New 1988 R30 Classic Custom owner, need help

[af77]

Title sort of says it all.
I just bought this truck yesterday, told it was all rebuilt, had no issues running and driving. Just ugly (bad shape) interior, some exterior ugliness, and had to be started with a flat head screw driver instead of a key.

Well, I'm an idiot who needed a truck badly and a vehicle and I got swindled/lied to.

On the way home I discovered it wouldn't make it above 40mph, then 30, then 25. It gets worse the longer I drive it. Died a few times. It seems to get slightly better if I turn it off and back on. It will die if I floor the gas when it gets this way (struggling to hit 20mph) but then starts right back up. It didn't act like a transmission issue, and it isn't. The truck had a few back fires (mild/rare) but it really is just a "loss of power" issue like its starved for gas/air/something.
It acted like it was starved for gas which is why I did all the work on the pump and fuel filter.

So I got home and today I changed out:
The fuel filter
The fuel pump (verified working, watched the full injector spraying gas and watched it suck gas all the way through the new filter and get sprayed in)
Spark Plugs
Spark Plug Wires
Air Filter
Coolant
Oil Change

All brand new now and functional.

It idles fine and doesn't die at all after it warms up for a minute or so.

I checked for vacuum leaks as best I could by spraying starter fluid all over the vacuum hoses/etc under the hood and it never revved up so I don't think it's a vacuum leak.
There are also no signs of leaks/fluids on the engine, and no oil drips.

My suspicion is the exhaust system, but I honestly have no idea where to start/how to diagnose those/that.
It has no catalytic converter and the mufflers are glass packs. It's Fuel Injected.



I can't afford to not have a vehicle, and I really got screwed here. I can work my butt off to fix things, like I did today, but I need to know what to check/what you guys think it likely is.
If you think I should start a new thread outside this intro asking for help please let me know. I need to start figuring this out tomorrow morning/this weekend.

 

[Old60Driver]

Just my .02, but I doubt the exhaust is the culprit. Lack of cat, not to mention glass packs, 'should' give no problem with excessive exhaust pressure. Air, fuel and spark are my go to's. How did the old plugs look? Have you checked timing? Maybe a sticky float? What type of carb are we talking about? Any weirdness in the coolant when you drained it? Or the oil? Give the gurus here (not me), and they'll have a better chance of helping.

Good luck!

 

[SirRobyn0]

If it is exhaust it the heat riser. If it's stuck shut it probably won't cause the problem your having, but I've seen them break off on work their way down to the muffler and block it off. I suppose if it's stuck shut and the cross over is plugged with carbon that's also a possibility.

We need to know if it's carbed or injected. Welcome to the forum!

 

[af77]

Just my .02, but I doubt the exhaust is the culprit. Lack of cat, not to mention glass packs, 'should' give no problem with excessive exhaust pressure. Air, fuel and spark are my go to's. How did the old plugs look? Have you checked timing? Maybe a sticky float? What type of carb are we talking about? Any weirdness in the coolant when you drained it? Or the oil? Give the gurus here (not me), and they'll have a better chance of helping.

Good luck!

It's Fuel injected.

Nothing wrong with coolant or oil.
I haven't played with distributor cap/timing because it doesn't miss or idle rough.

It does show the Service Engine soon light occasionally but it's intermittent and goes away quickly. Only pops when it is really struggling with power.

I wonder if it's too much oil in the engine... dipstick isn't showing that but I don't trust the dipstick. Would that cause this? Too much oil = too high pressure?

 

[af77]

If it is exhaust it the heat riser. If it's stuck shut it probably won't cause the problem your having, but I've seen them break off on work their way down to the muffler and block it off. I suppose if it's stuck shut and the cross over is plugged with carbon that's also a possibility.

We need to know if it's carbed or injected. Welcome to the forum!

It's Fuel Injected.
If I completely remove the exhaust system as a test would that make it work? Wondering how to figure out if the exhaust system is the culprit.

 

[SirRobyn0]

It's Fuel Injected.
If I completely remove the exhaust system as a test would that make it work? Wondering how to figure out if the exhaust system is the culprit.

That would be the standard test, typically just unbolting the pipe at the manifold and pulling it down some is what we do at the shop if we don't want to use the back pressure gauge, however be sure to either remove the heat riser from the manifold, or pull the pipe down far enough to make sure it's open.

Since it's an FI engine, if the exhaust checks out ok I'd look next at the timing, followed by the MAP sensor and coolant temp sensor.

 

[SirRobyn0]

It's Fuel injected.
It does show the Service Engine soon light occasionally but it's intermittent and goes away quickly. Only pops when it is really struggling with power.

You really should find out what code is stored. That could point you in the right direction right there. As an amendment to my previous post I would find out what code is stored before doing anything else.

 

[af77]

Could it be the TPS? Do the symptoms I'm describing match that?

Walker Products 200-1042 Throttle Position Sensor https://www.amazon.com/dp/B019XF5UAM/ref=cm_sw_r_cp_api_i_MKU9EbHAEZRXP

 

[af77]

You really should find out what code is stored. That could point you in the right direction right there. As an amendment to my previous post I would find out what code is stored before doing anything else.

It's a 1988, you can check codes on those? I don't see a place to plug in an OBD reader. I don't think you can check codes on it.

Edit: did some googling. I'll go find that DLC connector and watch for the flash pattern. Thank you.

 

[af77]

That would be the standard test, typically just unbolting the pipe at the manifold and pulling it down some is what we do at the shop if we don't want to use the back pressure gauge, however be sure to either remove the heat riser from the manifold, or pull the pipe down far enough to make sure it's open.

Since it's an FI engine, if the exhaust checks out ok I'd look next at the timing, followed by the MAP sensor and coolant temp sensor.

I have a MAP sensor on a 1988 R30? I didn't think I had one.

 

[SirRobyn0]

It's a 1988, you can check codes on those? I don't see a place to plug in an OBD reader. I don't think you can check codes on it.

Edit: did some googling. I'll go find that DLC connector and watch for the flash pattern. Thank you.

Yes that's the way to do it. I use to use a paper clip.

I have a MAP sensor on a 1988 R30? I didn't think I had one.

All or at least all conventional FI system use a mass air flow sensor or manifold absolute pressure sensor (MAP), the 350 has a MAP sensor, usually on the side of the passenger side of the intake manifold with a vacuum line and a electrical connection, most of the connector were green.

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[af77]

Replacing these today. Also, here's a video of my engine/under the hood.

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[af77]

Okay I replaced the TPS and the MAP sensor and I finally got the trouble code.

The code is 44. Now I need help figuring out which of these is causing a "Lean Exhaust":


http://www.misterfixit.com/code44.htm

 

[SirRobyn0]

I assume it's still running bad after the sensor replacements? I'd check fuel pressure and see if it is ok. possible fuel pump, clogged filter. Possible coolant temp sensor, and check the wiring for that, in the video it looks like it has been spliced, but I'd think that would set a code. Vacuum leaks, clogged injector(s). Sometimes the charcoal canisters come apart on the bottom and make a hard to find vacuum leak That's what comes to mind.

 

[af77]

I assume it's still running bad after the sensor replacements? I'd check fuel pressure and see if it is ok. possible fuel pump, clogged filter. Possible coolant temp sensor, and check the wiring for that, in the video it looks like it has been spliced, but I'd think that would set a code. Vacuum leaks, clogged injector(s). Sometimes the charcoal canisters come apart on the bottom and make a hard to find vacuum leak That's what comes to mind.

I've replaced everything (fuel filter, pump ) and those sensors. Same issue. Even after disconnecting and reconnecting battery.
Sprayed all of under the hood with starter fluid to search for vacuum leaks, didn't find any. I'm checking fuel pressure next "just because".

Running a lean condition, definite power issues/won't get above 35 at best.

Any forums you suggest I take this to for expert advice, or is this the place?