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Old 11-19-2019, 04:52 AM   #1
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86 P30 and California Emissions

Hi all,

I'm new, and recently got an 86 Chevy P30 bus built by Thomas.

It's wonderful; born in Philadelpha and did a tour in a township as an extra pool bus before moving to Oregon in the early 2000s at 50,000. Now at 86,000 on original engine, and has been registered in Oregon as an OHV operating at a tree farm for the last two decades with what appears to be immaculate maintenance records.

The previous owner managed to register it as an OHV in California as an SUV

Now, I am trying to get it smog-ready and am trying to locate an appropriate catalytic converter. I can find a CA compliant converter for 1987 P30, but not the 1986. Should it matter?

It did not have a cat coming in, nor did it have an EFE valve. I was able to fix the exhaust and replace the EFE

new vacuum hoses and got the routing down correctly.

The THERMAC (air intake valve from the heatstove) actuates but stays closed - I suspect that the vacuum valve in the air cleaner is bad

The smog pumps have an external filter can missing an air filter that needs to be fixed (on order)

NEW PCV and air cleaners next week

EGR is a crappy 'new' 'oem' part that appears to open, but is loose. Possible that the TVS sensor for the EGR is defective

I have no idea how to check the deceleration valves.

guess my main question is about the catalytic converters..anyone in CA with an 86 chevy that can shine some light?

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Old 11-19-2019, 10:13 PM   #2
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When you bring it to California you take your vehicle to a local testing station. They will do a cursory inspection and run a sniffer test where they insert a probe in the exhaust pipe and run the engine at different rpms to determine outputs exhaust gas levels. If it doesn't pass they can sometimes recommend potential repairs (smog test stations are not allowed to make repairs due to potential conflict of interest). I have a 98 P30 bus. Had a new engine put it in and sweated passing smog because OBD2 ((your bus is too old to have) kept throwing errors but it passed the sniffer test without problem

Stephan
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Old 11-20-2019, 07:00 AM   #3
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Are you sure an 86 would have had one? They (epa) starting with smaller vehicles, cars, then light trucks (pickups) and as time went by required heavier vehicles to have them. So you might not have had one in 86 but 87 got them.
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Old 11-23-2019, 05:00 AM   #4
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Yes, that's the question. 86 didn't have cats, but 87 required 'em. I'm wondering if I could throw some cats on there to help pass smog. Currently its failing, but that was before EFE, EGR, and Thermac issues were identified..
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Old 11-23-2019, 06:28 AM   #5
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I would not put cats on if they were not required for the year of build.

Have you checked ignition timing, including full advance ? this plays a big part. Pulled any spark plugs to see what the overall condition of the engine? Nice and clean or a bit oily, sooty, burned to a crisp? Reading spark plugs is a great way to determine what is going on in an engine.

The other thing to check is fuel, I am assuming by 86 it has throttle body fuel injection. Are the injectors spraying a nice even mist? oxygen sensor good? temp sensor checked and good? If it is fully warmed up and the computer thinks it is cold it will run rich. So just some thoughts to look into.
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Old 11-23-2019, 07:37 AM   #6
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the way I helped a friend pass smog in ohio years ago when they tried snog here was pour a couple bottles of Octane boost in the tank, made sure the EGR was working, advanced the base timing a couple degrees, ran the hell out of it got it nice N hot and stopped into the smog station when there is no line and passed in flying colors...



that car did have a CAT on it as it came factory...
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Old 11-26-2019, 05:46 PM   #7
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Quote:
Originally Posted by Ronnie View Post
I would not put cats on if they were not required for the year of build.

Have you checked ignition timing, including full advance ? this plays a big part. Pulled any spark plugs to see what the overall condition of the engine? Nice and clean or a bit oily, sooty, burned to a crisp? Reading spark plugs is a great way to determine what is going on in an engine.

The other thing to check is fuel, I am assuming by 86 it has throttle body fuel injection. Are the injectors spraying a nice even mist? oxygen sensor good? temp sensor checked and good? If it is fully warmed up and the computer thinks it is cold it will run rich. So just some thoughts to look into.
So funny story, I was looking at the emissions routing diagram and in teeny tiny font casually mentions needing 89 octane....been putting in 87

It has a carbureted rochester 4bbl with new springs that was also serviced recently.

I haven't checked the ignition timing, though I was told the distributor and spark plugs were replaced prior to sale. When I start it up, it starts right up.

EFE was not connected originally and the vacuum line was left open. The ported vacuum sensor (aka TVS used by EFE and the thermac (air intake control)) had a broken vacuum port that the previous mechanic tried to glue, causing it to lodge globules of glue in some of the vacuum hoses leading from the TVS. Replaced the TVS and got the EFE installed...and the thermac closes now when it starts but the vacuum temperature sensor in the air bin doesn't seem to bleed off the thermac when the engine gets warm so I think I need to replace that sensor.

I replaced the EGR with a universal OEM and I'm displeased; it rotates way too easily and I got conflicting directions from the service manual and the directions for the EGR: service manual says if the EGR can be rotated, it should be replaced. EGR directions say to rotate it until it feels 'somewhat tight'. I can feel vacuum on the EGR line but it feels weak, so I am replacing the EGR with a true OEM unit and the EGR vacuum coolant sensor

Smog pumps are original and have an external air box that needs a filter. Seems like the previous owner ran it without a filter for some time, and the smog pumps themselves don't have any so Im trying to source one.

Water filter, hydrobooster, brake cylinder have all been replaced, but the brake cylinder has a small leak in the cover from an over-tightened screw holding down the reservoir.

Alternator also recently replaced when I noticed that it was not charging up the new battery I installed.

So far only issues with drivability aside from smog are:
-almost stalls when put in drive if I don't wait 3-5 minutes to warm up (typical from what I am reading)
-surge / chuggle (engine loses power) when over 3500rpm or 40mph, however it is very intermittent. I've been able to get up to 65mph on flats before encountering the issue but its pretty rare. Letting off acceleration and dropping the speed seems to help and I haven't full on stalled the bus yet. Obviously want to get it sorted.
-no heat
-occasionally doesn't start unless in neutral (I'm guessing a loose wire or ground)
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Old 11-26-2019, 05:56 PM   #8
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Have you put a vacuum gauge on it for testing? If vacuum is low it will though off timing advance and make high speed driving feel weak.

Vacuum should be at 17-18 or above at idle.
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Old 11-26-2019, 07:47 PM   #9
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If the motor doesn't ping with the 87, using 89 would just be a waste of money.
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Old 11-27-2019, 08:08 PM   #10
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Quote:
Originally Posted by Ronnie View Post
Have you put a vacuum gauge on it for testing? If vacuum is low it will though off timing advance and make high speed driving feel weak.

Vacuum should be at 17-18 or above at idle.
I will do that this weekend and report my findings.. where would I measure vacuum from? FYI, EFE does slowly open properly as the vehicle warms, so I know vacuum there is working, and the thermac shuts without a problem so vacuum is there too...presuming you mean EGR or the vacuum hose for the timing?
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Old 11-27-2019, 08:09 PM   #11
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Originally Posted by o1marc View Post
If the motor doesn't ping with the 87, using 89 would just be a waste of money.
I don't /think/ its pinging then again it makes a lot of noises sooooo
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Old 11-27-2019, 09:07 PM   #12
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Quote:
Originally Posted by yuletree View Post
I will do that this weekend and report my findings.. where would I measure vacuum from? FYI, EFE does slowly open properly as the vehicle warms, so I know vacuum there is working, and the thermac shuts without a problem so vacuum is there too...presuming you mean EGR or the vacuum hose for the timing?
Vacuum hose for timing
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Old 12-04-2019, 07:23 PM   #13
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Quote:
Originally Posted by yuletree View Post
So funny story, I was looking at the emissions routing diagram and in teeny tiny font casually mentions needing 89 octane....been putting in 87

It has a carbureted rochester 4bbl with new springs that was also serviced recently.

I haven't checked the ignition timing, though I was told the distributor and spark plugs were replaced prior to sale. When I start it up, it starts right up.

EFE was not connected originally and the vacuum line was left open. The ported vacuum sensor (aka TVS used by EFE and the thermac (air intake control)) had a broken vacuum port that the previous mechanic tried to glue, causing it to lodge globules of glue in some of the vacuum hoses leading from the TVS. Replaced the TVS and got the EFE installed...and the thermac closes now when it starts but the vacuum temperature sensor in the air bin doesn't seem to bleed off the thermac when the engine gets warm so I think I need to replace that sensor.

I replaced the EGR with a universal OEM and I'm displeased; it rotates way too easily and I got conflicting directions from the service manual and the directions for the EGR: service manual says if the EGR can be rotated, it should be replaced. EGR directions say to rotate it until it feels 'somewhat tight'. I can feel vacuum on the EGR line but it feels weak, so I am replacing the EGR with a true OEM unit and the EGR vacuum coolant sensor

Smog pumps are original and have an external air box that needs a filter. Seems like the previous owner ran it without a filter for some time, and the smog pumps themselves don't have any so Im trying to source one.

Water filter, hydrobooster, brake cylinder have all been replaced, but the brake cylinder has a small leak in the cover from an over-tightened screw holding down the reservoir.

Alternator also recently replaced when I noticed that it was not charging up the new battery I installed.

So far only issues with drivability aside from smog are:
-almost stalls when put in drive if I don't wait 3-5 minutes to warm up (typical from what I am reading)
-surge / chuggle (engine loses power) when over 3500rpm or 40mph, however it is very intermittent. I've been able to get up to 65mph on flats before encountering the issue but its pretty rare. Letting off acceleration and dropping the speed seems to help and I haven't full on stalled the bus yet. Obviously want to get it sorted.
-no heat
-occasionally doesn't start unless in neutral (I'm guessing a loose wire or ground)

Why is it failing smog? Too much CO2? Too little CO2? etc. Parts changing without diagnosing doesn't always work. Been there, done that too many times.
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Old 12-09-2019, 03:50 PM   #14
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Hey there,

It failed smog because the EGR was not engaging, and as a result I had high nOX. I could post the results here for those that are curious.

However...I did take the bus to my neighborhood mechanic after diagnosing no EGR vacuum from the carb. They were unable to fix it and passed it back to me. I'm about to go take the carb out and drive it down to a well known carb remanufacturer to have it properly cleaned.

I have this thinking, that either the previous owner / mechanic didn't properly clean the carb, or maybe blocked the EGR vacuum port, since this vehicle did live in Oregon and was registered OHV never needed emissions. Would explain the missing EFE hardware I had to reinstall too. When I was fixing other vacuum parts, the previous owner had the bright idea to use glue to reattach the nipple back to the TVS (non egr) sensor, and I found glue clogging the line in and out of that sensor.

Edit: Just talked to the previous owner. After driving it down with no issue, his mechanic friend did try to repair the vacuum nipple with glue, presumably after possibly breaking it while doing other work troubleshooting a coolant leak. I'm expecting to see the vacuum port with some glue in it.
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