Hi all,

I've been trying to track down a "hiccup" @ idle. I've done a whole bunch of replacing parts, with no improvement. I logged my drive to work today; is anyone interested in taking a look at it?

2 notes- 1)BLM's and the integrators are way off from one another, but i just put in new injectors yesterday...( i thought i had a drippy injector)

2)Knock retard is 11* !!!! at 5600rpm ouch!!! what's up with that?

If someone is interested i will email the log in .csv format.

thanks much,
Dave

 

For the love of God dude.... Check in all places where you would never think of.....

Here is my experience: One night I parked at night and car was runing just fine. Next morning I cranked her up and bang!!! Misfiring through the mufflers. It wasnt even consistent. Random at best. Engine shaking but not blue/black smoke. I popped the AutoXray Scanner. "Nothing" everything looked fine but the engine would shake and pop randomly. I Swear I thought my opty Had popped for sure. I was so upset I took her for one last WOT run..... Left the scanner loggin and bam!! 14* retard on the shift 1 to 2nd. Then then car ran just fine at part throttle... Next morning it was even worst.... To make a long story short, I cleaned injectors, replaced the ignition wires (it sucked), Replaced the Coolant temp sensor..(long story behind this move) Almost replaced the MAF...(ran the car without it and it did not help at all) Replaced the IAT (I swear it ran way better after that) ..... and then bingo!!! I replaced the spark plugs. Number 1 had the inside insulator cracked!!! the misfiring caused the plug to collect lots of grey deposits. It was a hair line crack almost invisible running from the tip down and into the spark plug body. After that The engine ran like brand new again.... I took her for another Logged WOT run!! and Bam!! between 11 and 14* knock retard between 1st and 2nd shift again... Ran car fine otherwise...

I replaced the Knock sensor with the LT4 one... and Bam again Same amount of spark retard...... so I decided to run the tank down to empty and then buy race gas and test her again..... only I friggin ran out of Gas on my way to the Performance parts Shop!!!!! I had to walk for a long distance to get gas and it got late so I called it a day... on my way home I did one more Logged WOT run with the gas from this other station and then imagine me looking at the scanner with a moronic look not believing my eyes....... No spark retard at all......You could say I was disapointed!!! How could this thing had fixed itself up!!!

I had been buying some Bad Gas... I bet they (gas station) were pumping 87 octane in the 92 octane underground tanks. Since that day I buy my gas from another gas station and its been fine since then.

Point being.... Check everywhere.


Marvin

 

Marvin,

Thanks for your input. I have checked all the basics- ie. new plugs and wires, cleaned IAC, TB, new injectors, PCV, etc. Everything looks normal in Freescan, but i'm not 100% sure. My next step is going to be a compression test, just to make sure that's OK. I was hoping someone could look at the log, just incase i'm missing something obvious.

Dave

 

I'll look at the log for you if you like, but if you say there isn't anything most likely there isn't (provided you have some experience with freescan).

One thing I don't understand as of yet, several people have experienced retard in excess of 10 degrees, is this because of changes in programming? I was under the impression that 10 was all the comp could pull out.

Jonota

 

I remember reading that 15 degrees was the limit, I know for a fact I had up to 12 degrees because of bad plugs before I got them fixed......atleast that is what my auto-xray scanner got from the car ;D

 

Jonota,

I have NO expirience with freescan. I've read about what is "normal" but this is the first EFI car I've had... I think I read Injuneer's Datamaster results paper, but that's it really.

Can I e-mail you the log I have? It's like 1.3mb...

Dave

 

certainly, email it to weberc002@hawaii.rr.com

Jonota

 

Jonota,
Did you get the file ok?

dave

 

yes, I recieved the file, I will be deciphering what I can tonight and let you know...

Jonota

 

I forgot to ask if you've done any tuning, or had someone do a tune for you. If so, please also send me the .bin or .lt1 file that you have, or if you haven't, you can still download tunercats and get the file out of your car and send it to me. Also, does the "hiccup" happen when it's cold as well? Do you NOTICE the spark retard when you're driving? Any SES lights?

Jonota

ps if you need the definition file for tunercats, I've got it.

 

Alright, a little bit of info:

High spark retard: I noticed that in several of the cases where you got large retard was when you went off throttle momentarily (15,789 range), then got back on throttle. This causes the spark advance to try to go from a high value (low load) to a lower value (high load). What happens is the timing is too far advance, and so you get knock counts, and this pulls the timing out. Your tune must be other than stock though, since it pulls out up to 12 degrees. The answer here is that you shouldn't let off then immediately jump back on, if you do, expect some knock retard. I couldn't really tell what was causing the miscellaneous small retards throughout (the .1's and so forth)

"hiccup": from what I can tell of your car at idle, the only problem seems to be a miss. There are several instances where you O2 volts just drop out for no reason, which often times is a result of an engine misfire sending all the unburnt oxygen past the O2 sensor. I particularly noticed this in the 6000's range of your scan log. It appeared to be running a bit rich as well, but that's not too out of the ordinary.

one last thing was your injector pulsewidths seemed a little off. I noted you said you replaced the injectors. did you use stock replacements? if not, were they of different size or of different pintle design? also, if they were other than stock, was your computer reprogrammed for them?

that's pretty much all that I noticed. I would still like to look at your flash file if you can get it, and a log of you car warm at idle only would be helpful

jonota

 

Jonota you rock!

Ok, I will try to answer all of your questions. As far as I know there is no tune on the car. I've had it for about 10mos. I really don't know it's history before me. The "hiccup" happens when dead cold, but it's not as severe as when the car is warm and in closed loop. I have never had any SES light.

When you say it seems to have a miss at idle, you mean an ignition miss, right? Should I start looking at the OPTI for problems?

Injectors- The day before the log, I had just replaced the stock injectors with Accel 26# replacements. The computer has not been "informed" of this change. I thought that a leaking injector was the cause of the hiccup, and due to time constraints it was easiest to just swap them out.

I think I can pull the .LT1 file off the computer with the freeware PCMComm. I will try to send it to you. I will be able to get an idle log tonight. (don;t have the laptop @ work)

Also, I noticed that someone descreened the MAF, could this be part of the problem?

Lastly, If you think I should get a tune, can I go with a mail order tune?

Thanks so much for taking the time to do this,
Dave

 

The idle miss I would attribute to ignition yes, but it is possible that it is fuel. Your pcm does indeed need to be reprogrammed for the new injectors, as I believe they are bosch pintle style and therefore there is some things that need to be changed so that the PCM knows how to use them. I've heard that a good test for ignition faults is to turn all your lights off at night and run the car with the hood up, and look for arcing. If this still doesn't find the problem inspect all of your wires CAREFULLY. People have experienced faults from as little as cracks in the inside of the wire boot.

To check faulty/leaking injectors, the best thing to do is remove the fuel rail with everything still connected, and pressurize the system. Watch it for a while and see if any visibly leak. A quick way to do this without removing the fuel rail is to connect a fuel pressure gauge to the rail, pressurize, then turn the pump off and watch the pressure. If it falls rather quickly, then you probably have leaky injectors, if not, probably not.

What ignition parts have been replaced? You said plugs and wires, what about the ignition module? The ignition coil? The coil you can test to see if it's doing alright. I would think that you either have multiple plugs/wires not working correctly, or the fault lies (if it IS an ignition fault) with one of the common components, as you were getting a miss on BOTH sides of the engine.

Descreening the MAF has been an iffy subject. Based on your air flow readings, I would say no, it doesn't really matter. You have slightly higher than normal air flow at the upper rpms with the throttle open, but your idle air flows are normal, leading me to believe that your MAF calibration has not been altered enough to really matter. If at any time you do indeed feel that your MAF is having problems, try disconnecting it and driving and see if the problem goes away.

As for tuning there are several methods available. There are the mail order tunes to do. You could get Tunercats or LT1 edit and try it yourself. If you download Tunercats, I will send you the definition file you need and you could pull your tune that way. I will do some tuning if you would like, but I would need to know EVERYTHING that has been done to the car.

Let me know

Jonota

 

Jonota,

First, an update on running conditions. In the last few days the engine is significantly rougher than it has been. The only change was the new injectors.... I don't know if it caused an existing problem to get worse, or if i'm having new problems, but it def. feels like a normal miss, rather than just the hiccup it's always been.

I checked for fireworks under the hood last night and didn't see anything arcing.

This weekend I'm going to pull the plugs and go over the wires with a fine toothed comb. Also, I'm not 100% happy with the wire routing on the pass. side, so I'll try and fix that up. Hopefully something turns up.

I have a new coil, but the module is old. Original OPTI (80,000mi) as far as I can tell anyways. New plugs and wires as we said. SOOooo, Common components would be the OPTI, and the module... Is there a way to trouble-shoot the module?

I will pull the .lt1 file later today, maybe that will tell us something.

Also, here is the rundown on my car, in case we decide to do some tuning.


1995 z28, M6, 275-40-17 on zr1 rims, K+N filter, descreened MAF, Accel 26# injectors, Hooker cat-back. I think that's all the mods i can think of. I run 93 octane fuel. let me know if you need anything else...


Thanks,
Dave

 

I haven't heard of a specific way to test the ignition module, but if I remember correctly it's a pretty cheap part. Does it seem to go away at the upper rpms, or continue throughout the rpm range? As for the .lt1 file, just send it to the same email...

Jonota