No LED flasing in slot 2 OBD. Slot 6...Yes. 740gl

Jeff Schubert · Post by **Jeff Schubert** » 14 Dec 2016, 02:11

I've been chasing gremlin in my 89 740gl wagon for weeks. I WAS able to use the OBD on both slot 2 and slot 6. All of the diagnostics were working to test the different sensors.

Now...the LED will NOT flash codes from slot 2, but WILL from slot 6, which flashes 1-1-1, or, no codes.

I currently have the FPR bypassed in 30, 87-1, and 87-2 for testing purposes. I also just replaced the connectors to the radio suppression relay. The car -still- does not run right.

Will bypassing the FPR be cause for not being able to read codes from slot 2 of the OBD?

I have a new Stribel FPR ordered and on its way. I attempted to reflow the solder in my original relay, but am not 100% I didn't short anything in doing so.

I am curious on how I would I be able to read 6 but not 2.

I am near the end of my rope in completely giving up on this car, especially considering my electronics skills are lacking. I had assumed up to this point it was a fuel issue, but I'm starting to wonder.

I am still searching, but any advice would be great.

93Regina · Post by **93Regina** » 14 Dec 2016, 20:37

Jeff Schubert wrote:I am still searching, but any advice would be great.

Diagnostic codes only point in a direction...So, what's the problem...gremlin ?

Jeff Schubert · Post by **Jeff Schubert** » 14 Dec 2016, 22:11

It seems to start fairly well. Not immediately but usually within a few revolutions. That leads me away from a crank positioning sensor issue. It always starts.

It will idle fine for 3-5 minutes and rev up well, then start dropping off. The tach does not flucuate or stop working. If I am feathering on and off the throttle it will stay running. That's when it starts with the eye burning rich (inside garage) and backfiring.

Then sometimes it suddenly clears up and runs great. I am not finding a definite pattern.

I have not yet changed the fuel filter but do not think that would be a random occurance. I did find the fuel pressure regulator leaked and replaced it with a new one.

I've tried to tap on the inline fuel pump while its not running well. No change. It currently has over a half tank of gas, however I have not yet inspected the in tank pump. I wouldn't think that would be a random occurance either.

I cleaned the cap and rotor until I am able to get a new one. The plugs were replaced recently.

I've tried to bypass the fuel pump relay. No change. I have not tried to bypass the RSR yet.

I also have the symptoms and codes I found in my other post regarding Fuel pump relay testing.

I also found that my gas cap hisses when I remove it, and in searching that could be an evap issue. I have yet to chase that problem down, I thought that may have been normal.

I also recently replaced a leaking fuel line between the tank and pump.

This car does not seem like it was maintained well from the previous owner. I bought it in a pinch when my other car died. I do like it but it she seems rather finicky at times.

I'm old and cranky sometimes too, but..dang...

Jeff Schubert · Post by **Jeff Schubert** » 15 Dec 2016, 02:35

A friend of mine suggested the engine coolant temperature sensor, however that code did not come up before, and I still can't seem to get codes from slot 2.

The check engine light came on again after disconnecting battery, but I CAN still read 6 which is 1-1-1.

I have bypassed both the FPR and RSR with no apparent improvement.

I will do more research tomorrow on testing the ECT sensor tomorrow. A clue, no change when I unplugged it...? (The 2 prong one by knock sensor)

It would make sense on why its so rich and hunting for idle, but..no code.

I've bypassed everything else lol can I bypass the ECT too? A resistor of some type to fool it?

Thanks again.

lummert · Post by **lummert** » 16 Dec 2016, 09:57

Try searching within this section:

http://www.volvoclub.org.uk/faq/EngineOBDCodes.html

Jeff Schubert · Post by **Jeff Schubert** » 16 Dec 2016, 14:40

I had seen that site before, Ive been trying to use and interpret the codes, but can be rather vague. As well, some symptoms may cause false readings in other components. I believe a too lean too rich code may or may NOT be the O2 sensors cause for fault...it could be a fuel issue causing an out of range, but not necessarily a 'bad' O2 sensor....true?

93Regina · Post by **93Regina** » 17 Dec 2016, 19:56

Jeff Schubert wrote:start fairly well. Not immediately but usually within a few revolutions.

So, just a drop in fuel pressure...not an issue, but check valve or an injector issue.

idle fine for 3-5 minutes and rev up well, then start dropping off.

So, Bosch CPU is running in open loop, and giving more fuel; later, closed loop is engaged (start dropping off)

feathering on and off the throttle it will stay running. That's when it starts with the eye burning rich (inside garage) and backfiring...Then sometimes it suddenly clears up and runs great.

So, its running rich, and its running lean.....which tends to point to this

.
So, clean it up, or get a new one...check electrical connections first.

Jeff Schubert · Post by **Jeff Schubert** » 18 Dec 2016, 04:04

93Regina wrote:
So, just a drop in fuel pressure...not an issue, but check valve or an injector issue.

Early on I started checking vacuum lines, when finding a -small- amount of gas (not a huge spray when running though, I tried) are the Fuel pressure regulator. I replaced it with new.

Two FPR references get confusing.... Not the relay, the regulator...well, also. Yes, BOTH.

93Regina wrote: So, Bosch CPU is running in open loop, and giving more fuel; later, closed loop is engaged

So, its running rich, and its running lean.....which tends to point to this

I was really hoping you were going to point me in the -other- 'too lean to rich' as being oxygen sensor problems..

Oddly enough I was going to remove, clean and benchtest the...O2 sensor. It was mostly whitish, I was almost expecting black and sooty.

I had started going through the .1 to .9 volt sweep test. I hopefully read correctly that any sensor over .9 volt was no good. Not only was it closer to 1.5 volts when I heated it....rattled. I could see chucks inside and the meter when nuts when I shook it. I've never heard one rattle like that, ever,. Not good, it just..can't be. Sooo...

If somebody dropped it to break it, it wasn't me. All I did was unbolt it and it and bring it inside to check it. It's cold out there!!

I have a new O2 sensor ordered. A friend ordered one for me actually, and its a Walker brand. I had him make positive it was for a Bosch (not Regina) fuel system. I know Walker has been in exhaust products forever, so If imagine it should be ok quality wise.

If in fact the problem is STILL not fixed after the O2 at least I know of one less part that needs to be done again anytime soon. Ugh...

Ill know where to check NEXT if this isn't it, thanks for the info and link.

I may as well get a new cap and rotor while im waiting. It needed a lot of TLC, I think it was just cranky and fed up.

It'll be back to singing again soon! I...hope.

Jeff Schubert · Post by **Jeff Schubert** » 18 Dec 2016, 11:30

Im pretty sure I recall hearing the IAC working, when I was able to run OBD tests.

I could hear the pump and injectors, I know that for sure. It seemed everything that was supposed to make noise..did....I THINK.

Im at a standstill and waiting for parts. Maybe now would be a good time to remove and clean TPS, IAC, and AMM. What else can i clean up while im at it? Is it best to remove the throttle body to clean it is imagine? Any recommendation on products that work well that don't do damage?

Im more of an old school, V8, 4 barrel carburetor type guy, FI and electronics are not my forte but I am trying to learn. New tricks for an old dog

This old girl is getting Seafoamed once it runs well enough. I've talked to people that have had great results doing that. Make for a nice smoke show anyway.

Jeff Schubert · Post by **Jeff Schubert** » 18 Dec 2016, 21:20

Found this info...here

Forums member Bramdeman replied:

Simply unplug the o2 sensor and go for a drive, if it behaves any different (popping in the exhaust, rough idle, stumbling engine) than the sensor was fine. If it makes no difference its probebly dead. One more way, take it out of the exhaust and shake it, if it rattles 9 out 10 times it’s dead. I would simply replace the sensor with the same kind that was in it. I don’t think it will work any other way. A Bosch parts store will tell you for sure.

That looks like 4 for 4 symptom wise almost verbatim... All of the above. Found some confirmation on my rattle at least, I kind of figured.