1987 EFI 4.9 problems
Thread Starter
|
Senior User
Joined: Mar 2003
Posts: 105
Likes: 0
1987 EFI 4.9 problems
My 4.9 starts, then stalls out when I first start it in the day. Once I drive it down the road and it is warm or cold it hesitates/boggs down like the computer or some sensor isn't working properly. It does run well most of the time except for the bogging part which seems to happen when accelerating. I pulled the codes and it came up with TAD, IAC and TAB solenoids not working or not working properly. Without having to replace all three sensors can anyone recommend which one to try first. Also, where are these solenoids located on the engine????? What does the distributer do when it is starting to go bad?? Thanks, Brian.
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
1987 EFI 4.9 problems
The IAC is a motor mounted to the throttle body, and they commonly foul with carbon & varnish. Sometimes, cleaning them (off the truck) with EFI-safe throttle body cleaner will get a little more life out of them, but they have to be replaced eventually.
The TAB & TAD are the vacuum-control solenoid valves whose lines run to the diverter valve on the smog pump's plumbing. They're probably mounted on the top L rear of the engine beside the slightly larger EVR solenoid valve, but check the vacuum map.
Before you buy any new parts, test each with a multimeter using the Haynes procedure.
The distributor can go bad if its bearings get worn from poor oiling, or its gear slips/strips, or the cap & rotor can corrode from the ozone generated by the sparks, or the PIP (sensor under the rotor) can go bad, but that's rare.
The TAB & TAD are the vacuum-control solenoid valves whose lines run to the diverter valve on the smog pump's plumbing. They're probably mounted on the top L rear of the engine beside the slightly larger EVR solenoid valve, but check the vacuum map.
Before you buy any new parts, test each with a multimeter using the Haynes procedure.
The distributor can go bad if its bearings get worn from poor oiling, or its gear slips/strips, or the cap & rotor can corrode from the ozone generated by the sparks, or the PIP (sensor under the rotor) can go bad, but that's rare.
