Chester thinks thinks it's a vac leak , I do not..Clean your old IAC properly and put it back on.

Until you can explain WHY PO300 exists your barking up the wrong tree . Like I said before , I have experiance with this code. A vac leak is not the problem IMHO. You never answered my questions - so I cant help no more..

Good Luck tho.

 

I am not sure what question that I did not answer but I greatly appreciate all the info. If it was was question about what my IAC looked like I did answer that one. The one I took out looked just like yours but the one I put in did not have the spring.

Anyway....... Something weird happened this moring.

I started it at about 6:00 am and it did the same as always. It ran like crap. I only let it run for about 1 minute, just enough to see if the problem had gone away. When I went to leave for work at about 7:00 am it ran great! I started it up and it idled perfect!

For the last six months that it has had this idle problem it has always tryed to idle at about 600-700 rpm in park. When I started it the second time this morning at 7:00 it idle up to 1000 RPM and ran perfect. When I put it in drive it drops to 700 RPM and still runs perfect.

I can't explain this one but I am very happy about it. I did nothing to the the truck between 6:00 a.m. and 7:00 a.m. other than curse it. Last night I cleaned the MAC, Throttle body, and the PVC valce. None of which made any difference at 6:00 this morning.

I can't wait until the morning to see what it is going to do. I hope the problem has vanished for good.

Any ideas?

 

You could if you want to. I'm trying to think optimistic here. MOST problems with rough idle are attributed to vacuum leaks. Especially when there are no other driveability issues. But if you would, please post again exactly when and how you noticed this initially. What you did in the mean time, and how the situation has changed. I tried reading this thread from start to finish, and I got lost. The way I see it, you are only having problems at idle. Right? Does it fix itself when the engine warms up?

 

With all due respect... could you please call it by the correct name too?

It's MAF not MAC(these are noodles) & PCV not PVC(this is white tubing)


now back to the regular scheduled posting.....

 

Your statement is correct. I only have/had a problem at idle when cold.

Recap:

About six months ago it started to idle rough in the mornings. The problem progressively got worse over about 2 weeks. After about 2 weeks it would just stall out if you did not keep it reved up in the mornings. The check engine light came on about this time. I ran it like that for a while. The colder it is, the longer it takes to run steady. Its base line idle is 600-700 rpm in park. It tries to idle there at 600-700 rpm but bounces up and down from there like a yo-yo. It will eventually stall out if I don't rev it up to around 1200 rpm.

1. I changed the air filter. No change in condition.
2. I replaced the IAC. No change in condition.
3. I "visually" checked for vacuum issues. Nothing found.
4. I cleaned the MAF, Throttle body, and PCV valve. No change in condition.

Step 4 was yesterday. When I started it this morning at 6:00 it was no different. It still would not idle. I only let it run for about 2 minutes. I was just checking to see if the things I did last night made any change. It did not even get a chance to think about warming up. About an hour later I went to leave for work and to my surprise it ran perfect when I started it this time. It idled perfect at about 1000 rpm in park and when I dropped it into drive with my foot on the brake it went to about 700 rpm and continued to run perfect. It had not warmed up at all yet but ran perfect.

I did nothing to the truck but swear at it. Maybe it just needed a good talking to? I can not explain why it all the sudden started running good the second time I started it. I was as cold as a witches ______. Maybe some sort of delayed effect from the things I did the night before?

I can't wait to see what it is going to do tomorrow morning!

 

Have you reset the computer after changing these parts or disconnected the battery?

 

lol - he doesn't listen very well lol

 

I listen very well. I was typing my last post when he posted those comments. I did not get to read it until after I made my self look dumb again.

 

I reset the computer after changing the IAC. The light has not come back on since then even though the problem persisted until this morning.

 

Just a thought mine was doin similar and it was IAC wish i could help more so its still fffdup?

 

Did yours produce a PO300 - That 's a pretty serious frickin code.

First the monitor has to get thrown in gear which a certain criteria has to be met just to do so.

Then for your monitor to detect speratic misfiring is worse case scenario.

Next - the cats will get hot and the PCM will shut down his injectors - not just safe mode - the truck won't run until you wipe the KAM and zap the pram (parameters)

 

No thank god! It was idling about how his was but it was just the IAC.

 

I'll post the questions once more, you need to answer correctly..

Eric - did you have a blinking check engine light since you owned your truck?

If so , when?

After your truck reaches 45mph and then shifts into overdrive - what does it run like immediately after the shift into OD?

Reason I ask - this is where a PO300 code will shine. During any given drive cycle, this COP load is a favorite among failures. If your truck misses , hesitates, sh^ts, anything.

Monitor hack - reset your KAM , pull your negative cable from the battery. Touch it to your positive cable. - Don't worry you won't blow up lol..Reconnect your neg cable immediately. (If someone chimes in and says there no loop - don't listen , trust me) . Start your truck and find an area where you can speed up to 60mph and let it coast down to 40mph without touching the gas or brakes. Do this three times within the same drive cycle - it doesn't have to be consistent, just within the same drive cycle. If you don't have a light yet - shut it down and start it back up, you should have a light real soon if you do indeed have a PO300 problem - it's pending..

Go get it read, if you have a 300 , change all COP's..

 

Jbrew,

I have never seen the blinking light you describe. When it shifts into overdrive it seams fine. I will have to go out and do the 45mph test today. I did notice that a couple times (not every time) in the past few days that when I am up to speed and I let coast it feels like any engine brake gets engaged. I did not pay any attention to what mph it did this at but I will get back with you. It is hard to describe........ it's almost like what happens when you put your hand over the intake while it is running.

Other than what I described above I have not noticed any othe problem when I am up to speed like this.

Thank you so much for your help.

 

What is a KAM?