Help with 230k mile old 1987 F250 w/302 and 4spd stick....

OK, I scanned for codes and fixed everything up that I had codes for. The problem is now the truck still runs like crap! It loses power going up hills, and it idles and runs rough as crap. I mean the shifter shakes in the floor rough too. It seems to run worse the more the engine warms up. When the engine is cold, it stalls a couple times and I have to put my foot on the gas to get it going a sec, but when i shut it off after it's warmed up, it starts up fine.

I have replaced the EGR, EGR sensor, IAC valve, TPS, spark plugs, spark plug wires, front lift fuel pump, high pressure inline fuel pump, EEC relay, and fuel pump relay. My fuel pressure is good -- at idle it's 31psi, floored 40psi, vacuum line off is 40psi. My TPS voltage is right on .9 VDC closed, and like 4.6 VDC WOT. I also cleaned the TB with TB cleaner.

I've got a new TFI module I'm going to put on, but I have to pull the distributor to get the stupid thing off, and I have no timing light yet.

I'm getting no codes when I scan it KOEO and KOER. Any ideas what the problem is?

 

have you reset the computer?

 

Yes, I reset the ECU and ran a 1/4 tank worth of fuel out letting it readjust. It still runs bad though and it surprises me that it is running so bad and not triggering any codes.

 

One possibilty is a clogged cat. converter.

 

i will throw out one more, check for vac leaks, like the circuits for the heat and air, and then theres some contol stuff for the engine. On my old straight six i found several leaks and it ran alot better afterwards, so might wont to check the vac system if all else fails..

LAter chris

 

I won't get a code from the O2 sensor, or for the cat being bad?

This makes sense because when I started it up and soon as it got a bit warm, I floored it (tap it to the floor then at like 4k rpms let off) a few times and it would hesitate, bog down, pop pop, and then rev up. Every time it backfires when floored, it blows this rubber air hose off this weird valve sitting on a pipe behind the engine -- looks like it connects to the heads or something.

So you think it's a cat and no the vacuum system, or ignition?

 

A 96 and up truck will throw a code.

I've heard that a quick way to check for a clogged cat is to remove the O2 sensor and run the truck around the block. If its clogged, this O2 hole will allow more exhaust to flow out, thus a bit more peformance.

For vacuum leaks, I usually spray something flammable around the vacuum lines. If theres a leak, the solvent will get sucked in and the engine will rev up.

Of course, it could be the ignition and timing, too.

 

What if I just unbolt the whole friggin Y pipe to see if it runs better? Will the O2 sensor not being in the exhaust stream mess up my air/fuel ratio and make it run like crap while I'm testing it?

 

I'll throw in my 2 cents on this thread and vote for the cat. being clogged. It sure sounds, from the way you describe throttle response, that the cat is plugged pretty much solid. My old girl is a 91 with only 150K miles on it and when the muffler shop put the 3" pipe on he cut open the cat and commented to the effect that it was 85% plugged up already. It might be worth a shot as it sounds like you are getting a ton of back pressure going back to the motor when your revving it up.

Regarding the vacum leaks, although I'm not a really huge fan of the method, I have tried using propane on the various vacum lines. The other idea of WD40 or something like that works well too.

Cheers!

Mike

 

Heck, the unbolting thing works too. Now, if you remove the O2 sensor, remember to unplug it. If you leave it hanging out, it will read very Lean. The truck will run without an O2 sensor ( i think the EEC uses old stored data.)

 

IT uses it's failsafe mode when it doesn't detect an O2 sensor. It just runs full rich no big deal if you're checkin for a plugged cat.

 

I bet it's the cat. my dads 92 dodge has the same problems as your truck, I told him it was clogged up, he didnt believe me, but while he was going to take the truck to a shop to let someone else look at it, the truck died and he called me to come and help him get the truck back home, so I swung by autozone and picked up a hacksaw before I went to help him. after I hacked the cat off and put a length of pipe in its place. the truck started and after he cleared all the carbon that had built up in the engine it ran like it was on speed. now I'm trying to get him to get a new exhaust on the truck, he'll probly have to wait until it falls off before it's replaced.

 

No kidding..............

Man, I took a trip to Bowling Green, KY from Hermitage, TN to film a track day for www.tennesspeed.net (mod there) when all these problems started. I ran the truck pretty hard going around 80mph the whole way there and back in 90F+ temps. It seemed to run kind of funny and I heard this weird noise when I got home in the driveway which turned out to be that rubber hose popped off that air valve behind the heads. I slipped it back on, hooked up my trailer, and took off to my storage garage to get my lawnmower.

When I got half way there the truck started bucking and missing just like if you turned the key off and then the wheels jump started the truck back on, I was going up a small hill and it felt like I didn't even have the gas pedal down, but I was in it like 3/4 trying to get it going. It kept quitting the whole way home. It eventually got so bad I burned up the starter getting it home.

I had thought this problem was my fuel pump because my front lift pump shorted out and melted some wiring. I fixed all that and the wiring and it has not quit on me since, but I haven't taken it out on any long road trips either. Just mainly up and down my street between working on it and letting it idle in the driveway.

I'm thinking the cats now too because this thing is making a huffing sound out of the muffler (thought that was the ignition misfiring making it do that) and keeps blowing that air pipe off when I step down on it and it backfires, or pops.

Looks like NAPA has an OE replacement cat with Y pipe for $274 and Advance has one for like $265. Which parts place do you all think has the best quality part?

 

both advance and autozone should be ok. but think about this for what you'r going to pay for an exhaust y pipe, converter and exhaust system , you could opt up for a dual system for probly the same $$$. LMC truck has a cat-back dual system for $280. and both jegs and summit sell many different brands that can run $320.

and what I ment to say before was that my dad wont replace the exhaust system untile it falls completly off. hes just that way.

before I realised it was the cat that was plugged on his truck, I checked for any trouble codes. and what I found was 2 codes one was the o2 sensor and the other was the egr sensor, so I followed the haynes book to test the egr valve and the book said to reach under the valve and move the diafram to see if it's stuck. and sure enough it was, so we bought a new one from autozone about $40 buck's and I used a ohms meter to check the o2 sensor according to haynes and it was good, I figured the egr valve had caused a false reading from the o2 sensor. after installing the egr valve and checking all hoses and vacumme lines . I started the truck up and it ran the same as before, it had a slight mis and while driving, it wanted to surge and lugg at 55mph and when I came up to a stop it would die on me. I also had tryed to floor the truck to see if it was just built up carbon , but it was like it was governed to go only 40 or 45 mph. still I didnt know what was wrong with it ,so I pulled up into the drive way and checked for any codes only to find the same 2 codes were back, so then I took the new egr valve off and exchanged it at autozone for anouther, and bought the o2 sensor. put them on the truck and my brother test drove the truck . I followed just in case it were to die on him. while I was following him I could tell when he stomped the gas because I couldn't hear or see any exhaust comming from the 3inch pipes , it's when he let off the gas I could see some smoke and hear the exhaust a little. he told me it still ran like crap. and we took the truck back home, and I told my dad that I thought it was the clogged cat that was causing all the trouble with his truck. then after a few days he decided to take the truck to a shop to have someone else look at it. I gues he thought I didnt know what I was talking about, but after he tryed to drive the truck 35 miles to a shop, and the truck died on him before he traveled 20 miles . and had to call me to help him, and I show up with a new hacksaw still in the package , and started to hack at his exhaust on the side of the road. and then the truck ran like it should>"and in my opinion sounded much better with straight 3inch pipes". and a rusted out muffler.

 

i would not recommend that.

get a vacuum gauge, you can check the convertor or plugged exhaust with that.