Ok here's the deal with my truck and i'm stumped at this point. Here's all the things i've done to it mechanically in the last year.

K&N FIPK
TPS sensor
IAC
plugs and wires
PCV valve
fuel filter
belt
t-stat

At this point i'm thinking it's my EGR system not functioning properly. I don't have a check engine light on so i'm kinda on my own here. Here's what the truck does

Initial start up with no acceleration: erratic idle. The new IAC didn't do jack for it. It's not a factory one, it's a borg warner brand. A factory one would cost me $124!! The idle smoothes out eventually after the truck has warmed up alittle

When the engine is lukewarm: If I ever so slightly push on the gas, the RPM's fluxuate between 1000 and 1500 up and down and hesitation.

Like I said, at this point i'm stumped. Someone told me on GBO it could be my EFE system going out. Anyone second that or have other ideas? You think it could be the EGR system? -Mike-

 

Well, I've been posting this test a lot lately, as I had to do it with my daughters truck. The test is even described in the Ranger's service manual.

Unplug the MAF and run the truck. Chances are if it runs better, you may have a bad MAF. The truck can run open loop without the MAF using just the TPS and the oxygen sensor to trim -- though it's not optimum. Still, it runs surprisingly well without it in a pinch.

Edit: If the problem started after the FIPK, the MAF may just be dirty. By the way, my daughters truck is a 1998, 2.5 liter Ranger also.

Interestingly enough, the all-plastic 4 liter SOHC MAF fits the 2.5 and even calibrates properly -- at least on my daughters truck. The 2.5 has an awfully large intake tube for a small displacement engine. It's bigger than my 3.0 V6.

 

thanks for the info. Your describing the test in open loop some i'm assuming you mean do the test with the engine cold? or doesn't it matter?

The problem didn't start till about a couple of months ago right after i replaced my TPS sensor. That was when the tranny was not shifting right, all is well now with the new TPS sensor. When I installed the FIPK, the truck ran fine for the following months and never had 1 issue.

One other question, would a MIL on the secondary 02 sensor have any effect on this? i was running w/o a cat for awhile but then replaced with a new one because my truck sounded like absolute crap, though i never took the MIL off. Would that contribute or be the culprit of the problem? Thanks again for the info. -Mike-

 

Generally, the second O2 sensor only verifies the catalyst -- but it will light the MIL.

A/F ratio is controlled by the first O2 sensor.

Have you taken the battery terminal off for 20 minutes then restarted? Some problems go away when the PCM is fully reset. After you start it, let it idle for 15 minutes before you drive it.

Open loop is probably the wrong thing to say when I think about it. What's happening is the basic fuel curve that is mapped to MAF reading isn't being used. Not sure how it works, but some secondary method of deciding how much fuel to feed is used based on throttle position. I just know that for certain driveability problems, it's a standard test to unhook the MAF and see if things get better.

Bad TPS would definitely affect the tranny, as you found out.

Can't think of much more to suggest, but may rwenzing (Bob) might read this and jump in. He's an engineer who worked for Ford and has an excellent understanding of nuances of our trucks.

 

I haven't tried to disconnecting the battery yet. I can give that a whirl tommorow too while i'm at it and see how the truck reacts.

I've always blamed alot of problems on the MIL just because removing my perfectly good factory cat and installing that stupid thing, alot of things just started going to hell. I put a cat converter back on and things are back to normal, almost anyway.

I can try out the battery test and MAF test tommorow when it's daylight and report back my results. -Mike-

 

I also have a this similar problem with my truck where would be the best place for me to start. I have also done most of the stuff that mike9825 has done to his truck except the IAC.

 

man i want my first car back!! carburetor, some vacuum lines and a distributor ignition lol! -Mike-

 

ok just finished up working on the truck. I disconnected the battery for about 25 mins and cleaned the battery terminals and cable terminals with some water and baking soda and toothbrush. They weren't really dirty but might as well clean them anyway while i was at it.

Reconnected the battery and started the truck. The idle jumped up to 1500RPM and then slowly come back down to about 850 like is usually idles. Although while coming back down to normal RPM, it did hesitate alittle bit but not much, a few spits and then returned normal idle @ 850RPM or so. I let the truck idle for a good 15 mins without touching anything.

Keep this in mind, when my truck is allowed to idle for more than a couple of mins, the RPM's will slowly make there way up 1000RPM and stay there until the throttle is used.

I also tried that MAF test. I shut the truck off, unplugged the MAF, then waited a minute or 2. I restarted the truck and it idled normally. However, the truck while idling for a good 10 mins while the MAF Was unplugged, the RPM's DID NOT go to 1000RPM's like i thought it would. It just kept at 850RPM the whole time and never hesitated and idled beautifully with the Flowmaster in the background just rumbling away lol! The check engine light never came on either which i also expected it too. Which concludes me that my MAF is causing the truck to go up to 1000RPM's when left at idle for a period of time. It also tells me that my MAF is irrelevant to the cold idle sputtering. As mentioned before, since i resetted the computer, the sputtering is still there but it is smoother somewhat. I'll try and clean the MAF with some electrical contact cleaner i have and see if that does anything for the RPM's going up.

While i didn't totally fix the idle hesitation issue, i did learn that my MAF is causing the RPM's to go up to 1000RPM. Thanks for the help n3elz! i appreciated it very much! -Mike-

 

i just did the test where you unplug the IAC while the truck is running and rpm's droped, so where should i go from here could it be the tps?