Hi all,

Still working on this brick.

'89 740GL NA. Exhibited "idle hunt", and would die when idling down. Disconnecting the Idle Air Control caused it to die.

Oil/filter change less than 100 miles ago, oil now looks dirty (not black, but not new either).

Replaced the IAC. This kept it from stalling during "idle hunting", but did not eliminate the idle hunt.

Plugs cap wires rotor. NKG plugs. No spark, wet plugs. Pulled plugs, cranked motor to clear, replaced with old plugs (Bosch, which were black, cleaned before replacing). Car starts reliably with these and has been running OK.

Propped TB butterfly valve open, cleaned TB with cleaner, toothbrush and rags until it wiped clean. Did not remove TB as I did not want to risk snapping the linkage bar (I live in New England, and if there is a snow emergency, I will *have* to move my car, or it gets towed).

Performed "water torture"/Seafoam cleaning. Chinese Water Torture (a SeaFoam recipe) - Turbobricks Forums Car made copious amounts of white smoke.


This is a new symptom, or at least now consistent enough that I just noticed it: Car will redline in park if given 3/4 throttle. Under WOT, it tops out at 3K RPM.


I will be checking all these from the list heading Poor Performance; Rich Mixture Smell: Diagnostics And after that, under the list heading Rich Running Problems: General Diagnostic Notes. Engine Tune and Performance

So far I have eliminated the Fuel Pressure Regulator, I swapped it out with a known good one and no change.

Again, thanks in advance.

Dave

 

any fault codes on the OBD box ? an 89 non-turbo should have the diagnostic reader.

follow this to read the codes:
Engine and OBD Diagnostic Codes

I would expect any engine running that badly to throw some codes.

btw, warmed up, no AC, parked, with the IAC unplugged, it should idle about 500rpm, you adjust the throttle air screw til you get it idling around 500. then make sure the idle switch is closed when its at idle, and opens as soon as you get off idle, and when the IAC is plugged in, it should idle at about 700-750.

I'm wondering if you have air leaks in your intake, or something like that. or a bad MAF (unless its a Regina car, they don't have an MAF, they have a MAP, thats like a vacuum gauge and work on a whole different principle).

 

Thanks Pierce,

It was throwing a 113 and a 232 (rich running, too rich/lean at idle) prior to me testing the FPR. I cleared it before testing. Drove it, it didn't throw a code during the test drive.

Will check the idle tomorrow, along with the other stuff on those lists.

 

OK... (Mmmph...)

Went and got a MAF from someone who ran their brick w/a dodgy cooling system and cooked it, so I figured it was worth $20 and a short trip. This MAF has an adjustment screw on it. Also disconnected the pre-heater hose even though the airbox thermostat looks OK (was going to replace it, waiting for the penetrating oil to free up the intake plumbing), just in case the previous MAF got cooked.

Anyway, no topping out at 3k RPMS, starts right up, idles well (750RPM), runs a hellofa lot better once all warmed up. Yay! Also cleaned and used bulb grease on what looked like the injector grounds (four black wires with crimped eye terminations that bolted to two places on top of the intake manifold). Did not get to the injector ground wires and harness (will do tomorrow).

However...

I pulled the IAC plug, and it proceeded to surge and hunt between 1200-1300RPM.

Replaced IAC plug, shut it down, turned it back on, normal idle. Everything seemed fine.

While I was jotting down these notes, the check engine light came on at idle. Codes it threw were:

113 Fuel trim (lambda control) too lean or rich Mixture incorrect; O2S wiring fault; High fuel consumption

232 Fuel trim (lambda control) too lean or too rich at idle }If too rich: high fuel press., leaking injector } various driving problems

223 Signal missing to/from idle air control valveCircuit fault to IAC or faultyEngine difficult to start; low idle speed IAC valve

I figure that the 223 signal was from me pulling the IAC plug.

Have not checked the MPGs yet, but they will suck because all I have done is blast it WOT from 1st to 2nd gear around the neighborhood testing it out. It seems to be running well enough to take out on the highway to check the MPGs and not require a call to AAA.

Have a new set of el cheapo plugs for an emergency, I can put them in to see if they carbon up. Will do the DIY injector clean procedure at some point, but I'm not sure this is a sticking injector as all the spark plugs were black, it seems they would all need to be sticking to make them black, and that seems unlikely.

New/old MAF is kind of dirty, will any MAF-safe cleaner work, or is there a preferred product? Will probably clean/replace the old MAF just to verify.


I would imagine that I need to check the O2 sensor wiring as the next logical step?

TIA

 

if you use MAF cleaner, hold the MAF such that the electric module is on top so that the runoff doesn't drain down into it.

 

Thanks Pierce,

Any MAF safe cleaner is OK, I'm guessing. Hate to pooch this one, especially since I probably replaced a good IAC on this (derp).

 

Anyway, running really nice now, despite the codes. Starts quick, idles smooth, doesn't surge and hunt, pulls strong...

Thanks for the help, Pierce!

Next up, flush and change the transmission fluid... Assuming that I don't pull a lot of metal chips out of the drain plug (I put a super strong magnet on it just in case the plug didn't have one), in which case...