M20 rev problems

[Stackede30]

Hi Guys,

Having another problem with my e30. I did some digging and found another guy with the same problem but he did`nt get much feedback on that specific problem.

Diablo also with the same problem - Dated back to 2006

http://www.r3vlimited.com/board/showthread.php?t=63904

Problem is:

At about 5500rpm when I`m full on the throttle it will feel like the car is hitting the rev limiter, but if I back off the throttle and ease it through you can continue to redline. But as soon as you go full on the throttle the car will misfire/choke all the way to redline. It does this on every gear as soon as it gets to 5500rpm.

So far I have changed:

Crank Sensor
Idle Control Valve
Inspection 1 service - (Oil Filter, Spark Plugs, etc)


I thought it could be because the car does not have a o2 sensor, so the car was leaning out at high rev`s maybe . When I was under the car there is a nut in the o2 sensor socket and its welded shut.

When I contacted the mechanic who did the engine swap for the previous owner he said that the engine and ECU on the car is from a UK spec 325i, therefore it does not need an o2 sensor because they did`nt come out with o2 sensors on the English e30`s. Any truth to that statement? Because I thought all Motronic 1.3. needed it run an o2 sensor and catalytic converter.

Any advice would be greatly appreciated.

Cheers,
Trish

[Sagaris]

The first thing that comes to mind is a crack/tear in the intake boot. I usually find them hidden in the very inside middle of the bend so the average person tends to miss the crack. The crack can stay sealed until you get enough torque to make the engine move inside the engine bay, which opens up the crack in the intake boot and causes the intake leak.

The next thing that comes to mind is fuel pressure. The car may have enough fuel pressure to run normally, maybe even a bit lean at part throttle up to high rpm but when the full throttle switch is engaged it could be requiring more fuel than the car can handle.
I would start by changing the fuel filter and checking the fuel pressure and looking for fuel leaks.

[Stackede30]

Cheers for that advice, Will have a look at both those suggestions and get back on that. Once I get back from work i`ll get stuck into it

[lennon]

I think some parts of the world did get cars without o2 sensor systems, and realoem shows exhaust without cat convertor or o2 sensor. That doesn't mean I'd believe the ECU story without checking it out for myself. A disconnected o2 sensor on a car that uses one won't make the car run lean, assuming there is not some other problem.

[myfirst325]

I just got my e30 back on the road after sitting for 10 years. I took my first test drive and after 20 mins of 60-65 mph cruising the car would sputter with the check engine light flickering. I inspected the intake boot and sure enough its cracked. Tomorrow I'm replacing it along with the fuel filter. Stacked E30 - Please update us with your findings as I am curious to see if it can be anything else.

[Stackede30]

Ok I just pulled out the intake boot and its perfect, wiped it down and not the slightest bit of wear and tear on it.

Next I`m about to check is the fuel filter. But 1st some lunch :D

[jlevie]

This sounds like a fuel delivery problem. Replace the filter and run the fuel system checks in the Bentley. If the fuel system checks out with the car stationary, zip tie a gauge to a windshield wiper and see what the fuel pressure is when at high rpm where the problem occurs.

[Myster-E]

I would also swap out the fuel pressure regulator with another one to see if that's the problem.

[Stackede30]

Hey guys,

Sorry I haven't been keeping you guys posted. just been super busy at the moment, before I do anything else I`ve ordered a copy of the Bentley manual, waiting for that to arrived, and then i`ll start looking at my fueling.

[bmwstephen]

isthis car an auto or manual

[Stackede30]

isthis car an auto or manual

5 speed manual

[BlackBox]

Hey my car does the same exact thing at about 4K rpms! You're not alone!

[laz]

My car is doing this as well... I already swapped fuel pump, and the filter is new-ish. Need to pick up fittings to test fuel pressure... and then I guess find an AFM.

I need to solve it in 3 days due to a race this weekend, and a race car without full throttle is no fun to drive :)

[jlevie]

Check the TPS to see if the WOT switch is closing (electrically).The AFM isn't a player above about 4500rpm, but the WOT switch in the TPS is. Above the cutoff point of the AFM the DME runs a full throttle map based on rpm and temperature if the TPS is working correctly.

[Stackede30]

Hey Guys

Got back from my holiday, I`ve taken the car to the mechanic that did the engine swap for the previous owner.

He has tried the following so far:

- Swapped out old AFM with new AFM
- Check fuel pressure regulator
- Swapped out my 173 ECU with a different 173 ECU

And it still the same problem. Still going through the car will keep you guys posted