Need help with this one.

[irarref215]

Hey there auto community! My name is Eric and I live in the PNW.

I finally found an 81 close to my area. I have never seen the engine run correctly. The PO made attempts to fix the problem, and when I got it, it had the problems it has now. It will start, idle high at about 1500 and settle down to a reasonable idle. Cracking the throttle (I would assume coming off the idle switch) causes the engine to chug, backfire through the intake and blow unburnt fuel out the exhaust. It is pretty violent how this happens. The PO was revving it up as he was demonstrating this for me and I could see something was wrong. So the car will idle, but that is all it will do. When asking for help, people are asking what it does when I drive it. It has not gone anywhere in years. I would not attempt to drive it like that. I would not let it warm up, since it reeks of fuel. I went to see it and he told me all the things he 'fixed' with the car. They included:

Fuel plump replacement/cleanout
Spark plugs
Fuel distributor
He had been messing with the idle screw trying to get it to run right


I did these things:

verified I had a poor spray and volume from injectors so I replaced all of them
replaced the ignition coil since it seems like an ignition problem.
Verified I have 78 lbs to the distributor with the jumper
Fixed many vacuum leaks including some missing parts left out by the PO
Verified the distributor is at #1 and crank
verified firing order and plug wires ok
spark plugs
New fuel lines
fuel filter

Findings:

FV not buzzing, but something else is near the AC compressor
Tried the dwell meter but the needle did not move
Plunger in distributor operational

I have been told CPR and disassembled this partially, found the diaphragm was not sealing from aluminum corrosion. Good now, holds vacuum on both ports. Any ideas?

[sdg3205]

You need to re-establish a baseline mixture. Is the factory mixture plug still in place on the mixture unit or do you see a CO plug (looks like a question mark)? May also be a golf tee!

EDIT - not sure what you mean "distributor at number 1." Have you verified timing with a gun? Also, have you traced plug wires to distributor cap and is the cap on correctly and NOT 180 off?

Where are you in the PNW?

[Bitsyncmaster]

Sounds like your lambda system is not working. Most common fault for that is someone put the wrong relay into the lambda relay socket. Next fault is the RPM relay if it has the double contacts (which original ones had).

But even with the lambda back working, your mixture is probably way off and will need adjustment once the lambda is fixed.

[irarref215]

You need to re-establish a baseline mixture. Is the factory mixture plug still in place on the mixture unit or do you see a CO plug (looks like a question mark)? May also be a golf tee!

EDIT - not sure what you mean "distributor at number 1." Have you verified timing with a gun? Also, have you traced plug wires to distributor cap and is the cap on correctly and NOT 180 off?

Where are you in the PNW?

I see a rubber coned plug on the mixture unit. I think it idles OK so doesn't this screw just adjust idle? Does it have an effect off idle? I pulled the mixture unit off again and the #1 mark on the distributor lines up with the TDC mark on the crank. So the distributor is indexed correctly. I am from the Portland, Oregon area. I have read every thread regarding fuel delivery. I have spoken with some 'gurus' on this and can not get people to talk about this problem. Is this the way it is supposed to work? I find it hard to believe anyone would buy a car with the PRV engine if it reeked of fuel and backfired through the intake when cold. Maybe I should let it warm and see what kind of surprises I get.

Thank you for your reply.

[Jonathan]

The rubber coned plug sounds like your mixture has been adjusted in the past. That mixture screw doesn't affect idle directly. It doesn't affect what the O2 sensor reads in your exhaust stream directly either, but that is what you adjust for. I'd suggest you read the fuel and lambda systems descriptions in the workshop manual and make note of the diagrams. It will show you a side profile of what that screw does and the lever arm underneath and what it affects. It mostly changes fuel pressures, on both sides of the equation.

I would suggest figuring out how to get your frequency valve buzzing. You can test by jumpering the power on via the RPM relay receptacle. Once that is in place, you don't need the ignition on to have power going to the frequency valve. You should easily hear it buzzing, especially so since the engine won't be on and making any noise. It could be as simple as the connector (electrical) is not making good contact. That could be the source of your fuel smell.

If you are indeed getting unburnt fuel directly out your exhaust, and not just condensation, your catalytic convertor might be in bad shape. You likely need to replace your O2 sensor before all of this is said and done too. You should/can get your lambda system to respond properly without a new one in there. Once everything is better, then put the new one in.

If your engine is truly doing something violent and dangerous, then proceed at your own risk, but adjusting the mixture to somewhere "about" in the middle of rich and lean to at least let you continue with the troubleshooting would be ideal. My mixture adjustment went from stall to stall in only one half of a turn. I don't know if there are physical stops if you were to try and get it in the middle of those two ends while doing it with the engine off. Turn it rich to the right and lean to the left (rich = clockwise and lean = counterclockwise). I suspect you want to lean out your mixture by turning it left (counterclockwise). Try small changes, like in terms of minutes on a clock, not hours, as you only have "6 hours" from stall to stall.

The dwell needle not moving isn't that bad of a sign. Might just mean your O2 sensor is fouled, or not warmed up, or some other issue with the Lambda ECU that a couple of us have seen recently for whatever reason.

[sdg3205]

Dave M makes a good point. Double check the lambda system is actually getting power. Other than the wrong relay being in the socket, the spade connectors on the back of the socket can work themselves out the back. Check AND clean the pins at the bulkhead very well. If you establish you have power the frequent valve could be seized. If so, hit it with a hammer.

Once everything is powered and operating take the injectors out and place them in clear jars. Jump the fuel pump at the rpm relay and adjust the mixture screw to lean until they stop spraying. This is your new baseline. Reinstall the injectors and proceed with mixture adjustment and dwell procedure.

I have no idea what u mean by people not wanting to talk about this problem. Fuel delivery problems are probably the number one topic on this forum.

[David T]

Dave M makes a good point. Double check the lambda system is actually getting power. Other than the wrong relay being in the socket, the spade connectors on the back of the socket can work themselves out the back. Check AND clean the pins at the bulkhead very well. If you establish you have power the frequent valve could be seized. If so, hit it with a hammer.

Once everything is powered and operating take the injectors out and place them in clear jars. Jump the fuel pump at the rpm relay and adjust the mixture screw to lean until they stop spraying. This is your new baseline. Reinstall the injectors and proceed with mixture adjustment and dwell procedure.

I have no idea what u mean by people not wanting to talk about this problem. Fuel delivery problems are probably the number one topic on this forum.

Other possible reasons for the frequency valve not to buzz include a bad connection at the plug to the valve and if the mixture is way off. Remove and replace the plug a few times, that usually gets it going if that is the problem. There is a procedure to roughly adjust the mixture screw to get it close so you can fine tune it with a dwell meter once you get the frequency valve going. Do you feel resistance when you push on the air sensor plate? If not, the fuel plunger may still be stuck. If the plunger is stuck the mixture will be VERY rich. You will see the muffler turn red if you let the motor run long enough.

[irarref215]

Other possible reasons for the frequency valve not to buzz include a bad connection at the plug to the valve and if the mixture is way off. Remove and replace the plug a few times, that usually gets it going if that is the problem. There is a procedure to roughly adjust the mixture screw to get it close so you can fine tune it with a dwell meter once you get the frequency valve going. Do you feel resistance when you push on the air sensor plate? If not, the fuel plunger may still be stuck. If the plunger is stuck the mixture will be VERY rich. You will see the muffler turn red if you let the motor run long enough.

Thank you everyone for your help. The help I have asked for so far has been on the phone only. Seems like people were just too busy to talk on a land line, even some that I have spent money and done business with in the past. This is the first time I have solicited help from the net.

The Frequency Valve looks like an injector and I tested it with my injector simulator. It feeds a 50% duty squarewave to it and it is useful for cleaning in the ultrasonic bath. It does work by itself. I have excellent connections right at the Frequency Valve as I see others have had issues in this area.

I feel resistance when I press the sensor plate, I believe the plunger is working fine. I have run an injector volume/spray test and it appears to operate as it should. I will set the idle screw as suggested by David T, just at the point it stops spraying fuel.

I guess the question I have now is that when I was doing the flow test for the injectors, I jumpered out 30 and 87 terminals I believe. Is this supposed to get the frequency valve to buzz? If so, it wasn't.

No doubt that the Cat is probably plugged at this point. It still would not account for the engine being able to idle just fine, but just cracked off idle it dies and backfires. Is there anything in the valley that could cause this? I have not pulled the entire intake off but there is some thermally operated switches in there. Could they cause such a problem? Want to check before I put the mixture unit back on again (5X already) and discover it still has the problem.

[Bitsyncmaster]

You jumper the brown wire to the double white/red wires on the RPM relay socket to power up the lambda.

You should get a buzz of 50% duty cycle when you do that jumper.

[axh174]

You jumper the brown wire to the double white/red wires on the RPM relay socket to power up the lambda.

You should get a buzz of 50% duty cycle when you do that jumper.

+1 on this.

I had a similar problem when the connection at my frequency valve got corroded. Idling was fine, but as soon as I left off the idle speed switch, the engine would sputter and choke. Jumpering the RPM relay pins is what helped me track down the problem (I could hear the lambda relay closing, but no valve buzzing. Following the circuit to the valve revealed the corrosion).

If you've jumpered the RPM pins and don't hear the valve buzzing, do you hear the relay clicking?

A helpful resource is the Lambda Circuit diagram found 3/4 of the way down in this post (DMCTalk Resources).