83 308 qv running rich

Hello everyone. A little back ground first. I have an 83 308 qv that is running rich 4%CO at idle with a slight miss. I have read many of the archives and have followed many of the system diagnosis test as well as replace some things when I did the major this winter. New: plugs, plug wires, fuel injectors, fuel distributor rebuilt, and everything else involved with a major service. The car ran rich before I replaced these things and I thought I might get lucky and fix my problem with some new injectors that I needed anyway. No such luck. LOL

So I began the process of trying to find out why my car will not lean out. Using what I have learned here I just tested my fuel system preassure and all of the test where within spec.

I then moved on to the ignition system. After checking all of the plug extenders, spark plug wires, Digiplex's properly grounded, distributors, checking wiring harness, and testing the resistance in the flywheel pickups, nothing was out of the ordinary.

I then put the timing light on my car and sure enough the timing is jumping around some what erraticly by a few degrees at idle. I can't really tell exactly how much the timing is moving but it does coincide with the miss. It does this as you increase rpm also. Something I had not noticed before, probably because I have never really tried to hold a constant high rpm.

This is where I am now. Trying to figure out what to test next. Digi's , maybe a flywheel pickup is going out intermitantly, or a loose wire between the flywheel pick ups and the Digi's. Hopefully I am on the right track to fixing this problem and not out in left field? LOL I am sure I have missed some things so please ask away and any help would be great.

Thanks

Bill Smith

Bill,

the miss could be related to a pick-up sensor, but not the 4% CO.

Have you adjusted the metering screw inside the FD itself?

Hey JRV,

Yes, I have adjusted the metering screw wth no luck. Checked just about everything and it still runs rich. I am leaning towards the crank sensors messing things up. Would the crank sensors acting up not mess with the mixture to get the car to run?

Bill,

the crank sensors would not affect mixture on the CO side very much, certianly not enough to cause the CO to run 4%.

I would check the CS Injector for leaks, the Hieght of the Air Flow Plate and Determine if the Air Bypass screws are allowing in enough air, and the Position of the TPS if so equipped. Do you have L-Jetronic (US or Euro?)? If so, that is likely where the problem lies.

Thanks for the suggestions JRV. I have adjusted the Airflow plate once already with no effect to the CO. What is "CS injector" the injector itself or the FD? I have installed the new brass injectors but it is possible that I have a bad one or damaged one some how. I have played with the Air Bypass valve with no luck. By the way I Have a US version QV with no cats, and no air pump. K Jetronic fuel system so no TPS.

First, I think I need to fix my timing issue then I can move on to the mixture issue. What do you think?

Bill

JRV, timing question?

I was looking at my owners manual last night and it looks to me like the timing is set by the Digiplex's to 10* btdc at 1000rpm. When I was checking the timing (eng. warm) with my timing gun, the timing seemed to be around the AF3* mark on the flywheel. That to me seems to be after TDC and an incorrect timing. YES/NO? If yes, could that cause my rich running problem? AM I barking up the wrong tree here?

Thanks
Bill

Hi Bill,

yes Timing is controlled by the Digiplex, in conjunction with the cold start system and the coolant temp sensor on the right side, sorta bottom of the Header Tank. When cold the timing is advanced for higher idle and smoother running, after 140 f, the timing retards to help burn off Oxides of Nitrogen (NOX). No timing adjustment is possible.

I truly feel that the timing is not causing the rich running condition.

Thanks JRV

I plan on getting my wonderng timing issue solved first then see where I am and go from there. Any suggestions would be great.

Thanks
Bill

You might try looking to the WUR on this one. I have been trying to dial in a Bosch system, an '82 and I know the frustration. In my case by observing the gauges as it went from cold pressure to warm gave a hint.I had set up the WUR to be adjustable, per this link (I believe I found it here some time ago):
http://www.pelicanparts.com/techarti...warmup_reg.htm

I found the discrepancy when knocking the pin, and not getting the proper response on the gauge. a quick check of the WUR showd it had a bit of dirt in the valve part, and it could not close well This of course acted to the distributor like a cold signal, and it stayed fat, or rich.
I have found the adjustability a real bonus when running larger than stock cams, as the low vacuum signal they have at idle speeds acts like an open throttle signal to the distributor, and it richens the mixture.
I have a queston on the Bosch.
My friend looked back thru his records, and found an earlier shop mentioned that the fuel distributor was "weak". am not familiar with the term in this application. Any ideas?
Thanks!
Kermit

Hey Kermit

Thanks for the ideas. I actually tried messing with the WUR pin but after reading the article it looks like we where moving the pin in the wrong direction. We nocked the pin down and from reading the article we where just richening the mixture. We then thru on a different WUR and we got the same %CO results. We did all of this without the CIS fuel PSI gauges though because I did not have them at the time. I think I will have to revisit the WUR with the guages hooked up. Question: I tested the fuel psi with the engine off and running. The warm psi was not within 3.4 to 3.6 bar until I started the engine. Should I test the fuel PSI with the engine running or with the engine off? Thanks

Bill