1991 B150 5.2L 318ci A/T

Randomly stops charging and kicks code 34 for Speed Control Circuit, but
I read things saying it could be vacuum to cruise control, voltage/resistance issues anywhere, ECM, a sensor, anything. Can someone give me the truth on where I need to begin?

Idle speed servo moves in/out when key put in "On" position, but resistance may be too high or low or could be faulting internally? How to verify?

Cruise control works, but I think both buttons on the right of the steering wheel accelerate (will need to double check). How to verify? Can I just pull a fuse and not use the whole circuit?

1 - Is code 34 putting it in "limp mode" causing "no charge" when it's not a charging system issue?

2 - Which components are related to Code 34? (Idle or cruise speed?)

 

FYI -

No smog pump
No A/C components (anymore)
>>>Problem happened ~1yr after removed
No EGR(?) valve on air cleaner

New battery
New 120A alternator
ECM is 1.5yrs old (bought reman from Autozone)
New engine coolant sensor
New Throttle Temp Sensor (pending installation)

 

Still looking for help.....

What do I look at to fix code 34 on a 91 b150?

 

Did you ohm out the solenoid to see if it is shorted or open? Have you tested the wires running to the solenoid to see if they have continuity and are also not shorting?

 

A code 25 or 35 would indicate a problem with the Idle speed control actuator. A 34 is the crusie control.

If both buttons on the steering wheel do the same thing, I think there in lies your problem of the code.

I think the charging circuit issue is separate. For that check the battery connections, all grounds, and follow the big fat wire from the alternator (+) terminal to the battery. At some point, usually behind the brake booster, there is a fusible link. These are supposed to look burnt and stretch out when they fail, but at 21 years old they do not always do this and instead have intermittent connection, usually failing to pass current when the battery is asking for a lot.

 

**UPDATE**

Replaced IAC with one from Junkyard and still got IAC error 35

Replaced computer and it will charge again, but Code 35 remained (short on code 35 fried voltage regulator?)
- Symptoms then became
+ 1/2 the gas mileage
+ Would sputter, jolt, putt when throttle just above idle
+ Code 35

Today it wouldn't start at all. I thought it was flooded so replaced MAP & TPS

Symptoms now
- Code 13 for MAP sensor (brand new!)
- Has spark, turns over, doesn't run

Now that I have a voltmeter, what to do?

 

Find the Main engine ground. remove it, clean it up, retighten,

Search for a frame to engine ground. If none exists, add one.

The EGR valve, on the left side of the intake manifold, might be stuck open

The Map sensor senses engine vacuum. It sets a code when it sends a signal to the computer that id outside parameters. A code 13 does not necessarily mean the sensor is bad. Code 13 is common with a sputtering engine.

Check closely for vaccuum leaks
Make sure none of the spark plug wires are touching each other.

Make sure none of the wiring leading to the transmission is chafed or burnt looking. Make sure the throttle rod between throttle body and transmission slides back and forth on the spring at the throttle body without moving the throttle.

 

I might be making progress?

I...
- Installed a new o2 sensor
- Seperated spark plug wires
- Double checked the grounds at back of block, under coil mount, and there is a small one from battery terminal to firewall.
- Transmission linkage moves rear without moving throttle

Now I am only getting error 12 (I think, not much of a gap) for a recent battery disconnect, but still no start....

Gas is flowing into TBI and spark from wire to block.

Last test is tranny wire inspection as recommended and how do I verify if EGR?

 

I'm afraid I have a clogge cat from all the un-burt fuel from the very rich mixture or even a timing issue. I don't have a timing light.

Do you think these could be the issue?

This is getting to be an expensive month!
$175 computer (fixed charging issue!)
$50 o2 sensor (Code 13 attempt)
$27 TPS (for code 13 attempt)
$45 MAP sensor (code 13 attempt)
$100 battery (charging fix attempt)
$18 used IAC controller (for code 35)
$120 120-amp alternator (charging fix attempt)
$15 Throttle air temp sensor (Speed control circuit fix attempt)
$xx Coolant temp sensor

 

.....