My 96 f150 5.8 has a surge to it a low RPMs,and iv replaced all the O2 sensors and the only other thing I can think of is the TPS sensor..But I dont know which one it is,theirs a few of them n the throttle body,is it hard to replace or should I have it done?

 

I would presume it is setup the same as my 92 5.8L.

the TPS is on the underside of the throttle body. To replace it, you need to remove 4 bolts that hold it to the intake manifold (replace the gasket when you reinstall) and the TPS is held in with 2 screws.

To test the TPS, just unhook the connector on the TPS (with everything bolted up just how it is) and turn the throttle by hand and measuring with a multimeter.
I don't have my manual handy, someone should be able to give you the resistance you should read.

-Chris

 

On a 5.0 its right on the bottom of the throttle body. I don't think its that hard to do. It would probably be real easy with the throttle body off, but I imagine you can do it without removing the throttle body too. It has two screws that come in from the bottom that hold it on. Do you think thats where yours is??



guzzler96

 

Judging by the flowchart in my '94 service manual, there are a lot of causes for surging on acceleration. I don't know that the TPS is the only or most likely other cause, but you can get some help locating it if you go here . You might also find some other info on troubleshooting the problem if you look around. The difficult part is that engine control on these trucks is electronically controlled, and you really need access to the troubleshooting flowchart to figure out what the real problem is. Otherwise, you stand to spend a lot of $$ on parts. I recommend buying the factory service manual--sometimes you can find them cheap on eBay--or find someone who has one for your year truck. Good luck. That's a frustrating problem.

 

That flow chart page helped some,but they said it was mostly fuel related problems,I find it hard to believe its fuel because it only does it at the lightest throttle,and it surges just like you are tapping the gas pedel..So you sure wouldnt think it is starving for gas?

 

It's hard to see how fuel-related problems would be the cause if you only have the problem off idle.

I would say you really need to go with the Ford Service manual troubleshooting procedure for surge. It is a lot more detailed and looks more helpful. They mention fuel quality as a "preliminary step" and get into the good stuff after you have ruled that out as well as restricted air filter/intake tubes, vacuum lines, and wiring as potential causes. From there they have you check the EEC, then they have you use a MAP/Baro tester (whatever that is) to check the MAP/Baro sensor, then the ignition system, then the throttle body, the PCV, the a/c system (if surge occurs with a/c on), then the evaporative emissions system, the EGR system, the secondary air injection system, the cooling system, the transmission, the exhaust, air intake, fuel delivery, and finally the engine (compression, worn camshaft/valvetrain, etc.). Each of these has its own procedures.

The MAP/Baro tester would be a show-stopper for me, unless someone on here knows how to test it without the tester.

It sounds like you have really got some work ahead of you. I would be glad to look in my manual if you have something specific you want me to check, but keep in mind my manual is for '94. That may be more harm than good, but I thought it would at least give you an idea of how Ford tracks down the cause of the surge.

 

Were did you get your ford manual at? A delership? How much might one of them run me?

 

I got mine on eBay for $15 including shipping. It has already paid for itself. I have the CD-ROM version, which covers all the trucks for '94. The paper version is three volumes and goes for about $90 new from Helm Inc., who is apparently the publisher of the original manuals. From what I have heard, you can find them online (eBay, etc.), too, much cheaper than that. I highly recommend it. I have a Chilton's, and it is helpful for a lot of how-to stuff, but for any detail the factory service manual is best.

 

cool,I will check that out,I changed the TPS tonight and it didnt seem to change much,I put new O2 sensors in,new air filter,new fuel filter a year ago but im going to change it again tommarow..I havnt checked the egr/pcv out yet..What do I look for their?just a plugged hose?

 

For the EGR system, the manual says surge can be caused by "EGR valve malfunction/erratic operation, EGR valve contamination, EVR solenoid malfunction, and pressure/vacuum signal hose(s) leak (PFE/DPFE)."

To find out, you're supposed to perform a EGR valve functional diagnosis by 1) "checking EGR vacuum hoses for looseness, pinching, leakage, splitting, blockage and proper routing. Inspect EGR valve for loose attaching bolts or damaged flange gasket. 2) Run engine until normal operating temperature is reached. With engine running at idle, disconnect EGR vacuum supply at the EGR valve and check for a vacuum signal. NOTE: The EVR solenoid has a constant internal leak. You may notice a small vacuum signal. This signal should be less than 3.4 kPa (1.0 in-Hg) at idle.

If EGR vacuum signal is less than 3.4 kPa (1.0 in-Hg) at idle, you are supposed to check the EGR valve function by installing a tachometer (if you don't have one on the truck), disconnect the Idle Air Control (IAC) solenoid (9F715) electrical connector. Remove and plug the vacuum supply hose from the EGR valve nipple. Start engine, idle with transmission in NEUTRAL, and observe idle speed. If the engine will not idle with IAC solenoid disconnected, provide an air bypass to the engine by slightly opening the throttle plate or by creating an intake vacuum leak. Do not exceed a typical idle rpm. Slowly apply 5-10 inches of vacuum to the EGR valve nipple using a hand vacuum pump, Rotunda 021-00014 or equivalent. If the idle speed drops more than 100 rpm with vacuum applied and returns to normal (± 25 rpm) after the vacuum is removed then the EGR valve is okay. If not, INSPECT the EGR valve for blockage or contamination. CLEAN the valve using Rotunda 021-80056 EGR valve cleaner. INSPECT valve for vacuum leakage. REPLACE if necessary.

If EGR vacuum signal is not less than 3.4 kPa (1.0 in-Hg) at idle, reconnect the EGR vacuum hose and inspect the EVR solenoid for leakage. "

At this point, you're supposed to use some kind of test equipment to do a "Quick Test", which is described as "The Self-Test is divided into three specialized tests: Key On Engine Off Self-Test, Engine Running Self-Test, and Continuous Self-Test. The Self-Test is not a conclusive test by itself, but is used as a part of the functional Quick-Test diagnostic procedure. The PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.

The Key On Engine Off and Engine Running Self-Tests are functional tests which only detect faults present at the time of the Self-Test. Continuous Self-Test is performed during normal vehicle operation and stores any fault information in Keep Alive Memory (KAM) for retrieval at a later time."

For the PCV valve, first remove it and shake it. If the valve doesn't rattle, it's bad. Replace it. If it does rattle, reinstall it and then start the engine and bring it to normal operating temperature. Disconnect hose from remote air cleaner or air outlet tube (tube connecting mass air meter and throttle body). Place a stiff piece of paper over the hose end. Wait one minute. If vacuum holds the paper in place, the PCV system is working normally. If vacuum doesn't hold the paper in place, the system is plugged or the Evaporative Emission Valve is leaking (if equipped).

Is that more than you wanted to know?

 

By the way, this is probably a dumb question, but is your check engine light working? If so, is it on when your engine is running; i.e., you have some trouble codes in the system? If so, that can really help narrow the problem down. If you don't have a trouble code, that might also indicate the problem is caused by something the EEC doesn't monitor.

 

Thanks alot jay,no my check engine light is not on,I had the codes pulled with a handheld reader but nothing showed up in the permanet memory..

 

You can test it with a multimeter if your multimeter has duty cycle mode. Another way is to use a 6 cylinder tachometer, which will also give you the frequency. The values for atmospheric pressure and a vacuum are given in repair manuals. This method only works for frequency varying MAP/BAP sensors - if it is voltage varying, you can use a regular volt meter.

There can be codes stored even if the light isn't on, and even if there aren't codes in the memory, there can be active codes that might be pertinant. Also do an engine running diagnostic test to see if anything comes up there.

 

What is a engine running diagnostic test?

 

Set up the diagnostic connector (code reader if you have one) just like you would to check the codes with the engine off. However, instead of just turning the key to on, go ahead and start the engine - the computer will test all the actuators and sensors to make sure they work when in operation. Sometimes a code will come up here that doesn't appear in the regular engine off test.

On edit, I see that you have a '96, so I don't know if OBD-II does this or not. It might not, I do not know.