Schokkie

I have a problem with my recently bought 88.


When i start the car it runs for 2 seconds and then dies. No codes.
When i disconnect the MAF it starts and runs fine (but rich).
When i let the car get warmed up and then connect the MAF it will idle but very rough.


I checked the power and burn-ff relays, all good.
I hooked up an aldl scanner (Winaldl) and the output of the MAF seems ok 6-8 gr/s on idle, TPS =0.55 (0.2%) Coolant temp is giving the right temp also.
I also followed the FSM procedures for error code 33 and 36 an both check out fine.
So i suspect the MAF is ok (i also cleaned the MAF with MAF cleaner)


What else could i check next?


Any help would be greatly appreciated.

DanielRicany

Check BLMs on the scanner after it is warmed up. Needs to be running in closed loop mode to see them.

Schokkie

Thanks for your quick reaction


When it goes into closed loop and connect the MAF the BLM's go up to 160.
This means its adding (to much) fuel right?


I also notice that the MAF output is around 6-8 m/s with 1200 RPM's also.
Should this not be more like 12-15 g/s @1200 RPM?

DanielRicany

160 BLM means that the ECM is at it's maximum fuel correction capabilities. So essentially, something is causing the fuel mixture to be too lean, and the ECM is trying to correct it by adding more fuel. First thing I would check is fuel pressure before moving on to sensors.

Schokkie

I will check FP asap.
I dont have a FP meter at the moment.


But when the MAF is disconnected its runs fine, wouldnt that count for good FP ?

DanielRicany

I wouldn't attribute that for being an accurate diagnostic for fuel pressure.

Cliff Harris

The ECM goes into closed loop mode when the O2 sensor gets hot enough to report AFR.

A BLM of 160 means the engine is running very lean. It's impossible to say how lean because you're maxed out. I would suspect a vacuum leak.

The ECM matches the fuel flow to the air flow numbers from the MAF to arrive at the correct AFR.

Error code 36 is a MAF burnoff error. Burnoff is done AFTER the ignition is turned off.

Error code 33 indicates a communications problem between the MAF and the ECM. Check for corroded connector pins and problems with the wiring. This is also consistent with the error code 36 because it can't report the correct burnoff parameters back to the ECM.

DanielRicany

You should see if it still runs at 6-8 under throttle or cruise. If so, it's stuck.

aklim

What if the O2 sensor data wire was broken or somehow not feeding data? Wouldn't the ECM then think it is at 0 V and thus report it is very lean?

DanielRicany

That would be a possible outcome. However, I believe the ECM will stay in open loop mode if there are no cross counts.

Also, he is experiencing part of his problem at start up, where the ECM is in open loop mode and ignores any input from the O2 sensor. That in itself rules out the possibility of a bad O2 sensor.

Schokkie

I dont have any error codes when the MAF is connected.
I did only a check for error 33 and 36 from the FSM to check voltages and ground.


I did clean the connector to the MAF.
I dont have a vacuum leak and i did a check for broken wires.


The only odd thing i can find is that the output of the MAF is between 6 - 8 g/s with a high idle of 1200 rpm. (Idle stays @ 1200 rpm when the scanner is plugged in).
I noticed that when the MAF is disconnected the ECM reports around 12 - 13 g/s @ 1200 rpm (i think these are preprogrammed values).
Witch would indicate that the MAF reading is to low right?


I replaced the O2 with one from my 84 (brand new) and it makes no difference.


When the MAF is disconnected the engine starts and runs fine and smooth.

antfarmer2

can you swap the maf?

Schokkie

No i cant.
84 doesnt have a MAF.
THe MAF i need is only 88 and 89. (Bosch 009)

Schokkie

Only thing i can do is order from the US.


I live in Europe.


I want to be sure the MAF is bad before i order a new one. (High shipping and Tax and not easy to return).

DanielRicany

Smack the MAF sensor and see if it stalls or runs rougher.

Schokkie

I will try tomorrow.
I have to warm up the car with then MAF disconnected.
Then connect the MAF and start the car (car runs but very rough @ around 500 - 600 rpm)
What should happen when i smack the MAF?

DanielRicany

If it's good, nothing will happen. If it's bad it will probably stall, if not stall it should run really rough. Also, a MAF sensor may not respond to a smack even if it is bad.

Schokkie

I did the smack test of the MAF with no result.


Nothing changes when i smack the MAF.

Schokkie

Then next thing i will do is clean the electrical grounds near the oil filter. I understand this can solva a broad range of electrical problems.


I forgot to mention FP is good. around 40 psi. (on contact but not running)


Any ideas what i could try next?

aklim

2 things. Get it running and keep it running. Check fuel pressure when running and remove the hose to the FPR and see what it does for pressure. Tape gauge to glass and go for a run. At WOT, see what it does. Does it fall off momentarily and get back up or does it stay down, hence the lean condition?

How are the injectors? Have you cleaned and tested them lately?