5-8 CEL, no codes....

driving today, I notice the car lurching and bubbling at low rpm on occassion, with the 5-8 CEL coming on. When accellerating, it almost seems to be dropping to 4 cylinders for a second, and then kicking back in. At one point, I was fairly sure I was running only on 4, but with no CEL. Pulled over, did the battery reset trick, and the car started up fine, but started acting up again within minutes. I get home to check the codes, and did it with the car running and without. Car off, 1121 and 4121(I have the exhaust ecu unplugged) and car on, 4121, which I knew would happen. nothing else. I knew I was going to get those codes anyway, but no others popped up....Car at idle seems to be running poorly, and will occasionally show a 5-8CEL, but again, when I go to pull the codes, nothing but the above, which I expected.... Any thoughts?

 

I got the 1121 code because the car was turned off when I checked it. With the car on, no 1121.

Definitely sure about the correct bank.

Haven't checked any connectors yet, which I will do for sure. Just very puzzled about the lack of code with the CEL on, in addition to the problem.

 

Well, had a few minutes at lunch today, and decided to play "swap the relays" Swapped both ECU relays, no change. Swapped both fuel pump relays, just for fun. No change. THEN, I notice that whenever the car starts to stumble, the LH fuel pump relay clicks. Swapped relays a few times to make sure it wasn't them.

Now reading through some other threads, it appears that it could be a faulty crank sensor or wiring, as according to NoDoubt, it will shut down the fuel pump if there is an error. The PO told me that one of the two sensors was replaced, but I guess I need to go look at them. Any other suggestions for when I dig into it?

Also, and I don't know if this matters or not, but I had an injector problem, and tested them in the car, before cracking the fuel line to remove the faulty one. When I cracked the line, there was really no pressure, and not much fuel at all dribbled out. The car had new fuel pressure regulators installed to combat a hot start problem before I purchased it. Would my testing the injectors bleed off all the pressure, or could I have seen an early indication of the problem I am having now?

 

Finally got up under the car tonight. The right side (looking at the front of the motor from underneath) male plug had ALL the male wires not hooked into the connector,and so loose that when I pulled the female connector off, they fell out of the male side, so that wasn't good either, but I fixed that, with no change in the motor tendencies. I found the left side (looking at the front of the motor from underneath) wiring going to the sensor all electrical taped up... Undid the electrical tape to find about 5 repairs on the 2 wires and the shielding cord.... It was all soldered, but the shielding cord repair (one of the two) broke with just a little pull, so I'm hoping that this may be the problem. My next questions are these... Can I replace the entire wire back to the previous connector without pulling the engine? It goes up and away behind the cam covers, so I'm doubtful, but due to all the repairs that I need to remove to start over with, I'm not going to have very much room to work with at all, and am going to have to make each wire longer, so two splices per wire. Will going farther back into the wire covering, and removing even more of the shielding wire cause an issue? Boy I hope this fixes it....

 

Update... Didn't get around to checking my cam sensor wire again, but I did clean it about a week ago when I found that it had thrown a code. The wiring that I found all messed up actually turned out to be for the 1-4 bank, as I started the car with it unplugged to see the reaction, and got a CEL 1-4. I ended up not fixing it properly per Ernie, but did get it rewired. The proper fix may be a winter project. Still no change on the cutting out fuel relay. I decided to switch sensors to see if it were them, and it turns out that the 1-4 sensor won't fit where the 5-8 sensor goes (the upper one) due to a manufacturing defect. But it still works the 1-4, so I figure I'm OK with it. I put the 5-8 sensor in the 1-4 position and start the motor with only one sensor, thinking that if it is bad the car just wont start. It starts fine, indicating to me that it's not the sensor. Got interrupted by the GF, as time got away and I never got around to cooking dinner, so had to take her out, so stopped working on the car. I did notice that the 5-8 sensor was rather dirty and oily, but in no worse condition than the 1-4, which was working OK, so I'm pretty confident it's not the sensors themselves. I also checked the wiring for the 5-8, and it looks to be in great shape, no wear, and even the plastic loom covers weren't worn through anywhere. So it's got to be somewhere else, right?

I need to reinstall the 5-8 sensor in it's correct place, and put the 1-4 back where it goes, and start over, assuming my cleaning of the end of the sensor didn't do anything, which it being a magnetic pick-up, I would assume it wouldn't.

Based on the above, I now need to check:
wiring and relay connections at the relay block
check intake cam sensor connections - done couple weeks ago, maybe I didn't clean or seat properly
check and clean MAF connections - done couple weeks ago as well, when I had a bad injector
I'm assuming the wiring to the fuel pumps themselves? Don't know where they terminate at the pump yet though.

What am I missing?

I'm determined not to let it whip me, as I promised myself that the only time it would go to a shop is if I got in WAAAYYYY over my head on something, and this can't be that something...

 

further update.

Put everything back together under the car, cleaned all the sensors in the top of the engine bay - MAF, Crank, and the two after the MAF before the intake (been a long day).

ALSO, to eliminate the fuel pump as the culprit, I jumpered the fuel pump relay, fuel pump ran fine, and car still had issues. Figured I'd jumper the ECU (injector control) relay as well just for the heck of it, and everything still acting the same. On a whim, I switched out main ECU's, and still having the problem.

Discounting electrical problems in the fuse panel, which I am about to go check (hot, needed a break) WTF else could it be?????

 

and things get stranger.... I found a vacuum line #10 that had pulled off the "cut off valve" shown as # 8 in this picture. (probably did it when I replaced a bad injector) hooked it back up.

http://www.ricambiamerica.com/article_info.php?articles_id=207

I pulled all the fuses and relays in the passenger footwell for anything related to bank 5-8. Sprayed electrical contact cleaner on the fuses, relays, and fuse box.... Started the car and now it seems that the problem only presents itself when I floor the throttle. If I ease into it, it revs normally, but if I floor it, the revs drop momentarily, the 5-8 CEL comes on, and then it seems to rev normally sometimes, and sometimes on only one bank.

Finally, noticed the main ECU flashing the 4121 code at me after one of the issues. (Again, Cat ECU unplugged) Just out of the blue. And that was the only code it threw, after I tried to move to the next code. I'm getting even more confused now....

 

any help at all or am I gonna be forced to take it to a tech? Kinda dissappointed if i do have to....

 

Yeah, I'm going to set up an appointment with Tom Jones at Sport Auto in Greensboro NC on Monday, I think. I've heard nothing but good things about his technical expertise.

 

Posting this as a reminder to myself as I am going to print out this thread when I take it into the shop...

Drove it today to make sure it would make the 1.5 hour trip to the shop next week, and it still is showing the same symptoms, but I noticed today that whenever the CEL came on and I lost power, the tach would drop waaaaay down, and if I hit the throttle hard and quick I could get the CEL to come on about every time. So maybe it is still sensor related. Also, I was sitting at a light, and suddenly the idle jumped up to 3000 rpm, and held steady, with a variance of just a little depending on clutch in or out. Once I got moving again, about a minute later, the idle went back to normal. I checked the floormat while sitting at the light, and it was not hung up. No idea on why that happened.

 

Update, just in case anyone else has the same problems as i did. Knock on wood, my problem may be fixed....

Faulty plug wires had been suggested, so I had checked all the wires, and actually switched them from one side to the other, with no change.

I have been driving it with that annoying bank cutout under 2-2.5k rpms for quite a while now. Last week I noticed that I could also make it do it by blipping the throttle, even over 2k rpms, something that never occurred to me before (even though I noted it up above.....) So just for the heck of it, I switched MAF’s and TPSs to the other side. I also cleaned out the insides of the TPSs using electrical contact cleaner (filling the things up...)

After doing some research on TPS’s I figured out that they work inversely to each other. One starts at a low resistance and goes to a high one, and the other starts as high and goes to low, based on the position of the butterfly in the housing, even though they are the same part number.

After switching them around and cutting the battery, I let the ECU’s relearn everything, with NO stumbles seen. I then took the car out for a short drive, and did have a stumble and CEL flash momentarily, but I couldn’t tell which bank as it was so quick. Since then, (knock on wood) the car has been driving wonderfully. I’m assuming that the 5-8 TPS might have been worn on the low resistance end of it’s internals, but OK on the high, so when I switched them around, and it started reading backwards, from high to low, things were OK. Still need to do some pedal to the metal testing, as I would assume if this were the case then I would have problems with a WOT. Of course it could just be a cool weather thing too, as I have heard can happen…

Been too busy driving around town enjoying actually being able to shift under 3k when leaving from a stoplight.

Anyway, the problem is gone for the time being, and I'm keeping my fingers crossed. If it comes back again on 1-4, first thing will be a new TPS. (which, yes, I know, I probably ought to go ahead and do anyway....)
If it comes back on 5-8, then it will be wiring harness replacement time, assuming I can find one that's not outrageously priced. (Or I might have a local electrical specialist shop do the parts I need)

I’m finally enjoying the car like it was meant to be, which has changed my entire outlook on the marque.

 

On mine (94 spider), when checking the resistance, yes, the ranges read the same, but one resistance changes from high to low as the butterfly is turned (1-4 bank, IIRC), and the other resistance changes from low to high (5-8 Bank, IIRC) as the other butterfly turns.

You have a good point about the maf.

I did notice driving this morning that I went over some railroad tracks and the problem resurfaced, same bank, not the other as I had hoped, although only once in an hour and a half drive. I'm thinking there still might be some sort of wiring problem, which I may tackle this winter.

 

Thought I had the problem fixed, but it ended up coming back after a few weeks. Lived with it for a while, but then it started to get worse. Local guy here looked at it, but couldn't figure it out, so I had resigned myself that I was going to have to take it to Atlanta or Washington to have the guys with a breakout box do the diagnosis. After sleepless nights thinking about the time, effort, and money to carry it all that way, I decided that it would be just cheaper to start throwing parts at it.

About this time I was having a miss under throttle that went from sporadic to full time. I ordered all new replacement relays, and put them in, and the CEL problem seemed to lessen, but still was there, indicating that there may have been some issues with the original relays, or I just couldn't get the old ones clean enough. The miss was just as bad, and reminded me of when I had a bad #7 injector after purchase. Got a cheapo spark tester, and found out that the number 7 coil plug was not producing any spark. Replaced the coil, and KNOCK ON EVERY SINGLE PIECE OF WOOD I SEE, I've had about a month and a half, a thousand miles, and TONS of fun, of NO CELs, and no issues at all. I think the coil was intermittently going bad, and eventually conked out. What I still don't fully understand is how the coil could be causing my CEL's, but in reading through the Service Manual, apparently the ECU reads a bunch of stuff off the 5-7 bank that could cause strange errors. (forgive my lack of technical terms, but I was just glancing at the manual, and didn't really sit down and study all the impulses the ECU needed to read for everything to be right, I was just too excited to have fixed the problem)

So I think I finally got the problem licked, and didn't have to take it to the dealership. Cost of new relays, about $110 for 12 of 'em, cost of a new coil, $125. All new, at prices significantly lower than factory, found with a little help here and a little searching.

I'm sure that I just jinxed myself, by coming out and saying it's fixed... LOL

Ernie, special thanks for the phone call a while back, and making me think a little outside the box, as to switching up components I would never have thought to.

Just wanted to follow up with a post, as often I see posts that aren't answered, and I wonder if the problem was ever solved.

 

Randyleepublic and I exchanged a few PMs and he told me about a source for the relays: http://terminalsupplyco.com/Store/Default.aspx?CAT=EC070010&PCAT=12873#Categories
And I was lucky enough to find a coil on Ebay with a very cheap "buy it now" price. It was from a shop that i don't think was very familiar with ferrari parts, as all of the ones they had listed were cheaper than they should have been, and they didn't have much. It was almost like I was "supposed" to find it, which may have been God's way of making the last year of problems up to me... And as always, Ricambi had everything as well, but in this particular case, I came out a good bit cheaper. Most of the time, they are the way to go.