car jerks at randomly need help

[StereoInstaller1]

If the tach freaks out, almost always a bad main relay.

[scottinAZ]

Hit up Blunt, best place to get parts.

In the meantime, how about the OPs issue?

my advice doesnt change, AFM or possible boot issues. wont affect the tach unless its really bad.....

[StereoInstaller1]

i'm actively looking for one. i guess i should pony up and buy a new one, but mine is the one only found in models produced between 11/88 and 1/89 so it's harder to come by..

Hit up Blunt, best place to get parts.

In the meantime, how about the OPs issue?

[mkcman17]

Get a new boot. taping is putting a band aid on the problem. Many issues can be tied to a bad signal from the AFM, most are due to bad boot, but others are due to a crappy signal from the sensor. Yours is a bad boot.

i'm actively looking for one. i guess i should pony up and buy a new one, but mine is the one only found in models produced between 11/88 and 1/89 so it's harder to come by..

[scottinAZ]

phew okay good! driving mostly feather-footed i'm getting barely over 20 w/o ac in my stock b25. i was gonna be real disappointed if you got that from an 'i' motor!


oh and taping up my intake boot changed everything. no more lag, more punch, and seemingly a smoother idle and rev down.

Get a new boot. taping is putting a band aid on the problem. Many issues can be tied to a bad signal from the AFM, most are due to bad boot, but others are due to a crappy signal from the sensor. Yours is a bad boot.

[mkcman17]

yep, its an Eta, 23.1 is down from 27 in the winter when I dont use ac.

phew okay good! driving mostly feather-footed i'm getting barely over 20 w/o ac in my stock b25. i was gonna be real disappointed if you got that from an 'i' motor!


oh and taping up my intake boot changed everything. no more lag, more punch, and seemingly a smoother idle and rev down.

[StereoInstaller1]

BTW: OP, please post engine/vehicle data..."my e30" is pretty vague.

Anyway, take apart the injector power plug and clean it. It is one of those things that even if you don't need to do it, you need to do it.

The harness is directly below the throttle body. It screws together and they get all nasty and stuff. Use CRC "Electrical cleaner" to make it all better.

Luke

[scottinAZ]

scott, 23.1 mpg? i hope it's an eta..

yep, its an Eta, 23.1 is down from 27 in the winter when I dont use ac.

[u3b3rg33k]

Herein lies the problem. unless you're putting in a NEW afm, how can you be sure? I've tried other "known working" afms, and no dice - I get random quirks that show up at some point. We've got AFMs on a few of our older L-jet cars, and they are also a constant source of quirks.

[88e30dippin]

hmm i guess im going to try the afm then. i might just get a cheap good one that works and just get the millar maf and war chip too.

can someone give me a diagram or place i can go to and get wiring for a maf sensor. i have a maf sensor off a 95 volvo turbo and i would like to use that since its the 4 wire maf sensor. all i would need then is the war chip. i saw a guy have a conversion on his 318is and he had wires running from the 3" mazda or ford maf sensor because you have to run 12v or something like that and get a chip that will tell the computer to not run off the afm anymore. can someone steer me the right direction? lol

[Danny]

Afm

[u3b3rg33k]

if the tach doesn't drop, it's probably not the CPS.

I think it has absolutely nothing to do with the power steering. think about it. At idle, if you try cranking the wheel past full lock the ps belt will slip/squeal, even if properly tensioned. Do you think that the belt would do anything but burn off at cruise if the pump seized?

TPS only affects things when the throttle is closed, or WOT. in the middle it does nothing, therefore while cruising it should have no effect.

Oh, have I mentioned that my car does the same thing you're describing, but only at WOT above 3500rpm? I've currently got 6 injectors being cleaned/restored/flowmatched, and if that doesn't solve it, MAF+WAR chip is next. AFM be damned.

I did replace my plug wires, and that helped, sort of (it no longer hangs at 4k rpm when it's horribly cold and wet) but it didn't solve the problem.

[mkcman17]

i just cleaned out my icv and taped up some gaps in my icv boot. i have been having trouble starting the car when hot and occasionally having issues around 3k rpms, so i'm hoping that'll solve it.

also, some days my car is a total dog, and now and then it's a total rocket. don't really get why...i'm going to clean out the injectors next methinks.

scott, 23.1 mpg? i hope it's an eta..

[88e30dippin]

the tach doesn't move at all. if im doing 60 on freeway at 2300rpm to 2500 if im sitting on or in between those rpms it would sometimes just jerk like a back fire and then work fine. i have put new plugs (ngks), new distributor cap and rotor, and as for coil i am using stock one and have tried an aftermarket one and it did the same. right now im running oem coil connected to a jacobs racing ignition system. it did the jerking thing before the ignition stuff was added.

when it first started i changed the injectors, o2 sensor, afm, and the throttle body thinking the tps was bad. after i did all that the car worked fine till a few weeks ago. worked just fine for 4 months after doing the 5 speed conversion. its running a 89 525i 5 speed ecu. i keep thinking it might be because of my afm and that my steering rack leaks inside the rubber boots.

i was also wondering how to delete the power steering correctly?

[dinanm3atl]

Number of things.

AFM
Crank Sensor
Could be ignition related - Plugs, wires, distributor or coil and all associated connections.

I would start there.