I got my car back about three weeks ago from an Optispark change. I noticed that I had a hestitation in the lower RPMs, however, when I accelerated it seemed like normal. I noticed a ticking, hissing noise coming from the front of the y-pipe area and a friend told me it was an exhaust leak. I noticed that as I drove it every day the ticking, hissing noise increased. The SES light has never came on up until today. Along with the light, my car smelled like gas heavily in the front and the exhaust sounded like I had a heavy cam. It was also shaking very noticeably. What do you guys think??? I'm guessing an exhaust leak, but could that produce that many symptoms from the car?? Help!

 

I tried removing the MAF connection and that only made it worse. SO, I don't think it is the MAF. I really do not know what it could be. ANY SUGGESTIONS PLEASE???

 

Sounds like one of the wires may have popped off at the opti and set a misfire code (hence the SES light). Try to read the code. Get it scanned or something.

 

I went to get it scanned at AutoZone and three codes came up on their diagnostic scan. Two were random misfire codes and one had to do with the circuitry of the MAF or something of that sort. What do you all think it is??

 

check the plug wires at the opti, and look for arcing when it is dark. Also make sure no wires are reversed, IE: make sure the firing order is correct.

 

When the Optispark was changed, the mechanic replaced all the spark plugs, except he never changed the wires from the old Opti. Perhaps you think that might be it? Maybe a vacuum hose? Why do you think it would be the EGR Arctic??

 

Sounds like you are getting unmeasured air after the MAF. The EGR could definately provide "false air". Also, check for obvious vacuum leaks by spraying Carb Cleaner or WD40 around all of the vacuum fittings.

Check for any vacuum leak. It could give you a lean condition which could register as a misfire. It could also give false readings from your MAF tripping a code.

 

Thanks for the replies guys! Update: A friend of mine has an ATAP and a little while ago he scanned it and got more detailed information. My car had knock at a complete stop, he said the number was 10. ?? The air/fuel ratio was at a constant 16 no matter what the car was doing. The fuel/air trims were both at negative numbers, and the misfires would go off and then suddenly disappear, corrected, until another cylinder would go off and the process kept going on like that. All evidence seems to be pointing towards the MAF. However, I am not sure and nor was he. I am tempted to just buy a new MAF, but couldn't it also be the IAT sensor maybe? You don't hink it could be because the MAF is descreened could it? What do you guys think now??

 

A Knock of 10... I think they mean that the Knock Retard is 10* which is standard. If the MAF has been tampered with, it could be part of the problem. Sounds like it is running lean with an Air/Fuel Ratio of 16.

I would still like to investigate the possibility of a vacuum leak after the MAF. It would make your car run lean (A/F 16 is an indication).

I don't believe it would be in Ignition Misfire because it is a lean condition and not a rich condition. If the spark wasn't igniting the fuel, then it would rush raw fuel into your exhaust... rich condition.

 

You said you thought it had an exhaust leak. If the exhaust leak is before the O2 sensors, it will cause the engine to run excessively rich. The leak allows air to be pulled into the exhaust system under certain conditions, throwing the O2 sensors off.

You said the scan showed an MAF code. That is most likely because you disconnected the MAF sensor.... once you pull it, the code is set, and it stays in the PCM as a "stored" code, even after you plug the sensor back in. It takes a large number of "drive cycles" without the MAF disconnect reappearing, before the PCM will "clear" the stored MAF code.

Misfires also cause the engine to run excessively rich... again, when a cylinder misfires, the unburned air ends up in the exhaust, where the O2 sensors pick it up and assume its lean, and the PCM starts adding extra fuel it doesn't need. A "false lean". O2 sensors can only "see" oxygen... they can not tell if raw fuel it present.

And... AutoTap only shows you the A/F ratio the PCM is trying to achieve - the number it uses in the fuel calculations - NOT the actual A/F ratio. It seems extremely odd that is is attempting to set 16:1, since the stoichiometric A/F ratio of 14.7:1 is hard coded into the programming and can not be changed. This is the number you should see in AutoTap in closed loop/part load/part throttle operation. At WOT, you should see the PCM set a richer A/F ratio, typically in the range of 11.7:1 (it varies, but that's the usual number). But you don't see the ACTUAL A/F ratio on a scanner.

If you have the AutoTap file available in .csv format, I'd be glad to look at it and see if I could help you find the problem.

You also need to go back and make sure the harness connector for the Opti is fully inserted, that there is no corrosion inside the harness side of the plug, and that the pins are not bent. Make sure there are no high voltage wires near the Opti connector... the high voltage can induce spurious pulses into the Opti signal and throw timing off. Do the same with the Opti "test" connector... the gray 4-pin connector hanging on the bracket in the middle of the passenger side of the intake manifold. Then look at each plug wire and the coil wire at the Opti, to make sure the wire ends aren't corroded.

 

I see what Injuneer is getting at... I was understanding that the computer was reading lean and trying to richen the mixture. Not that it is rich and trying to lean the mixture.

Since you said your Opti was recently worked on along with the plugs... that could be an issue. I'd like to know if you see faint blue sparks popping near your plugs... find a very dark place a night, pop the hood, and let your eyes adjust. I just replaced my plugs two weekends ago and 4 of the 8 were bad. Turns out that the guy dropped the box at the parts store cracking all four... I didn't notice and had an intermittant spark. That is one possibility (having a bad plug).

Or, one of the spark wires wasn't loomed correctly and may be arcing. I had another buddy in the club who had #8 rub on the dipstick causing an arc after a plug change.

Injuneer, can he unplug his battery and reset his computer to see if he still gets the SES for the MAF?

 

Injuneer, then what do you recommend I do?? I bought an MAF already just in case. Do you think that perhaps it is the Opti again or is it the MAF, or even the vacuum or something as simple as the wires? I can do the MAF, the Opti will have to be taken to a mechanic which means more money. Bloodztone did the Autotap for me and he can send you the csv format of the scan. I'll let him know. In the meantime, in your honest opinion what do you think it is Injuneer, Wild1???

 

Kinda hard to do little more than "guess" from 1,300 miles away... ... but I think that the things that stand out are the misfires, the possible exhaust leak, and the recent Opti replacement. I'm not thinking its the MAF.

The other thing that stands out, if it is correct, is the 10deg of knock retard at idle. That tells me there is something wrong with the timing (Opti install problem, crossfiring) or there is some sort of excessive mechanical noise. You also talk about a "ticking" noise at the Y-pipe... is it loud enough that it could be affecting the knock sensor?

Have you friend send me the .csv format file. Try the e-mail address that pops up when you click on the button at the bottom of the message... if it won't go through, let me know in a post here, because I have a lot of e-mail ISP's blocked because they make no attempt to control SPAM.

 

The ticking noise is very loud and you can here it very clearly. I would not doubt if it is affecting the knock sensor. The only good thing is I just recently purchased headers and a new y-pipe so if it is an exhaust leak we will find out. I just hope that the headers aren't so loud that they too give off knock or even worse, cause more problems. My only concern is getting the car running 100% right before anymore mods. Money is an issue since I'm a poor college kid, but I have enough if I can nail the correct culprit. I emailed my friend and sent him your address, hopefully he will reply soon. Out of curiousity, what would the random misfires (again) be an indication of and what is crossfiring??

 

Injuneer that file is on it's way. It's 76.2KB.