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Old 11-19-2020, 10:45 PM   #1
Moyni
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Default 780 Bertone (PRV) Idling issue and some engine issues.

Car is running super rich (see sparkplug image), has a funky idle where it seems fine in drive but when its in neutral / park it will surge the RPMs. Doesnt want to rev over 2500 without shaking like the space shuttle Columbia. I just did new spark plugs, wires, rotor and cap.

Thinking try a new MAF and a fuel pressure regulator possibly. I also havent ruled out a vacuum leak.

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Old 11-22-2020, 12:42 PM   #2
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Pull the vacuum signal off of the fuel pressure regulator.... Fuel in that one? It may drip out or you may just smell it in the hose... Happens.

Coolant temp sensor and/or wiring to it. Ohm meter across the CTS... Open = pig rich.

Air mass meter much less likely; though everything about it is pretty old.

Give her a set of fresh plugs too. I'm fond of Bosch H6DC.

Check for vacuum leaks as doing so is good practice...Though a vacuum leak won't make her rich like this.
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Old 11-23-2020, 12:35 AM   #3
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Quote:
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Car is running super rich

As John noted, Coolant temp sensor...ohm spec it...in vintage GM vehicles, they go rich when they start failing..
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Old 11-24-2020, 05:07 PM   #4
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Originally Posted by JohnLane View Post
Pull the vacuum signal off of the fuel pressure regulator.... Fuel in that one? It may drip out or you may just smell it in the hose... Happens.

Coolant temp sensor and/or wiring to it. Ohm meter across the CTS... Open = pig rich.

Air mass meter much less likely; though everything about it is pretty old.

Give her a set of fresh plugs too. I'm fond of Bosch H6DC.

Check for vacuum leaks as doing so is good practice...Though a vacuum leak won't make her rich like this.
Ill give these a look, plugs are fresh too, should have mentioned that. Luckily we still have a few scattered NOS B280 parts laying around in the deep dark corners of the shop I can throw at it.
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Old 12-01-2020, 01:03 PM   #5
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Anyone have a diagram of where the CTS would be? I have the Haynes manual as well as the Volvo Green manuals but still cant find it based off the online part numbers.

This is the only sensor I have seen and I dont believe this is it
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Old 12-01-2020, 03:41 PM   #6
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Looks like a similar location for a 85-88 Pontiac Fiero...below the thermostat...either for the dash gauge, or for the ECU.

Google for ECU sensor...and compare:=_
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Old 12-01-2020, 03:51 PM   #7
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Footnote - If your thermostat is open, it should be replaced...this could skew temp readings by ECU.

Also, you most likely found the ECU's temp sensor...
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Old 12-01-2020, 04:20 PM   #8
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Quote:
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Luckily we still have a few scattered NOS B280 parts laying around in the deep dark corners of the shop I can throw at it.
Nice, for a while I wanted a B280. So I am glad someone is keeping the flame
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Old 12-01-2020, 04:51 PM   #9
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So after talking with the bossman here in the shop, and doing some of our own research on the ol VIDA, it does seem like that is the sensor I need to replace. I am sort of firing the parts cannon at this motor in hopes of resolving this, however I still need to pull it back inside the shop on a slower day and take my time testing all the electrical components.
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Old 12-01-2020, 06:06 PM   #10
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RE: firing the parts cannon

Replace coolant thermostat and coolant temperature sensor...Current CTS has been in there for "ages."
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Old 12-01-2020, 09:21 PM   #11
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Bosch LH-Jetronic 2.2 fuel injection....most likely then CTS

Last edited by 84B23F; 12-01-2020 at 09:28 PM..
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Old 12-01-2020, 09:44 PM   #12
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Footnote - If there is a cold start injector, then that circuit/injector needs to be evaluated.
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Old 12-02-2020, 05:07 AM   #13
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Quote:
Originally Posted by Moyni View Post
Anyone have a diagram of where the CTS would be? I have the Haynes manual as well as the Volvo Green manuals but still cant find it based off the online part numbers.

This is the only sensor I have seen and I dont believe this is it
Yes, that is the CTS
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Old 12-02-2020, 05:51 AM   #14
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Yes, that is the CTS
Not quite...that CTS has not been evaluated in years/years....nor has its terminals been cleaned up with spray contact cleaner.

OP: With LH 2.2, there should be new CTSs available
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Old 12-02-2020, 09:24 AM   #15
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Quote:
Originally Posted by 84B23F View Post
Not quite...that CTS has not been evaluated in years/years....nor has its terminals been cleaned up with spray contact cleaner.
One way or another, THAT is the CTS. It's condition is another thing, but the part has been identified correctly.
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Old 12-02-2020, 12:32 PM   #16
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Quote:
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part has been identified correctly.
On a CIS DeLorean, that would be a THERMOTIME switch...iitem #24.
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Old 12-02-2020, 04:43 PM   #17
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...are we discussing 780 or DeLerean here?
I've replaced this temperature sensor on my PRV too so I remember it quite well.
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Old 12-02-2020, 05:35 PM   #18
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Quote:
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...are we discussing 780 or DeLerean here?
Potential parts for the V6 PRV Parts' Cannon...
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Old 12-07-2020, 04:03 PM   #19
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Quote:
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One way or another, THAT is the CTS. It's condition is another thing, but the part has been identified correctly.
Yeah the book calls it a thermotimer, but I was able to get a new Bosch one for about $20. Seems to have fixed the terrible rev issues it had, however it still has a seeking idle. I can unplug the MAF and the idle stays the same so I have a buddy sending me a new (used) MAF to test with. If that works, I should be able to take it out on the street for the first time since I bought it.

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Old 12-07-2020, 05:04 PM   #20
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Yeah the book calls it a thermotimer
Weird...that part has nothing to do with time except it's a timebomb what is the part #?

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