum is fixed, miss is fixed, and hollowed the cat out till I can get everything lined out or until it courses other problems.

Currently after fixing the plenum the truck has been running cold. Heater off 174° heater on 169° according to tourqe app. Its cold here in Texas now so its hard to pin it all down yet but the truck idles at 1000 in neutral ones the truck is passed about 140° b4 that it idles normal. I've replaced both the tps and the IAC twice to make sure it wasn't them (they are bwd brand parts) its almost like the truck is holding the IAC open to get it to warm up more but it can't. I may have to go back to the factory 195 t-stat I've used the 180 just because it had one in it when I bought it. However I don't think it ever opens judging by the temp reading I guess the heater core is keeping the truck cool enough in this cold weather lol. Im wondering if having the cat hollow is letting too much heat out and the engine just can't get warm enough? Maybe the t-stat is stuck halfway open? (Its not flowing much in the rad with the cap open tho) I know the engine temp is right as I can put my hand on the head after driving an hour and I can just hold it there. Now the idle may not be related I've read a couple post where people had a frayed wire going to the IAC or the tps causeing idle issues.

Sorry for the long post but wanted to make sure I touch all the bases to delve into the weath of knowledge here thanks ahead of time guys

 

[Saltillo Express]

I can't imagine the hollowed out cat would cause it. Unless you damaged the upstream O2 sensor in the process. As in, if you cut the back or side of the cat and used a big screwdriver and hammer to do the deed and didn't remove that O2 sensor first? However, I would think it would set a code for that if that was it. Have you checked it for codes? If you back the throttle plate adjustment screw out, will it idle down? Or, is the throttle plate adjustment screw out of adjustment? If the IAC and TPS are new - are they positively clicked into the harness? What about the MAP sensor on the front of the TB? Is it fastened correctly with the hose on the port and all that?

 

[Merc225hp]

96 has two temp sensors one for the pcm and one for the gauge. Replace the one for the pcm and replace the iat. Do a hard reset on the pcm, let it relearn and post back.

 

[Hotrod1988]

No codes being thrown according to my torque app and didn't think the throttle had an adjustment on these trucks? I will look now tho to be sure.

Of the two temp sensors one has 1 wire the other has 2. The one with 1 wire is the PCM correct? If so I just changed it (bwd part) i am going to change the other one too as my gauge in the truck reads different that what it shows on touqe app. The iat sensor seems to be working as I can see it on my app. That however does not mean it is ofcouse. Seeing as I had a leaking plenum pan it likely has some buildup on it.

Thanks guys will report back when I replace those sensors

 

[Hotrod1988]

Well I'll be a son of a &@%@%@......I sure as heck has an adjustment on the tbody......took the air hat off and there that torx head screw was staring at me.....I think it was laughing and saying rude comments too....lol. Backed it off and idled right down.....what is a good idle to set it to now that I'm over feeling like an idiot for chasing this for 2 years? Hahaha

 

[Merc225hp]

Should I tell u you should not adjust that screw, oh well its running better lol.

 

[Hotrod1988]

What's the reason to not adjust it? I am thinking that the previous owner may have jacked with it trying to solve some of the problems I have fixed since getting it....or hell I may have done it one drunk night working on it and forgot lol never can tell sometimes. It does run good now tho, feels like a new truck. Heck I might even try n race my moms hemi hahaha

 

[Merc225hp]

Factory pre set and are not to be adjusted. Adjusting it will through the tps, iac, map, the whole nine yards outta wack. As for what was done before oooh well, its running up to your liking so that's good.

 

[Saltillo Express]

What's up big Merc? This is Chance from Fl. Agreed on the adjustment. I just didn't know if it might have been messed with prior to. Glad you got it going OP.