Bought an '02 FX4 Ranger with a 5-speed and51K on the clock a few months ago, but the engine has a stumble or stutter when letting out the clutch. It also does it if the clutch is all the way out and I'm at low RPMs (less than 1500) and giving it gas.
I replaced the plugs and wires and cleaned the MAF sensor with some electrical cleaner to no avail. Any ideas? IAC valve maybe?
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I had a similar problem with my 01 (54,xxx on the clock), but mine is an automatic. It would "shutter" when I would brake, or go into reverse. A new IAC solved the problem. I would suggest that you take yours off and try cleaning it, it might do the trick - but I would bet that's your problem.
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2001 Ford Ranger XLT 4x4, Off Road package, SOHC 4.0 automatic, Line-X bed liner and step rails, Alpine CDA-7894, Alpine R series speakers, Undercover tonneau, Rancho RSX shocks, Clifford Matrix RS2 remote remote start/alarm, BFG All Terrain T/A ko's. 06 emblems, clear corners, Wet Okole seat covers
Before I went to the dealer I decided to have a last look around. I ended up replacing a piece of cracked vacuum hose. It is a piece of 90 degree angled rubber tube that is on the end of a hard plastic tube, and connects to the throttle body, and it still idled poorly. It is on the passenger side of the throttle body. After I did that, I went ahead and dropped it of for the service appointment. The dealership re-set the computer, and did a full test of the vacuum and idle performance. It tested out perfect, and now runs perfect. I think you should try re-setting your computer, that seemed to do the trick.
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2001 Ford Ranger XLT 4x4, Off Road package, SOHC 4.0 automatic, Line-X bed liner and step rails, Alpine CDA-7894, Alpine R series speakers, Undercover tonneau, Rancho RSX shocks, Clifford Matrix RS2 remote remote start/alarm, BFG All Terrain T/A ko's. 06 emblems, clear corners, Wet Okole seat covers
As far as I know, they just reset it. What are these upgrades? I've never heard of that. Did you pull that piece of hose and check it? The Tech told me that is very common.
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2001 Ford Ranger XLT 4x4, Off Road package, SOHC 4.0 automatic, Line-X bed liner and step rails, Alpine CDA-7894, Alpine R series speakers, Undercover tonneau, Rancho RSX shocks, Clifford Matrix RS2 remote remote start/alarm, BFG All Terrain T/A ko's. 06 emblems, clear corners, Wet Okole seat covers
First issue. I thought the Ricken's truck was rough upon take off - right after clutch engagement or already engaged but just idling. Now don't you have the throttle pressed down at this point and attempting to accelerate? If so, the IAC and any vacuum leaks you may have have a much lessor affect on engine performance than they would at an idle with the throttle closed.
At idle, nearly no air makes it past the throttle valve and the IAC oscilates allowing air into the intake manifold to maintain the target RPM ~650. The linear position sensor on the IAC tells the PCM how open it is and the PCM adjusts the injector pulses to provide a relatively rich idle A/F mixture. Rich runs a little cooler and a little smoother.
If you have a vacuum leak, the PCM doesn't know that extra air is coming in, only what the IAC tells it, so the mixture tends to go lean and the O2 sensors will send signals to try and adjust so the idle then goes a bit wacky.
And if the IAC is not operating properly or sending the wrong signal to the PCM, it will idle bad. With no other air sources into the motor, vacuum leaks and IAC have full control over engine performance.
OK then, let's hit the gas. Now you have a higher manifold pressure and if at full open throttle manifold pressure is full atmospheric pressure. You have a boat load of air running into the engine through the throttle body and the MAF sensor is telling the PCM so it opens up the injectors a bunch. Now that vacuum leak is still present and if the IAC was bad it too is still present. (IAC goes full open at WOT by the way but that's OK because the PCM should add extra full for it.) But the key is that the vacuum leak and IAC are now say 5% of the air into the engine with say 95% going through the MAF sensor. At idle, this was inverted. So when you press the throttle to move the car, the issues affecting idle have much lessor affect on engine performance.
You need to look at the things that could affect both idle and WOT performance. Such as plugs and wires which are neede for both - I see you already changed these. May want to consider the O2 sensors too - especially now tht you crossed 50K.
Now PW01 comments could be very valid. If you had the poor idle problem for a while, the PCM has been creating correction factors that are multiplied against the base tables that control A/F mixture and spark advance curves. If the PCM thought you were lean because, well you were with a vac leak or bad IAC, then it has created correction factors to increase the fuel ratio to run richer or back to the O2 specs. Now that the extra air is not there, the correction factor is still pouring in extra gas. So now you could be running rich.
Well the computer didn't know you fixed the problem. Communication is key in any relationship right? So you need to tell the computer not to think to much and just go back to what it was originally programmed for without any corrections. You do this by killing it and then reincarnating it. Disconnect the battery and let the capaicitors die a slow 10 minute or so death. you see, the KAM, keep alive memeory, is fueled directly from the battery even with the key off. this memeory stores the correction factors as well as any DTC - diagnostic troubleshooting codes.
So when the dealer reset PW01's computer, they were trying to get the computer (PCM) back to a baseline. Now any hardware changes will have a fair chance at performing the way they should without the "smart" computer getting in the way. you need to do this with any major hardware change - even plugs/wires.
The upgrades that Ricken refers to are periodic changes to the PCM's basic computer code. They somethime update the A/F or spark curve base tables due to customer complaints, internet hackers, whatever - just like microsoft does with Wondows upgrades you can get off the web. Just kidding about internet hackers into your car by the way. So you guys are lucky now that your PCM's are flash-able. You can get an aftermarket programmer and do just about anything you want to control performance. My old one needs a seperate chip added, which can be done, but no one wants to take the time to do it for my apparently rare, one off PCM code.
By the way, if you're sitting at a light and it's hot out and the engine heats up past 250 degrees or so, the PCM will kick up the idle speed to help burn the rich idle mixture to control emmisions. This is normal and not considered an idle problem.
Try disconnecting the battery and see if it idles and accelerates OK. if not, check O2 sensors and DPFE valve on the EGR - I heard these go out early on the newer trucks.
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