Half second ignition cuts and stalling

[billythekid]

My 325is has had an issue since I changed the timing belt and water pump all that good stuff. Since then I've also changed the cps and that didn't solve my issue. When I'm driving and rev the motor to around 4 to 5000 it bucks hard(spirited driving) and when it does the cel flashes then turns off. I check the codes and It tells me I have no errors, would this just be an issue with a part in the ignition? Also I plan on getting a new distributor rotor and cap. The one that's in the car is cracked in two spots but I don't think that's the cause because it ran flawless before it was off

[e30austin]

this is a very common issue with M20 engines. does it generally happen at full throttle, at roughly 4200 RPM?

[billythekid]

Unless the tires are spinning(roads are covered in ice and snow) then yes. It's progressed to the ignition cutting out randomly while I'm cruising even when there almost no load being put on the motor at highway speeds. Cel flashes and mpg meter moves to the left faster then normal. If I don't keep the motor at around 1k rpm it will die at a stop. I'm about to go out with a flashlight and check the ground I had off when I overhauled my cooling system

[billythekid]

Small update i believe it's a fuel pump issue. Tach doesn't drop to zero when it cuts and I can't hear the in tank pump.

[MrBurgundy]

If it cuts out quickly and really slows the car down for a split second, it's most likely an ignition problem or injector cutoff.

Excessively fouled plugs caused by leaking injectors can create this problem.

Fuel pumps on these cars tend to work or not.

Since you said this happened after the water pump service I would look at the wiring of the CPS and make sure its not being shredded by the WP pulley.

Then work your way back through everything.

Make sure you the rotor is tight, cap is on tight, plugs are clean and crack free, and the harness plug under the intake is nice and tightly plugged in.

Don't change your fuel pump just yet.

[tomstin]

Is it better or worse with a full tank of fuel versus near empty? Junk in the gas tank can cause the filter sock to clog with high fuel demand. The lower the level in the tank, the more prone to this happening.

[billythekid]

The fuel level never really makes a difference. I've ordered a few cheap things that have never been a problem before but due to the drastic drop in temps could be now. Intake boot and I'm gonna clean the tps and icv while I'm in there. I know the rotor has two cracks in it but it wasn't a problem before. Either way a new ones coming along with a distributor cap. If I drive it right it will pull all the way to redline sounding healthy but as soon as it's most or all throttle most problems occur there now. I know I fixed a ground issue but the cuts still remain. I routed the cps wire over the distributor so it should never have contact issue with the water pump pulley. But I am going to check the harness it plugs into and make sure it didn't get yanked on or damaged when I did the timing belt. I don't have service records from previous owners aside from a tire shop so I'm assuming everything I haven't touched is original. I know the in tank fuel pump is because the insulation above the pump had never been torn up and there's not a spec of dust underneath it or where the seat meets carpet. I'm buying a replacement pump, and a new sock for it. New ignition wires and spark plugs all on Friday. All need to be changed anyway so I might as well knock it out

[Gregs///M]

A failing AFM will cause this exact issue. See my thread on AFM service to read and understand why a failing AFM will cause this. https://www.r3vlimited.com/board/for...afm-s-for-sale

many people think that cleaning the internal chamber will "clean" or "fix" it but they are completely wrong. Its the degradation and copper oxidation of the electrical section which causes voltage drops on the signal output. As you can see in the thread, when the volts drops, the DME thinks the motor is receiving a significantly less amount of air and thus cuts fuel drastically, all suddenly and briefly, then power returns.

[billythekid]

Ok ok, thanks for giving me some direction to go into because I wasn't hoping to just throw money at it. After all I want to buy some fun things too. Is there any good write ups for cleaning/restoring the afm?

[billythekid]

Cleaned air flow meter contact points and cleaned the passageway out with carb cleaner. Cleaned tps, icv, and throttle body. Replaced intake boot. Dizzy cap and rotor as well overall runs smoother and seems happier. Still cuts though. Now sometimes it feels like it hits a rev limiter at around 4000. And it will keep bouncing there. But if I control the throttle right and I don't punch it immediately it will go all the way to red line smoothly. Also now my idle is low and car lopes like it's cammed. When I get home tonight it will be pretty dark so I'm going to try and see if the plug wires arc out and I'm also going to swap out fuel pressure regulators for my old one that worked when I took it off the car to replace it

[Gregs///M]

Cleaning the carbon track does not do much. Its the electrical connectors which develop copper oxidation and thus a higher resistance connection to the DME. This means the entire electrical section of the AFM must be disassembled and refurbished. This is how the signal is restored. Cleaning the carbon track and inner chamber doesn't really do much help.

[ForcedFirebird]

The CPS also mimics the AFM issue around 4-4500 RPM. There's several issues with them, first being the wire is rock hard with age and breaks off at the sensor where the wire is epoxied in. When on the throttle, the wire moves and cuts ignition. They also tend to rub on the back of the water pump, eventually stripping the wire sheathing and grounding the wires on the water pump pulley. There's supposed to be a plastic conduit there, usually they are gone/broken - so you can just run the wire over the timing cover.

I"m with Greg on thi the AFM cleaning. Cleaning the track does nothing if the carbon has been worn completely through with the wiper arm. Only way to remedy is to move the wiper to a new spot on the track. Be careful when doing this. I have had professionally refurbished AFM's that had the wiper moved and it went off the end of the end of the track in certain scenarios - we couldn't figure out why the car was going lean above 5500 - opened the AFM and observed the wiper during the runs. Adjusted the wiper and the car went to 167whp and 6500 straight away.

[billythekid]

The cps was replaced about a year ago and it helped nothing. Cleaned afm. Changed to old for to see if that was the problem and it filled my intake with gas. Did a few miscellaneous things like rotor nd cap cuz those needed replacing anyway. Alternator stopped working the other night and so I just changed it today because I had to drive to work. After that I get a actual solid full throttle pull to redline with zero issues. And then it starts cutting out again. 20 minutes later on the interstate it starts cutting out non stop I can barely maintain speed. Every time I stop it stalls. But I turned it on again after stopping in a parking lot and it idles perfectly at 750 to 800. It won't throw a code and when it does it cuts out again and then the code dissapears. I'm going to clean the shit out the battery posts and connecters and see if it helps any because I might have put the post on in a way where it gets that one corroded spot or some shit. I've used half a tank of gas but my mpg gauge says 4.6l/100km which is about 50 mpg. I'm stopped in a parking lot waiting for a friend to show up so he can follow me home in case I break down. When it cuts out it seems to affect every gauge except the gas gauge and the speed gauge. I'm grasping at everything right now and trying to stay calm and think about what it could be. But I'm starting to worry it's something more serious like the dme or hopefully something stupid like a relay. I doubt the afm could cause the violent non stop bucking issue but again any advice or tips in the right direction would be greatly appreciated as this is my only car

[Gregs///M]

The cps was replaced about a year ago and it helped nothing. Cleaned afm. Changed to old for to see if that was the problem and it filled my intake with gas. Did a few miscellaneous things like rotor nd cap cuz those needed replacing anyway. Alternator stopped working the other night and so I just changed it today because I had to drive to work. After that I get a actual solid full throttle pull to redline with zero issues. And then it starts cutting out again. 20 minutes later on the interstate it starts cutting out non stop I can barely maintain speed. Every time I stop it stalls. But I turned it on again after stopping in a parking lot and it idles perfectly at 750 to 800. It won't throw a code and when it does it cuts out again and then the code dissapears. I'm going to clean the shit out the battery posts and connecters and see if it helps any because I might have put the post on in a way where it gets that one corroded spot or some shit. I've used half a tank of gas but my mpg gauge says 4.6l/100km which is about 50 mpg. I'm stopped in a parking lot waiting for a friend to show up so he can follow me home in case I break down. When it cuts out it seems to affect every gauge except the gas gauge and the speed gauge. I'm grasping at everything right now and trying to stay calm and think about what it could be. But I'm starting to worry it's something more serious like the dme or hopefully something stupid like a relay. I doubt the afm could cause the violent non stop bucking issue but again any advice or tips in the right direction would be greatly appreciated as this is my only car

You would be a fool to not take the advice of me and Forced Firebird, as we have worked on and fixed many hundreds of E30s and have been participating on this forum for over a decade.. If you believe the AFM will not cause violent non stop bucking after both he and I explained it to you, then its probably best you pay a professional mechanic to fix your car or sell your car.

See my article on the topic of AFM's, as you can clearly see. When the signal output has a huge voltage drop, the DME thinks the amount of air entering the combustion chamber to be significantly less, thus the fuel is cut off significantly. This will result in sudden and brief power loss, or bucking. https://www.r3vlimited.com/board/for...afm-s-for-sale

[billythekid]

It's not the air flow meter. After that whole shit show I ended up putting gas in the tank and poof works perfectly. Now putting more gas in it had never made anything better before. And I doubt it was bad gas. But now it's just whenever the tank gets low I have the issue. I was going to buy a afm money was tight but I had to do the alternator first. I'm pretty sure the symptoms of when it's low it seems to starve means fuel pump