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'98 GP SE injectors: different types?


jarl
09-03-2010, 02:53 PM
Posting this on a different thread to keep the discussion focused... Sorry about the length of the post...

The car/problem: '98 Grand Prix SE, ~140K miles, L36 engine. The car was bought recently and had a bunch of codes stored (P0137, P0140, P0141, P0202, P0302, P1404). The previous owner said he had scanned the car before and was told the #2 injector was bad and needed to be replaced. The symptoms in the car (other than the SES) was the engine running rough from time to time. I also noticed some white smoke when the car was accelerated to ~4k RPM, but there wasn't any coolant smell to it and there's no oil on the cooling system or viceversa.

First question: Since we were going to the junkyard anyway (other thread), we bought one used injector from another car with what looked like the exactly same engine. I'm not positive which car was it, but externally the engine was exactly the same (normally aspirated L36) and the same model year. However, when I went to install the (junkyard) injector, it looked different from the ones in the car (the ones in the car have a plastic tip and four holes, the replacement has a wide metal opening with six holes). Are these different, but equivalent, injectors, or are they incompatible?

2nd question: The car worked fine for around ~30 miles, but then the SES light started flashing. When scanned, the car had a new P0302 (#2 misfire) code in it. We cleared the codes and drove the car less than one block and the SES started flashing again. The scanner showed two P0302 codes this time. The O2 and EGR codes were not present. Also, the idle was very rough.

Both old injector and it's replacement show abot 13 ohms on the multimeter, and when energized the old injector "clicks", so I'm guessing it's ok after all. The pink cable on the #2 injector connector has 12V when the key is on, so it seems to be fine. So I'm starting to think the injector was fine all along, and the P0202 was set for some unknown reason (previous owner disconnecting the injector, perhaps?).

So, right now there's a misfiring engine with two P0302 codes, a rough idle, and some unknown problem still lurking around. What should a cash-strapped person do next (short of selling the car, that is)? Is it possible the LIM is shot and is causing the misfires somehow?

tblake
09-03-2010, 07:57 PM
A compression test would be my first method of attack.

Jrs3800
09-03-2010, 10:40 PM
Have the plugs and wires been checked or replaced? If not, short of the the compression test I would check the plugs and wires...

jarl
09-07-2010, 08:27 PM
Hello people,

I have not done the compression test yet (I would need to borrow the tool), but so far I have done the following:
- Put the old injector back, and changed the spark plugs. The car worked fine for several miles (enough to drive the car back to it's owner). However, the misfires came back as soon as he drove on the freeway
- Swapped the coil driving cylinder #2 with the one for cylinder #4, and there was no change (misfire still in cyl #2)
- Swapped the cables for the #2 and #4 spark plugs, and there was no change either

So... If I'm not mistaken the only thing I can still test on the electrical side is the ignition module. I have one module sitting around from my '94 3.8 TransSport (Series I). Is this module compatible?

After writing this, I just realized I still have the old spark plugs sitting around. The attached image corresponds to the cylinder locations (#1 wasn't replaced because "someone" broke one spark plug while tightening it :P). #2 looks wet, but I don't know what this means. It doesn't smell like coolant, if that's any help. Any good spark-plug-to-english translator in house?

tblake
09-08-2010, 12:43 AM
Looks like #2 is wet with gas. I'd put a spark testor in the ignition wire and make sure the spark can jump across. If it can, you should probably check compression.

jarl
09-08-2010, 02:49 PM
Well... I invested some more time in this car:
- Removed the spark plugs (installed for 2 days). I was expecting to find #2 fouled, but it wasn't that bad
- Measured the compression on cylinders #1, #2 and #3. The three reached ~190 PSI, and I don't see any difference in behavior between them (i.e. the needle climbs as fast on #2 as on the other cylinders). I hope this precludes a burned valve :rolleyes:
- Reinstalled plugs and connected cables.
- Corrected the two cables that were swapped :uhoh:
- Tested the car to see if the seating of the cables had changed anything. Answer: No
- Swapped the ignition module w/ another (used) module I had. No improvement in symptoms

So, as I see it, either
a) All the cables are needing to be replaced (I had swapped two of them before to see if there was any change) and for some weird reason only #2 is misfiring with the current ones
b) The junkyard injector had exactly the same problem as the one on the car. However, the car now has the original injector in, and I had run carb cleaner through it so I don't think it's clogged. I had previously measured voltages on the connector pins and they were Ok
c) Something else is broken. Any suggestion as to what can be wrong?:confused:

tblake
09-08-2010, 03:47 PM
Pull the wires off the coil towers and have an assistant crank the motor for a few seconds. You should see spark arc across the adjacent coil towers. If it doesn't on one coil pack, you should be able to swap coils around and diagnose whether its a coil or ignition module.

How is your injector pulse? Could the injector trigger wire be shorted to ground causing the injector to flood the cylinder?

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