Hi all,
I've got a 97 coupe. I dropped it off for winter storage in december, and due to a flurry of issues, was barred from getting the car back until a couple weeks ago. The car is presenting a rough idle (not consistently rough, but a bit surge-y here and there) and a cylinder misfire. All in all, codes P0307 and P1316 (also P1000, but my understanding is that that's not actually a diagnostic code but indicative or recent code-clearing or battery change/shorting). I dropped the car off with about half tank of gas, and I suspect stabilizer was not added beforehand (I know, I know--full tank and add stabilizer when storing). The car has been checked for vacuum leaks (fine) and coil packs (also fine). The message center is saying "Engine Fault: Poor Vehicle Performance" but not giving me the red or amber warning lights.

I'm now thinking that the issue could be old fuel gumming up the injectors, as I'm also getting horrible fuel economy compared to what it used to give me. The car will drive down the road fine, and the codes came up after about 5 miles. I parked, shut it off, called the mechanic. 5 minutes later, I started it back up and it was fine--no CEL or codes. Now, after about 40 miles, the codes have returned.

Should I try putting some kind of fuel system cleaner in the tank with new gas first? Will I do damage to the engine by driving with a misfire (even with new gas and fuel system cleaner)? I have about 1/8 tank of gas left.

 

The P1316 indicates excessive misfire and possible catalyst damage if it continues. P0307 says your misfire is on cylinder 7. With excessive misfire it probably isn't firing at all. You have 4 possibilities.
1. Bad injector
2. Bad coil
3. Bad plug
4. Bad wire connection.
I would start by switching the coil out and see if the trouble code travels to the new location. That would prove bad coil. Keep in mind if you still get a misfire in the old location and the new the coil has damaged the plugs replace with new.
While in there I would start by cleaning the coil connector and replacing the spark plug. If the misfire goes away bad plug or connector.
If it still misfires on that cylinder it would be most likely bad injector.
I would just fill it up with fresh fuel at this point.

Give it a try and get back to us with the results.

 

Thanks avern1! I think, given that advice, it has to be an injector clogged up with 9 month old fuel (again, I'm ashamed of this). Coil packs have been switched around, tested, replaced etc. All spark plugs have been replaced with the proper NGK items.

After doing a bit of research, I'm going to have the fuel system professionally cleaned out tomorrow and see how that goes. I have a couple bottles of Techron on hand, as well, but I'm going to wait until it's cleaned and until I need another tank of fuel (they will be adding something similar--I don't want there to be too much fuel system cleaner in the gas).

I will check back in tomorrow and let you know how it goes!

 

To update: I couldn't get the fuel system cleaned out. So, I decided to just drive off as much of the old fuel as I could without stranding myself and fill up with clean, fresh fuel and a bottle of techron. I cleared the codes after doing so, and after 160mi they still have not returned. Idle has smoothed out considerably, and the car seems happy again. Crossing my fingers that this'll be a lasting solution. Hopefully there's no damage to lines/pump/cat.

I'm not sure if Techron did any heavy lifting here (I tend not to believe in things that advertise an easy fix) or if it was primarily the fresh fuel, but the combo certainly didn't hurt.

 

Techron is a solid product. All of our vehicles get a 20-ounce bottle down the hatch at every oil & filter change / tire rotation interval. Techron is the only fuel system cleaner additive that I am willing to spend money for, and I always purchase it at half-price during the BOGO sales that the big-box auto parts stores run from time to time....

 

Just for fun (laughs and giggles as they say) row the gearshift (J-gate) a bit, either with the engine off or while driving.

I've been having similar problems (including an 0307 as a matter of fact) with my '97 coupe and even had a no start issue. Finally an 0706 code popped up, which (sometimes...always sometimes) has to do with the adjustment of the J-gate or more probably, the micro-switches in the J-gate. Switches that hang up apparently can cause a Restricted Engine Performance situation. Since your car was sitting, sticky switches aren't out of the question.

Might be a long shot, but it shouldn't cost you anything (well unless the switches actually break...but then, that was going to happen anyway) and it might point to or fix the problem.

...In other words, I may be shooting for answers to our '97 Coupe problems like Roland, the Headless Thompson Gunner, but don't want to let Van Owen get the upper hand.

 

When you decide to tear into your ZF, be sure to blow those microswitches from there to Johannesburg....

 

More updates: Swapped the coils as well, and after 192 miles on fresh fuel and techron, I got P0307 and P1316 again. So we can at least definitively rule out the coils (but I somewhat wish they had been the issue). Called my indie (who was a master jag tech for 20 years), agreed that this was weird because a) the codes didn't show back until almost 192 miles later b) the car is pretty much asymptomatic. Rough idle seems pretty much gone, and the car has plenty of power. Fuel Economy has been steadily improving.

I have driven the car quite hard since with no issues. Changed the oil and the oil filter yesterday and went out for 75 miles on another fresh tank of fuel and another bottle of techron. So far so good, but I am thinking next weekend I'll replace the fuel filter, too. It can't hurt, and I'm not sure when it was last replaced. It's probably gunked up, too.

And, yes, rowed through the J gate this morning on my sunday drive. Worked perfectly and shifted smoothly. I wonder if the oil fuel varnish has pooled at the bottom of the tank or something, as both times that I got the codes, I had around 1/4-1/8 tank of fuel.

 

When you changed out your coilpack did you do a hard reset? The next thing to check is your plug then the injector.

 

Alright, more news. Talked to my indie, cleared the codes, put another tank of fresh fuel w/ a bottle of techron in there and the codes stayed away for 370 miles. But then they came back, same ones: P01316 and P0307. I figured since the fuel/techron mixture seemed to be helping, maybe it's the injector after all. So, I swapped the injectors on 6 and 7, cleared the codes and went out for a 10 mile drive. Obviously that's not a full drive cycle, but I scanned the car after and it had P0307 and P1316 pending...

Could we be looking at a connector on the fuel rail or something? Pretty stumped now.

 

My understanding is that the detection of misfire is done by analyzing the fairly high resolution signal from the crank sensor. If the computer detects a part of the rotation where the peaks and valleys are more separated, i.e. slower section, it indicates the cylinder responsible for that part of the rotation misfired. In other words, it is not "detected" somehow off the coil signal. I am trying to say that, to my understanding, that code means the corresponding cylinder is not producing its share of the work and therefore it is not necessarily just spark related. There was a series of posts recently about a similar problem leading to a compression test and a more mechanical root cause (low/no compression in that case).

Separately, the earlier cars are known for ECU problems showing as seemingly incurable ignition issues. Has this ECU ever been rebuilt? Others on this forum are much more informed to the details of the early car ECUs.

Best of luck, keep us posted.

 

The 97's often suffer from ECU problems due to leaking capacitors. In fact, it's almost guaranteed to happen eventually. If the compression is good and swapping coils and injectors doesn't help, I would send the ECU out for testing. Several years ago I sent mine to ASI, and the cost of testing was $55 at that time. The module was found defective and the test cost was deducted from the repair cost.

Automotive Scientific Inc. Your #1 Source for ECU, TCU, ABS, EBCM, Climate Control and Speedometer Repairs

 

The 97 ECM definitely is a bag of tricks

One quick check you can try is to swop the connectors to the ignition control modules over and see if the misfire moves. They're mounted on the firewall just below the scuttle in the middle, and I believe there's just enough slack on the harnesses.

 

Thanks! Yeah, ECU was remanned this winter (along with the ABS control module). We're now wondering if there's a level of carbon buildup on the valves that might be preventing full open/close. We're gonna try and clean em out next week, and then we'll see.

Just bizarre stuff. Injectors working, new plugs, coils fine, ECU remanned, rough idle but fine under load. I do need to change the fuel filter (if I'm being honest, should've done that a while ago...)

Incidentally, I did get a set of used injectors just in case...perhaps a bit premature, but hey. Can't hurt to have em around (if stored properly.

 

I have done the ignition module swap in the past, that's a good check.

 

I had m0st of the symptoms mentioned above so I opened the hood andlooked around and noticed the duct running to the throtle valve had slipped off . the tabs that hold it down are in poor shape and I had recently it off to replace the plastic coolant "Y" which had sprayed coolant all over the engine(this may have something to do with the problem). I put the duct on and the idle smoothed out but the check engine was still on s0 i pulled off the neg batt cable and put it back on to clear the message. For the next week the problem came and went several times. I had noticed in the past that that the engine would run rough when climbing a steep hill so I tried forward and backwards on a steep driveway - no problem. I pulled the neg cable for 60 secnds then went for a test run and the problem is gone. i cleaned the outside of the throtle valve and sprayed the moving parts and crossed my fingers. i'll let you know if it fails again.....
chuck

 

You could have a small air leak or a bad coil. Both need fixing I'm afraid.

 

Your car being a 97 it is an AJ26 and that is a little different than an AJ27 because you have two ignition modules. I would swap them first as suggested and see if the misfire goes to the other side. You also have a plug PI1 that I think is directly behind the throttle body that you should check the connections.

I asked about the hard reset because any time you pull a plug you should disconnect the battery and do a hard reset before restoring power.

 

Hey Gus, my indie swapped the coils initially, but I'm not sure if he did a hard reset. That said (just to make sure), last night I swapped the #8 coil into #7, and performed a hard reset. Same codes (P0307 and P1316) this morning.

Also, before I go unplugging stuff, does anyone know of a diagram or a picture of the ignition modules? I know this is probably quite simple, but I saw a multiple plugs back there and just want to make sure I'm doing things correctly (though not new to cars, I am still quite new to wrenching (but learning quickly, thanks to the forum)).

 

Unable to get the link but wiring diagrams are on my page.

Gus
www.jagrepair.com