1994 6 Cylinder Occassionally Runs Rough

[Aceman]

1994 F150 occassionally runs very rough at speed, causes check engine light to come on but does not throw any codes. Doesn't appear to make any difference whether it is cold or hot.

New plugs, wires, distributor intenals including pick up coil & O2 sensor.

Even at 80 mph it occassionally feels like it is cutting out then after 5 or ten minutes it kicks in and runs fine.

Help !

 

[LEB Ben]

I'm not up on what throws codes and what doesn't, but the symptoms sound like a TPS problem.

 

[optikalillushun]

TFI module, pick up in the distributor. u sure its not throwing codes? anytime a check engine light comes on it should store a code.

 

[Aceman]

Yesterday I was driving it and it started skipping & bucking, the check engine light came on. I immediately (within 10 minutes) got it to my mechanic's shop without turning the ignition off. On the way the check engine light went off.

He checked it for codes and there were NO stored codes. The thing has run normal since.

His suggestion was try to bring it in with the check engine light iluminated and maybe we can then get a code.

Any other suggestions ?

 

[5.0Flareside]

uh. the mechanic must not be checking the codes correctly. because as long as they have not been clear I.E. with code reader or disconnecting the battery, the computer will store all codes.

best few bucks ive ever spent...... http://www.amazon.com/Equus-3145-Fo..._1?s=automotive&ie=UTF8&qid=1277915376&sr=1-1

 

[LEB Ben]

Damn...I never knew code readers were damn cheap, I always thought they were a couple hundred. Today is payday, guess that means I get to buy one. Thanks for the link.

 

[5.0Flareside]

Damn...I never knew code readers were damn cheap, I always thought they were a couple hundred. Today is payday, guess that means I get to buy one. Thanks for the link.

no problem. but its only OBD-I codes itll read. its specially made for the Ford(Lincoln,mercury) OBD-I system

 

[LEB Ben]

Dammit I need OBDII for Thunder and OBDI for the van.

 

[5.0Flareside]

OBD-II a cheap one....

http://www.amazon.com/OBDII-Engine-..._3?s=automotive&ie=UTF8&qid=1277924900&sr=1-3

 

[LEB Ben]

Well sir...you earned yourself some rep.

 

[5.0Flareside]

why thank ya sir.

 

[optikalillushun]

again, TFI module, pick up in the distributor or there is a TSB out for the shielding wiring chaffing the spout wiring causing said symptoms. search fullsize bronco dot com for the TSB under steve83s supermotors.

u can have the TFI module tested at any good parts store and also follow the diagnostics outlines in a hayes manual.

 

[Aceman]

Thanks for all the suggestions.

FYI:
Found some indepth info on why the CEL lights and computer might not store a code - http://fordfuelinjection.com/?p=44

 

[gsxr1238]

This was the reader i bought at Amazon awhile back:Actron CP9410 PocketScan Plus Diagnostic Code Reader for OBDII Vehicles.Cost $40.00

 

[ctuckF150]

I had a similar problem on my 93. It wouldn't throw codes for along time but it come on twice & when I checked for codes using a friends Matco scanner it was vacuum related. I found & fixed several vacuum leaks caused by cracked plastic lines. I checked it again after clearing then driving for several days still having severe drivability problems & no codes where present nor did the CEL come on. I replaced everything that you've replaced including cleaning the throttle body & IAC, TPS, swapped computers & under hood relays. I replaced the ACT which cured the problem. It was like a new truck.