revs drop, car jerks, been searching for 2 weeks

[whiltebeitel]

Same symptoms here for a while, check for a big intake leak. I forgot to tighten down my intake boot, got this crap for 2 weeks straight. Went to take the AFM out (swapped it recently) and I felt the boot half-on, half-off. Put it on right, snugged it down, all is good. Intake leaks after the AFM (or carb) will give you this kind of crap. I learned this from driving old shitty cars. :D

[kronus]

Same symptoms here for a while, check for a big intake leak. I forgot to tighten down my intake boot, got this crap for 2 weeks straight. Went to take the AFM out (swapped it recently) and I felt the boot half-on, half-off. Put it on right, snugged it down, all is good. Intake leaks after the AFM (or carb) will give you this kind of crap. I learned this from driving old shitty cars. :D

+1

I had a similar problem, turned out to be a cracked vacuum line coming off the intake boot.

[nando]

I would check for coolant leaks around the throttle body. If you see anything oozing out, chances are the round plug under the manifold is corroded. Try unplugging the TPS and drive the car around, see if the hiccups go away. If it does, you need a new injector harness. If the ECU thinks the TPS is sending it a signal it can do wierd things like you describe - your check engine light will flash when it drops out as well.

and a vacuum leak isn't going to give you tach dropouts.

[sticksdaman]

Very helpful thread... My car began to mysteriously hiccup similar to yours (OP) a few hours ago. It happened right after i filled my tank but i doubt its a case of "bad gas". I poured in a bottle of injector cleaner to see if a clogged filter or injectors might be the issue.. but to no avail. I'm going to start checking the spark related connections tomorrow and see where it goes from there.

[TopOfTheLine89]

what is the thing that is right next to the frame rail to oil pan ground? Is it just a sensor or is it something else, its kinda big and is bolted into the oil pan and has a red wire plug in coming off of it, there was nothing on my wiring harness to plug into it and it it the first time i have seen it.

[sticksdaman]

are you talking about the oil level sender?

[e30.4.life]

The Bentley manual says that vacuum leaks cause erratic idle.

I just want to state that I have some vacuum leaks, (Good ole eta has a leaky head gasket that I refuse to fix) but things were much worse when I first got my $1500 pride and joy. My idle used to stumble all over the place and bounce around from 1000-2000 rpm at initial start up and then as the car got warm the rpms would start to bottom out and and occasionally the car would die at a stop sign or when I'd try to give it gas at launch. All I did was adjust the fuel pressure regulator a bit, so that then car idled a little bit higher than usual. When cold the rpms are @ ~1000, and when warm down to 800 with a slight stumble in the needle. This has worked fairly well for me over the last 2 1/2 years and I even managed to pass CA smog after driving the car around for an hour+ and immediately putting it on the test machine!

[sticksdaman]

I just replaced the hose that connects the Fuel Pressure Regulator to the intake manifold along with the spark plugs. I had been using the Bosch Platinum +2 plugs (they suck btw). I replaced them with plain old champion copper plus plugs and all is well.

I'm certain it was the spark plugs that caused this issue in my car. I reread the thread and I see that you didnt mention replacing your plugs. I think its worth a try if you havent already gone this route. Good Luck!

[TopOfTheLine89]

plugs may be worth a try, im running champion coppers right now as well, they have been fouled and cleaned quite a few times if that mkaes a difference, they are only a year old if even though.

[Knockenwelle]

Oil fouled?

[TopOfTheLine89]

fouled from running rich i believe.

[Knockenwelle]

Rich fouling takes quite a lot of fuel...

[TopOfTheLine89]

Don't think i'm burning oil. I hate my e30 :(

Messed with it some more today and learned nothing, started out driving fine but as it warmed up or was driven for a bout 4 minutes the problem goes from minor and infrequent to constant and crippling.

[Faviolosky]

i dunno if it migh help but have you checked the blue cap sensor on the thermostat housing. i think it influences fuel output

[acefreely02]

I would check for coolant leaks around the throttle body. If you see anything oozing out, chances are the round plug under the manifold is corroded. Try unplugging the TPS and drive the car around, see if the hiccups go away. If it does, you need a new injector harness. If the ECU thinks the TPS is sending it a signal it can do wierd things like you describe - your check engine light will flash when it drops out as well.

and a vacuum leak isn't going to give you tach dropouts.

why the injector harness????? if the problems go away when the tps is unplugged wouldnt you replace the tps??? cus thats whats sending the signals.. the idle and wot switches.. i did the stopm test on my 87 325is and came back with a 1233 code. wot sensor.. so i unplugged it and been driving aroudn and so far it hasnt bogged or anything..