1990 Bronco 3.51 HELP!!!

Ok guys heres my problem, I have a 1990 Bronco EB I have been haing problems with the check engine light. I can drive it to and from work < about 4 miles each way > with no problem but if I go a while longer my light comes on. I can stop turn off the truck and start it back and it will be gone for about 15 minutes of driving. I cheked it and they said it was the o2. so I replaced it. Then they said it was the erg valve so I did that too. Now they tell me the code says ho2 right side < this is the lighter one with just one 02 > it also says tps sensor. They said I might have some sort of vacume or air leak with is causing my engine to idle rough when I am stopped and its causing my o2 sensor to read bad when its not. they said I should replace the upper intake gasket set. But I cant find anything but the lower, and honestly I love my truck but its turning into a money pit. Will this fix it. how do i do them both I checked my chiltons book and there is nothing for a tps sensor replacement. and how can i find out where the air leak is. Remember I'm just learning but I want to get it fixed myself so please help

try using a propane torch....DO NOT LIGHT IT! just use the escaping fuel to be sucked into the vaccum leak. since it is a combustible fuel...once drawn into the leak, it should cause the idle to smooth out. I have found this to be very handy when tracing out vaccum leaks.

May also want to check your fuel delivery system...pressure test.

is ur bronco EFI or carborator?

its a efi

I have checked my pressure system and its ok I have just recently put in a new fuel pump. I cant seem to figure out why it comes on after 10 minutes and then I can shut it off and it will come back after a few minutes. What would make it read bad h02 right side when i just replaced it. I swear this is going to drive me nuts

There is also a pipe that runs on the back of the engine, between the heads. (Right against the firewall.) Check that for leaks. I had to get a new valve for the top of that, when the old one broke. (I forget the exact details of what was wrong when I did it, but it sure made me feel better to spend that $12 at the Ford Dealership)

There is, as you know, about 12 mi.s of vaccuum lines under the hood, so use locopny's advice with the torch.

in addition to replacing teh egr valve, you can also replace it's sensor, that might help. i am having the same problem and a trusted mechanic told me to do that.. I hope that helps

I have found one leak in my break booster. Now it is telling me to check my ignition sysem. I think it was code 14. Someone told me once that if you have a 1990 truck with the port under the hood you can check the codes yorself with a paper clip is that true? it would sure save some time

yes you can do it yourself...
with a paperclip, short wire, etc...

Do you have a manual? the Haynes is by far the best one I've got (besides the Factory Helm Manuals) and its available at many auto retailers..

The proceedure is spelled out in the manual and has a few codes listed.

if not, check out FordFuelInjection.com Its Ryan McCormarcks site(probably butchered his last name spelling...sorry) Dude knows his stuff and has some very helpful info to help troubleshoot.


hope this helps ya.

Got it back from the shop and they said no vacume leak. but still a engine light. comes o after about 15 inuts. if i turn the truck off and back on its gone. then back in 10 to 15.HELP!!!!

Thermostat? How's it reading? If there's near a billion miles on the thing, all the sensors might be cooked. How's the oil pressure?

Therm works as far as I can tell. and as for the oil pressure it shows around the 1/2 to 3/4 mark on the guage

I went and had the codes read again today hers what its reading
Memory code 41
h02s sensor
lack of switching right side
KOER Code 42
HO2S sensor system rich
HELP!
I just put in a new 02 6 months ago. and I beleive this unit only has 1
could this be why the check engine light comes on after 10 to 15 minutes but when i turn off the truck and back its gone?

May also want to check your fuel delivery system...pressure test.


I hate to sound like a broken record...but this SOOO sounds like the cr@p I went through when my Fuel Pressure Regulator went bad. Chances are your O2 sensor is working just fine....it is telling you there is a problem (rich condition). I'm also guessing there wasn't anything wrong with the last one.

Not what you want to hear I'm sure. The codes are helpful in troubleshooting the problems, but dont read them as a mandate that a part is "bad"...but rather a place to start looking (this is where a manual comes in REALLY handy). I know it is not fun to sit and research the manual, but it is rewarding when you can figure out the problem without spending a fortune in un-needed parts replacements. I've been there, and also learned my lesson.

There is a nice simple proceedure in the Haynes manual that will walk you through the fuel pressure test (about 4 or 5 proceedures)....turns out for mine it was the final proceedure that failed and was the cause of the code (41)


and despite what the repair manual says...it is possible to swap it out without pulling the the upper plenum and fuel rail.


I wish you well. Happy hunting.

i installed it today and so far so good, the regulatior was on top of the engine on the back end the hardest part was getting the bolts off with a allen wrench
will post agin if it dosnt work