Loading up at idle

[Michael]

My car started loading up at idle (I think).

It will idle all day just fine unless it's in gear where the rpms dip. After about 2 minutes, it will finally die and take forever to start up in which I can smell Sulphur or the smell of a lit match. Now if I hold a little throttle on it, it's fine. If I am stopped at a red light and not adding throttle, it will eventually die or if I'm not there too long, upon pulling out, it will miss and sputter until the fuel is worked out and run perfect.

After talking to a few people, the consensus is I'm getting too much fuel dumped when the idle circuit is engaged. I could find no broken or loose vacuum lines. WUR and Fuel Distributor are Dgo rebuilds and about 4 years old. Idle computer is a oe DMCH unit about 10 years old. I haven't pulled it yet to visually look at the board. Frequency valve is about 12-13 years old from DMCH. Brand new injectors and lines about 4 years ago.

Problem is I just don't know what to look at first but I do have a K jet pressure test kit and I suppose agter visually checking the idle computer for obvious damage, I could just start with the diagnostic procedures in the manual but I was hoping someone who has seen this issue before could zero me in on a possible or likely culprit.

[Bitsyncmaster]

Pull your CSV connector and see it the problem stops.

[Michael]

I could not replicate the issue today. I let it idle in the driveway until the fans kicked in, so I know it was in closed loop, and even in drive, it never loaded up. I did pull the idle computer and didn't see any obvious damage (which means little). I guess I just need to get it back out and drive it until the issue reappears. Took it about an hour to show up yesterday.

[JBaker4981]

Pull your CSV connector and see it the problem stops.

I agree with Dave. I had my Thermo-Time Switch fail to where its sending constant signal to flood the motor via the CSV.

[Jonathan]

Michael, I had some ongoing idle issues recently and some sounded similar to yours. Dipping idle when in gear and outright stalling if you aren't on the gas a little. I also had some loss of power when trying to first set off that seemed to go away after the car warmed up.

I had the kit to replace the wiring connector on my OEM style fuel pump and did that and it seems to have corrected my issues. I'm still monitoring but I have had a half dozen drives on the new connector and a few hundred miles and it's been good.

Might be something easy to check. The two rings that tightened right to the top of the pump I suspect were fine but the plastic connector end looked quite sketchy. Replacing it has made a big difference.

[Jonathan]

Here's a pic of the old connector and the new...

71730

[David T]

Other things to check, the opening pressure and spray pattern of all of the injectors, The stop setting on the throttle plates and the decel valve springs, play in the quadrant link ends, valve adjustments. Maybe you are due for a tune-up?

[Michael]

Update:

Finally got it out for a bit. After about 30 minutes, it started to show up. Only at idle. I unplugged the CSV and it didn't change anything.

I have a new connector at my fuel pump which is also a DPI modern pump.

Brand new injectors, seals, Fuel Distributor (rebuilt) and CPR(rebuilt) and valley cleaned and all sealed aboit 2.5 years ago. Valve adjustment approx 5k miles ago.

[dmcman73]

Update:

Finally got it out for a bit. After about 30 minutes, it started to show up. Only at idle. I unplugged the CSV and it didn't change anything.

I have a new connector at my fuel pump which is also a DPI modern pump.

Brand new injectors, seals, Fuel Distributor (rebuilt) and CPR(rebuilt) and valley cleaned and all sealed aboit 2.5 years ago. Valve adjustment approx 5k miles ago.

Check the WOT switch that's mounted to the throttle spool (the small white switch). I've seen those begin to stick when the temps get up there from age or from the screws being overtightened. When the issues appears again, simply unplug the white plug(s) at the throttle spool (one plug is used on manuals and two are used on automatics). It's just a thought and could cause the issues.

[Michael]

Check the WOT switch that's mounted to the throttle spool (the small white switch). I've seen those begin to stick when the temps get up there from age or from the screws being overtightened. When the issues appears again, simply unplug the white plug(s) at the throttle spool (one plug is used on manuals and two are used on automatics). It's just a thought and could cause the issues.

Thanks! I'll try that

[Michael]

No luck with unhooking wot switch but I did check the dwell again this morning to make sure the mixture was still on point at cold closed loop and warm operation. It was swinging perfectly 15-20?

Then something happened. I shut the car off for a few minutes, went back out and started it and the needle was centered and not moving. That didn't surprise me as I thought it may have cooled off but after 15 minutes of idling, still no activity on my dwell. Even after reving it up...it should 100% be working at this stage so I'm thinking a bad or intermittent frequency valve or a bad o2 sensor?

PS; I hooked up my spare ecu from Dave Mckeen which doesn't work well with my cammed car but I could at least use it to rule out a bad idle computer. Which his computer in place, still no activity on my dwell meter. I'm really glad this happened, because now I at least have something to go on.

[Bitsyncmaster]

No luck with unhooking wot switch but I did check the dwell again this morning to make sure the mixture was still on point at cold closed loop and warm operation. It was swinging perfectly 15-20?

Then something happened. I shut the car off for a few minutes, went back out and started it and the needle was centered and not moving. That didn't surprise me as I thought it may have cooled off but after 15 minutes of idling, still no activity on my dwell. Even after reving it up...it should 100% be working at this stage so I'm thinking a bad or intermittent frequency valve or a bad o2 sensor?

Bad FV would make the dwell swing full one way after the O2 sensor is warmed up. It takes about 3 minuets to warm up the O2 from a cold start. Would be less time on a warm start.

[Michael]

Bad FV would make the dwell swing full one way after the O2 sensor is warmed up. It takes about 3 minuets to warm up the O2 from a cold start. Would be less time on a warm start.

So you think I just need to replace the O2 sensor?

[Bitsyncmaster]

So you think I just need to replace the O2 sensor?

That's what I would do. Not a big expense. Easy to do if you have already replaced before.

[Michael]

That's what I would do. Not a big expense. Easy to do if you have already replaced before.

Thanks...this will be my third I believe. I guess after 15+ years, that's OK as the other two times were just out of precaution

[Michael]

My O2 sensor should be here maybe today but yesterday I remembered I had a cheap Dgo sensor that I ran for a few days before realizing the voltage was just too sporadic to really work, so I tossed it in the spares.

It may suck but at least it won't load of my system and let me know I'm on the right track. I put it on and after about 30 minutes of driving, no signs of hesitation. Once I install a good one, I'll take it out for a long drive and make sure the problem is put to bed.

[Michael]

Car is fixed. The O2 sensor from DMCH is absolute dogshit. Dwell meter was all over the place and as far as I could tell, closed loop was at best, nowhere near normal. It's no better than the unbranded ones that dgo sells.

I got a Bosch from PJ Grady and my voltage range is spot on. I set the mixture, took it for a long drive then zereod it in once the probe was hot. She starts and idles perfectly again and no sign of any loading up even after idling in gear for 5 minutes.

It was lucky that I had the dwell meter hooked up when that happened because apparently the O2 sensor was failing intermittently. It's about 5 or 6 years old but then again, I got the new one with the wire and plug attached just to rule out a damaged wire.

[JohnZ]

Hi there Michael! Glad you fixed your problems.

You referred to DeloreanGo Lambda probe: actually there are two of them. The aftermarket one (https://www.deloreango.com/it/oxygen-sensor-lambda-probe.html) and the Bosch one (https://www.deloreango.com/it/lambda-probe-oxygen-o2-sensor.html). They're about 35 dollars apart from each other... I just bought the Bosch one, because I don't think my probe has been replaced after 44 years! (for sure not in the last 12 years)

I guess the Bosch probe is the one you refer to as being high quality!

:)

[Michael]

Hi there Michael! Glad you fixed your problems.

You referred to DeloreanGo Lambda probe: actually there are two of them. The aftermarket one (https://www.deloreango.com/it/oxygen-sensor-lambda-probe.html) and the Bosch one (https://www.deloreango.com/it/lambda-probe-oxygen-o2-sensor.html). They're about 35 dollars apart from each other... I just bought the Bosch one, because I don't think my probe has been replaced after 44 years! (for sure not in the last 12 years)

I guess the Bosch probe is the one you refer to as being high quality!

:)
Yeah I had the dgo one from years ago...I don't believe they offered a Bosch option when I bought it, or I didn't see it.