1989 F250, 5.8, C6. I really like my truck and it is very physically sound and drives good. It lopes when warm at idle intermittently sometimes getting very bad and nearly stalling. It runs rich. No black smoke but definite smell, not while driving, normally at start up and shut down and while idling. When I switch into neutral or park it normally clears up almost completly. It seems to lack power, almost like a slight miss?, plugs, wires, cap, rotor are 3 years and 12k miles old, coil is brand new.


I have searched for hours upon hours, i have trouble shot for hours upon hours

Codes pulled KOEO 13,46,33,36, KOER 85, 33,62? (It has a C6),63

CANP and canister have been pulled (Not by me) same with smog pump. Replaced IAC and cleaned TB in december by qualified mechanic (to fix this problem, which it didn't, though it helped and at the time it wasnt as bad.

Exhaust - slight manifold leak but not bad, it is trual daul all the way back with some dang loud Magna flows the guy talked me into. It does have a brand new O2 sensor

Today I threw $50 at it TPS was reading .17 with key on engine off. new one installed, same reading. When I spray carb cleaner into the egr it usually idles up/smoothes out a bit. Cant find any obvious vacum leaks although the tab/tad sensors look like junk , tops are gone and springs showing, but I am told this should not have the effect I'm getting. There is a red vac line by the EGR that is capped off, no idea where this goes. Rear tank leaks so I have it always switched to the front.

I dont mind throwing a few parts at it but I am getting really frustrated. EGR, FPR maybe? Any ideas would be very appreciated. It is my daily work truck and has been amazingly reliable and I have done a lot of work to make it look good and serve my purposes. The condition is a complete pain in the butt and constantly worries me. When pulling a trailer (I do every day, it is really a pain to drop into neutral at each light.

Please help

 

What exactly do you mean when you say "When I spray carb cleaner into the egr it usually idles up/smoothes out a bit"?

Engine at idle and you spray the egr valve where exactly?

Shouldn't do that the egr valve shouldn't be albe to suck carb cleaner into it at any point engine at idle, if it is sounds like its a vacuum leak. The egr valve should be fully closed at idle and at no point open to atmosphere, only point it should be able to suck anything in would be the exhaust port the tube that connects to the exhaust manifold.

Stuck part way open and or sucking air past its diagram or both its toast. Goes with your code 33.

Check that out then other issue your symptoms lean toward might suggest late ignition timing, last time anyone checked/set the base timing?

36, sounds like it runs weak like crap so little doubt it could fully control rpms.

63, you state "TPS was reading .17 with key on engine off" if tested correctly you're gonna have to get into that and correct it.

Fuel Injection Technical Library » Throttle Position Sensor (TPS)

Should be between 0.6-1.0 volts fully closed position but sounds like you already know that, make sure the factory seal is intact no one has screwed with the throttle stop screw. You should see a yellow or redish glob of material locking that screw in place, if someone turned it it will no longer appear undisturbed. If so that's a problem you will have to address to move forward.

 

Thank you for the reply.

When I spray carb cleaner at the body of the egr it sometimes idles up noticeably. I just ordered an egr as it didnt look very dirty but something is up obviously.

I retested the TPS and it tests good.

No idea on the timing. I would probably rather leave that to a shop unless its easy. I will search here and consider that.

What exactly does 36 mean?

Its sounds like I am narrowing it down which would be nice. I just ordered plug caps and rotor as the cap and rotor looked kinda rough and plugs were less than perfect.

How hard is it to set timing? Like I said I will search. I dont see any vac lines going to the distributer so that should make it less complicated.

 

36 = insufficient rpm increase during speed control test.

KOER self test starts the computer increases then holds the rpms for several seconds looks for proper rpm change during test.

36 means it didn't change or change enough during that period or it simply had no control over the engine speed, if running weak/bad no or little throttle response and or loopy idle speed up and down and or nearly stalling as your post suggests it stand to reason it'd throw that code.

Forgot your timing question!

Setting base timing is fairly straight forward.

Find the 10Deg BTDC mark on the harmonic balance wheel its outer edge, make a line across the wheel at that point it with something white. Myself I use some of my DW white finger nail polish (don't let her see ya do it!).

Loosen the dizy hold down bolt little bit so you can turn it but with some resistance. With the engine at full running temperature remove the spout jumper, aim a timing light at the pointer mounted to the bolts on the timing chain cover over the balance wheel, rotate the dizy until the mark you made lines up to the edge of that pointer (if necessary, if hasn't been checked/set in a long time probably will be off needing adjustment to make up for wear in the chain).



Same time you should check chain for wear limit.

Rotate main shaft by hand with a socket on the main bolt until mark you made to check/set timing comes around and lines up to the pointer. Next remove the distributor cap. Now rotate the main shaft the other direction while watching the rotor in the dizy, stop rotating the main shaft the moment you see the rotor start to move. The distance the mark moved designates the total wear in degrees it has in the timing chain (use the graph on balancer to judge total degrees, marks are 2 deg apart). I'd have to look it up but I believe 5 deg is the suggested wear limit, at 5 degrees or more the chain and gears should be replaced.

Image below is not a 89 351 but an example of what the marks look like, remember you want the 10deg btdc mark (you can bump it little bit from that point to increase performance but should stick with 10deg for trouble shooting, work the bugs out first then go for more) At that point the limit would be as much advance as you can get but without suffering spark knock.

 

Oh, just to add a symptom, I get 6mpg pulling a trailer...6! And only 8mpg city with no trailer. This is annoying but I have always dealt with it

If that gets better I may pass out from excitement!

 

Time to be honest and look like an idiot... When I went to restart after new parts (FPR,TPS,EGR,cap,rotor, fuel filter). It would cough horrible and no start. I was about to walk into traffic. I started digging. When I tuned up 3 YEARS AGO! i had the plug wires going to the wrong cylinders!!!. Fixed that, what a difference. So I have lots of new parts, I am still getting code 85 CNAP which is gone, I think I will remedy this, and 41 lean? Any ideas here? before it was obviously running rich. COuld 85/41 be related? I am also getting 31. I should probably test the egr solenoid and sensor. at this rate I may just throw them on, whats $50 more

Any more help would be appreciated. While I am at it I plan to pull the A.I.R. pipes (the pump is gone) and plug them off, it looks like they are just piped together? Not sure where they did or do go to unless I am missing something? I will do this just to get stuff out of the way (plus I burn the crap out of my hand when I check the tranny fluid while plowing). As far as I can tell also the pump was disconnected long ago. Where do I block the holes these hoses went to? It may be contributing to a louder than normal exhaust. Thank you very very much for the help. I feel Like I have a new truck!

Z

 

Sounds like you need to address your leaks before going further.

Fully eliminate the air system, solid plug all ports in the exhaust and yea probably reason or at least part reason you have exhaust leaks. Check valves and or tubes burnt through.

Probably be won't be easy especially if live in the rust belt but remove all air tubes seal those ports with plugs.

41, there is a small chance those same leaks cause your lean condition, if sucking fresh air into exhaust upstream of the O2 sensor for example.

You replaced EGR valve so no longer suffer vac leak there? did you check?

31, EGR valve for the moment not an issue provided its fully closed and stays that way.

Once you have the exhaust quited down it'll make it easier to determine if suffers any major vac leaks, one large enough to cause lean condition.

That said if sucking a lot of air enough to cause a lean condition its idle speed should be high....everything else as it should be of course.

85, I wouldn't worry to much about canister purge for the moment either, should restore the system if can easy enough its a safety thing for you and yours. However in the short term troubleshooting as long as have no open vac ports/hoses because of it its not causing you any problems need dealt with right now.

I'd do that first then the normal make sure no vac leaks verify fuel pressure up to spec that is if fixing the leaks doesn't correct the reported lean condition. See what correcting the leaks does for it first though, needs done anyway so might as well get it over with.

 

Will do! Thank you so much!

Are the air tubes just connected to each other? Best I can tell they come off the manifolds and hook to each other in the back of the engine? Also any idea where I look for the holes that the air pump was hooked up to? I looked all over and have no hoses to follow. Maybe these were hooked to the air pipes?

Thank you again.

Z

 

The air tubes on that one couldn't be sure as you're is a 90, more than a single configuration for em over the model years.

Two tubes disappearing down over the back of the upper plenum from the right side? If so they either go to the back of the exhaust manifolds one each side just above where the exhaust pipes bolt up.

If single tube doing similar probably tees into a crossover tube running between the back of both heads. If so that crossover tube at the back of the heads can be removed. The holes in the back of the heads can then be plugged with 5/8-11 x 3/4" bolts.... IIRC that bolt size?

Bottom line you gotta follow where they go do whatever necessary to properly plug them off, you'll be much happier in the long run nice quiet truck that stays quiet.

You may need a torch to remove some of those fittings, glowing red hot they'll come right out regardless how rusty they might be. One of them little hand held propane torch isn't gonna cut it if comes to that.