Another hesitation / misfire / bogging / rattle rattle pop pop thread

[smackley]

PROBLEM SOLVED - final issues in last posting pg 2.

OK, so I've owned my e30 325iC for all of 2 months now, and I've been able to drive it problem free for maybe 2 weeks of that time.

The first week of driving the car, it would drive fine on a cold start, but after warming up the car would rough idle and almost stall. If I blipped the throttle in neutral at a stop light, it would hesitate immensely, go up in RPM, then drop down and stall. If I managed to keep it from stalling at a stop light, once I put it in gear to go forward, it would simply not accelerate once RPM's went past 1500. In first gear, once I hit 2k rpm, the car would actually hold speed no matter how far I had the pedal mashed down. While mashing the pedal down, the car would intermittently spike in RPM, then...rattle rattle pop pop...and back down. If I was lucky enough to get some down hill speed, I could upchange the gears and start building speed. Regardless of the gear, if I put the pedal down, it would just backfire and would actually start to decelerate.

So, in the 2nd week, I replaced the following based on several different threads I've read all over the net:
-Coolant temp sensor
-plugs/wires
-fuel pump and sock (no rust in the tank)
-fuel filter
-fuel pressure regulator (tested at 3bar, checks out)

I also then cleaned the ICV, checked the AFM, and tried to check the vacuum lines as best I could. All of this did just about nothing.

The next week, I removed the 02 sensor connector to remove signal if it was fouled...huge improvement. If I unplugged it, the car ran fine. Plug it back in, and the car would take a dump. This all pointed to a fouled 02. I removed it, replaced it, and everything seemed like a huge epiphany moment. Fixed!

Well, fast forward a month and welcome to my new problem. The car idles great, I can blip the throttle and it is relatively responsive (for an m20), and it starts up just fine. However, once I put it in gear and begin to accelerate...I'm back to rattle rattle pop pop and hesitation galore!

In first gear, it actually runs great from 2k to 3k rpm. In all the rest of the gears, it runs great from 2.5K to 3.5K. I can get up to speed and cruise in that rpm range just fine. Below and above those rpm ranges, the car misses and hesitates. If I mash the throttle at 3.5k rpm, the tach will start to bounce and the car will have intermittent acceleration. Idle is still smack dab on 800rpm with no problems.

My next thoughts are CPS or the toothed dampener assembly. I haven't checked the gap of the CPS or if the dampener is loose at all, but I was reading this thread and it seems a likely culprit. http://www.r3vlimited.com/board/showthread.php?t=147102

Bavauto seems to like to suggest a CPS to all the FAQ's on their site

http://blog.bavauto.com/5241/1990-bmw-325is-e30-m20-stumbles-during-acceleration/

Anyone have thoughts or other experiences?

[smackley]

update

I just tried the stomp test, but I can't get it to work. I turn the ignition to position one but don't turn the motor over. I stomp on the accelerator 5 times in rapid succession and nothing blinks...not even the standard one blink if there were no codes. I wonder if the check engine light bulb is out or was pulled by the previous owner? Could I not be stomping fast enough?

[Edit - I'm pretty sure a bulb is out because my check engine light is not even lit in the 'on' position prior to turning the motor over] If this fucker pulled a light before selling me the car, somebody is getting a fucking slap!

[jlevie]

If the CEL doesn't light up when the ignition is switched on, the bulb could be burned out or not connected. You'll have to pull the cluster to find out. Once you get the CEL woking properly you can try the stomp test again. If the stomp test doesn't on an 88 325i/is/ic or later car, which should have a 173 or later DME, it is usually because the TPS isn't working correctly. If either switch in the TPS isn't working or the TPS is misadjusted the stomp test won't work.

If you see the tach needle dropping significantly when the car is in gear and in motion accompanied by a loss of power the cause is likely to be a bad CPS. And a new CPS should be the first action in trying to solve the problem. Everything else that has been described suggests the presence of intake leaks. Have smoke test run.

[smackley]

I appreciate the good info. Here's some new info...

Later today after rattle popping into work, I shut the car off and went back out at lunch to give it a fiddle. I noticed that the tubing going into the throttle body from the check valve was loose. By 'loose' I mean that the metal fitting the tubing was pressed onto was backing out of the metal throttle body housing. I figured there would be some vacuum leak there. I pushed them back in (both upper and lower) and wammo...car ran great. It ran great all day, cold and hot temp. I'm not sure if it's a directly related fix or just that for some reason, after cooling down from my shitty morning drive, the cps decided to get back to work?

Now a new symptom popped up. The speedo has gone wonkers. The speed on-throttle is showing just fine. When I go off throttle, and the car is still in gear, the speedo bounces all over the place. I assume the sensor in the differential is toast. I had to disengage the sensor when I lowered the diff to install my coilovers. All the plastic portions of the connector literally crumbled to pieces. I guess I'll order a new sensor and cable connector for my upcoming diff flush...

If the CEL doesn't light up when the ignition is switched on, the bulb could be burned out or not connected. You'll have to pull the cluster to find out. Once you get the CEL woking properly you can try the stomp test again. If the stomp test doesn't on an 88 325i/is/ic or later car, which should have a 173 or later DME, it is usually because the TPS isn't working correctly. If either switch in the TPS isn't working or the TPS is misadjusted the stomp test won't work.

If you see the tach needle dropping significantly when the car is in gear and in motion accompanied by a loss of power the cause is likely to be a bad CPS. And a new CPS should be the first action in trying to solve the problem. Everything else that has been described suggests the presence of intake leaks. Have smoke test run.

[smackley]

Ok, so CPS replaced. No changes. I can still climb RPM if I slowly accelerate, but if I try to accelerate quickly, it pops misses and doesn't climb in RPM until I get a surge and then it climbs. First and second gear are the worst, but still happens in 3/4/5.

The next item checked was the AFM again. I adjusted the resistor arm so it can make new tracks in the potentiometer's resister track (if that makes sense). While I had the AFM out, I pulled the TB boot and the throttle body itself. I disengaged the TPS and cleaned all the oil out of it making sure the two contact points had good engagement. I then cleaned the TB with brake cleaner and checked for cracks in the boot and all associated vac lines. Everything seemed solid enough. After everything dried out, I put it all back together and... still have problems. I do have a slightly higher idle now so now I have two issues. I must have fudged something with the AFM causing the idle issue.


I'm about fresh out of possibilities here other than swapping my motronic for another to see if it helps at all. Smoke test is a good plan, but before I take it to my mechanic, I'd like to make sure I've had all my bases covered that I can handle on my end.

[jlevie]

One of the things you haven't done, that needs to be done, is to tee in a gauge and see what the fuel pressure is, at idle and while driving. I know you have replaced the pump, filter, and FPR. So now we need to find out if the pump may be loosing power while the car is being driven. You also need to have that smoke test run.

Have you checked, electrically, the TPS? A visual and sound test means essentially nothing.

[smackley]

Smoke test complete. No vac leaks.

I'm heading out to carquest now to get a T fitting and an FP gauge. I guess I'll strap it to a wiper arm and check it out while driving vs idle. I guess I just T it in before the FPR? Do I need to bleed the air out of the added t line that goes up to the FP gauge or can I just add the t fitting and let the system force out any air that is introduced?

I'm also going to pick up a main relay for the ECU for no other reason than I haven't replaced it and it's one of the last ones I haven't done for the sake of being anal.

I did not check the TPS electrically, but only that it makes proper contact with the WOT connection and engages the idle micro switch. Idle is fine in the car so I'd suppose that isn't a test point. I may have overlooked testing the WOT position contacts since I get hesitation and popping even at mid throttle up to the 70% range where the WOT contacts begin to engage in the TPS. Regardless, you are correct. It should be tested properly.

One of the things you haven't done, that needs to be done, is to tee in a gauge and see what the fuel pressure is, at idle and while driving. I know you have replaced the pump, filter, and FPR. So now we need to find out if the pump may be loosing power while the car is being driven. You also need to have that smoke test run.

Have you checked, electrically, the TPS? A visual and sound test means essentially nothing.

[jlevie]

Tee the gauge in to the hose that goes directly to the fuel rail (that is the supply side). You don't need to bleed air out. A very good source for the parts to fab up a pressure gauge is a home improvement center (Lowes, Home Depot).

There are other possibilities, but I don't want to go there until the simple causes have been ruled out and those fixes are expensive.

[smackley]

Thanks for your reply. I teed in the gauge as you described and here is what I saw...

At idle there was ~30psi of pressure. On throttle, there was about 47psi (3bar). I'm going to assume this really just rules out the fuel filter, pump and FPR. I could have really dirty injectors? Need a valve adjustment? ...or what I dread...Motronic problem?

Am I chasing the next logical leads here?

Tee the gauge in to the hose that goes directly to the fuel rail (that is the supply side). You don't need to bleed air out. A very good source for the parts to fab up a pressure gauge is a home improvement center (Lowes, Home Depot).

There are other possibilities, but I don't want to go there until the simple causes have been ruled out and those fixes are expensive.

[smackley]

Going to pull the fuel rail / injectors tomorrow for an inspection. Any thoughts here from any of you long time m20 owners? I had high hopes of swapping my motronic for my buddies '87 vert motronic just to test, but unfortunately he doesnt have the same updated version.

Any Raleigh area people interested in a case of beer for an afternoon of trouble shooting?

[e30rapidic]

is your distributor tightened down?

[FLG]

Going to pull the fuel rail / injectors tomorrow for an inspection. Any thoughts here from any of you long time m20 owners? I had high hopes of swapping my motronic for my buddies '87 vert motronic just to test, but unfortunately he doesnt have the same updated version.

Any Raleigh area people interested in a case of beer for an afternoon of trouble shooting?

Doesn't matter if its 1.1 or 1.3 it'll work.



Sent from my Galaxy Nexus using Tapatalk 2

[smackley]

Thanks. I will give it a go if the injectors don't pan out.

Doesn't matter if its 1.1 or 1.3 it'll work.

[smackley]

Update 7/28... Injector day

So I finally got around to testing the injectors. Prior to doing that, we put my buddies AFM in my car and there was no improvement.

I pulled the fuel rail and all 6 injectors to find the dirtiest set of injectors I've seen in a long while. See the pictures. I was very hopeful this was my problem. It wasn't. The new ones went in and everything ran great until the car got to operating temperature. As soon as the thermostat opens, the car starts back firing and losing RPM on throttle. I can gingerly apply throttle and the car runs great through every gear, but as soon as I apply even more than 30% throttle while accelerating, the car dips RPM as if it's taking in too much air. The car will backfire/misfire and then decelerate regardless of throttle position. If I back off on the throttle, the engine seems to catch up with itself and moves fine.

I also plugged in my buddy's ICV to make sure it wasn't a stuck open vane in my ICV. It didn't help. My last thoughts are TPS or Motronic...

[smackley]

It gets worse

Ok, so new TPS. New Main Relay. Check.

It all seemed to work just fine. I was stoked. I shut the car off for a few mins and went inside to get my wallet to go for a test drive to make sure everything was all better. I came back out and turned the car back over and now the car was only running on 4 cylinders!!! WTF?

I removed the cap and checked the contacts. They were a bit corroded so I cleaned them a bit and reassembled. I pulled each cylinder's plug wire until I isolated which ones were not firing. It's 3 & 4 that have no spark. I pulled the plugs on each to see if there was something amiss. They had a bit of fuel on them (I suppose due to no spark), but they were brand new so nothing stood out as being problematic.

Is it possible that I need wires/cap/rotor? Maybe, but it's really odd that this happened all of a sudden.