WGM114, did you replace your throttle position sensor? I'm going to get some prices for TPSs tomorrow. Should I get the part from Ford or are aftermarket parts just as good? I have tested it a few times with results specked out in the haynes manual but I suppose there could still be dead spots that the computer picks up and the VOHM doesn't show! I'll keep everyone posted.

Cricket, Had you tested your TPS before replacing it? What name brand did you buy?

I'll keep you all posted on my progress
Guy

1992 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

No I didn't test the TPS before replacing it. The ford mechanic I talked to said that the TPS is noted for causing an eratic idle. Also the O2
sensors. I got mine from the Ford dealer.

 

You know it's funny how find out how many people have the same problem with their trucks! You would think that ford look at this and try to fix the problems that people are having! Guess if they do that they would be loosing money in the parts department. Yhe first time i had my truck fix i went to a "Fuel injection specialist" garage and they said that it would cost me $650.00 to fix it! I asked for the parts list and they were pretty much going to replace every sensor on the truck. I said forget it. Went to a small garage near home and he looked at it and said it was the TP sensor and IAC. Said he would replace the parts and clean the injectors for $200.00!!! The point I'm getting at is the mechanic at the small garage had the little black test unit that ran the truck through several tests to see what the problem was. If guys and gals like us could get our hands on a tester like this we would be set up! I looked at a few places and Eastwood had one but they said they don't think it does the test like the one at the garage does. I was thinking of looking for a snapon product. Anyone know where we might be able to find a tester like this? I have a small one but that just reads the codes. could do that with a piece of wire. Even if it costs a few bucks to purchase one of these it would take a lot of the pain out what we are doing now. So get those fingers going on the net and see what you can find and hopefully we can get our hands on one a sleep a little better at night!! Sorry such a long post

 

Yeah you have a good point there flareside. Ford sould have a web site which points out all the fixes to the most common problems, especially idling problems. I suppose that is why there is an awesome site like this one.

Well just thought i'd let you all know that I am a sucker for wasting money. I just blew $50 on a new TPS and the truck is still having the same problem. So now, the only sensors left to replace are the ECT, and ACT. I shouldn't replace them either because they test ok, just like the TPS did. I think I am going to get a new set of plug wires, cap and rotor next. I read a post once about routing the plug wires a certain way to prevent the spark from crossing over to other wires. If anyone has any info on this I would greatly appreciate it. Hope this post helps some of you in that you don't go out and buy sensors for nothing. I'll not be continuing this post it's getting too long. I'll start a new post if and when I get the spark plug wire info I need. I see that I am not the only one with this nagging problem and I hope this helped you too. Again, thanks again for all your input.

Guy


'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

I had the same Stinking problems with my 88 F-150. After $1,000 in two years of trying to make it run right. All new sensors, (1) new distributor, (3) sets of plug wires, (??) sets of plugs, New exhaust (stock) from the engine back with new cat, K&N filter, Numerous calls to Ford, trips to 4 different shops (all of which told me 4 different things.) Like "the tps is shot", or "you need a new computer", "you need a new distributor", the final place I went to told me to go to the muffler shop & have the Cats checked. Sure enough the rear cat was totally plugged. Then I had the carbon cleaned out of the engine and it ran like it was brand new (most of it was anyway!)

Do some calling around and find out if any of the local shops have a machine called "MOTOR-VAC" This thing is awesome!

Also, try disconnecting your battery cable to clear your computer codes. If you can leave it off for about 12 hours, just to be safe. Hope some of this helps.

By the way. I finally got tired of working on the 300 6 cylinder I had and switched it over to a 5.0
Only cost me about $1,000 more to do the engine conversion but I get better fuel mileage now. My 6 got about 12-13. The 302 I put in gets between 14-18.

 

this may sound dumb but did you replace the pcv valve? my brother in law had a problem with his chevy truck the same as your ford i replaced the pcv valve and e was gleeming for it straightened out the choking and dying. let me know if you did change it.

 

I have an appointment on Monday to get the cats checked at the muffler shop. It's free too! I should have started with that. I am not sure what equipment they'll be using but thanks for naming that machine. I'll be sure to ask them lots of questions on how and why once they give me the results. As for my pcv valve, it's pretty new and it still pulls vaccum when I put my finger on it. I take it that is what it's supposed to do. I hope to find the problem soon because I am running out of patience and losing my confidence in ford....as they don't seem to be able to help me out with their own product, not to mention that i am running out of money. I'll add a reply to this post with the cat test results next Monday..


Guy


'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

Hey Guy I'm on pins and needles here what happened on monday ?



1988 F-150 351W

 

Well this is it. There is nothing wrong with my truck, it's normal for it to get 10mi/gal, run rich, belch black smoke form the tail pipe, and almost stall at traffic lights. No really, my co-worker suggested I try premium unleaded gas. I had the cat's checked and the guy even drove my truck and said they're still ok. They checked the cat's with an infra red thermometer(the ones you just aim and shoot with the little laser light) and he said this test is pretty accurate. If it's extremely hotter before the cat, it's a good sign of blockage. Mine were about 50 celcius hotter before the cats. As for my idling problem, I don't know anymore...I have other questions but i'm starting a new post. Thanks for your help.

Guy


'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

I had similar problems with my '93 4.9l. Dealer wanted to keep hanging parts at my expense. I found several vacuum leaks. the leaks tricked the computer in thinking the mixture was too lean and compensated by going over rich. the leaks I had were: canister purge valve, egr control valve, and rusted out vacuum storage canister.

good luck

 

I have seen this problem before, on Ford trucks, Chevy trucks and even some Japanese brands. Here's the deal: When it starts to spew black smoke, what is happening is that you have a pressure bubble in your fuel tank. Fuel cannot return via the return fuel line. Sometimes the pressure gets so great that the return line becomes another supply line. Your engine computer tries it's best to deal with the problem (hence the wild idle swings) but cannot. There is just too much fuel present. Next time it happens, pull over and remove your fuel cap. Stuff a rag in it and drive around for a while. Did that clear the problem? If so, you have a clogged tank vent. Good luck.

 

WOW...you guys covered just about every thing in the books and then some not in the books.


I read the whole thing and I am wondering what the muffler shop said as well. doesn;t seem to be much left other than the cats. altho a plugged EGR can make your engine cough and idle ****ty

 

Thanks for the tip Timlg. I will try this when the truck acts up. Although you mention the fuel pressure gets so great that the return line becomes another supply line, I have tested the fuel pressure and it is stable through this stumbling and I keep getting a "lean" "no HO2S switching" code(43 I think). O2 sensor is new. Problem persists on either tank. Are both tanks piped into a common vent? I thought they vented to the purge cannister and from there to the intake manifold through a solenoid valve? I have let the problem go for a while but your idea has given me some ambition to tackle it some more. Thanks

Guy

'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

[font size="1" color="#FF0000"]LAST EDITED ON 19-Sep-00 AT 04:10 PM (EST)[/font][p]Tim, I was reading through all these posts and found one where i said the fuel pressure rose to 40 psi while the engine stumbled and then returned to 32 psi regular idle. This was after I wrote the previous one. That is definitely a good test to do. Do you know of anyone who has stats on how high of a pressure those pumps can deliver?

Guy

'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.

 

I had the same problem with my 92 truck this week. The truck had a new coolant temperature sensor and oxygen sensor on it. The truck started belching black smoke out the tailpipes. Checked all the sensors and they checked out OK. Put a fuel pressure gauge on and it would idle at 38 psi. If I left the fuel pressure gauge on the truck and let it idle for about 3-5 minutes the gauge would start climbing to 40-42 psi and then would jump and fluctuate between 85-90psi. I changed the fuel pressure regulator on the fuel rail and the problem was solved. Hope this might help.