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Discussion Starter #1
So this is a very long and ongoing issue. I will try to keep this post as information relevant as possible.

To start, I did a 2.5 duratec swap. The car is a 2004 zx3 (originally 2.3) with 220k miles. I sold it to my brother in law a couple of years ago and he got his fingers in it and did his "modifications" then blew the engine. I got it back then decided it was a good time to do the swap.

I've been tuning with Tom and nearly everything is going perfectly. Tom has made the car very drivable but we keep getting snagged on a couple of issues that we can't figure out. Maybe it's mostly me and I'm being impatient, but nevertheless, the issue is still there and it's driving me crazy.

First of all, the idle issue. The car has no vacuum leaks. I've checked that about a dozen times. The IACV is new and I've tried several of them. What's going on is, usually while driving, the car will want to stay is 3,000 rpms. I'll push in the clutch and the rpms will hang there. Sometimes if I blip the throttle they will drop to normal idle speed but sometimes they won't. If they do drop and I continue to drive as normal, they will hang there again, and sometimes climb to 3k rpm even if I'm cruising at 2k. Sometimes if I turn the car off while driving, with the clutch in, and restart, it will act normal, but they will go back to a 3k idle. It's happening almost every time I drive the car. Today I noticed that if I'm cruising and take the car out of gear and release the clutch so it's in neutral and rev it up, the rpms climb very roughly, hang wherever I release the throttle, and my a/f is all out of whack. It's almost like there's a sensor that's not communicating with my idle air. I can't figure it out and I don't want to start tinkering beyond repair. I'm at a loss with this issue.

What other sensors or tweaks can be done that might have something to do with the idle issue?

One other thing to note, the car has an airbag light from when my brother in law owned it. I haven't attempted to figure out why but is it possible that it could be part of the problem?

I think I explained the issue in full, but maybe there's more. Ask me questions if you have any and I can also post pictures if needed. Thank you.
 

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Airbag is a separate issue.

Duratec TBs are well known for sticking butterfly if slightly overtightened and once done it may not fix without a new one. The hang following adjusting throttle screams it; '...hang wherever I release the throttle...' That.
 

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Discussion Starter #3
It's a new throttle body and not sticking. I confirmed that through datalogs. Throttle position goes back to its normal idle position when I let off the pedal and rpms still hang high.
 

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Then vacuum leak (or unmetered air) all you got left. It should show at O2 sensor live data reading by being too low in volt at idle. An evap leak can do it too. Intake manifold leak?

What is your absolute dead idle TPS volt?
 

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Discussion Starter #5
The evap solenoid is not connected to the intake manifold because the 2.5 manifold doesn't have a port for it. I was told to just let it vent to the atmosphere.

The intake manifold doesn't have any leaks, I've checked that several times.

Not sure what the idle tps voltage is, I'll try to check that soon.
 

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Discussion Starter #6
TPS idle voltage is:

Yellow wire 5.51
Brown 0.05
White 1.11
 

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Discussion Starter #8
I'm pretty sure it's not the person at all... Same issue even with the factory tune.
 

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Can't swear to it myself but others have reported issues with dead idle TPS at over 1 volt (white wire). Supposedly even though the absolute TPS swing gets an algorithm overlaid on it to come up with what the PCM wants, if the idle is over 1 volt things can mess up as 1 volt is a number the PCM recognizes as not dead idle but idle rising and it then begins to change a lot of things. I know I had trouble with it way back when I figured out how to make MTX TPS work on ATX cars, I had to make sure the beginning idle was definitely under 1 volt. I used somewhere around .9ish IIRC.

I got that as well from a Ford engineer way back in the day. The caused issues sounded similar to yours.

If I have questions the only way I would accept intake being sealed would be to block all ports off and run a vacuum leak test on it. Spraying like carb cleaner around the engine is too vague and too easy to miss things. I'd be likely blocking IAC off as well to not let ANYTHING in it. And probably killing the TB absolute aircrack at idle just to see if the issue stops then figure out how to get idle back. Block PCV off if it is still there. What if the PCV metering orifice is too big for that engine?

Leak in brake booster? Not impossible. Leak at TB throttle shaft? There are seals there. Dunno if the TB has a side channel like zetec that can leak internal to not be found, the IAC air bypass channel. If TB changed with no new gasket can leak there too. Those old gaskets look great but often cause issue, the silicone exposed to heat loses about half its' density and the crush then drops way off. Squeeze an old gasket and brand new one and get surprised.
 
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Discussion Starter #10
I know very little about checking and adjusting voltages to specific wires in the car. Although anything is likely at this point, I'm going to try the obvious mechanical tests first.

I didn't check the brake booster, but there wasn't a leak to that vacuum line to the intake manifold. I will check the booster itself though. The TB is new, but it's definitely worth checking again,and it has a new gasket. I want to eliminate the TB adapter I bought through massive because I don't like the paper gasket that came with it for the IACV. So with that, I will also try the 2.3 IM and use an adapter for that instead.

It's so difficult to check the pcv since it's in such a tight spot, but it is new and I always make sure the tube is fully connected.

I'll also do my best to do a vacuum leak test on anything I can.

I have my suspicions with the brake booster though. No particular reason why, it's just something I haven't looked at. My brakes feel solid and respond well. I just hope it's not electrical because that's not really possible for me to troubleshoot while driving. Unless I run leads to different locations and have the voltmeter inside the car. And with that, I don't know how much of what I should be looking for.
 

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Discussion Starter #13
I will do another smoke test, last time I didn't think to check the brake booster. The brakes feel good though. Could they feel good and still have a vac leak at the booster? The earliest I'll be able to check is Monday.

Rodknock, I just looked at my last datalog and short term fuel peaks at 1.3 and it's lowest point was something like 0.8.
 

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Discussion Starter #14
Just pulled off my brake booster vacuum line and tested the check valve by blowing into both ends. Sometimes it makes a good seal and other times it let's me blow through both ends. I don't have much experience with these so I can't imagine this would be the ultimate problem I've been having.

Either way, the valve seems to work intermittently and now I'm having trouble finding a replacement hose or check valve. No part number and nothing is coming up in my searches. Anyone know?
 

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Discussion Starter #15
Today I unplugged my IACV and let it warm up then went for a drive. RPMs dropped quickly with every shift and the idle was smooth. I did throw p0511 for idle air control a couple of times but reset them on the fly. No hanging idles, none of the issues I've been having. Normally I'd think the IACV is bad but I've replaced it a few times and finally bought a Motorcraft one, so I know it's not the issue. Can't be coincidence that every IACV I've tried is bad. Clearly no vacuum issue either. There has to be something telling the IACV to stay open. The a/f was bouncing around more than normal during the drive but I'd say the average was still 14.7. WOT was steady and very close to, but not over, 13.2.

During this test at idle I turned on the AC and the compressor didn't kick on. I feel like some wires might be crossed somewhere. I already know there are some wiring issues with the car, so I'll try to dedicate some time to trace down the ones I know about and fix them. I do feel better knowing that the car wants to drive normal.
 

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If you think it's tied to IAC action maybe you need to restrict the absolute openings somewhat, it lets the IAC go where it wants and you adjust the restriction to be what you need as to real world idle.
 

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Any pictures of how your iac was mounted? When I did my 2.5 swap it idled at 3k till I flipped my iac 180 degrees on my 5.0 throttle body. Mine idles perfectly on factory tune, but does stumble at low rpm. With toms tune it runs good across the board but my idle does seem to act up a bit (Hits 2500 rpm when defrost/ac is on on cold start).

I still need to dial it in some but I stopped messing with it because the new slave /throw out bearing is making noise in neutral and ive got a small drip from the rear main (the only gasket I didn't change). Its a 4th car for me so its on the back burner again.
 

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Discussion Starter #18
I'm using the massivespeed throttle body adapter for the throttle body and IAC. I might make a new gasket and just cut out smaller holes to try restricting the airflow. To me, that seems more like a patch to the actual problem though. We'll call it a temporary solution.

Rodknock, I'll take a picture of it on Monday. Going into work early in the dark and leaving work late in the dark makes tinkering difficult lol. Right now I believe it's oriented in the only possible way that clearance allows, but I'll double check it. Sucks about your car though, sorry to hear that.
 

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I assume its this adapter? I have no experience using it but I'd think they tested it to make sure it flows properly. Your description sounds exactly like when my iac was flipped. With your fuel trim that low there's no vacuum leak.
308014
 

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Discussion Starter #20
Yeah, that's the adapter. You got me really curious now, because I have my IACV turned the other direction on my adapter... If I recall, turning it how it is in the picture, it rubs on something. I might have to try it out in the dark tonight because that makes sense and something I haven't tried!
 
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