rich running low idle e30

[mannyuk]

Hello ladies and gentleman, i'm new to the forum. quick question.

my car just past smog with flying colors (still original cat) however it is running rich and a little rough. there is like a 2 second mini jump or something. gas mileage not that amazing. any thoughts? anybody have similar prob. Rough idle isn't a big rough. changed spark plugs, fuel filter, threw in chevron techron.

thanks y'all

[Raxe]

Year and engine?

[Kershaw]

vacuum leak.

clogged injector.

o2 sensor.

fpr.

afm.

dme.

check in that order.

to get you started: 1. pull the oil dip stick out. did the idle change? no? check for vacuum leaks. 2. pull out a spark plug WIRE. did the idle change? no? put it back in and repeat. (if they are brand new spark plugs, are they clean or do they show signs of combustion?)

[mannyuk]

92 325i vert. Kershaw it cant be the 02 sensor as i just past smog with flying colors i was below average on everything. just threw in some techron fuel injector cleaner. i just changed plugs so will check them. pull plugs out while car is running would be okay?

thanks guys i appreciate your assistance and knowledge

[Threehz]

Pull out a spark plug?

[Kershaw]

my bad. i was on my phone and apparently my brain condensed two things into one.

1. pull out the spark plug WIRE 1 by 1 to verify if idle changes. if the WIRE is not connected and it has no affect on idle, that cylinder is not operational. it's either fuel or spark.

2. pull the fuel pump fuse. pull out a spark plug. insert spark plug into wire. holding the wire, put the spark plug close to the shock tower. have a friend crank the car. verify that it sparks. do this for all cylinders.

using that information you should be able to determine if you have a clogged injector and which cylinder(s) are the problem.

lol.

[e30vert]

As Kershaw indicated as the FIRST thing to check is vacuum leaks.
His list is well formulated in the order to approach troubleshooting the issue.

The M20 has the intake boot that is super prone to cracking and splitting after they reach a certain age. Flex the rubber intake boot with your fingers along the molded in rubber spines and look between the spines . See cracks? Any splits? If so, rip that boot out and throw the shit away! Get a new one pronto. They are so inexpensive I would just replace it as part of general upkeep and preventative maintainence.

Update the thread with your findings so we know what the culprit(s) were.

[cferb]

I would hope he'd be able to tell if it was running on 5 cylinders, that'd be more than "a little" rough, and I doubt you could pass smog.

+1 on everything else here though. Vacuum leaks are really common on cars this old, the rubber gets brittle after all the years. One spot that seems to be common is there is an elbow going into the throttle body on the side of it that tends to get loose, might check there.

Things like this are difficult to troubleshoot since it can be so many different things, but a lot of it is stuff that needs attention anyway.

[mannyuk]

thanks guys. will take a look tomorrow when i put new control arms in keep you posted. cferb yes i mean little rough nothing major like a pulse every 2 or 3 seconds.

[702pjc]

+1 on everything else here though. Vacuum leaks are really common on cars this old, the rubber gets brittle after all the years. One spot that seems to be common is there is an elbow going into the throttle body on the side of it that tends to get loose, might check there.

Do you mean the break booster and IAC lines?

And yeah, idle problems can be a bitch. My car is running like shit too. Any vacuum leak will cause your idle to rise. So it could be a multitude of things... gasket, injector oring, hoses, or an ignition problem.

Not sure how you passed smog with a misfire.

[mannyuk]

Past smog way below average on everything. And it still has the original cat n exhaust.

[mannyuk]

And there is a gas smell out of exhaust. Going through
Gas like a motherf#+*er. Obc saying 17.5 miles
But I'm thinking like 10mpg.

[mannyuk]

hey guys so firstly thanks for all in the input. latest, went to mechanic friend and pulled off the oil cap and there was big idle difference, same with the dipstick. pulled off the spark plug wires one by one as kershaw suggested and the difference was minimal. put the wire to valve cover and no spark. could a faulty ignition coil be the culprit. checked for vacuum leaks with carb cleaner and there was none. i also tried checking for a code and after depressing accelerator 5 times in 5 seconds got no reading at all.

once again i give thanks to you all

[Raxe]

Have your friend test fuel pressure, a faulty fuel pressure regulator can cause a rough/rich idle and fuel smell if it's leaking internally. Also check the small section of vacuum hose that runs from the FPR to the intake manifold, very common failure that can directly affect regulator operation.

[benbear12]

Hi
Welcome to this Forum Site, here you can find lots of things, I suggest you for your question you have to contact any other expert right now iam not able to give you answer-------


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