87 K20 TBI 350........issues :(

[FahnSquatch]

Alright, so of course this dingus at the dump the other day had to tell me that my old girl would never die. As soon as I pull out the dump, she decided that she wasn't going to be told how to live her life and died on me. I was able to limp her home but she was running very rough and barely able to accelerate and wanted to surge and then stall. Here is my prognosis as this happened out of the blue and I have zoned in on some key differences I now notice when I listen and watch it try to idle.

1. Surges high bogs low and tries to stall.
2. At idle it seems the injectors are just full on blasting, no pulsing.
3. Press on gas and it makes a loud sucking sound and bogs down before reving up.
4. Side note: would not start a week ago, found fuse for ecmb had blow. Replaced and it ran fine until this past weekend.

Any thoughts are appreciated! Thank you!

 

[Big Chip]

Sounds like my junk when a vacuum line came off. I don't know what those have for vacuum lines but I'd check those first because it's easy. Or a bad gasket under the throttle body?

 

[FahnSquatch]

Sounds like my junk when a vacuum line came off. I don't know what those have for vacuum lines but I'd check those first because it's easy. Or a bad gasket under the throttle body?

Thanks for the response Chip! I have checked all my vacuum lines and all seem to be in working order. I have not checked the throttle body gasket. Could be the issue. I am wondering however, if the full blast injectors is at all related to the random ecmb blown fuse. Maybe it's the TPS....?

 

[Big Chip]

Thanks for the response Chip! I have checked all my vacuum lines and all seem to be in working order. I have not checked the throttle body gasket. Could be the issue. I am wondering however, if the full blast injectors is at all related to the random ecmb blown fuse. Maybe it's the TPS....?

I can’t help you there, I have zero experience with that setup but it should be easy enough to see if the injectors are just dumping fuel and see if it’s a signal issue or an injector issue.

 

[FahnSquatch]

I can’t help you there, I have zero experience with that setup but it should be easy enough to see if the injectors are just dumping fuel.

Yes sir, I am still trying to dig through all of the information online to troubleshoot. Problem is a lot of people just start replacing parts and not really troubleshooting so it's been tough going so far.

 

[Vbb199]

Alright, so of course this dingus at the dump the other day had to tell me that my old girl would never die. As soon as I pull out the dump, she decided that she wasn't going to be told how to live her life and died on me. I was able to limp her home but she was running very rough and barely able to accelerate and wanted to surge and then stall. Here is my prognosis as this happened out of the blue and I have zoned in on some key differences I now notice when I listen and watch it try to idle.

1. Surges high bogs low and tries to stall.
2. At idle it seems the injectors are just full on blasting, no pulsing.
3. Press on gas and it makes a loud sucking sound and bogs down before reving up.
4. Side note: would not start a week ago, found fuse for ecmb had blow. Replaced and it ran fine until this past weekend.

Any thoughts are appreciated! Thank you!

1 and 2 sound like a MAP sensor that's quitting on you OR a intake leak OR like @Big Chip suggested, the throttle body gasket

Does the exhaust smell really really rich?
Faulty/unplugged MAP will generate a excessive rich condition, poor idle, and terrible performance
So will a intake/gasket leak.

Cheapest start to diagnosing is checking wiring to map, to ensure its not unplugged, and step 2, CAREFULLY spray carb cleaner around the intake and throttle body's base (small bursts at a time) and see if idle randomly increases.
Diagnose methodically. Don't just hose the motor down in cleaner and start a fire LOL.


On your #3, that sounds like an exhaust that's plugged up. That could've been a result of the rich condition clogging up the catalytic converter that was already close to being toast.
But don't assume that just yet.

I've been thru alot of hell and bs With TBI motors. But there's a couple other guys here that have alot of knowledge here too.

 

[FahnSquatch]

1 and 2 sound like a MAP sensor that's quitting on you OR a intake leak OR like @Big Chip suggested, the throttle body gasket

Does the exhaust smell really really rich?
Faulty/unplugged MAP will generate a excessive rich condition, poor idle, and terrible performance
So will a intake/gasket leak.

Cheapest start to diagnosing is checking wiring to map, to ensure its not unplugged, and step 2, CAREFULLY spray carb cleaner around the intake and throttle body's base (small bursts at a time) and see if idle randomly increases.
Diagnose methodically. Don't just hose the motor down in cleaner and start a fire LOL.


On your #3, that sounds like an exhaust that's plugged up. That could've been a result of the rich condition clogging up the catalytic converter that was already close to being toast.
But don't assume that just yet.

I've been thru alot of hell and bs With TBI motors. But there's a couple other guys here that have alot of knowledge here too.

The map sensor is plugged in and all connections seem to be in good working order. Could be that it is faulty, however, i have yet to try the brake cleaner method, need to pick some up. Thanks for the leads!

 

[ctandc]

Test the TPS Sensor - it doesn't cost you anything but time. I would also pull codes and see if the computer is trying to tell you anything.

 

[FahnSquatch]

Test the TPS Sensor - it doesn't cost you anything but time. I would also pull codes and see if the computer is trying to tell you anything.

I'll check that out. That was something I had thought of as I believe the main cause of the bogging at idle is the engine is being flooded?? I don't have a check engine light on but i'll jump the 2 pins and see if any codes read out,.

Additionally, I just went out and fired up the ole girl to see how she was doing and if the fairy came to visit and fixed the issue. It did not...but, I held the throttle at a slightly high idle to see if it would still bog down and it did not. It was definitely a high idle and nothing i would want the truck to run at so i will not be adjusting the screw, but i wanted to be sure that the screw did not somehow back off.

Thanks!

 

[Snoots]

Sounds like a messed up IAC to me.

 

[FahnSquatch]

It's fixed!

I found out that my cap and rotor needed replacement as well as the throttle body needed to be cleaned. The hold in the butterfly for air intake at idle was gummed up and causing that sucking sound. Still needs some tuning but back to running and driving as it did before. Thanks for all the suggestions.

 

[Triv]

If your intake was gummed up, it would probably pay dividends to rebuild the throttle body. There's a kit that is like $40 if I remember correctly, and it's not difficult. It made a noticeable difference on my '87.

 

[Patterson]

Can I jump in here ???? I can’t figure mine out. It’s a 1987 r10 350 tbi Runs great but low acceleration is rough. That’s what kicked me off the smog test. I did the iac,engine temperature control, knock sensor,map sensor,02 sensor, set my timing, rebuilt my tbi all new gaskets new injectors , rotor, I sprayed and can’t find any air leaks. I think I may try a new distributor next