91 Blz Timing & Low speed surging

[ariesseeks]

Howdy

First Problem Ignition Timing.
Bought truck & figured tune up. replace cap & rotor. Distributer not tight. Need to reset timing. Manual says disconect ???? behind distrib. BUT WHAT & WHERE ????? Then degree setting???

Second Problem Low speed surging
Also engine surges in low speed after taking foot off throttle. MAP Sensor ? I replaced the TPS. No changes.

After welding in the steering box frame kit from Off Road Designs with Arm. good to go.

Billy
Tacoma

 

[ariesseeks]

31 people looked at my post. Not even a howdy do. Is my question overwelming? I just dont know what to disconect to reset Distrib Timing.

Am i using this thing right????

 

[trustyrusty]

Never done it on my 91, but I do know you set it @ 0 degrees
Sorry I can be of no real help. `

 

[Dogman12]

Shuold be a tan wire with a black line and has a disconnect torwards the drivers side fire wall, low speed idle surging is somtimes caused by a bad or stuck egr valve. If you search in the injection section you will find tons of info on this stuff from members who have swapped in tbi, also many good links to wiring diagrams to find the est (tan/black) wire you are looking for. Is the SES light on, the codes will help diagnose your issues. Some of the older repair manuals or mercruiser repair manuals have better info for setting the timing on a sbc. A 9/16 wrench with a nice bend at the box end makes loosening the distributer hold down easier you can take it for a drive and and adjust as you go for fine tuning.

hope this helps

 

[ariesseeks]

Thanks
I will look for est where you said.
There were no faults dealing with EGR. or anything else in the fuel system.

As far as surging goes. TPS was one of about 3 easy fixes for this prob from where i started reading. So cheapest is the TPS. It was giving me bad values on multi meter. But the problem persists. I will put a vacume pump on EGR valve & see if any difference. Then only thing esle would be MAP sensor.....

Tomorrow

 

[ariesseeks]

I would apreciate any lead on an honest shop in my are.

 

[Jessie James]

First, check your SES ("Service Engine Soon" dash warning light) codes. Jump terminals A and B (the two top right terminals) of the computer plug under the dash just below the steering column and turn the ignition on but do not start your truck. Count the flashes of the light. It will blink two numbers, pause, repeat three times, then go to the next code. See the link in my signature for the buyers guide, scroll down to download the document which tells you what the codes mean. This will take only a few minutes and can save you hours of useless and expensive guessing and replacing working parts, like the TPS you already replaced!

Then, if there are no codes, the shop manual says to check this list for a "hunting" idle (surging is considered an issue while in motion, not while at idle says the manual).

> Motor mounts damaged, grounding on frame, mispositioned
> Battery cables clean and secure. Loose or bad grounds will cause the ECM to not have a consistent idle.
> Timing (doh!)
> IAC (Idle air controller). The manual says if it's stuck open, high idle. Stuck closed, low idle. If stuck part way, rough idle and "will not respond to engine load changes". Reset it by turning the ignition on then off one time. Remove and inspect for clogging, clean or replace if needed.
> Alternator less than 9 volts or more than 16 volts
> PCV valve
> MAP - to test, start engine, unplug electrical connector. If idle improves, replace it.
> A/C refrigerant pressure too high. Check for overcharge or faulty pressure switch
> Leaking fuel injectors
> Fuel pressure. Less than 9 PSI will cause problems. Too high will cause rich condition and gas odor in exhaust.
> Sticking throttle shaft. If a high idle, the ECM will not control the idle.
> Vacuum leaks
> EGR - there should be no EGR at idle.
> Inspect O2 sensor for silicon contamination. If it's got a white coating, replace it. Check for voltage less than 300 mV (0.3 volt). 800mV or more means contaminated O2 sensor.

I am experiencing something similar - an occasional miss at idle - and I think it's the IAC but will confirm after I put the one from my other truck in there.