My first (and last I hope !) backfire

[plissken97]

Hi guys,

I'm Julien, I live in France and I owned for 4 years now a beautiful black 1990 ZR-1.

I made this backfire last friday...
My SES light came on.
I got 3 fault codes after my diagnosis : H33 H45 H65.
I solved 2 codes which were the H33 and H65 by putting in place the MAP sensor hose at the back of the plenum.

Unfortunately, it remains my SES light with a H45 code.
It says "Oxygen Sensor (System Rich)".

Can you help me to solve this issue ?

Thanks a lot.

Julien

[tccrab]

Julien:

The backfire might have popped off the pvc hoses when it popped off the hose on the Map sensor.
Also check the fuel regulator vacuum hose, it lives on the bottom of the fuel pressure regulator.
And your Map sensor might be still leaking a little, especially if the hose has gotten soft over the years.
If the Map sensor isn't working right, it will cause the motor to run rich will cause the codes you're still seeing.

https://www.jerrysgaskets.com/hose-map-sensor-vacuum-new-90-95-13d4/

Crabs

[plissken97]

Hi Crabs, and all the members,

Thanks for your reply.

I double-checked all these hoses, and they are okay. I noticed that when I turn the ignition on without starting the V8, the vacuum pump on the passenger side, near the front right wheel, keeps running : it starts/stops 3 secondes then restarts/restops etc.

However, I decided to start the engine, and it runs very well. There's no SES light, and the car seems to be in great condition (the car idle is ok : 700/750 rpms), although I haven't driven it on the road yet due to the bad weather in Paris in order to be sure that all the horsepower are delivered.
I ran another diagnostic test and there are no more codes.

I am a bit worried about the vacuum pump running continuously.

If anyone has any input, I'd appreciate it.

Thanks a lot et thank you all.

Julien

[A26B]

Sounds like you have a vacuum leak, likely in the Secondary Port Throttle (SPT) System. There is a rubber hose connection, near the alternator, in the hard plastic line from the vacuum pump to the SPT system. Disconnect the line there.

Key on- Engine off, put finger on end of hose going to the vacuum pump to isolate the pump from the SPT system. The pump should only run a short time and stop until you release your finger. If this is the case, the vacuum leak is in the SPT system. Re-connect the hard plastic line.

Before removing the plenum, Remove the vacuum line from the pipe located on the driver side of the plenum at the center. Key on, Engine off, plug the removed hose. If the vacuum pump stops and/or the stop cycle is significantly longer between starts, the problem is likely the check valve under the plenum is faulty. If not, then the leak is under the plenum.

[plissken97]

Thanks Jerry for your feedback, this is really appreciated.
I will try your tips.



Before removing the plenum, Remove the vacuum line from the pipe located on the driver side of the plenum at the center. Key on, Engine off, plug the removed hose. If the vacuum pump stops and/or the stop cycle is significantly longer between starts, the problem is likely the check valve under the plenum is faulty. If not, then the leak is under the plenum.

In these both cases, whatever the problem is, it seems that it is are located under the plenum !

[A26B]

Thanks Jerry for your feedback, this is really appreciated.
I will try your tips.
In these both cases, whatever the problem is, it seems that it is are located under the plenum !

True, but as a temporary measure, if the check valve is bad, you can install a good check valve on the outside of the plenum, between the pipe & hose, until you get around to pulling the plenum

[plissken97]

So I followed your tips and:

The issue comes from the Throttle System.
It does not come from the check valve.
In conclusion, the problem seems to come from under the plenum...

However, after I unplugged/plugged the hose near the alternator (the one that goes to the vacuum pump), I noticed that the vacuum pump now starts and stops every 10 seconds approximately, not as fast as before.

Do you think I still have a leak?

Thanks a lot.

Julien

[A26B]

So I followed your tips and:

..............................after I unplugged/plugged the hose near the alternator (the one that goes to the vacuum pump), I noticed that the vacuum pump now starts and stops every 10 seconds approximately, not as fast as before.

Do you think I still have a leak?

Thanks a lot.

Julien

Yes, just not as bad. When the engine is running in closed loop, vacuum for the SPT is supplied from the engine intake (the port on the driver side) The SPT vacuum pump is to open the SPT when little or no vacuum is available from the engine, i.e. WOT for sustained periods.

It's not something that urgently needs resolved.

[plissken97]

Thanks Jerry.

As soon as I can, I'll drive and test my ZR-1 at full power to see if everything is ok, if I have all the power available.
I will see if the SES light is displayed.

Thanks for helping.

Julien

[RSLyrick]

Salut Julien,

I'm also french :)

I also did what Jerry recommended when you get a failure from the check valve of the secondaries vaccum system under the plenum. I placed it outside of the plenum on driver side as I didn't have the capability to lift it up at that time. Worked like a charm. The vacuum is held for 2 to 3 minutes for me, it was only 3 seconds initially.

I agree with Jerry that it is not a "critical" thing to solve. However, your pump will cycle quite a lot, meaning that you are "logically" shortening the life of the pump.

I also recommend you to purchase one of these vacuum pumps to really measure if your system is holding vacuum properly (I have a Mityvac MV8000 I think). There might be other vacuum components inside which are faulty (solenoid, vacuum tank....). If you do not have such pump, then the cycling time of the pump can only give such info.

But I don't see how the secondaries vacuum system correlate with your rich oxygen DTC code.

I would have a look at the fuel pressure regulator vacuum connection (if clogged) as proposed by tccrab and mesure the fuel pressure at the fuel rails.

Bonne chance!

Guillaume

[plissken97]

Hi Guillaume, and all,

Thanks for your post.
I haven't had the time to test my ZR-1 on the road yet, but I will post an update here once I do.

As for the oxygen issue, I think it was related to the missing hose on the MAP sensor, which likely altered the fuel/air mixture in the system.

Julien

[DRM500RUBYZR-1]

Did the backfire occur during startup?
:cheers:
Marty

[plissken97]

Did the backfire occur during startup?
:cheers:
Marty

Yes, I released the key too soon =D>

[DRM500RUBYZR-1]

Yes, I released the key too soon =D>

:thumbsup:

:cheers:
Marty

[plissken97]

Hi,
I tested the car, it has its usual power and no SES light, so everything's running smoothly.
All's well that ends well... until next time !! That's why we love our "old" cars !
Thanks for your help.
Julien