Wanted to see if anyone here has had this issue and knows what exactly it is.
I have a 1990 F-150 XLT Lariat, with a 302, auto and 2x4. I believe that's all that is relavent but if you have any questions regarding it ask away!

Okay, the truck has quite a few issues but I will do my best to discribe it.
After I just start it up if I put it into drive and come to stop for too long the engine dies. I also have to give it some gas as I crank it to have it start back up. If I let it idle for too long when I start it up and try to pull away it also will die (or if I try switching to reverse or anything like that until it's at running temp.) Also when I'm going down the highway if I go a little too hard for too long it'll lose power. The engine wont completely shut down. As I pull over and am trying to give it gas sometimes it'll kick back up and start driving again where as other times it will completely shut off before I even come to a stop. The gas pedal loses resistance during these times when the engine loses power. (not sure if its related but thought id mention it) Also the rad had a leak for a bit and now that ive fixed it, it does not die as easily coming to a stop early on. Doesn't make sense to me and also not sure if that is because the weather is getting warmer now that its spring. I am completely lost as to what the issue is. Best guess i've gotten is ecm, maybe a sensor or electrical wiring. Was hoping someone could narrow that down cause even at that it'd take forever to find the exact issue.

Any help is hugely appreciated!!! The truck becomes a heat magnet always dying on the side of the road! (also gets quite annoying...)

 

First place to start is to check for ecm codes. Even if the check engine light isn't on now, it may have some codes stored that'll help you out.

Fuel Injection Technical Library » How To Run a Self-Test

 

Thanks Bob, I'll be reading the codes this afternoon also going to try a compression test to see if that tells me anything will post results of both here once I am done.

 

Codes as they appeared:
11 - System OK
10 - ??? Can't find this one anywhere ? Any one know what this code is for?
41 - oxygen sensor circuit indicates system always lean
29 - insufficient input from vehicle speed sensor
41 - oxygen sensor circuit indicates system always lean
29 - insufficient input from vehicle speed sensor

 

Code 10=cyl #1 failed the cylinder balance test, which, if you didn't do it, is kinda weird that it showed up.

I'm guessing you only did a KOEO (key on engine off) test?

If so:

29, the vss. This sensor is located on top of the rear differential. It's possible that the sensor is bad, or the wiring to it is bad. I don't think that alone would cause your truck to run the way it does though.

41, O2 always reading lean, could be a few things. This code means that the computer has added as much fuel as it's commanded to, and the O2 still reads lean. Possible causes are a vacuum leak, weak fuel pump, or fuel filter. It could also be possible that your O2 sensor is bad, and if it hasn't been changed in a long time it may be worth replacing, but it may not necessarily be the problem.

I'd start by chasing down vacuum leaks. Spraying some carb cleaner around the vacuum lines, and listening for a change in engine idle rpm will help you track down leaks. Another common area for a vacuum leak is the metal canister that looks like a coffee can , that's mounted on the passengers side inner fender. They're prone to rotting through, which causes a huge vacuum leak.

After that's done, check the fuel pressure when it's running. If you don't have one, a fuel pressure tester can be rented free at most parts stores like autozone or advance auto. I'm not sure what the exact reading should be, but you should be somewhere up around 35-40 psi.

 

Code 11 (KOEO) System Pass

10---> Separator code

The others indicate historical codes of a loss of VSS signal (29) and the system was running lean.

 

[quote=Bob Gervais;13016600]Code 10=cyl #1 failed the cylinder balance test, which, if you didn't do it, is kinda weird that it showed up.

Most code readers interpret the separator code between the KOEO tests and CM display as Code 10.

 

First of all thanks for all the help!
I did the compression test and here are the results from that:
1 - 130
2 - 175
3 - 150
4 - 120
5 - 160
6 - 150
7 - 170
8 - 170

So 1 & 4 are weak. Also noticed the engine has built up a lot of sludge on the spark plugs when I pulled them (They were new a month or two before the issues started)

I'll be trying the new o2 sensor on saturday (or sooner depending on free time) as my buddy has a spare in his garage for me. So I'll let you know how that one goes.

Another thing I noticed while doing this that I somehow never noticed before. Above the throttle body is a green line, looks like a wire without the actual wire inside. it 90's off down towards the bank of spark plug wires on the passenger side of the engine. it then links up with what appears to be three other lines red yellow orange I believe. They appear severed about 4 inches from the 'T' towards the front of the engine. Cant see where they were connected to and was wondering what they were?

I live in Ontario so there is a good chance that coffee can's rotted out. I'll take a look at that and the lines coming off that.

I'm determined to fix this issue! haha! Thanks again for all the help!

 

Also almost forgot to mention. I am missing the little plastic gear that goes on the end of the speedo sensor into the tranny. The previous owner lost it while putting a new sensor in. I haven't had the best of luck finding a new one but I believe that may be the issue with #29. I could also be completely wrong on that being related though.

 

[QUOTE=rla2005;13016620]Good info. Never knew that!

Michael, that green line you mentioned is a vacuum line, and if it's severed, there's your vacuum leak. On these old trucks (at least on my two), I found it easier to replace the hard plastic vacuum lines with regular rubber vacuum line. There should be a vacuum diagram sticker under your hood. If it's still legible, that'd be your best bet on getting everything in order there.

I completely missed the fact that your truck is a 90. Yes, the gear missing off the vss will cause that code. Perhaps a dealer, or trip to the junkyard for that one.

Compression readings vary quite a bit. Ideally, you want the largest spread to be 10%. Given that your plugs looked dirty, you could have some blow by fouling them out, but that could also be caused by the vacuum leak, and the computer dumping fuel trying to keep up with the vacuum leak.

 

the little end on the sensors are colour coded,if you pulled the sensor from the tranny,thats where they break,and there was no gear on it,I happen to live in ontario and can give you one,I have a tan,white and orange,I beleive thes are coded to gear ratio,number of teeth sort of thing they are held in place with a funny little e-clip. hope this helps

 

Thanks Sticky58, unfortunately it was never in there so I have to figure out which colour it is online. But once I have that figured I'll pm you. Thanks again it's been such a hassle trying to source them. I tried three dealers and half a dozen parts stores non of which could even tell me gears or colour. Except one dealer could tell me its not red for my truck haha.

Vacuum line it is! I'll work at fixing that tomorrow and see where that gets me So vacuum line, o2 sensor and the gear and my truck should run a lot better! (also I'll know my speed which will be a nice treat )

I have no idea why I waited this long to try and tackle this. Thanks again for all the help and input!

 

something I could try is counting the teeth on each one, if they are real close,we could try one and match it with a gps.it could be real close

 

Just finished with the vacuum lines although I havent had a chance to test drive it. The o2 sensor is seized in there damn good. Tried shocking it with a hammer (on the socket) and penetrating oil a few times but nothing has even budged it. Any tips? I'm getting a breaker bar out tomorrow and going to try that. Fingers crossed!

 

Heat for the O2. Even if it's just a MAPP gas torch, it'll help.