Hi all,

Replaced plugs/wires/cap/rotor on my 740. Old plugs were Bosch, and black. Attributed this to O2 sensor being disconnected for some time by previous owner before I bought it. New plugs were NKG.

Started it up last night in near zero weather, kind of a hard start (initally sounded like it was running on two cylinders, but once warmed up enough it ran fine) but no problem!

Tried to start today, high 30's... Problem! Acted just like before, but failed to run.

Starting fluid made no difference. Pulled plugs, cranked it to clear it in case it was flooded, smelled a lot of gas, probably flooded it. Replaced plugs. No start.

Called wife and asked her to put some warm clothes on (mumble, grumble) and help me. Checked the new plugs for spark. Spark was way down the electrode from the cathode and intermittent. Cleaned plugs. Spark was still ****.

Retrieved the old black, sooty Bosch plugs... Good spark. Cleaned them and put them in, and the brick fired right up.

Anyway, seems like I should stick with Bosch for plugs.

But any tips on where to start with what looks like an overly rich mixture would be great!

 

Were the new NGK plugs gapped correctly? Wires brand?

 

Hi Lev!

Gapped them according to the manual @.028, wires are aftermarket from RockAuto, Standard Motor Products Pro Series; OE Equivalent with OE Style Boots & Silicone Wire. New wires work fine with the old plugs (good start).

Old wires had three original and one different one, looks like they had a bad wire and replaced it with whatever was lying around that worked.

Old Bosch plugs were black with soot, new NKGs were in the process of becoming black with soot.

Thanks!

 

what year is this 740GL ? is it a 'regina' or 'bosch' car?

bad ECT can cause way too rich running. so can air leaks in the intake manifold and intake air plumbing. if its regina, a bad manifold pressure sensor (MAP) can do this too.

 

...Derp. It's an '89 GL

Says Bosch on the intake manifold sensor, so I'm guessing Bosch.

 

if its Bosch, it has a conventional cylindrical ignition coil, and a "MAF" in the intake pipe between the air filter box and the throttle body. if its a Regina, the ignition coil is a square transformer-shaped thing, and there's no MAF, instead it uses a manifold pressure sensor.

 

Yep, it's a Bosch.

 

so an 89 bosch non-turbo should be LH2.4, does the ODB box show any codes other than 1-1-1 on both injection and ignition?

Engine and OBD Diagnostic Codes


if you were running without an O2 sensor for awhile, for sure there'd be at least some codes, so I'd clear them and drive it some more then check again.

also, just fyi, next time you buy sparkplug wires, get the volvo B230 specific bougicord set thats sold by IPDusa and FCPeuro (and probably others). I won't use anything else on these cars, had too many problems with whatever brand 'premium sets' ... not saying this is your problem, just next time around...

 

Hi Pierce,

It was showing a 2-3-2, which for the LH system would be 2-3-2* Fuel trim (lambda control) too lean or too rich at idle }If too rich: high fuel press., leaking injector } various driving problems
But after clearing the code and driving it, the code has failed to return.

Seemed to idle fine now too.

I did notice black soot coming out the tailpipe when I revved it up. It doesn't smoke though. Maybe that's because I sprayed a lot of TB cleaner into it earlier. Mmmph.

Guess I'll have to drive it a bit and see how it goes. I'll take a spare set of spark plugs and tools with me, but I'm used to that now.

 

Anyway, it did the idle surge & hunt routine today again.

Annnnddd... I came across this

Engine Tune and Performance

Whiiiiich might have something to do with your suggesting I remove and clean the TB, no?

DERRRRRP DE DERP DERP DERP