E30 1986 325E Surging Idle, poor acceleration

[andrewliebner]

So this issue was there when i purchased the car. When i would give it gas the acceleration would be hesitant, and would stay around the same rpm's until it leveled out and got better around 3k rpm's. I decided that my issue had something to do with my coil so i replaced it, that obviously didn't help.

After I replaced the coil, i thought it would be a good idea to unplug any wire i could see and spray electric connection cleaner on all of them (bad idea on my part) . The next day i started the car and it instantly revved to 3k and stayed there for about 1 minute before i shut it down. I proceeded to start the car and shut it off many times, tapping on the ICV, TPS, Air box sensor and had no success in fixing the problem. I believe that when i was tapping on the TPS i may have thrown it off of calibration, because these sensors are supposed to be screwed on a certain way.

My next course of action, was to pull some stuff apart, I removed the airbox, the throttle (because TPS is connected on the underside), and ICV. I started by cleaning the ICV and shaking it, it is making a clicking noise so i believe it still works (it also vibrates when ignition is on)!? I bought a new TPS and air filter, and installed both. I believe that the TPS was bad because people having the same issue say that this usually fixes it, and when i would pull the throttle (with the car off) i could not hear the microswitch clicking.

After assembling the new parts, and everything back together, i started the car. It was no longer high idling at 3k rpm's but was now surging, between 1k and 2k constantly, and also the fuel economy gauge was going from 0 to 40 along with the rpm movement. I think i messed something up when i switched the TPS but i am not experienced enough to know what lol. I am hoping maybe someone has had the same issue or knows what my next move should be. I was thinking of getting a smoke test done, to be sure that there are no vacuum leaks going on. Another reason i believe it may be the TPS is that, oil and coolant was getting on everything under the throttle including the tps and the original one was covered in gunk.

I am very new to the forum and hope someone can help me, i also have a video that i took today showing my gauges as the surging occurs. https://www.youtube.com/watch?v=cyIW...Y&spfreload=10 (video of the car idling weird) https://www.youtube.com/watch?v=d3NncT62mJ0 ( video of the gauges)

[dworthy]

Welcome to the Forum!

Well you would have been better served buying a Bentley Shop Manual and a Digital Voltohm Meter instead of purchasing all those parts. First rule of thumb on BMW's is to test first before condemning any part. Surging can be cause by either a clogged fuel filter, so test fuel pressure. Next I would look at the quality of the ignition system: Coil wire, plug wires, plugs, rotor, and distributor cap. Then I would have a look at all the vacuum lines for you may just as well have a vacuum leak too.

Lastly since you just purchased the vehicle, do you know how old the timing belt is? If there is no sticker or something indicating when it was changed, stop driving the car and replace it NOW! Changing the waterpump would also be a good idea as it is right there, and nothing worse then finding out 6 months after replacing the timing belt, it goes bad. If that timing belt breaks, the motor will be toast as those engines are what is called an interference engine.

[andrewliebner]

Welcome to the Forum!

Well you would have been better served buying a Bentley Shop Manual and a Digital Voltohm Meter instead of purchasing all those parts. First rule of thumb on BMW's is to test first before condemning any part. Surging can be cause by either a clogged fuel filter, so test fuel pressure. Next I would look at the quality of the ignition system: Coil wire, plug wires, plugs, rotor, and distributor cap. Then I would have a look at all the vacuum lines for you may just as well have a vacuum leak too.

Lastly since you just purchased the vehicle, do you know how old the timing belt is? If there is no sticker or something indicating when it was changed, stop driving the car and replace it NOW! Changing the waterpump would also be a good idea as it is right there, and nothing worse then finding out 6 months after replacing the timing belt, it goes bad. If that timing belt breaks, the motor will be toast as those engines are what is called an interference engine.

Believe it or not the day after i bought the car i got a bentley manual haha. And i read alot of things online saying to check the voltage or ohms on the TPS so i bought a voltmeter too! I will have a smoke test run on the car tomorrow, the shop i bought the car from says that the timing belt was changed within the last 5k miles, not sure about the waterpump. I doubt that this is a fuel issue as it was running relatively okay when i decided to mess with the coil, airbox, tps, and icv. The biggest issues arrived when i started messing with these sensors.

[dworthy]

How long was this car parked for? Funny enough but fuel injectors can act normal for a week or two and then start to go wacky cause running issues making you chase all kinds of stuff around.

[andrewliebner]

How long was this car parked for? Funny enough but fuel injectors can act normal for a week or two and then start to go wacky cause running issues making you chase all kinds of stuff around.

The car maybe sat for a day without driving at most. But before i bought the car (i bought the car about 3 months ago) it may have been sitting for a long while. But i wouldnt think that the injectors would make the car surge on idle!? Ive attached a video of the car "surging" i thought it was the TPS but i am now thinking it could be a vacuum leak. I will not discount the injectors though, what should be my first recourse? Taking them out and cleaning them?

[MarcoZandrini]

Unless you have written documentation that shows that the timing belt was replaced in the last 5 years or within the last 50k miles I highly suggest you replace the belt and tensioner. As previously noted, this is an interference engine. That means the pistons will hit any/all open valve's. This will interfere with your wallet!

[dworthy]

Unless you have written documentation that shows that the timing belt was replaced in the last 5 years or within the last 50k miles I highly suggest you replace the belt and tensioner. As previously noted, this is an interference engine. That means the pistons will hit any/all open valve's. This will interfere with your wallet!

+30000

Sticking injectors can cause it to stumble, and leaking injectors can cause surging, or even rich running. Something else that would be worth looking into is the cold start system on that car.

[andrewliebner]

+30000

Sticking injectors can cause it to stumble, and leaking injectors can cause surging, or even rich running. Something else that would be worth looking into is the cold start system on that car.

Would you advise me to clean the injectors myself or have them professionally cleaned? also i have heard that too about the cold start, i believe it is a sensor, will try to clean this and see if i have a positive result.

- - - Updated - - -

Unless you have written documentation that shows that the timing belt was replaced in the last 5 years or within the last 50k miles I highly suggest you replace the belt and tensioner. As previously noted, this is an interference engine. That means the pistons will hit any/all open valve's. This will interfere with your wallet!

I understand and believe you and all, but right now the car is not running well enough to be "driveable", are you saying maybe the timing skipped a tooth, or are you advising me to keep an eye on it and do this in the future or are you saying this is the reason my car has a "surging" idle?
Dr-Evil-Laser.jpg

[bmwdirtracer]

dworthy is going to tell you that if you clean the injectors, you need to send them to a professional cleaning service, like RC Engineering in California. How do I know this? He sent his injectors to them -- FROM GERMANY! I'll also mention that I've sent MANY sets of injectors to RCE, over the years, and every time, they have proven to be the best investment in the automotive world. I'm finishing a complete rebuild of a fellow instructor's S50B30 engine right now....sent his injectors off to RCE....two injectors were almost 30% off, on delivery, and were dripping....every injector is now absolutely perfect, within 1/2 %, by computer test results which RCE provides. (Cost $25 per injector)

I absolutely agree with both of the guys above about the timing belt and water pump, because it's the difference between a long-lived engine, and a very expensive bunch of bent valves.

I will say however that the timing belt is not likely to be the cause of your current issue.

My best guess is that you have a major intake leak, or a faulty idle air control valve.

The only thing that causes 3000 rpm is AIR. If the timing's bad, the engine will spit and run like crap. If there's too much or too little fuel, the engine will sputter, or stall.

The engine cannot rev to 3000 rpm without a lot of air. Even if the TPS is bad; even if the AirFlowMeter is bad, to achieve that sort of RPM, there is unauthorized air. The fact that your revs are now surging dramatically would make me first suspect that the Idle Air Control Valve is malfunctioning. With a little ingenuity, you can actually create a restriction on the airflow to that valve, for testing purposes, with something as simple as a washer, or a pair of needle nose pliers.

A smoke test of the intake system, done with a professional smoke machine at a good shop, will easily point out all intake leaks.

[thejlevie]

I agree with Chris.

[andrewliebner]

dworthy is going to tell you that if you clean the injectors, you need to send them to a professional cleaning service, like RC Engineering in California. How do I know this? He sent his injectors to them -- FROM GERMANY! I'll also mention that I've sent MANY sets of injectors to RCE, over the years, and every time, they have proven to be the best investment in the automotive world. I'm finishing a complete rebuild of a fellow instructor's S50B30 engine right now....sent his injectors off to RCE....two injectors were almost 30% off, on delivery, and were dripping....every injector is now absolutely perfect, within 1/2 %, by computer test results which RCE provides. (Cost $25 per injector)

I absolutely agree with both of the guys above about the timing belt and water pump, because it's the difference between a long-lived engine, and a very expensive bunch of bent valves.

I will say however that the timing belt is not likely to be the cause of your current issue.

My best guess is that you have a major intake leak, or a faulty idle air control valve.

The only thing that causes 3000 rpm is AIR. If the timing's bad, the engine will spit and run like crap. If there's too much or too little fuel, the engine will sputter, or stall.

The engine cannot rev to 3000 rpm without a lot of air. Even if the TPS is bad; even if the AirFlowMeter is bad, to achieve that sort of RPM, there is unauthorized air. The fact that your revs are now surging dramatically would make me first suspect that the Idle Air Control Valve is malfunctioning. With a little ingenuity, you can actually create a restriction on the airflow to that valve, for testing purposes, with something as simple as a washer, or a pair of needle nose pliers.

A smoke test of the intake system, done with a professional smoke machine at a good shop, will easily point out all intake leaks.

Chris, you seem like a very smart and experienced individual when it comes to these things. First off i want you to know that i have always loved E30's since i was a little kid and i plan to keep this car for a very long time, so things such as a timing belt and water pump are soon to come. I would agree that it is either an intake leak or the IAC, i have a pep boys appointment for them to only run a smoke test on my car tomorrow. The only strange thing is if you watch the 2 short video i made (i linked both in the first post above ^) i unplugged the icv in the video and the surging continues but at a faster pace. Does this mean the ICV itself is broken? Or does this mean it is working properly? Also ive seen many videos of people "surging" engines but i haven't heard of any of them having their MPG gauge moving as well (also shown in the short youtube videos i shot). Thank you for responding and helping me! keep up the great work

[andrewliebner]

I agree with Chris.

Me too! lol

[dworthy]

Yes, and I got my Injectors back yesterday. They included the old filters and o-rings, and wrapped the cleaned injectors in bubble wrap. Normally they only ship UPS, but as a favor to me, they returned them via USPS. I have attached the report, as the car these injectors came out of was a 97 Z-3 with the M-44 1.9l motor. I will be installing them later today as I have one or two injectors that are sticking.

[E39MGirl]

The economy ('MPG') gauge signal comes from the engine control computer (DME). As the engine revs drop and the engine comes close to stalling, the DME reacts and injects extra fuel to prevent the engine stalling. When the DME injects extra fuel the economy gauge will fluctuate. The other people probably didn't mention it because the gauge is doing what you would expect given the circumstances.

[andrewliebner]

The economy ('MPG') gauge signal comes from the engine control computer (DME). As the engine revs drop and the engine comes close to stalling, the DME reacts and injects extra fuel to prevent the engine stalling. When the DME injects extra fuel the economy gauge will fluctuate. The other people probably didn't mention it because the gauge is doing what you would expect given the circumstances.

So could the DME be another reason the idle is erratic?

[MIKYZZ4]

Did the smoke test confirm any leaks?
Do you have an oiled cold air intake filter installed?

[dworthy]

Yes it could be, however we need to ensure that the DME is getting the proper inputs before condemning it.

[E39MGirl]

The point I was making is that the gauge is behaving as it should in response to the DME inputting extra fuel, since you said that other people who experienced erratic idle didn't mention the gauge. My comment was not a statement about whether or not the DME might be a problem.

At this stage there is nothing to suggest the DME is the problem as it is also behaving as it should in response to the car nearly stalling. As Dworthy said, there are other things to check first before suspecting the DME.

[andrewliebner]

Did the smoke test confirm any leaks?
Do you have an oiled cold air intake filter installed?

No I have a normal airbox/ filter ,havent run a smoke test but i am trying to make my own with a small pump paint can and oiled rag.

[bmwdirtracer]

I tried 3 times to make a smoke machine, before buying one. I recommend you take the car to a good BMW / Euro shop, and have the smoke test done.

[andrewliebner]

I tried 3 times to make a smoke machine, before buying one. I recommend you take the car to a good BMW / Euro shop, and have the smoke test done.

Yes, and I got my Injectors back yesterday. They included the old filters and o-rings, and wrapped the cleaned injectors in bubble wrap. Normally they only ship UPS, but as a favor to me, they returned them via USPS. I have attached the report, as the car these injectors came out of was a 97 Z-3 with the M-44 1.9l motor. I will be installing them later today as I have one or two injectors that are sticking.

So, i fixed my e30's erratic idle, it was the ICV, i must have used carb cleaner to clean it instead of wd-40 and it dried it or the part was faulty. Thanks to everyone who gave advice. My next course of action will be to change the fuel pump, some lines, a pressure regulator (damper), and cleaning my injectors, so that i can hopefully fix the original issue the car had.