Please Help me get this truck going!

[305_Square_Body]

Ok, I have a new spark plugs, a new map sensor, a new fuel filter, and a new coolant temperature sensor. 1987 R10 Silverado With a 305 engine. It is running very rich and none of the above fixes has changed anything. In fact, I can’t really get it to run it wants to cut off. The throttlebody appears to be in decent shape. The fuel Injectors are spraying. Where do I go from here?

 

[Redfish]

O2 Sensor? How does that look? A rebuild kit for the throttle body is relatively cheap and is easy to do. The ignition module inside the distributor can affect things also.

On my '87 every single part I replaced had a noticeable effect on performance. The ignition module, the distributor, the MAP sensor, plug wires... I replaced a bunch of things.

 

[chevytech87]

Took me 6 months to finally replace my o2 sensor on my 87’. Incredible difference, should have done it day one. Wild question but is there an engine light on? They’re primitive systems but they do give you a direction to go in

 

[fast 99]

MAP has the largest input on fuel trim. O2 is secondary. Sounds like it runs bad from start up. O2 does nothing until it reaches temp.

Check manifold vacuum
EGR partially open
Coolant sensor connector, they were prone to corrosion, pin back out
Grounds, especially at thermostat housing
Alternator AC voltage

Really would be nice to have data. If you're going to have one of these older vehicles purchasing a used red brick scanner should be considered. They aren't expensive.

 

[305_Square_Body]

O2 Sensor? How does that look? A rebuild kit for the throttle body is relatively cheap and is easy to do. The ignition module inside the distributor can affect things also.

On my '87 every single part I replaced had a noticeable effect on performance. The ignition module, the distributor, the MAP sensor, plug wires... I replaced a bunch of things.

The only thing that has made a difference is unplugging the coolant sensor. It is like it breathes new life into the engine. Still stalls when accelerating though.

 

[305_Square_Body]

Took me 6 months to finally replace my o2 sensor on my 87’. Incredible difference, should have done it day one. Wild question but is there an engine light on? They’re primitive systems but they do give you a direction to go in

The engine light is out. Blown bulb maybe. Tried the paper clip jumper trick but no luck.

 

[Ricko1966]

Check values on the cts, if your cts always thinks it's -40 you will always run rich. Check for A/C ripple it will freak out the ecm and do weird stuff, not probable but an easy check @fast 99 gave you very good advice also. Well I feel stupid now fast already mentioned a/C ripple. So all I can add is check values on the cts.

 

[305_Square_Body]

Thanks everyone! Chipping away at this. New MAP sensor, new CTS, new O2 sensor. That O2 sensor replacement took a year off my life. Hopefully I didnt cross thread it but it’s location makes it very difficult to get it threaded. TBS on the way.

Also, I took the dash apart and replaced the light bulb for service engine light. Did the paper clip jump. So far, the most satisfying thing I have done. Two codes. Flash pause, two flashes and flash, pause, five flashes. That led me to replace O2 sensor. Keeping the faith this thing will fire up nicely and be humming soon.

 

[Ricko1966]

If it's not running right from a cold start up 02 sensor isn't going to fix it. Throwing parts at it hoping to fix it is a costly way to fix it. Have you done what fast told you?have you done what I told you?

 

[Maknwine]

I guess you could still do an ohm's test on the old coolant temp sensor to see if it was within spec? Just to be able to know that it may be worth keeping in case the new one becomes an issue. I'm sure there's tables on the net to show a range of values at different temps. I think I did it many many years ago for my S-10.

 

[Rusty Nail]

ahh don't pay Ricko no attention bro, I say keep throwin parts at it. Eventually you'll get the right one eh?
AND THEN the rest of it will be brand new!

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[Ricko1966]

@Rusty Nail thanks. LOL I needed that.

 

[305_Square_Body]

Part of my issue is I'm a novice. So, throwing parts is my default. Definitely would love to try everything above. Just not sure how.

 

[Rusty Nail]

ahh!
all you need to get started is?
a digital voltmeter!

like this ! they run 10-15 bucks.
mostly all you do is measure the voltage or resistance across terminals with it, it's not hard.
This is a must have tool for squarebody owners like yourself.
read the instructions and youll be a pro.
Additionally they sell fancy CODE KEYS at AUTO ZONE for reading your computer's trouble codes. Mine is at the house but ill snag a pic tomorrow for you, just bustin your balls a little in the meanwhile.

Pickin up a good multimeter is on your list of things to do now. They run on AA or 9V batteries... compact and handy.

like this:

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the rest is very, very, basic hand tools you may already own. Wrenches, pliers and such. Aint no need for a forty dollar socket!

You'll need a pocket screwdriver though.

 

[305_Square_Body]

Funny you should say that! I checked voltage on the battery yesterday. It was over 12 and stayed strong with the engine running and with accessories all turned in. What I don’t understand is the drastic impact on the engine when I
Simply turn on the headlights. I did the unthinkable yesterday and adjusted the TBI idle screw. Got it sounding really good. Did better popping it into gear and better on initial takeoff. Still wants t bog down if acceleration is modest. Once it gets to 45 and up, it flies. Startup still sucks. Chugs, tries to shut off and something kicks in to keep it running. Repeats this pattern til it finally warms up to idle. Idle sounded good this AM but the rich smell is back.