Alright guys, I have a (new to me) 1992 w250 360 tbi manual trans 41xxx miles. When I start the truck in the morning it will sometimes star for a sec and die requiring me to feather the gas to keep it running. It only does that when its really cold. The thing it does all the time is when i get in it and start to drive it it starts to stall when i put the gas down. it studders then it usually pops and misses until i put the clutch in and rev it higher and feather the clutch out. it is almost undriveable unless i let it idle for ten or fifteen miuntes in the morning. The truck no longer has no preheater on it and the air pump has been disabled. I found a vac line from the preheater system (farthest to the driver side on the front of the TB) that was juast open and i cut it off the throttle body an capprd the port off. this has not fixed this issue (may have helped it run under normal driving conditions though). I have tested all sensors on the TB and the coolant temp sensor. all check out within specs. I reset the computer and got codes 12(normal) 25 and 35 then 55(end of codes). 25 is the idle air control target idle not reached/ VAC leak found. 35 is fan control relay. I have also done plugs,wires,cap,rotor (standard for any vehicle when i buy it). I did not do the fuel filter though...

I've read lots of articles on here and some had my problem but none posted followups to what was wrong so those didnt help. I alsohave read that the CAT may be plugged, but with my mileage I dont think its likely. I would really like to fix this problem soon as I dont like waiing for 15mins before driving when leaving school! I appreciate all help! also, it runs really well and throttle is responsive and the idle smooth when its warm.

 

You may have more than one problem here. I would use carb cleaner or propane to look for a vacuum leak because of the code. I would also dump a can of Seafoam into a full tank of gas. Run that tank thru before refueling. You may be experiencing the beginnings of a sticking injector problem. The cold tends to accentuate this problem.

 

Thanks SEAL! Ive gotten a can of seafoam to run through it so well see if that helps... ive tried looking for a vac leak with carb cleaner, but couldnt locate one (not that that means anything!) but Ive got a mightyvac pump i might use to see if i can isolate a leak anywhere... As far as injectors go, do you think I'd be stupid to just buy new ones? I mean they are almost 20 years old and not that expensive... May be a quicker solution. again thanks for your help and i look forward to hearing from you!

Brian

 

I would give the Seafoam a chance first. Mainly because I am cheap and refuse to waste money on unneeded parts. If the Seafoam works and then the problem comes back I would then replace the injectors. If the Seafoam doesn't work I would bet the injectors are not the problem. Your money, your choice.

 

SEAL,

I pulled the air filter and noticed that the injector on the driver side isnt spraying anything at all, just dripping a bit. so I found a replacement injector and put it in. The problem is that when i installed it, i forgot to pull out the old bottom injector o ring. I didnt notice it until I drove it around. It ran great! When I noticed that I didnt pull the old o ring out I took the injector out and removed the o-ring. when i went to put it back together, it wouldnt stay idling and it missed like crazy. smelled really rich. I reset the computer and same results. The thing i did notice is that it looks like I stretched out one of the o rings on the upper side of the injector close to the cap. (There were two o rings, a thicker one then a thinner slightly larger diameter one) the one that stretched is the thinner larger diameter one. could this cause my problem? I cant keep it running now. What could be the problem? and it does smell very rich!

Thanks,

Brian

 

UPDATE!:
I went outside and put the old lower oring back in. It runs great now! my question is why? The haynes manual says to be sure to remove the lower oring. the new injector did come with one installed already... so why should I have to reuse the old one to make the truck run? could it be the wrong injector? could it be that the injector isnt seating all the way? (the cap doesnt quite fit tightly on the bore but the pin is lined up and i cant push it down any farther and it still seals... so wtf is the deal? should I leave it?

Thanks for all your help!

 

if it runs good i don't think i would mess with it

 

If everything is tight and it runs good and the spray pattern looks good, go with it. Did both injectors look the same when you had them both out?

 

Seal,

So far I have tested all sensors on the throttle body as well as temp sensor and all are working correctly. I replaced my fuel filter. I have good fuel pressure. after doing some extensive research, I have found some information that may be helpful... The previous owner removed the air pump belt (air pump is seized either due to the belt removal or prompting it) but all associated parts are still on the vehicle. also, the air preheater is no longer on the vehicle. I have not found a person on here who has had a problem doing these mods, but none the less I thought I should ask. Something that struck me is that my symptoms parallel those of people with a plugged cat. Sound plausible? how do I tell. I have called local garages and they claim to not have a pressure gauge for testing back-pressure. Now my questions are:

1. will the airpump being disabled influence the o2 sensor reading causing a running problem when cold (since that is when the airpump does the most work) since the ecu has not (and according to local shops cannot be) been reflashed.

2. if the answer to 1 above is no, then is it possible that my problem is stemming from a plugged cat due to the lack of an airpump?

3. if yes to 1 above what should I do to remedy the problem and should I assume my cat is already plugged since the airpump has been disabled?

4. If cat is plugged, should I replace o2 sensor, egr valve, etc since these components are typically those commonly affected by a plugged cat.

5. what other possibility is causing my issue? bad egr? how do I test?

P.S. Sorry for the long post, but I am also getting around 8mpg in town driving so something is wrong.

Truck: 1992 w250, 5 speed manual, 360motor, 40,000 miles

THANKS!!!

 

it is possible that your truck has a clogged cat if it has a magnum engine. the magnum engines have a plenum gasket on the bottom of the intake manifold that tend to start leaking and sucking oil into the engine.