Hi all. Glad you are here . (First post for me.)

I bought my '92 325i this past winter. It's in good condition and is generally a great car. The engine performance at low RPMs (below 2,500) is, well, weak, but it really storms when I rev it up a bit. I have not driven other recent 325s, but I have been assuming it was running normally.

The car has about 97,000 miles and has been well cared for. It was serviced before I bought it including a tuneup. There is an occasional miss at idle, but nothing I would normally worry about.

However, now that the weather has warmed up it has developed a new symptom - when the engine is warm, if I step on the throttle at low RPMs, (say, 1,500) there is almost no accelleration for one or two seconds. Then the power starts to build slowly, and once it is around 2,500-3,000 it is again pulling strongly. Also a couple times the idle speen has started to hunt, bouncing between 500 and 1000 RPM.

I've run a can of fuel system cleaner (44G ?) and taken a quick look at the intake boot connections (nothing obvious wrong) and the diagnostic display is not reporting any codes.

So, I plan a more careful inspection of the intake plumbing, and I should inspect the vacuum hoses (how do I get to them???). Anything else I should check before seeking professional help?

I have not yet purchased a Bentley. Does the manual give diagnostic procedures for the various electronic sensors (like the mass air flow, throttle position sensor, or however this engine does it)? Or are the sensord digital or something and not conducive to the home tester?

Thanks in advance for your advice!

Gary in Atlanta

If you have a Digital Multi-Meter (DMM), you can diagnose a lot of stuff. The most important tools you can buy are a good DMM, a Bentley manual, and the obvious hand tools. If you are a DIY kind of guy, you can fix a lot of things on your own that would otherwise drain your wallet.

I do not think your 325i has VANOS. There will be a bulge in the valve cover/timing cover right in front of the intake cam if you do have VANOS. You may have vacuum leaks, clogged injectors, a faulty throttle position switch, worn plugs, faulty O2 sensor, etc.

JamesM

Thanks for your thoughts James.
Gary

Gary, I have a 92 325i also and no, it doesn't have VANOS. Actually, I have the same exact symptoms you have - like it has no pep under 2500, but around 3000+ it has power. I also have the miss at idle where the engine starts to rock a little (same as you?). I have replaced the O2 sensor since it failed, but it hasn't helped. I read out a code once that indicated a faulty lambda control? anyone know what that is? My next guess is to do new plugs and check vacuum lines. I'll post my findings, and hopefully if you find out more info, you can post as well? Car is a little quirky, but a lot of fun to drive. Good luck with yours!
:stickoutt

Thanks for the input JB. If I remember my car magazines from 20 years ago when Saab first intoduced Lamda, it was the O2 sensor feedback technology that is common today. OTOH, maybe you got a diagnostic message specific to O2 sensors later on... That might mean I am wrong. Perhaps someone else knows.
Gary

Lambda is the greek letter used to represent fuel mixture. Thus, a lambda error would mean either too rich or too lean a mixture. The question I have (being that I have a '92 325i w/ the same problem) is what effect the throttle position sensor would have on the mix, and what other symptoms might indicate the sensor is bad?

I got the lambda control error along with the code for the O2 sensor. i replaced the O2 sensor but the lambda control code remained....regarding the TPS, i believe it must be used by the DME in conjunction with the O2 sensor. I have no clue what the DME uses the feedback information for....:dunno

Phaedrus, shouldn't you be riding an old Honda instead of driving a modified BMW...

I think my engine behaves as though it has a lean mixture at low RPMs. Last night I inspected my intake elbow and the portions of the vacuum lines I could get to, but didn't find anything conclusive. I also performed a running leak test (hose down all potential leak points with carb cleaner or WD-40) and the engine RPM didn't change at all, which probably means it is not an intake leak.

I also think the behavior could indicate retarded timing, perhaps as though I have severe carbonization in my head causing knock, or perhaps (one of ?) the knock sensors is sending false signals. Any idea how to test that theory?

Both the TPS and the hot wire air flow sensor (whatever it is called) are extremely easy to swap. I had them both off last night. I'd sure like to find someone in Atlanta whose car runs well, and who would swap those parts with me for an hour or two.... (hint, hint). That way I could easily rule those two parts in or out.

Thanks for your input.

Gary in Atlanta

Originally posted by gbeale
Phaedrus, shouldn't you be riding an old Honda instead of driving a modified BMW...
Enlightenment comes in many forms. :cool:

You can check the hot wire sensor easily. Take out the air box so you can see inside to the hot wire. Start the car and run it for a minute. Once you turn it off, look inside at the hot wire. After a couple of seconds, it will light up for a second or two while it heats itself to burn off anything that may have gotten caught on it.

As to TPS, you need a DMM to test it. I just checked mine to rule it out and it was fine.

Functionality btw the TPS and DME is that as the throttle opens wider, more air is let into the engine. DME uses the output from the TPS to determine the throttle's position (imagine that) and then adjusts the amount of fuel released accordingly. If your car is running in a way so that the mix is off and the o2 sensor is out of range (triggering a lambda or o2 sensor error) DME operates in an open loop mode and ignores all inputs and just continuously dumps fuel into the system as if the throttle were wide open.

My problem has been a rich running car that triggers the o2 sensor error. I've replaced the o2 sensor, fuel pressure regulator, intake air temp sensor, block temp sensor, cleaned the ICV, changed the fuel injectors, and tested the TPS; nothing has fixed it. My latest theory is either that there is a short somewhere btw the O2 sensor and the DME (anyone that could help me figure this out w/ my DMM would be appreciated. Connection btw the o2 sensor and heater relay is fine), or that I have bad cats causing the exhaust to backup and the o2 sensor is taking readings from the backup. (If anyone can offer an opinion on this theory...)

Regardless, let me know if you discover anything.

Turned out to be straight-forward...

Here's an update on my drivability problems with my '92 325i:

Problem was engine very sluggish at low RPMs when warm, especially noticeable right after shifting..

ECM finally produced Check Engine light. Code indicated bad O2 sensor. Replaced it and Voila! Performance is now good. O2 sensor had apparently been going bad but took a while to fail and produce code. Glad it is fixed now.

Thanks for everyone's advice.

Gary in Atlanta

Yo everyone, hmmm I curious I have a 92' 325i, what are your guys performance times such as your 0-60 times on your cars? Since you have have similar models as me (the 92's with non-vanos) I wanna compare mine cuz I think mine is sluggish. Mine's about 9.3 secs 0-60 and I feel like it has no power at all unter about 3k-3,500 rpms, I mean an old civic w/ 200k miles (my friend's) can keep up with my at low rpms, makes me feel ashamed...:bawl ASll your theories may hold true to my car as well...im gonna do research with you guys. (BTW this 0-60 time is with a CAI and Dinan Chip....sigh)

I don't know what my 325's 0-60 time is, but I bet it is not very good unless I'm willing to abuse the clutch mercilessly.

Even though tne new O2 sensor "fixed" my low speed running problems, the engine performance is still weak at low RPMs (under 2,500-3000). Especially when I have the air on the car can hardly get out of its own way until the revs come up... My car has about 100k miles on it, but has been very well maintained and I don't think there is anything really "wrong" with it (anything that could be fixed.)

I'm not an expert on the '90s motors, but I think I remember BMW changing things in '93 and '94 to boost low RPM performance. The 328 (for example) makes only about the same HP as my '92 325, but makes better torque at low RPMs. I don't have high expectations for the low-speed performance of my '92, but I do wish it was better than it is. Perhaps I still have something minor that is not working right that I will eventually find and fix. For now, I avoid drag racing unless I'm willing to beat the crap out of my car.

Gary

I have a '92 325i and also see the same problem - no power under 3K, then it takes off. I have been eating up O2 sensors too. I've replaced 3 O2 sensors in the past year, and I think my current one is shot too, so it tells me that I'm probbaly running rich. Think my plugs are fouled up? Next plan is to change the plugs with NGKs and see if that helps. Any other thoughts? When I replaced the O2 sensor before, it didn't really give me much more power. Every once in a while, while I'm idling, the car will start rocking (engine misfire?)...might be related...

Though perhaps forgotten in this day of computer controls and direct ignition, debugging engine problems should ALWAYS start with the ignition system. You can screw around with injection all day, and it won't help if you have dirty plugs, a bad coil, bad grounding in the ignition harness, etc., etc. Unfortunately I don't know how to go about finding the problem, but I bet your Bently would be helpful.

If you have been eating O2 sensors your plugs are probably covered in soot, and you may be on the way to replacing your cats (cat?)! The classic situation that will cause this is a bad temp sensor that tells the engine it is still cold, thus requiring a richer mixture. It may be a different sensor than what govern's the display gauge. Bentley will tell.

Gary

Hmmmm....thanks Gary. I'll look into that. The thing is that there could be one little problem that is causing all these litte chain effect contributors. The problem is that even if we fix the cause, we might have a resultant failure causing the poor performance. Ugh..:confused:

Just gotta take it as it comes... One thing at a time...
Gary

Im chasing u jb! 92' 325i 126k miles ;) ....I wish my car had better lwo end response.

Sounds like you all are having the same kind of problem I just fixed. First though I would like to explain some things about the Non-Vanos engines that I have discovered in my extensive research. These engines were produced for the 325 and the 525 for only 3 years. There are several major differences including: double valve springs, thicker valve stems, no knock sensor, hotter cams than the vanos cars, hot wire air flow meter instead of a "paper" air flow meter, and some of the cars were fitted with coils that go bad (zundspule ?sp). These are just a few things, I'm sure there is more. In my opinion they were better built engines.
Ok, now for my fix. The symptoms I was experiencing were very similar to what has already been described, i.e. hesitation at low rpm's, misfire at idle, sluggish under 3000 rpm's and a general rough idle feeling. The first problem was the valve cover gasket leaking oil into my #1 cylinder which caused some major hesitation at low rpm's especially after warm up. The second problem was a bad coil. BTW it is recommended that you replace all of them at the same time to avoid damaging the DME computer, also if you let a coil go bad for a long period of time it could also damage the DME. Fixing these two problems cured all my hesitation problems. Now if you are getting a fault code in the computer you should address that FIRST.
As far as being sluggish at low rpm's and having a rough idle that is just a characteristic of the non-vanos engines. The hotter cams result in a rougher idle in just about any car. For all you power junkies swapping cams with a non-vanos 525 is a little known upgrade. Another thing to remember is that vanos engines have a considerably flatter torque curve. This means more low end power, but a little less top end. So, if you want more power just remember to keep the rpm's up. Another thing that is pretty cool about these engines is they handle higher rpm's much better than a vanos engine therefore they are a great choice for auto cross.
I hope this information has helped. Good luck and have fun driving!

Thanks very much for your comments Arcticblue92! You have confirmed some of the things I had been thinking (but am too new at this BMW stuff to be able to speak authoritatively).

1) Careful attention to ignition is key to good performance! Always start with a careful analysis of the ignition system. Fix that stuff first before looking at the FI system.

2) The early E36 motors (pre-Vanos) are typical small-bore high performance motors... not much torque at low RPMs, but lots of HP at high RPMs. If you want to make the puppy perform you have to wind it up!

I do have a couple questions for you: Did you mean that your valve cover gasket leaked oil into the #1 plug/coil area causing ignition problems? How was it determined you had one/some bad coils? Did you do that or a shop?

Thanks,

Gary

Hey Gary,

You are correct about where the valve cover was leaking oil, sound like you have had experience with that. This added to the coil failure. As far as trouble shooting the coils I swapped them with a set from a buddies bimmer and the misfire went away. So, I got the Bremi coils to replace the old ones from BMP Designs (www.bmpd.com) for $45 a piece. Pretty good since the $tealer wants upwards of $70 a piece. I also replaced the plugs at the same time. If you have any other questions don't "hesitate" to write.

Jim

I think most of the 4-valve motors suffer from the same "valve cover gasket-oil in the plug wells" problem. In my case it was a Ford Probe with the (Mazda) V6.

Thanks fo the info.

Gary

Wow - cool. There was an article in a recent edition of Roundel (I think that's where) that mentioned that there were two types of coils put in these - Bosch and non-Bosch. I believe that it was the non-Bosch that had some failures. I'll check and post back later. Definitely checking out the ignition system. When I bought the car last year, it had a lot of power in the sub 3K range. Somehow it lost it - and I attricute it to possibly the igniotion system too. I haven't changed plugs, so I might do that.

RRdawho? - I am up to 133K miles and it is still running strong. Just need to get the low end up a bit. I wish bundy would post - he has a 92 325i with 190K miles. I wonder if he has the same problem.....

Good luck all. Do us all a favor - if anyone else fixes the problem too, PLEASE post what you did! Thanks! :D

BTW Thanks Arcticblue92, your tips are really insightful and I will look at that...now finding a tool to read the computer in my car...whats a good choice? lol. Hey I checked the Bavauto website and they have these plasma ignition systems which are supposed to help low end torque by providing a 100% gain to the secondary output to the spark plugs. What do you guys think of this thing? Anyone have it?
Back to the quote yep mine has 126k and climbing, I just had to place all the hoses cuz they were sweating (they were all freaking from original purchase too...dang!) other than that, just regular maintainence and changing the transmission flex disc. Oh my A/C is leaking though and its not at the hoses, any ideas? ITS HOT HERE IN CALI AHHHH!:eek:
Originally posted by jb325
Wow - cool. There was an article in a recent edition of Roundel (I think that's where) that mentioned that there were two types of coils put in these - Bosch and non-Bosch. I believe that it was the non-Bosch that had some failures. I'll check and post back later. Definitely checking out the ignition system. When I bought the car last year, it had a lot of power in the sub 3K range. Somehow it lost it - and I attricute it to possibly the igniotion system too. I haven't changed plugs, so I might do that.

RRdawho? - I am up to 133K miles and it is still running strong. Just need to get the low end up a bit. I wish bundy would post - he has a 92 325i with 190K miles. I wonder if he has the same problem.....

Good luck all. Do us all a favor - if anyone else fixes the problem too, PLEASE post what you did! Thanks! :D

aftermarket for $39, Bosch for $50. I've bought stuff from them twice and they were great!

Gary