Duke

As some of you may know I had a massive water into cylinder leak after I installed a MLS headgasket.

Well, now I did the headgasket all over again but this time with a stock gasket. I was extremely thorough with the whole procedure.

So when I started it up earlier today it and ran fine to begin with and then started run only on 3 cyl. irraticly. Just as with the MLS gasket.

With the throttle steady at about 3500 rpm the car ran very well for a while. Luckily I had my wideband o2 installed so I could verify that the mixture was fine. But then, still with steady throttle, the rpm's started to fall off and it sounded like it ran on 3 cyl. At the same time a/f mixture got leaner and leaner. The revs fell to about 1000 rpm and I had to use a lot of throttle to not letting the car die (almost full throttle).
At the same time the mixture leaned out extremely (leaner than 19:1) and I heard the engine pinging a lot.

This is EXACTLY the same behaviour as previous with the leaking MLS gasket.
So of course I pulled all the plugs and inspected. All of them were dry and I turned the engine by hand and all cylinders seemed dry.
So the headgasket seems to be sealing well (at least at idle).

The car has new Delphi 72 lb/hr and Guru K27 chipset. The FQS is set to 7 for 72 lb/hr and 2 degrees retard.

Those things were NOT installed the last time the engine ran fine.
So switching the chips and injectors back to stock is of course the next obvious things to check

Other than that the ONLY things than have been changed or switched since that last time the car ran fine is:
* Oil cooler seals
* Oil pressure sender (but it broke during installation so only 1 wire is attached)
* I dropped (!!!!) the camhousing so the rotor and it's metall thing broke. But it has been replaced and the camhousing shows no other signs from the drop.

So if the headgasket seals, what can cause the behaviour my engine has?
I'm thinking this:
* Bad chips
* Bad injectors (doubt it, they are new and flow matched from Racetronix)
* Bad injector harness.

The thing is that it's very irratic. For some moments at steady state higher revs the engine runs fine.


I need wine, women and song... lot's of it. Lucky for me it's saturday!!
I'm going to paint my kitchen ceiling now to calm down...

AlexE

What is your fuel pressure..... I am assuming you are using an adjustable FPR with those 72lbs...

Duke

Correct, and it's set to 3 bar to suit the chips.
(I also have a FPR gauge so the pressure is verified)

fast951

Did you check the DME relay? Fuel pump? Fuel pressure before/during?

Danno

Check the injector wiring... about 10-15% of people who install injectors end up with shorted connectors because of the brittle wiring. It's especially prone to shorting at the point where the wire 1st enters the connector.

Duke

Thanks for the answers!

I have not checked the DME relay or pump.
I sat in car during startup so I did not have the chance to check the FPR gauge when the car ran lean. But it showed 3 bar directly after I shut down the engine when it ran super lean.

Is there any easy way to check the injector harness? Besides just looking at it of course.

turbite

I second that.
I did this myself just trying to get the clips off, and Danno himself helped me fix it.
You could try unplugging one injector at a time while running.
If it has no effect...

Mike B

I third that! I used an inexpensive noid tester (a little light that plugs into the injector connector) to locate one wire shorting with another.

AlexE

I fourth that!

I had to completely rewire my harness.... all four corroded . It was so bad I am surprised the car even ran!

Duke

Thanks, any ideas on how to check the harness besides from visual inspection?

Tomas L

Diconnect the DME and measure the resistance between DME connector pin 15 and one of the pins for injector 1 and 2. Measure at DME pin 14 for cylinder 3 & 4. Then you measure from the other pin on each injector connector against DME pin 35.
You can make it easier if you can short the two injector terminals for one injector a time. Then measure between DME pin 15 and 35 when you have shorted injector 1 or injector 2 and between 14 and 35 for injector 3 or 4.
Disconnect the battery while doing this.

Tomas

Swedeboy

Duke - have you driven your car much since the winter storage? Otherwise it might be something simple like bad fuel, fuel filter or clogged injectors.

Duke

The engine is unfortunatly running far to bad to be caused by bad fuel or similar.

I'm going to head out to the garage now to see what I can find out about that injector wiring...

Danno

Here's another test for the injector connectors, lets you track which one, or more is bad. The 1st set of tests checks for proper operation of the +12v power line to the injectors and the 2nd continuity tests check for the condition of the ground (activation) wires on the injector harness.

1. disconnect DME
2. disconnect idle-stabilizer, CV-cycling valve
3. disconnect all injector connectors

POWER-LINE TEST

4. using battery-ground as ground, use a voltmeter to check for +12v on each pin of injector connector
5. all rearward pins should have +12v
6. all forward pins should have ZERO volts
7. if you have ANY voltage on the forward pin, then you've got a short in that connector.

GROUND LINE TEST

8. Also check ground pairs (forward pin)
9. set voltmeter to ohms and check continuity between forward pins of injector #1 & #2: should read zero ohms (connected)
10. check between forward pins of injector #3 & #4: should read zero ohms (connected)
11. check between forward pins of injector #1 & #3: should read infinite ohm s (not connected)
12 check between forward pins of injector #2 & #4:should read infinite ohm s (not connected)

Duke

Thanks for the detailed instructions guys.

I just got back from the garage and here's how it went:

* First I followed Tomas directions and checked the resitance. All connectors vere fine according to that test.

* Next I switched the FQS to #1 position. The car then idled better but still didn't run clean and then eventually it died.

* Then I switched the 72 lb/hr injectors to stock injectors. Same results.

* And finally I switched the Guru DME chip to a stock one and that solved the problem!

So I guess I need a new chip!

BTW is it normal for the A/F mixture for some moments be as lean as 16-17:1 at idle?

Extremely annoying that I originally had two different problems but with similar results. The leaking MLS gasket which screwed up my A/F ratios and made the engine go on 3 cyl. If the chips had been working at that time the effect probably had been less noticable.

And now with the new gasket and the car still ran on 3 cyl...
But this time it didn't act as a flamethrower