I recently started working on my 88 lb9 auto.

I had the fuel system replaced after sitting for 10+years new pump, tank lines flushed and clean all fluids replaced. still had plugs and wires. Idles and runs well but super rich.

Well today finally hooked up moates and checked vac leaks. I found the rear of the plenum has missing vac line (for hvac and cruise i think) I hooked up my vac gauge and it idle better but surged.

Using moates and DVM i measured the TPS and it was at .33 on both. so I tuned to .54 and immediately ran better. then I set the IAC and it idles at
650-750 on the moates but sounds good. noticed some oil smoking on the exhaust manifolds and hear what sounds like exhaust leaks pulsing under the car but it sounds great

after warmed up it starts to pick up idle speed, kicks down a little with some throttle but seems to go up to 850-1000.

I checked the timing. But when running the mark is not even on the timing marks and they are rusted not sure which one is zero.

Moates shows no errors or CEL and the CEL does not come on. Incredible IMHO

I drove it around runs better still rich and bog. I think the timing needs to be adjusted, then check MAF.

Also, surprised again, the Vac gauge in open loop sits dead even at 21" HG

So I think the bottom end and valves and fuel is good. Still need to check fuel pressure again.

Probably a ECU forum question but I think crosses over: So using moates as well as normal tune up. Any tips on trying to dial in the timing, runnign rich and it seems to not be dropping into closed loop even when temps hit 180.


My electrical is hacked I think too since not sure if fans kick on so I need to check for that wiring. Where are wire/relay for fans to simple way to test?

 

Also along with vac lines cracked for HVAC and cruise it appearfs the otehr egr ones and udner the plenum are ok. But the Heater core valve has a vac line that looks like it connects to the throttle body but it is unhooked and also right next to it is a PCV line from the pass side that hooks up to the pass throttle body as well. They are both unhooked.

It is the top vac port on the pass side of the throttle body. the lower port is hooked to the radiator.

This looks wrong. I will replace heater core to be safe when I pull the dash but wondrign if I can uncap the throttle body ports (assume TB bypass) I live in florida so cold not much of an issue.

 

First thing to understand is, it does NOT just up and move itself out of the clear blue. There's a good chance that a car could roll out of the factory and NEVER in its ENTIRE LIFE need it to be "set", unless somebody dinks around with it first.

Second thing is, "timing" is no different in an electronically-controlled system than it is in a mechanically controlled one. The dist is installed with its parts mechanically lined up to some "reference" kind of setting; then as an offset to that, either the springs weights & vac can take it from there, or the ECM looks up values stored in a table that do exactly the same thing. There is NO DIFFERENCE between the end result. Gasoline still burns, it still requires a certain length of time to do so which varies under varying conditions, and the control system still adjusts the spark timing to essentially the same points regardless of which control system is doing it.

To check the timing, you first disconnect the "timing set" connector. The timing will then be at its mechanical "base" setting, equivalent to the "static" setting with a mech distributor. It will be retarded around 20 - 25° from its "normal" idle value; exactly how much depends on various other conditions.

You then set it to .... something. You could use the stock "spec", whatever that is, for your engine; you could experiment with different settings and see what happens. Most likely, the "mark" will NEVER line up with the "tab" EVER, as long as the "set timing" mode is not invoked by unhooking the wire.

Third, and most important, your PCV lines being broken / not hooked up / etc. is at least part of your problem, and maybe THE WHOLE PROBLEM. Reason being, the MAF's job is to measure the mass (amount) of air entering the TB; it literally COUNTS the molecules. The ECM then supplies the correct amount of fuel to match the amount of air, by varying the injector duty cycle (proportion of time the injector is injecting). If any air enters the system without passing through the MAF, then the air quantity reported to the ECM will be wrong, and the quantity of fuel it supplies will also be wrong. Now... the PCV system involves a vacuum port that sucks on the crankcase through the PCV valve - NOT through the MAF - and this air is therefore unmetered. The solution is for the "makeup" air that is let into the crankcase to replace the air the PCV sucks out, to be drawn from a point DOWNSTREAM OF the MAF (thereby getting metered), but of course UPSTREAM of the TB. Since air out = air in over the long term, this allows the ECM to be informed about the ACTUAL amount of air entering the engine, and thus allows it to fuel the motor properly. Without BOTH of those lines properly hooked up and operating, the ECM will NEVER EVER be able to put the right amount of fuel in, especially at idle and other high-vacuum low-speed conditions, because there will be air coming in that it has no knowledge of; and it will therefore NEVER idle right.

Therefore, my advice would be, LEAVE THE TIMING ALONE; and instead of messing with something that most likely is perfectly fine, concentrate on fixing stuff that's actually broke... like the PCV lines.

 

Thanks for the detailed post. Points taken. I think my corny about being untouched should have been unadulterated given these cars usually are hacked by now for junkyard finds.

The tps and idle were played with but rest papers factory.
I did not check base timing so probably why no line ups in marks

Also the MaF appears ok with tap test but bottom cover is off is there a way to check resistance of the MaF for good/bad?

Could jut be that and vac leaks


I am not sure where the passenger side PCV goes? To the throttle body? Under the plenum?

 

The MAF isn't a "resistance" type of deal, like the coolant temp sensor for example. I think it's safe to say that at this point, if the ECM isn't unhappy about it, it's probably OK.

Should be 2 PCV fittings on the TB: the one in front of the blades goes to the PCV valve, the one behind the blades goes to the other valve cover.

 

I know the MAF operates on change on voltage as the resistance changes across the elements. You usually can verify the elements are working by checking the voltage across the whole unit. Some people modify this voltage to trick the system into delivering more fuel.
My 88 300zx was the same. My IROC has the cover off the maf and it looks like there is an adjustment screw. I want to check that it is still working ok.

Using Tunerpro, the MAF reads at 2900air flow range at idle. That seems high.