High Idle

[Damienmore]

my 2000 SOHC 4wd is idling high at 1400 rpm in park, I just replaced the IAC valve but I can't figure out how to tone down the idle.

 

[koda2000]

Is your CEL on? High idle is usually caused by a vacuum leak somewhere. Idling at 1400 is a pretty big vac leak and will usually be accompanied with P0171/0174 ODB II codes.

 

[J_C]

It was doing that before you replaced the IAC, or only after and if after, was it from the moment you started the vehicle after? Wondering if something went wrong with that, perhaps the IAC isn't seated well or stuck open or something?

Not knowing the above, I'd also wonder if you just accidentally knocked a vac line off or disturbed one such that it was brittle and developed a crack.

 

[Damienmore]

I drove the truck for about 4 months with a PO171 and 174 code until the first cylinder stopped firing and the truck died, we had all the hoses in the engine replaced (some were only held on by zip-ties, as well as a timing kit was done, the oil pan was replaced, and the rear main seal was replaced for the third time in a year, and the second tune up in a year was done) and the day after I got it back this code appeared, I took an IAC valve off a junkyard explorer and put it on mine, but the code came back, then I bought a new one with a gasket and put it on this morning, I drove about 30 miles before the light came back on with the same code. At the same time the thing doesn't like to stop and fights me whenever I use the brakes, but then occasionally I will have to floor the gas to get it up to 45-50 mph keeping up with traffic. All this has happened since I got the truck back from the mechanic, I already have to take it back because it leaks an entire bottle of freon in 3 hours, the windshield has started leaking, and the IAC valve issue began.

 

[koda2000]

With low vacuum your power brakes don't work very well as you lose power assist. The codes P0171 & P0174 indicate you have a large vacuum leak(s) somewhere. This means un-monitored air (air the MAF sensor isn't seeing) is getting into the engine. In addition to the problems you're experiencing your engine is running lean (too much air, not enough fuel). This can ruin your engine because it causes cylinder temps to be very high and of course causes your high idle. There are many places where vacuum leaks can occur, for example:

Leaking/defective power brake booster
Any and all vacuum lines (including the evap system front & rear of vehicle)
HVAC lines/controls
Cracked vaccum ball
Upper and lower intake manifold O-rings/gaskets
PCV grommet, hoses and/or elbows

The best way to find vacuum leaks is to have a smoke test done. There are no easy answers, someone just has to methodically approach the problem and find it.

 

[Damienmore]

With my luck I wouldn't be surprised if there were leaks in every part, but I forgot to mention PO 1506 is the only code I have now, does everything above still apply?

 

[koda2000]

P1506 is saying your idle is too high and that the IAC/PCM can't adjust it to where it should be. If you're not getting the P0171/0174 codes any more it means your vacuum leaks aren't as bad as they were, but there's probably still a leak somewhere which is causing your idle to be higher than it should be. When fully warmed up your idle (depending on which engine you have) should be 500-650 RPM (SOHC around 500).

How are your brakes now?

 

[Damienmore]

I didn't have a problem with the brakes until after I got the truck back, replacing the IAC valve didn't change them at all, but it didn't change the code either.

 

[koda2000]

Maybe whoever did the work forgot to hookup the rubber hose from your intake to your power brake booster... ? I'd take it back to whoever did the work and tell them you idle is still to high and your power brakes aren't working properly.

 

[Damienmore]

That's what I'm going to do, we paid him a good 4000 dollars to get the truck to run again. Thanks Koda

 

[koda2000]

Not that I'm criticizing you, but why in the world would you spend $4000 to get a $1500-$2000 truck running. You could have bought another one w/low miles in excellent condition for less than that and you could have gotten a V8 instead of the troublesome SOHC V6.

 

[Damienmore]

I didn't spend the money, I came up with a plan for my grandparents to purchase a different truck that isn't a lemon, and pay them back the money with a plan that I could afford, but they decided they would rather repair the engine. It was out of my hands even though I'm the sole driver

 

[koda2000]

Well, I'd raise holy hell with the shop that did the work. If they can't get it right I'd take them to court, though no matter what your grandparents wont be getting their $4000 back. The shop should have told them doing the repairs weren't worth it before they started, but there's no law against paying too much to fix something.

 

[Damienmore]

They knew the repairs weren't worth it, it was a mess figuring out whether to replace the engine, repair the engine, or buy a new truck, and they decided to repair it. I'm calling the shop today and I'm going to put it back in after I graduate, but I'd like to do a v8 swap on it. There's a nice 5.0 mountaineer that was rear-ended, in a junkyard by my moms house in WV I'd like to get, the staff wouldn't let anyone dismantle the engine since it still ran.

 

[koda2000]

A V8 swap is possible, but it's a lot of work. Engine, transmission, AWD transfer case drive shafts, exhaust system, power brake booster, radiator, PCM all the wiring. You'll be amazed at how much stuff you'll need to install the AWD V8 into a 4x4 V6 vehicle. You need the entire donor vehicle, not just the engine and trans and you better be capable of doing all the work yourself. Paying someone to do it would be nuts.

It's not worth it. Especially after having just spent $4000 on the V6. Get it running right, drive it or sell it and look for a clean V8. It will be cheaper and a whole lot less work.

 

[J_C]

Document the bills, your correspondence with the mechanic. When acceptable, send certified letters and text messages instead of voice phone calls, or if legal in your state, let him know you're recording calls and do so.

$4k and then it not running right is nuts. You shouldn't touch the vehicle, leaving it the way the mechanic did and getting a professional 3rd party opinion of what's wrong, a documented repair estimate and description detailing what the prior mechanic did wrong (this is important) to take to small claims court.

 

[Damienmore]

I didn't know all that was included, I just thought it was the engine, radiators, and transmission, but I just got off the phone with the mechanic and its going back in the shop next week, Ive started documenting the calls, 4k is crazy though, more than twice its value.

 

[Damienmore]

Trucks dead, nothing from the first cylinder

 

[Flash]

If you've had a your timing chains, guides and tensioners replaced with later, better quality parts then your SOHC engine is no longer troublesome and can be expected to go for another 200k assuming you do all the other maintenance.

But that dead cylinder has to be a warranty issue.

 

[koda2000]

Dead how? No compression? No spark? No fuel? What did the shop that did the work say?