Hi all, this is a tough one...

1988 B250 318 TBI Auto, 50K miles, all stock Safari Conversion.

No codes.

It won't idle well with CTS plugged in hot or cold (surges, dies, tip in is bad), though CTS Sensor ohms out correct hot and cold?

When CTS is plugged in passenger side injector doesn't fire at idle, but does when throttle is opened?

With CTS unplugged both injectors fire all the time and it runs/idles fine after it warms up?

Have checked the following...

TPS and Idle Switch, Brake/Park/Neutral Switches, MAP, ISC (internal gears good), IAT, TCS Sensor, Injectors ohm the same (1.4 Ohms), spray fine, and when swapping injector caps the problem does not follow. Timed at 10* BTDC @ 800 RPM, and Idle is adjusted per FSM (Factory Service Manual, i.e 2800 RPM with CTS and ISC disconnected). When idling well with TCS disconnected vacuum good at 17Hg, no vacuum leaks, and the Timing is steady. Battery fresh and voltage good.

Hall Effect is clean but the magnet is slightly corroded (starts and runs fine except idling with the CTS plugged in, not an issue IMO?), new Distributor Cap and Rotor, Plug Wires, Plugs are clean and gapped .035, new Fuel Filter, and no leakage from Fuel Pressure Regulator. Cleaned all engine harness connectors and grounds.

AIR Pump has a noisy bearing but still spins, and no exhaust leaks.

So, any ideas?

TIA for any help!

Doug

 

Your right that is a tough one, personally I don't have much experience with TBI so can't really help but hopefully learn something.

 

So replace the CTS, what's it like 10 bucks. I'm all for diagnosing and trying to replace the correct part, but some things just aren't worth the time to keep playing with. Engine vibration or vehicle level voltage could be causing it to act up, which you won't detect with an ohmmeter.

 

the man knows what he is talking about

 

Thanks everyone, appreciate the responses!

Ok, today after swapping the injectors themselves in the TBI I found that the trouble follows, so it's looking like a strangely intermittent injector that ohm's out fine, but I'll keep you all informed after I replace it tomorrow (assuming I can get one that fast etc).

Thanks...

 

autozone has 'em

 

Ok, I swapped the bad fuel injector out and it's running fine now, so I'm assuming unplugging the CTS forces the ECM into reading from some limp home table?

Summary: The problem was a intermittently failing fuel injector (during low pulse-width operation, i.e. idle and tip-in).

Thanks to all for the help!