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Old 01-11-2019, 06:10 AM   #61
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1991 35' Airstream 350
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Quote:
Originally Posted by bkahler View Post
I haven't looked at my throttle body while revving the engine but I'm wondering if you're getting to much fuel which is bogging the engine down?



Unfortunately I'm not in a position where I can start my engine to compare.



To my untrained eye that just looked like an excessive amount of fuel coming out of the injectors.


I thought the same. My wife asked if maybe itís getting too much fuel pressure. Iím ordering the actron tbi fuel pressure tester this morning. Never gonna hurt to have the proper tools and spare parts on hand.
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Old 01-11-2019, 06:18 AM   #62
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Quote:
Originally Posted by Air345Fly View Post
Your video sure sounds like the accelerator pump failing in a
carburator of that era. When the pump didn't work the engine would
stall if you stabbed the gas pedal. But if you accelerated slowly
the engine would run OK.


Since you have a TBI system you probably don't have an accelerator
pump. Is that true? If you accelerate the engine slowly can you
get it to run fast? If so, then your problem must be that you don't
get that extra shot of gas that the engine needs to accelerate.


In a TBI system how does the computer know when to give the
extra shot of gas? Is there a manifold vacuum sensor that

connects to the computer? Is there a temperature sensor that
connects to the computer?
MAP sensor (manifold air pressure) and TPS (throttle position sensor) along with engine RPM work together to determine how much fuel should be injected.

There is also a temperature sensor that helps the computer to determine the correct mixture.

It will be interesting to see what happens when he slowly pushes on the throttle.

One other possibility I can think of is if work has been done to the injectors at some point, were the correct ones installed? Just a thought.

Brad
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Old 01-11-2019, 07:52 AM   #63
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Old 01-11-2019, 07:56 AM   #64
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My money is still on the throttle body and/or one of the associated sensors.

Is it possible that a partially clogged catalytic converter would also cause those symptoms. Mine has a CC, but not sure whether there were standard outside of California or indeed whether your coach has one.

Quote:
Originally Posted by bkahler View Post
MAP sensor (manifold air pressure) and TPS (throttle position sensor) along with engine RPM work together to determine how much fuel should be injected.

There is also a temperature sensor that helps the computer to determine the correct mixture.

It will be interesting to see what happens when he slowly pushes on the throttle.

One other possibility I can think of is if work has been done to the injectors at some point, were the correct ones installed? Just a thought.

Brad
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Old 01-11-2019, 11:31 AM   #65
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How's this for a long shot: the coach is nearly 30 years old and is reported to have very low mileage. Any chance that it has the original set of spark plugs? Might be worth pulling #8 just to take a look.
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Old 01-11-2019, 12:34 PM   #66
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1991 35' Airstream 350
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I will pull a couple plugs to check....

Got it timed today - 4 degrees btdc.

Put in tps -

Results the same .... The IAC is next - napa should have it within the next couple hours - there are two possible choices (12mm or 14mm)- only one avail locally so hoping its the right one - I have mine out to match it up.

I also bought an o2 sensor. Have not installed that yet.

The catalytic converter is also something I have considered - I may disconnect it to see if it has an effect. Its just behind the muffler on this motorhome.

As to slowly increasing rpm - I can get it to a higher rpm that way but it still eventually bogs down (under no load) - In drive (under load) I cant get it much above 2000-2500 rpm

I am learning alot about this motorhome which is good.
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Old 01-11-2019, 01:23 PM   #67
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Quote:
Originally Posted by sraab928 View Post
I will pull a couple plugs to check....

Got it timed today - 4 degrees btdc.

Put in tps -

Results the same .... The IAC is next - napa should have it within the next couple hours - there are two possible choices (12mm or 14mm)- only one avail locally so hoping its the right one - I have mine out to match it up.

I also bought an o2 sensor. Have not installed that yet.

The catalytic converter is also something I have considered - I may disconnect it to see if it has an effect. Its just behind the muffler on this motorhome.

As to slowly increasing rpm - I can get it to a higher rpm that way but it still eventually bogs down (under no load) - In drive (under load) I cant get it much above 2000-2500 rpm

I am learning alot about this motorhome which is good.
Getting the correct parts for the Motorhome chassis is not always as straightforward as one might hope. I spent days (as did Martin and Brad) trying to sort out a fault code on my coach caused by an incorrect knock sensor. One thing I have found useful is the AC Delco parts look up by VIN, which is here:
https://parts-catalog.acdelco.com/ca...log_search.php

I usually cross ref with RockAuto to try and get a clear picture on which is the correct application for my 250.

TBI UNIT MODEL 220 6C1-1 - detailed stuff/parts etc in this section of the Light Truck Unit repair manual, link below

The GM parts wiki goes into even greater detail where you can see blow outs for parts catalogues in different months. A lifetime's work...and worth checking out if you get really stuck for parts
http://www.gmpartswiki.com/query

It works well in concert with the unit repair manual, garage manuals etc

1991_Chevrolet_Light_Truck_Service_Manual
http://www.73-87chevytrucks.com/tech...ice_Manual.pdf

Light_Truck_Unit Repair manual 1991
http://www.73-87chevytrucks.com/tech...air_Manual.pdf

Fuel, Emissions and Driveability 1991
http://www.73-87chevytrucks.com/tech...iveability.pdf

Wiring manual 1991
http://www.73-87chevytrucks.com/tech...ing_Manual.pdf
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Old 01-11-2019, 03:08 PM   #68
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Quote:
Originally Posted by Boom Sounds View Post
Getting the correct parts for the Motorhome chassis is not always as straightforward as one might hope. I spent days (as did Martin and Brad) trying to sort out a fault code on my coach caused by an incorrect knock sensor. One thing I have found useful is the AC Delco parts look up by VIN, which is here:
https://parts-catalog.acdelco.com/ca...log_search.php

I usually cross ref with RockAuto to try and get a clear picture on which is the correct application for my 250.

TBI UNIT MODEL 220 6C1-1 - detailed stuff/parts etc in this section of the Light Truck Unit repair manual, link below

The GM parts wiki goes into even greater detail where you can see blow outs for parts catalogues in different months. A lifetime's work...and worth checking out if you get really stuck for parts
http://www.gmpartswiki.com/query

It works well in concert with the unit repair manual, garage manuals etc

1991_Chevrolet_Light_Truck_Service_Manual
http://www.73-87chevytrucks.com/tech...ice_Manual.pdf

Light_Truck_Unit Repair manual 1991
http://www.73-87chevytrucks.com/tech...air_Manual.pdf

Fuel, Emissions and Driveability 1991
http://www.73-87chevytrucks.com/tech...iveability.pdf

Wiring manual 1991
http://www.73-87chevytrucks.com/tech...ing_Manual.pdf


Thank you for the detailed reply. The part at Napa was not correct. We did use the vin number and rock auto as a reference. Hopefully the correct one will be there in the morning.
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Old 01-11-2019, 04:00 PM   #69
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Originally Posted by sraab928 View Post
Thank you for the detailed reply. The part at Napa was not correct. We did use the vin number and rock auto as a reference. Hopefully the correct one will be there in the morning.
What a pain. I put more trust in that AC Delco VIN lookup given that they are the 'official' GM parts supplier, but that isn't fool-proof.

Nick
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Old 01-12-2019, 10:22 AM   #70
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Well new iac valve installed and same result. She runs great up until about 2000-2500 rpm. If I push the throttle really slow under no load I can get her to 4000 before she bogs down. My next step is to wait for my obd1 setup to come and use tuner pro rt on the laptop to see whatís going on. I have not looked yet but I assume the connector will be under the dash somewhere?
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Old 01-12-2019, 01:22 PM   #71
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Quote:
Originally Posted by sraab928 View Post
Well new iac valve installed and same result. She runs great up until about 2000-2500 rpm. If I push the throttle really slow under no load I can get her to 4000 before she bogs down. My next step is to wait for my obd1 setup to come and use tuner pro rt on the laptop to see whatís going on. I have not looked yet but I assume the connector will be under the dash somewhere?
Yep, mine is just to the left of the lower part of steering column, kinda tucked away, but if you contort your body, stick your head in the footwell and legs in the air, you'll see it.
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Old 01-12-2019, 04:50 PM   #72
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One more thing: the inside of your distributor does not look familiar to me. Is it an HEI distributor with the ignition coil inside the distributor? If you did not get a new coil with the distributor, replacing the coil is my next guess. Either way, itís cheap PM.
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Old 01-12-2019, 05:23 PM   #73
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New plug wires, sparkplugs, OBDII readers, IAC valves, MAP sensors, O2 sensors, ICM, pick-up coil, coil trigger, fuel filter, fuel pump, new distributor, rebuilding carburetor accelerator pump, TPS sensor; and it's still not working right......

You still haven't found the infamous leaking exhaust manifold beside the starter yet.

When my guy makes up motor mounts to mount my Cummins in the P30 chassis, do you want me to get him to make another set at the same time for you?

Still wishing you success.
Sidekick Tony
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Old 01-12-2019, 06:23 PM   #74
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Quote:
Originally Posted by Isuzusweet View Post
New plug wires, sparkplugs, OBDII readers, IAC valves, MAP sensors, O2 sensors, ICM, pick-up coil, coil trigger, fuel filter, fuel pump, new distributor, rebuilding carburetor accelerator pump, TPS sensor; and it's still not working right......

You still haven't found the infamous leaking exhaust manifold beside the starter yet.

When my guy makes up motor mounts to mount my Cummins in the P30 chassis, do you want me to get him to make another set at the same time for you?

Still wishing you success.
Sidekick Tony

No new plugs or plug wires yet -

What has happened so far...
New Fuel Pump and Filter - (Installed before I purchased)
New Distributor including cap and rotor - (the was to replace the pickup coil and ICM) - Timed 4 degrees before TDC using plug 5 and bottom indicator.
New IAC
New MAP
New TPS

I have the o2 sensor but have not installed it yet - Just got my cable for the OBD1 and Tunerpro RT software - hoping to hook that up early this week and see if it tells me anything.

My next step after that would be to pull a couple plugs and look - then consider dropping the catalytic converted. I also ordered the Fuel Pressure tester with the fitting needed for me to test the fuel pressure myself (relying on the what the shop I had it at for that info so far - they said 13psi)

To answer the other question above - the coil is separate from the distributor and has not been replaced as of yet. I am getting a nice collection of spare parts....lol I am not discouraged..... My wife has already mentioned a new motor - but honestly I think this motor is gonna be a strong runner when I get it sorted.
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Old 01-14-2019, 01:00 AM   #75
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Quote:
Originally Posted by sraab928 View Post
No new plugs or plug wires yet -

What has happened so far...
New Fuel Pump and Filter - (Installed before I purchased)
New Distributor including cap and rotor - (the was to replace the pickup coil and ICM) - Timed 4 degrees before TDC using plug 5 and bottom indicator.
New IAC
New MAP
New TPS

I have the o2 sensor but have not installed it yet - Just got my cable for the OBD1 and Tunerpro RT software - hoping to hook that up early this week and see if it tells me anything.

My next step after that would be to pull a couple plugs and look - then consider dropping the catalytic converted. I also ordered the Fuel Pressure tester with the fitting needed for me to test the fuel pressure myself (relying on the what the shop I had it at for that info so far - they said 13psi)

To answer the other question above - the coil is separate from the distributor and has not been replaced as of yet. I am getting a nice collection of spare parts....lol I am not discouraged..... My wife has already mentioned a new motor - but honestly I think this motor is gonna be a strong runner when I get it sorted.
I have no doubt you'll sort this soon and suspect it will be a cheap fix (aside from your time). You'll also have a pile of spare parts which might just get you out of trouble one day. Also, worth putting vacuum leaks around the throttle body/hoses on your list as you work through it.
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Old 01-14-2019, 06:03 AM   #76
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There are no vacuum leaks in the engine area. I have also vacuum tested the ports individually to see if ones clogged. The only thing I havenít checked in the line that I assume runs all the way to the gauge on the dash. I get around 15Ē at idle at the gauge in the dash.
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Old 01-14-2019, 06:19 AM   #77
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Since you've not mentioned it (or at least I don't think you have), does the exhaust appear to be rich? In other words as you start to accelerate does the exhaust start turning black or does it smell rich?
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Old 01-14-2019, 08:00 AM   #78
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Since you've not mentioned it (or at least I don't think you have), does the exhaust appear to be rich? In other words as you start to accelerate does the exhaust start turning black or does it smell rich?


No smoke of any kind at anytime. It does smell like typical 90ís exhaust. Lol.
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Old 01-14-2019, 09:58 AM   #79
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There are no vacuum leaks in the engine area. I have also vacuum tested the ports individually to see if ones clogged. The only thing I havenít checked in the line that I assume runs all the way to the gauge on the dash. I get around 15Ē at idle at the gauge in the dash.
including all the gaskets on the Rochester 220 and the small hard plastic hose in front of the throttle body.
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Old 01-14-2019, 10:12 AM   #80
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I'l be watching this thread very closely. I currently have a 1991 AS Land Yacht with a 454 TBI engine. Recently I had a very bad incident that caused a no start issue. After having a very close by lightening strike occur at the house (MH was plugged in) I found that the MH wouldn't start reliably. It started fine originally but wouldn't rev up. After a few starts it wouldn't start at all. Ended up having it towed to a near by truck repair center. They were able to diagnose it to a bad ECU. The power surge also fried my distributor model and the DRAC unit. After more money than I would like to say, they did replace the ECU and found it was damaged and the cause of most of my problems. The ECU was pricey and there was no reliable way to verify it was the cause of the problem. No codes were found. The did find a loaner that they swapped in and that allowed it to restart. Have had no issues with it since.


Good luck on yours. I have family that lives on Merritt Island so I'm familiar with the area. The Bridge over the Banana River is a bit steep so I can see your concern.
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